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Everything you and your teachers need to know about the learning brain.

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Everything you and your teachers need to know about the learning brain.

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Frontiers for Young Minds collection on the brain. CC BY 4.0.

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About this collection

Children go to school to learn, and learning takes place in the brain. In the age period of formal schooling, a child's brain is still undergoing major developmental changes. For these reasons, neuroscience (the study of the brain) and education are closely connected. Learning is possible because the brain is plastic: plasticity refers to the capacity of the brain to reorganize its structure and thereby change function and behavior.

But what exactly changes in the brain when we learn something new? What are optimal conditions for the brain to learn? Why do we also forget things? What developmental changes occur in the brain during childhood and adolescence, and how are these processes different or similar to the neural mechanisms of learning and memory?

Neuro-imaging research, or 'brain scanning', has accelerated our current understanding of brain development, learning, memory and other school-related skills such as reading and math but also creativity, metacognition and learning-related emotions and anxieties. But what do these brain scanning techniques actually measure? What kind of questions can we address with neuro-imaging, and what are the limitations?

In this Collection, we will provide an accessible overview of the current state-of-the-art insights into the mechanisms of brain development, learning and memory. The collection will help children understand how their brains learn and develop, and how these processes are shaped by their environment and their own efforts. Moreover, we will discuss why it is important that their teachers and other educational practitioners know about the brain and neuroscience methods. Finally, we will also explain what happens if wrong ideas about the brain circulate, or the correct knowledge is misinterpreted. Neuromyths such as 'we only use 10 percent of our brain' are persistent, but important to counter with explaining why they are false, and what is true instead.

In sum, this Collection will provide children with all the relevant knowledge about the brain to understand themselves and their learning processes better, and to equip them to distinguish myths and facts.

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Everything you and your teachers need to know about the learning brain

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Children go to school to learn, and learning takes place in the brain. In the age period of formal schooling, a child's brain is still undergoing major developmental changes. For these reasons, neuroscience (the study of the brain) and education are closely connected.

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This free course from Open Learn is published under a Creative Commons CC BY NC SA license. You are free to adapt and share for non-commercial use as long as you include an attribution and apply a CC BY NC SA license to your adaptation.

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The most ‘important and greatest puzzle’ we face as humans is ourselves (Boring, 1950, p. 56). Humans are a puzzle, one that is complex, subtle and multi-layered, and it gets even more complicated…

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Understanding Traumatic Injury to the Human Brain

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Understanding Traumatic Injury to the Human Brain

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Frontiers for Young Minds collection on understanding traumatic injury to the human brain. CC BY 4.0

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About this collection

Your noggin, your noodle, your coconut, your bean! There are many terms for your brain, that fantastic organ that sits inside of your skull, and runs, well, everything, whether you are thinking about it or not. Although the skull is a hard, purpose-built case to protect the brain, we live in an active environment, in which expected events and unexpected accidents may cause what we call a "traumatic brain injury" - everything from concussion on the sport field, to falls from a bike or a ladder or a snowboard, to car accidents and everything in between. These different mechanisms of injury may cause contusions or bruises to the brain, like a bruise to a muscle, and may also result in bleeds in or around the brain, called hemorrhages.

All of these types of brain injuries can result in damage to the actual brain tissue as well as cause interruptions to the complex electronic circuitry of the brain, causing symptoms like headaches, dizziness, fuzzy thinking, upset balance, memory loss, and poor sleep, to name just a few. Doctors are very good at treating the acute problems from a brain injury but we currently have no effective treatments for the actual injury to your brain and have to wait and see how the injury resolves on its own. While most people do recover spontaneously, for some, kids and adults alike, the symptoms can persist for a very long time, from months to years and sometimes permanently.

If there is any positive that can come from injuring the brain, it is that sometimes the only way to understand how something works is to "break" it, and watch how it puts itself back to together. In this collection of articles, we'll study the way we diagnose where and how the brain has been injured, how we treat the acute injury and discuss new models to enhance recovery of brain function. The first steps in our roadmap require a careful assessment of the details of the person's accident, examining the person thoroughly, and then reviewing special imaging studies called computed tomography (CT) or Magnetic Resonance Imaging (MRI) that show us the structures of the brain, and how they are connected or disconnected following the injury. New blood tests can identify the presence of special biomarkers that indicate that there has been an injury to the brain itself, rather than just to the bony skull. Other important information can come from electroencephalography (EEG), which uses small sensors attached to the skull to capture and measure electronic signals traveling around the brain, to see where the interruptions may be occurring.

We'll learn about special surgeries, including hemicraniotomy, where the neurosurgeon "pops your top", sometimes to relieve pressure on the brain, or to stop a hemorrhage from bleeding further, or to insert a protective metal plate. Surgeries and imaging studies give us a great deal of insight about the injured brain, but then what? Studies of other mammals, like rats and mice, can help us, but how, for instance, do we study a rat's memory? We'll find out how scientists accomplish this, and see how this knowledge might help patients recover memory after a brain injury.

Importantly, we'll also learn how can we protect our brains from injury, even when we can't avoid the accidents that come with everyday life. We'll explore emerging design of sports helmets and other gear, and learn how a strong neck and back can help prevent injury to the brain and spinal cord.

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Understanding Traumatic Injury to the Human Brain

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Your noggin, your noodle, your coconut, your bean! There are many terms for your brain, that fantastic organ that sits inside of your skull, and runs, well, everything, whether you are thinking about it or not.

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© State of Queensland (QCAA) 2019, licensed under CC BY 4.0

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This free course from Open Learn is published under a Creative Commons CC BY NC SA license. You are free to adapt and share for non-commercial use as long as you include an attribution and apply a CC BY NC SA license to your adaptation.

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This free course introduces you to critical thinking as a tool for psychology. As you work your way through the course you will learn what critical thinking is, and why it is important to use in...

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Frontiers for Young Minds is a free, online scientific journal that provides open access to articles written by scientists and reviewed by kids. The journal aims to make science accessible to children and teenagers, and to inspire the next generation of scientists. The articles published in Frontiers for Young Minds are written in a way that is easy for young readers to understand, while still maintaining scientific accuracy.

Frontiers for Young Minds also offers educational resources for parents and teachers, including activities and lesson plans that can be used to supplement classroom instruction. The goal of the journal is to encourage young people to engage with science and to foster a love of learning that will last a lifetime.

Articles are licensed under Creative Commons CC BY 4.0 license. You are free to adapt and share with an attribution.

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Frontiers for Young Minds is an open access scientific journal that brings the latest research in real time to school kids between 8-15 years old.

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This free course from Open Learn is published under a Creative Commons CC BY NC SA license. You are free to adapt and share for non-commercial use as long as you include an attribution and apply a CC BY NC SA license to your adaptation.

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One of the keys to understanding psychology is to know about its history and core questions. This free course, Investigating psychology, allows you to explore psychology using an interactive ...

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Enlighten your clock: How your body tells time

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Enlighten your clock: How your body tells time

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Weinzaepflen, C. & Spitschan, M. (Ed.) (2021). Enlighten your clock: How your body tells time. (C. Weinzaepflen, Illus.). DOI: 10.17605/OSF.IO/ZQXVH

This work is licensed under a CC BY NC-ND Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Weinzaepflen, C. & Spitschan, M. (Ed.) (2021). Enlighten your clock: How your body tells time. (C. Weinzaepflen, Illus.). DOI: 10.17605/OSF.IO/ZQXVH

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Beck, D. & Tapia, E. (2023). The brain. In R. Biswas-Diener & E. Diener (Eds), Noba textbook series: Psychology. Champaign, IL: DEF publishers. http://noba.to/jx7268sd

This work is licensed under CC NC SA Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License

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Any textbook on psychology would be incomplete without reference to the brain. Every behavior, thought, or experience described in the other modules must be implemented in the brain. A detailed understanding of the human brain can help us make sense of human experience and behavior. For example, one well-established fact about human cognition is that it is limited. We cannot do two complex tasks at once: We cannot read and carry on a conversation at the same time, text and drive, or surf the Internet while listening to a lecture, at least not successfully or safely. We cannot even pat our head and rub our stomach at the same time (with exceptions, see "A Brain Divided"). Why is this? Many people have suggested that such limitations reflect the fact that the behaviors draw on the same resource; if one behavior uses up most of the resource there is not enough resource left for the other. But what might this limited resource be in the brain?

Figure 1. An MRI of the human brain delineating three major structures: the cerebral hemispheres, brain stem, and cerebellum.

The brain uses oxygen and glucose, delivered via the blood. The brain is a large consumer of these metabolites, using 20% of the oxygen and calories we consume despite being only 2% of our total weight. However, as long as we are not oxygen-deprived or malnourished, we have more than enough oxygen and glucose to fuel the brain. Thus, insufficient "brain fuel" cannot explain our limited capacity. Nor is it likely that our limitations reflect too few neurons. The average human brain contains 100 billion neurons. It is also not the case that we use only 10% of our brain, a myth that was likely started to imply we had untapped potential. Modern neuroimaging (see "Studying the Human Brain") has shown that we use all parts of brain, just at different times, and certainly more than 10% at any one time.

If we have an abundance of brain fuel and neurons, how can we explain our limited cognitive abilities? Why can't we do more at once? The most likely explanation is the way these neurons are wired up. We know, for instance, that many neurons in the visual cortex (the part of the brain responsible for processing visual information) are hooked up in such a way as to inhibit each other ( Beck & Kastner, 2009). When one neuron fires, it suppresses the firing of other nearby neurons. If two neurons that are hooked up in an inhibitory way both fire, then neither neuron can fire as vigorously as it would otherwise. This competitive behavior among neurons limits how much visual information the brain can respond to at the same time. Similar kinds of competitive wiring among neurons may underlie many of our limitations. Thus, although talking about limited resources provides an intuitive description of our limited capacity behavior, a detailed understanding of the brain suggests that our limitations more likely reflect the complex way in which neurons talk to each other rather than the depletion of any specific resource.

There are many ways to subdivide the mammalian brain, resulting in some inconsistent and ambiguous nomenclature over the history of neuroanatomy ( Swanson, 2000). For simplicity, we will divide the brain into three basic parts: the brain stem, cerebellum, and cerebral hemispheres (see Figure 1). In Figure 2, however, we depict other prominent groupings ( Swanson, 2000) of the six major subdivisions of the brain ( Kandal, Schwartz, & Jessell, 2000).

Brain Stem

The brain stem is sometimes referred to as the "trunk" of the brain. It is responsible for many of the neural functions that keep us alive, including regulating our respiration (breathing), heart rate, and digestion. In keeping with its function, if a patient sustains severe damage to the brain stem he or she will require "life support" (i.e., machines are used to keep him or her alive). Because of its vital role in survival, in many countries a person who has lost brain stem function is said to be "brain dead," although other countries require significant tissue loss in the cortex (of the cerebral hemispheres), which is responsible for our conscious experience, for the same diagnosis. The brain stem includes the medulla, pons, midbrain, and diencephalon (which consists of thalamus and hypothalamus). Collectively, these regions also are involved in our sleep-wake cycle, some sensory and motor function, as well as growth and other hormonal behaviors.

Figure 2. A sample of neuroanatomy nomenclature. The colored boxes indicate the different groupings of the seven structures printed in black, with the labels matching the color of the boxes. The hindbrain, midbrain, and forebrain nomenclature stems from the development of the vertebrate brain; these three areas differentiate early in embryonic development and later give rise to the structures listed in black. These three areas further subdivide into the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon at a later stage of development.

Cerebellum

The cerebellum is the distinctive structure at the back of the brain. The Greek philosopher and scientist Aristotle aptly referred to it as the "small brain" ("parencephalon" in Greek, "cerebellum" in Latin) in order to distinguish it from the "large brain" ("encephalon" in Greek, " cerebrum " in Latin). The cerebellum is critical for coordinated movement and posture. More recently, neuroimaging studies (see "Studying the Human Brain") have implicated it in a range of cognitive abilities, including language. It is perhaps not surprising that the cerebellum's influence extends beyond that of movement and posture, given that it contains the greatest number of neurons of any structure in the brain. However, the exact role it plays in these higher functions is still a matter of further study.

Cerebral Hemispheres

The four lobes of the brain and the cerebellum. [Image: MIT OpenCourseWare, https://goo.gl/RwUEVt, CC BY-NC-SA 2.0, https://goo.gl/Toc0ZF]

The cerebral hemispheres are responsible for our cognitive abilities and conscious experience. They consist of the cerebral cortex and accompanying white matter ("cerebrum" in Latin) as well as the subcortical structures of the basal ganglia, amygdala, and hippocampal formation. The cerebral cortex is the largest and most visible part of the brain, retaining the Latin name (cerebrum) for "large brain" that Aristotle coined. It consists of two hemispheres (literally two half spheres) and gives the brain its characteristic gray and convoluted appearance; the folds and grooves of the cortex are called gyri and sulci ( gyrus and sulcus if referring to just one), respectively.

The two cerebral hemispheres can be further subdivided into four lobes: the occipital, temporal, parietal, and frontal lobes. The occipital lobe is responsible for vision, as is much of the temporal lobe. The temporal lobe is also involved in auditory processing, memory, and multisensory integration (e.g., the convergence of vision and audition). The parietal lobe houses the somatosensory (body sensations) cortex and structures involved in visual attention, as well as multisensory convergence zones. The frontal lobe houses the motor cortex and structures involved in motor planning, language, judgment, and decision-making. Not surprisingly then, the frontal lobe is proportionally larger in humans than in any other animal.

The subcortical structures are so named because they reside beneath the cortex. The basal ganglia are critical to voluntary movement and as such make contact with the cortex, the thalamus, and the brain stem. The amygdala and hippocampal formation are part of the limbic system, which also includes some cortical structures. The limbic system plays an important role in emotion and, in particular, in aversion and gratification.

The two cerebral hemispheres are connected by a dense bundle of white matter tracts called the corpus callosum. Some functions are replicated in the two hemispheres. For example, both hemispheres are responsible for sensory and motor function, although the sensory and motor cortices have a contralateral (or opposite-side) representation; that is, the left cerebral hemisphere is responsible for movements and sensations on the right side of the body and the right cerebral hemisphere is responsible for movements and sensations on the left side of the body. Other functions are lateralized; that is, they reside primarily in one hemisphere or the other. For example, for right-handed and the majority of left-handed individuals, the left hemisphere is most responsible for language.

There are some people whose two hemispheres are not connected, either because the corpus callosum was surgically severed ( callosotomy) or due to a genetic abnormality. These split-brain patients have helped us understand the functioning of the two hemispheres. First, because of the contralateral representation of sensory information, if an object is placed in only the left or only the right visual hemifield, then only the right or left hemisphere, respectively, of the split-brain patient will see it. In essence, it is as though the person has two brains in his or her head, each seeing half the world. Interestingly, because language is very often localized in the left hemisphere, if we show the right hemisphere a picture and ask the patient what she saw, she will say she didn't see anything (because only the left hemisphere can speak and it didn't see anything). However, we know that the right hemisphere sees the picture because if the patient is asked to press a button whenever she sees the image, the left hand (which is controlled by the right hemisphere) will respond despite the left hemisphere's denial that anything was there. There are also some advantages to having disconnected hemispheres. Unlike those with a fully functional corpus callosum, a split-brain patient can simultaneously search for something in his right and left visual fields (L uck, Hillyard, Mangun, & Gazzaniga, 1989) and can do the equivalent of rubbing his stomach and patting his head at the same time ( Franz, Eliason, Ivry, & Gazzaniga, 1996). In other words, they exhibit less competition between the hemispheres.

Gray Versus White Matter

The cerebral hemispheres contain both grey and white matter, so called because they appear grayish and whitish in dissections or in an MRI (magnetic resonance imaging; see, "Studying the Human Brain"). The gray matter is composed of the neuronal cell bodies (see module, "Neurons"). The cell bodies (or soma) contain the genes of the cell and are responsible for metabolism (keeping the cell alive) and synthesizing proteins. In this way, the cell body is the workhorse of the cell. The white matter is composed of the axons of the neurons, and, in particular, axons that are covered with a sheath of myelin (fatty support cells that are whitish in color). Axons conduct the electrical signals from the cell and are, therefore, critical to cell communication. People use the expression "use your gray matter" when they want a person to think harder. The "gray matter" in this expression is probably a reference to the cerebral hemispheres more generally; the gray cortical sheet (the convoluted surface of the cortex) being the most visible. However, both the gray matter and white matter are critical to proper functioning of the mind. Losses of either result in deficits in language, memory, reasoning, and other mental functions. See Figure 3 for MRI slices showing both the inner white matter that connects the cell bodies in the gray cortical sheet.

Figure 3. MRI slices of the human brain. Both the outer gray matter and inner white matter are visible in each image. The brain is a three-dimensional (3-D) structure, but an image is two-dimensional (2-D). Here, we show example slices of the three possible 2-D cuts through the brain: a saggital slice (top image), a horizontal slice (bottom left), which is also know as a transverse or axial slice, and a coronal slice (bottom right). The bottom two images are color coded to match the illustration of the relative orientations of the three slices in the top image.

How do we know what the brain does? We have gathered knowledge about the functions of the brain from many different methods. Each method is useful for answering distinct types of questions, but the strongest evidence for a specific role or function of a particular brain area is converging evidence; that is, similar findings reported from multiple studies using different methods.

One of the first organized attempts to study the functions of the brain was phrenology, a popular field of study in the first half of the 19th century. Phrenologists assumed that various features of the brain, such as its uneven surface, are reflected on the skull; therefore, they attempted to correlate bumps and indentations of the skull with specific functions of the brain. For example, they would claim that a very artistic person has ridges on the head that vary in size and location from those of someone who is very good at spatial reasoning. Although the assumption that the skull reflects the underlying brain structure has been proven wrong, phrenology nonetheless significantly impacted current-day neuroscience and its thinking about the functions of the brain. That is, different parts of the brain are devoted to very specific functions that can be identified through scientific inquiry.

Neuroanatomy

Dissection of the brain, in either animals or cadavers, has been a critical tool of neuroscientists since 340 BC when Aristotle first published his dissections. Since then this method has advanced considerably with the discovery of various staining techniques that can highlight particular cells. Because the brain can be sliced very thinly, examined under the microscope, and particular cells highlighted, this method is especially useful for studying specific groups of neurons or small brain structures; that is, it has a very high spatial resolution. Dissections allow scientists to study changes in the brain that occur due to various diseases or experiences (e.g., exposure to drugs or brain injuries).

Virtual dissection studies with living humans are also conducted. Here, the brain is imaged using computerized axial tomography (CAT) or MRI scanners; they reveal with very high precision the various structures in the brain and can help detect changes in gray or white matter. These changes in the brain can then be correlated with behavior, such as performance on memory tests, and, therefore, implicate specific brain areas in certain cognitive functions.

Changing the Brain

Some researchers induce lesions or ablate (i.e., remove) parts of the brain in animals. If the animal's behavior changes after the lesion, we can infer that the removed structure is important for that behavior. Lesions of human brains are studied in patient populations only; that is, patients who have lost a brain region due to a stroke or other injury, or who have had surgical removal of a structure to treat a particular disease (e.g., a callosotomy to control epilepsy, as in split-brain patients). From such case studies, we can infer brain function by measuring changes in the behavior of the patients before and after the lesion.

Because the brain works by generating electrical signals, it is also possible to change brain function with electrical stimulation. Transcranial magnetic stimulation (TMS) refers to a technique whereby a brief magnetic pulse is applied to the head that temporarily induces a weak electrical current in the brain. Although effects of TMS are sometimes referred to as temporary virtual lesions, it is more appropriate to describe the induced electricity as interference with neurons' normal communication with each other. TMS allows very precise study of when events in the brain happen so it has a good temporal resolution, but its application is limited only to the surface of the cortex and cannot extend to deep areas of the brain.

Transcranial direct current stimulation (tDCS) is similar to TMS except that it uses electrical current directly, rather than inducing it with magnetic pulses, by placing small electrodes on the skull. A brain area is stimulated by a low current (equivalent to an AA battery) for a more extended period of time than TMS. When used in combination with cognitive training, tDCS has been shown to improve performance of many cognitive functions such as mathematical ability, memory, attention, and coordination (e.g., Brasil-Neto, 2012; Feng, Bowden, & Kautz, 2013; Kuo & Nitsche, 2012).

Neuroimaging

Neuroimaging tools are used to study the brain in action; that is, when it is engaged in a specific task. Positron emission tomography (PET) records blood flow in the brain. The PET scanner detects the radioactive substance that is injected into the bloodstream of the participant just before or while he or she is performing some task (e.g., adding numbers). Because active neuron populations require metabolites, more blood and hence more radioactive substance flows into those regions. PET scanners detect the injected radioactive substance in specific brain regions, allowing researchers to infer that those areas were active during the task. Functional magnetic resonance imaging (fMRI) also relies on blood flow in the brain. This method, however, measures the changes in oxygen levels in the blood and does not require any substance to be injected into the participant. Both of these tools have good spatial resolution (although not as precise as dissection studies), but because it takes at least several seconds for the blood to arrive to the active areas of the brain, PET and fMRI have poor temporal resolution; that is, they do not tell us very precisely when the activity occurred.

A researcher looking at the areas of activation in the brain of a study participant who had an fMRI scan - areas of brain activation are determined by the amount of blood flow to a certain area - the more blood flow, the higher the activation of that area of the brain. [Image: National Institute of Mental Health, CC0 Public Domain, https://goo.gl/m25gce]

Electroencephalography (EEG), on the other hand, measures the electrical activity of the brain, and therefore, it has a much greater temporal resolution (millisecond precision rather than seconds) than PET or fMRI. Like tDCS, electrodes are placed on the participant's head when he or she is performing a task. In this case, however, many more electrodes are used, and they measure rather than produce activity. Because the electrical activity picked up at any particular electrode can be coming from anywhere in the brain, EEG has poor spatial resolution; that is, we have only a rough idea of which part of the brain generates the measured activity.

Diffuse optical imaging (DOI) can give researchers the best of both worlds: high spatial and temporal resolution, depending on how it is used. Here, one shines infrared light into the brain, and measures the light that comes back out. DOI relies on the fact that the properties of the light change when it passes through oxygenated blood, or when it encounters active neurons. Researchers can then infer from the properties of the collected light what regions in the brain were engaged by the task. When DOI is set up to detect changes in blood oxygen levels, the temporal resolution is low and comparable to PET or fMRI. However, when DOI is set up to directly detect active neurons, it has both high spatial and temporal resolution.

Because the spatial and temporal resolution of each tool varies, strongest evidence for what role a certain brain area serves comes from converging evidence. For example, we are more likely to believe that the hippocampal formation is involved in memory if multiple studies using a variety of tasks and different neuroimaging tools provide evidence for this hypothesis. The brain is a complex system, and only advances in brain research will show whether the brain can ever really understand itself.

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Any textbook on psychology would be incomplete without reference to the brain. Every behavior, thought, or experience described in the other modules must be implemented in the brain. A detailed understanding of the human brain can help us make sense of human experience and behavior.

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You Snooze, you DONT' lose - What is sleep and why is it so crucial?

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You Snooze, you DONT' lose - What is sleep and why is it so crucial?

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Frontiers for Young Minds collection on sleep. CC BY 4.0

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You Snooze, You DON’T Lose – What is Sleep and Why is it so Crucial? ..

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We spend an incredible amount of time sleeping – probably more time than we spend on doing anything else. This retrospective Collection of 8 articles takes a deep dive into sleep. Wow your brain and test your knowledge with this accessible overview of all things sleep(y).

The mystery of sle…

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Spielman, R.M., Jenkins, W.J., Lovett, M.D. (2020). States of consciousness. In R.M. Spielman, W.J. Jenkins, M.D. Lovett (Eds.), Psychology (2nd ed.). Open Stax. https://openstax.org/books/psychology-2e/pages/4-introduction

This book is licensed under Creative Commons CC BY 4.0. You are free to share and adapt the work with attribution. Access for free at https://openstax.org/books/psychology-2e/pages/4-introduction

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Chapter Outline

Our lives involve regular, dramatic changes in the degree to which we are aware of our surroundings and our internal states. While awake, we feel alert and aware of the many important things going on around us. Our experiences change dramatically while we are in deep sleep and once again when we are dreaming. Some people also experience altered states of consciousness through meditation, hypnosis, or alcohol and other drugs.

This chapter will discuss states of consciousness with a particular emphasis on sleep. The different stages of sleep will be identified, and sleep disorders will be described. The chapter will close with discussions of altered states of consciousness produced by psychoactive drugs, hypnosis, and meditation.

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Ch. 4 Introduction - Psychology 2e | OpenStax

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Chapter Outline Our lives involve regular, dramatic changes in the degree to which we are aware of our surroundings and our internal states. While awake, we feel alert and aware of the many important things going on around us. Our experiences change dramatically while we are in deep sleep and once again when we are dreaming.

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Shook, S. The science of sleep. Kapi'olani Community College. https://dspace.lib.hawaii.edu/handle/10790/6879

This book is licensed under Creative Commons CC BY 4.0 You are free to share and adapt the work with attribution.

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Skip navigation

Please use this identifier to cite or link to this item: http://hdl.handle.net/10790/6879

The Science of Sleep

Item Summary

Please email libraryada-l@lists.hawaii.edu if you need this content in ADA-compliant format.

This item is licensed under a Creative Commons License

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UH System Repository for the University of Hawaii: The Science of Sleep

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Skip navigation Please use this identifier to cite or link to this item: http://hdl.handle.net/10790/6879 Please email libraryada-l@lists.hawaii.edu if you need this content in ADA-compliant format. This item is licensed under a Creative Commons License

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UQ Psychology: Resources for QCE Senior School Psychology

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UQ Psychology: Resources for QCE Senior School Psychology

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Explains correlational and experimental research designs and contains interactive calculators for statistics i.e. Spearman, Wilcoxon, Mann-Whitney and calculating a P Value from a Z Score.

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Research Design

Correlational

Correlational designs are used to test whether there is a relationship between two measures. e.g. Is there a relationship between a person's age and their IQ? Positive correlation would mean that IQ increases with age. Negative correlation would indication that IQ decreases with age. No significant correlation (the null hypothesis) is that there is no significant relationship, i.e. a person's IQ is not related to their age. Correlational designs have no independent or dependent variables, and only test for the linear relationship between two measures.

Experimental

Experimental designs are used to test whether there is a significant difference between two (or more) groups or between measures at different times or under different conditions (e.g. experimental versus control groups/conditions). The alternate hypothesis is that the two groups/conditions are different. The null hypothesis is that the two groups/conditions are not different. Experimental designs have an independent variable that is the group/condition that is controlled by the experimenter and a dependent variable that is the measure assessed. Experimental designs test the effect of the independent variable on the dependent variable.

Experimental designs can use either:

Independent Groups: Two (or more) independent groups of participants are compared. e.g. Is IQ different in girls compared with boys? The independent variable is gender that is controlled in the experiment, i.e. the experimenter selects participants and assigns them to groups according to their gender (girls versus boys). The dependent variable is IQ that is measured by the experimenter. The experimental design tests the effect of gender on IQ. The null hypothesis is that IQ will not be different between girls and boys. The alternate hypothesis is that IQ will be different between girls and boys, either greater for girls compared with boys or lower for girls compared with boys. As groups are independent, there can be a different number of participants in each group.

Matched Participants: Two (or more) groups of participants are compared, but participants between groups are matched one-to-one on other relevant factors, to control potential effects of other factors that might influence results. e.g. Is IQ different in girls compared with boys, controlling for potential effects of age? The independent variable is gender that is controlled in the experiment, but the experimenter selects a pairs of participants, one girl and one boy, of exactly the same age, paired one-to-one between the two participant groups. The dependent variable is IQ that is measured by the experimenter. The null hypothesis is that IQ will not be different between girls and boys. The alternate hypothesis is that IQ will be different between girls and boys. Any difference in IQ observed between girls and boys cannot be influenced by age as the two groups are exactly matched in age. As groups are matched one-to-one, there must be the same number of participants in each group.

Repeated Measures: Two (or more) measures taken from the same participants under different conditions or at different times are compared. e.g. Is IQ different when measured at the start of the school day compared with the end of the school day? The independent variable is the time of day that is controlled in the experiment, i.e. the experimenter selects the times of day to measure IQ and compare. The dependent variable is IQ that is measured by the experimenter. The dependent variable is measured in all participants at both times of day (i.e. repeated measures) and compared. The experimental design tests the effect of the time of day of the IQ test on the measured IQ. The null hypothesis is that there will be no difference in IQ measured at the start compared with the end of the school day. The alternate hypothesis is that measured IQ will be different at the start compared with the end of the school day, either greater at the start of the day compared with the end or less at the start of the day compared with the end. As measures are repeated under both conditions in all participants, there must be an equal number of measures (i.e. equal participants) in each condition.

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psychology; uq; university of queensland; school of psychology; brisbane; australia;

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UQ Psychology - Queensland Certificate of Education - QCE - Resources for QCE Senior School Psychology

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Correlational designs are used to test whether there is a relationship between two measures. e.g. Is there a relationship between a person's age and their IQ? Positive correlation would mean that IQ increases with age. Negative correlation would indication that IQ decreases with age.

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Quality open access undergraduate psychology textbook with accompanying instructor and student resources. Includes annotated video guide, QTI test bank, instructor solution guide, enhanced lecture PowerPoint slides and more.

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Spielman, R.M., Jenkins, W.J., Lovett, M.D. (2020). Psychological research. In R.M. Spielman, W.J. Jenkins, M.D. Lovett (Eds.), Psychology (2nd ed.). Open Stax. https://openstax.org/books/psychology-2e/pages/2-introduction

This book is licensed under Creative Commons CC BY 4.0. You are free to share and adapt the work with attribution. Access for free at https://openstax.org/books/psychology-2e/pages/2-introduction

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2.1 Why Is Research Important? - Psychology 2e | OpenStax

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By the end of this section, you will be able to:

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Chapter 3.4

Spielman, R.M., Jenkins, W.J., Lovett, M.D. (2020). The brain and spinal cord. In R.M. Spielman, W.J. Jenkins, M.D. Lovett (Eds.), Psychology (2nd ed.). Open Stax. https://openstax.org/books/psychology-2e/pages/3-4-the-brain-and-spinal-cord

This book is licensed under Creative Commons CC BY 4.0. You are free to share and adapt the work with attribution.

Access for free at https://openstax.org/books/psychology-2e/pages/3-4-the-brain-and-spinal-cord

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Learning Objectives

By the end of this section, you will be able to:

Explain the functions of the spinal cord

Identify the hemispheres and lobes of the brain

Describe the types of techniques available to clinicians and researchers to image or scan the brain

The brain is a remarkably complex organ comprised of billions of interconnected neurons and glia. It is a bilateral, or two-sided, structure that can be separated into distinct lobes. Each lobe is associated with certain types of functions, but, ultimately, all of the areas of the brain interact with one another to provide the foundation for our thoughts and behaviors. In this section, we discuss the overall organization of the brain and the functions associated with different brain areas, beginning with what can be seen as an extension of the brain, the spinal cord.

The Spinal Cord

It can be said that the spinal cord is what connects the brain to the outside world. Because of it, the brain can act. The spinal cord is like a relay station, but a very smart one. It not only routes messages to and from the brain, but it also has its own system of automatic processes, called reflexes.

The top of the spinal cord is a bundle of nerves that merges with the brain stem, where the basic processes of life are controlled, such as breathing and digestion. In the opposite direction, the spinal cord ends just below the ribs-contrary to what we might expect, it does not extend all the way to the base of the spine.

The spinal cord is functionally organized in 30 segments, corresponding with the vertebrae. Each segment is connected to a specific part of the body through the peripheral nervous system. Nerves branch out from the spine at each vertebra. Sensory nerves bring messages in; motor nerves send messages out to the muscles and organs. Messages travel to and from the brain through every segment.

Some sensory messages are immediately acted on by the spinal cord, without any input from the brain. Withdrawal from a hot object and the knee jerk are two examples. When a sensory message meets certain parameters, the spinal cord initiates an automatic reflex. The signal passes from the sensory nerve to a simple processing center, which initiates a motor command. Seconds are saved, because messages don't have to go to the brain, be processed, and get sent back. In matters of survival, the spinal reflexes allow the body to react extraordinarily fast.

The spinal cord is protected by bony vertebrae and cushioned in cerebrospinal fluid, but injuries still occur. When the spinal cord is damaged in a particular segment, all lower segments are cut off from the brain, causing paralysis. Therefore, the lower on the spine damage occurs, the fewer functions an injured individual will lose.

Neuroplasticity

Bob Woodruff, a reporter for ABC, suffered a traumatic brain injury after a bomb exploded next to the vehicle he was in while covering a news story in Iraq. As a consequence of these injuries, Woodruff experienced many cognitive deficits including difficulties with memory and language. However, over time and with the aid of intensive amounts of cognitive and speech therapy, Woodruff has shown an incredible recovery of function (Fernandez, 2008, October 16).

One of the factors that made this recovery possible was neuroplasticity. Neuroplasticity refers to how the nervous system can change and adapt. Neuroplasticity can occur in a variety of ways including personal experiences, developmental processes, or, as in Woodruff's case, in response to some sort of damage or injury that has occurred. Neuroplasticity can involve creation of new synapses, pruning of synapses that are no longer used, changes in glial cells, and even the birth of new neurons. Because of neuroplasticity, our brains are constantly changing and adapting, and while our nervous system is most plastic when we are very young, as Woodruff's case suggests, it is still capable of remarkable changes later in life.

The Two Hemispheres

The surface of the brain, known as the cerebral cortex, is very uneven, characterized by a distinctive pattern of folds or bumps, known as gyri (singular: gyrus), and grooves, known as sulci (singular: sulcus), shown in Figure 3.15. These gyri and sulci form important landmarks that allow us to separate the brain into functional centers. The most prominent sulcus, known as the longitudinal fissure, is the deep groove that separates the brain into two halves or hemispheres: the left hemisphere and the right hemisphere.

There is evidence of specialization of function-referred to as lateralization-in each hemisphere, mainly regarding differences in language functions. The left hemisphere controls the right half of the body, and the right hemisphere controls the left half of the body. Decades of research on lateralization of function by Michael Gazzaniga and his colleagues suggest that a variety of functions ranging from cause-and-effect reasoning to self-recognition may follow patterns that suggest some degree of hemispheric dominance (Gazzaniga, 2005). For example, the left hemisphere has been shown to be superior for forming associations in memory, selective attention, and positive emotions. The right hemisphere, on the other hand, has been shown to be superior in pitch perception, arousal, and negative emotions (Ehret, 2006). However, it should be pointed out that research on which hemisphere is dominant in a variety of different behaviors has produced inconsistent results, and therefore, it is probably better to think of how the two hemispheres interact to produce a given behavior rather than attributing certain behaviors to one hemisphere versus the other (Banich & Heller, 1998).

The two hemispheres are connected by a thick band of neural fibers known as the corpus callosum, consisting of about 200 million axons. The corpus callosum allows the two hemispheres to communicate with each other and allows for information being processed on one side of the brain to be shared with the other side.

Normally, we are not aware of the different roles that our two hemispheres play in day-to-day functions, but there are people who come to know the capabilities and functions of their two hemispheres quite well. In some cases of severe epilepsy, doctors elect to sever the corpus callosum as a means of controlling the spread of seizures ( Figure 3.16). While this is an effective treatment option, it results in individuals who have "split brains." After surgery, these split-brain patients show a variety of interesting behaviors. For instance, a split-brain patient is unable to name a picture that is shown in the patient's left visual field because the information is only available in the largely nonverbal right hemisphere. However, they are able to recreate the picture with their left hand, which is also controlled by the right hemisphere. When the more verbal left hemisphere sees the picture that the hand drew, the patient is able to name it (assuming the left hemisphere can interpret what was drawn by the left hand).

Much of what we know about the functions of different areas of the brain comes from studying changes in the behavior and ability of individuals who have suffered damage to the brain. For example, researchers study the behavioral changes caused by strokes to learn about the functions of specific brain areas. A stroke, caused by an interruption of blood flow to a region in the brain, causes a loss of brain function in the affected region. The damage can be in a small area, and, if it is, this gives researchers the opportunity to link any resulting behavioral changes to a specific area. The types of deficits displayed after a stroke will be largely dependent on where in the brain the damage occurred.

Consider Theona, an intelligent, self-sufficient woman, who is 62 years old. Recently, she suffered a stroke in the front portion of her right hemisphere. As a result, she has great difficulty moving her left leg. (As you learned earlier, the right hemisphere controls the left side of the body; also, the brain's main motor centers are located at the front of the head, in the frontal lobe.) Theona has also experienced behavioral changes. For example, while in the produce section of the grocery store, she sometimes eats grapes, strawberries, and apples directly from their bins before paying for them. This behavior-which would have been very embarrassing to her before the stroke-is consistent with damage in another region in the frontal lobe-the prefrontal cortex, which is associated with judgment, reasoning, and impulse control.

Forebrain Structures

The two hemispheres of the cerebral cortex are part of the forebrain ( Figure 3.17), which is the largest part of the brain. The forebrain contains the cerebral cortex and a number of other structures that lie beneath the cortex (called subcortical structures): thalamus, hypothalamus, pituitary gland, and the limbic system (a collection of structures). The cerebral cortex, which is the outer surface of the brain, is associated with higher level processes such as consciousness, thought, emotion, reasoning, language, and memory. Each cerebral hemisphere can be subdivided into four lobes, each associated with different functions.

Lobes of the Brain

The four lobes of the brain are the frontal, parietal, temporal, and occipital lobes ( Figure 3.18). The frontal lobe is located in the forward part of the brain, extending back to a fissure known as the central sulcus. The frontal lobe is involved in reasoning, motor control, emotion, and language. It contains the motor cortex, which is involved in planning and coordinating movement; the prefrontal cortex, which is responsible for higher-level cognitive functioning; and Broca's area, which is essential for language production.

People who suffer damage to Broca's area have great difficulty producing language of any form ( Figure 3.18). For example, Padma was an electrical engineer who was socially active and a caring, involved parent. About twenty years ago, she was in a car accident and suffered damage to her Broca's area. She completely lost the ability to speak and form any kind of meaningful language. There is nothing wrong with her mouth or her vocal cords, but she is unable to produce words. She can follow directions but can't respond verbally, and she can read but no longer write. She can do routine tasks like running to the market to buy milk, but she could not communicate verbally if a situation called for it.

Probably the most famous case of frontal lobe damage is that of a man by the name of Phineas Gage. On September 13, 1848, Gage (age 25) was working as a railroad foreman in Vermont. He and his crew were using an iron rod to tamp explosives down into a blasting hole to remove rock along the railway's path. Unfortunately, the iron rod created a spark and caused the rod to explode out of the blasting hole, into Gage's face, and through his skull ( Figure 3.19). Although lying in a pool of his own blood with brain matter emerging from his head, Gage was conscious and able to get up, walk, and speak. But in the months following his accident, people noticed that his personality had changed. Many of his friends described him as no longer being himself. Before the accident, it was said that Gage was a well-mannered, soft-spoken man, but he began to behave in odd and inappropriate ways after the accident. Such changes in personality would be consistent with loss of impulse control-a frontal lobe function.

Beyond the damage to the frontal lobe itself, subsequent investigations into the rod's path also identified probable damage to pathways between the frontal lobe and other brain structures, including the limbic system. With connections between the planning functions of the frontal lobe and the emotional processes of the limbic system severed, Gage had difficulty controlling his emotional impulses.

However, there is some evidence suggesting that the dramatic changes in Gage's personality were exaggerated and embellished. Gage's case occurred in the midst of a 19 th century debate over localization-regarding whether certain areas of the brain are associated with particular functions. On the basis of extremely limited information about Gage, the extent of his injury, and his life before and after the accident, scientists tended to find support for their own views, on whichever side of the debate they fell (Macmillan, 1999).

The brain's parietal lobe is located immediately behind the frontal lobe, and is involved in processing information from the body's senses. It contains the somatosensory cortex, which is essential for processing sensory information from across the body, such as touch, temperature, and pain. The somatosensory cortex is an area of the brain which processes touch and sensation. The somatosensory cortex is fascinating because each different area of the cortex processes sensations from a different part of your body. Furthermore, the larger the surface area of the specific body part and the greater amount of nerves in that body part, the larger the area dedicated to processing sensation from that body part in the somatosensory cortex. For example, fingers take up a lot more space than toes. As you can notice from ( Figure 3.20), the amount of space to process sensation from fingers is much greater than that of toes.

The temporal lobe is located on the side of the head (temporal means "near the temples"), and is associated with hearing, memory, emotion, and some aspects of language. The auditory cortex, the main area responsible for processing auditory information, is located within the temporal lobe. Wernicke's area, important for speech comprehension, is also located here. Whereas individuals with damage to Broca's area have difficulty producing language, those with damage to Wernicke's area can produce sensible language, but they are unable to understand it ( Figure 3.21).

The occipital lobe is located at the very back of the brain, and contains the primary visual cortex, which is responsible for interpreting incoming visual information. The occipital cortex is organized retinotopically, which means there is a close relationship between the position of an object in a person's visual field and the position of that object's representation on the cortex. You will learn much more about how visual information is processed in the occipital lobe when you study sensation and perception.

Other Areas of the Forebrain

Other areas of the forebrain, located beneath the cerebral cortex, include the thalamus and the limbic system. The thalamus is a sensory relay for the brain. All of our senses, with the exception of smell, are routed through the thalamus before being directed to other areas of the brain for processing ( Figure 3.22).

The limbic system is involved in processing both emotion and memory. Interestingly, the sense of smell projects directly to the limbic system; therefore, not surprisingly, smell can evoke emotional responses in ways that other sensory modalities cannot. The limbic system is made up of a number of different structures, but three of the most important are the hippocampus, the amygdala, and the hypothalamus ( Figure 3.23). The hippocampus is an essential structure for learning and memory. The amygdala is involved in our experience of emotion and in tying emotional meaning to our memories. The hypothalamus regulates a number of homeostatic processes, including the regulation of body temperature, appetite, and blood pressure. The hypothalamus also serves as an interface between the nervous system and the endocrine system and in the regulation of sexual motivation and behavior.

The Case of Henry Molaison (H.M.)

In 1953, Henry Gustav Molaison (H. M.) was a 27-year-old man who experienced severe seizures. In an attempt to control his seizures, H. M. underwent brain surgery to remove his hippocampus and amygdala. Following the surgery, H.M's seizures became much less severe, but he also suffered some unexpected-and devastating-consequences of the surgery: he lost his ability to form many types of new memories. For example, he was unable to learn new facts, such as who was president of the United States. He was able to learn new skills, but afterward he had no recollection of learning them. For example, while he might learn to use a computer, he would have no conscious memory of ever having used one. He could not remember new faces, and he was unable to remember events, even immediately after they occurred. Researchers were fascinated by his experience, and he is considered one of the most studied cases in medical and psychological history (Hardt, Einarsson, & Nader, 2010; Squire, 2009). Indeed, his case has provided tremendous insight into the role that the hippocampus plays in the consolidation of new learning into explicit memory.

Midbrain and Hindbrain Structures

The midbrain is comprised of structures located deep within the brain, between the forebrain and the hindbrain. The reticular formation is centered in the midbrain, but it actually extends up into the forebrain and down into the hindbrain. The reticular formation is important in regulating the sleep/wake cycle, arousal, alertness, and motor activity.

The substantia nigra (Latin for "black substance") and the ventral tegmental area (VTA) are also located in the midbrain ( Figure 3.24). Both regions contain cell bodies that produce the neurotransmitter dopamine, and both are critical for movement. Degeneration of the substantia nigra and VTA is involved in Parkinson's disease. In addition, these structures are involved in mood, reward, and addiction (Berridge & Robinson, 1998; Gardner, 2011; George, Le Moal, & Koob, 2012).

The hindbrain is located at the back of the head and looks like an extension of the spinal cord. It contains the medulla, pons, and cerebellum ( Figure 3.25). The medulla controls the automatic processes of the autonomic nervous system, such as breathing, blood pressure, and heart rate. The word pons literally means "bridge," and as the name suggests, the pons serves to connect the hindbrain to the rest of the brain. It also is involved in regulating brain activity during sleep. The medulla, pons, and various structures are known as the brainstem, and aspects of the brainstem span both the midbrain and the hindbrain.

The cerebellum (Latin for "little brain") receives messages from muscles, tendons, joints, and structures in our ear to control balance, coordination, movement, and motor skills. The cerebellum is also thought to be an important area for processing some types of memories. In particular, procedural memory, or memory involved in learning and remembering how to perform tasks, is thought to be associated with the cerebellum. Recall that H. M. was unable to form new explicit memories, but he could learn new tasks. This is likely due to the fact that H. M.'s cerebellum remained intact.

What Do You Think?

Brain Imaging

You have learned how brain injury can provide information about the functions of different parts of the brain. Increasingly, however, we are able to obtain that information using brain imaging techniques on individuals who have not suffered brain injury. In this section, we take a more in-depth look at some of the techniques that are available for imaging the brain, including techniques that rely on radiation, magnetic fields, or electrical activity within the brain.

Techniques Involving Radiation

A computerized tomography (CT) scan involves taking a number of x-rays of a particular section of a person's body or brain ( Figure 3.26). The x-rays pass through tissues of different densities at different rates, allowing a computer to construct an overall image of the area of the body being scanned. A CT scan is often used to determine whether someone has a tumor or significant brain atrophy.

Positron emission tomography (PET) scans create pictures of the living, active brain ( Figure 3.27). An individual receiving a PET scan drinks or is injected with a mildly radioactive substance, called a tracer. Once in the bloodstream, the amount of tracer in any given region of the brain can be monitored. As a brain area becomes more active, more blood flows to that area. A computer monitors the movement of the tracer and creates a rough map of active and inactive areas of the brain during a given behavior. PET scans show little detail, are unable to pinpoint events precisely in time, and require that the brain be exposed to radiation; therefore, this technique has been replaced by the fMRI as an alternative diagnostic tool. However, combined with CT, PET technology is still being used in certain contexts. For example, CT/PET scans allow better imaging of the activity of neurotransmitter receptors and open new avenues in schizophrenia research. In this hybrid CT/PET technology, CT contributes clear images of brain structures, while PET shows the brain's activity.

Techniques Involving Magnetic Fields

In magnetic resonance imaging (MRI), a person is placed inside a machine that generates a strong magnetic field. The magnetic field causes the hydrogen atoms in the body's cells to move. When the magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their original positions. Tissues of different densities give off different signals, which a computer interprets and displays on a monitor. Functional magnetic resonance imaging (fMRI) operates on the same principles, but it shows changes in brain activity over time by tracking blood flow and oxygen levels. The fMRI provides more detailed images of the brain's structure, as well as better accuracy in time, than is possible in PET scans ( Figure 3.28). With their high level of detail, MRI and fMRI are often used to compare the brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This comparison helps determine what structural and functional differences exist between these populations.

Techniques Involving Electrical Activity

In some situations, it is helpful to gain an understanding of the overall activity of a person's brain, without needing information on the actual location of the activity. Electroencephalography (EEG) serves this purpose by providing a measure of a brain's electrical activity. An array of electrodes is placed around a person's head ( Figure 3.29). The signals received by the electrodes result in a printout of the electrical activity of their brain, or brainwaves, showing both the frequency (number of waves per second) and amplitude (height) of the recorded brainwaves, with an accuracy within milliseconds. Such information is especially helpful to researchers studying sleep patterns among individuals with sleep disorders.

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3.4 The Brain and Spinal Cord - Psychology 2e | OpenStax

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Learning Objectives By the end of this section, you will be able to: Explain the functions of the spinal cord Identify the hemispheres and lobes of the brain Describe the types of techniques available to clinicians and researchers to image or scan the brain The brain is a remarkably complex organ comprised of billions of interconnected neurons and glia.

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Chapter 9.3

Spielman, R.M., Jenkins, W.J., Lovett, M.D. (2020). The brain and spinal cord. In R.M. Spielman, W.J. Jenkins, M.D. Lovett (Eds.), Psychology (2nd ed.). Open Stax. https://openstax.org/books/psychology-2e/pages/9-3-stages-of-development

This book is licensed under Creative Commons CC BY 4.0. You are free to share and adapt the work with attribution. Access for free at https://openstax.org/books/psychology-2e/pages/9-3-stages-of-development

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9.3 Stages of Development - Psychology 2e | OpenStax

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This free textbook is an OpenStax resource written to increase student access to high-quality, peer-reviewed learning materials.

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Chapter 7

Spielman, R.M., Jenkins, W.J., Lovett, M.D. (2020). The brain and spinal cord. In R.M. Spielman, W.J. Jenkins, M.D. Lovett (Eds.), Psychology (2nd ed.). Open Stax. https://openstax.org/books/psychology-2e/pages/7-introduction
This book is licensed under Creative Commons CC BY 4.0. You are free to share and adapt the work with attribution. Access for free at https://openstax.org/books/psychology-2e/pages/7-introduction

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Ch. 7 Introduction - Psychology 2e | OpenStax

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This free textbook is an OpenStax resource written to increase student access to high-quality, peer-reviewed learning materials.

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This book is licensed under Creative Commons CC BY 4.0. You are free to share and adapt the work with attribution.

Access for free at https://openstax.org/books/anatomy-and-physiology-2e/pages/1-7-medical-imaging

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Learning Objectives

By the end of this section, you will be able to:

Discuss the uses and drawbacks of X-ray imaging

Identify four modern medical imaging techniques and how they are used

For thousands of years, fear of the dead and legal sanctions limited the ability of anatomists and physicians to study the internal structures of the human body. An inability to control bleeding, infection, and pain made surgeries infrequent, and those that were performed-such as wound suturing, amputations, tooth and tumor removals, skull drilling, and cesarean births-did not greatly advance knowledge about internal anatomy. Theories about the function of the body and about disease were therefore largely based on external observations and imagination. During the fourteenth and fifteenth centuries, however, the detailed anatomical drawings of Italian artist and anatomist Leonardo da Vinci and Flemish anatomist Andreas Vesalius were published, and interest in human anatomy began to increase. Medical schools began to teach anatomy using human dissection; although some resorted to grave robbing to obtain corpses. Laws were eventually passed that enabled students to dissect the corpses of criminals and those who donated their bodies for research. Still, it was not until the late nineteenth century that medical researchers discovered non-surgical methods to look inside the living body.

X-Rays

German physicist Wilhelm Röntgen (1845-1923) was experimenting with electrical current when he discovered that a mysterious and invisible "ray" would pass through his flesh but leave an outline of his bones on a screen coated with a metal compound. In 1895, Röntgen made the first durable record of the internal parts of a living human: an "X-ray" image (as it came to be called) of his wife's hand. Scientists around the world quickly began their own experiments with X-rays, and by 1900, X-rays were widely used to detect a variety of injuries and diseases. In 1901, Röntgen was awarded the first Nobel Prize for physics for his work in this field.

The X-ray is a form of high energy electromagnetic radiation with a short wavelength capable of penetrating solids and ionizing gases. As they are used in medicine, X-rays are emitted from an X-ray machine and directed toward a specially treated metallic plate placed behind the patient's body. The beam of radiation results in darkening of the X-ray plate. X-rays are slightly impeded by soft tissues, which show up as gray on the X-ray plate, whereas hard tissues, such as bone, largely block the rays, producing a light-toned "shadow." Thus, X-rays are best used to visualize hard body structures such as teeth and bones ( Figure 1.18). Like many forms of high energy radiation, however, X-rays are capable of damaging cells and initiating changes that can lead to cancer. This danger of excessive exposure to X-rays was not fully appreciated for many years after their widespread use.

Refinements and enhancements of X-ray techniques have continued throughout the twentieth and twenty-first centuries. Although often supplanted by more sophisticated imaging techniques, the X-ray remains a "workhorse" in medical imaging, especially for viewing fractures and for dentistry. The disadvantage of irradiation to the patient and the operator is now attenuated by proper shielding and by limiting exposure.

Modern Medical Imaging

X-rays can depict a two-dimensional image of a body region, and only from a single angle. In contrast, more recent medical imaging technologies produce data that is integrated and analyzed by computers to produce three-dimensional images or images that reveal aspects of body functioning.

Computed Tomography

Tomography refers to imaging by sections. Computed tomography (CT) is a noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body ( Figure 1.19 a). The technique was invented in the 1970s and is based on the principle that, as X-rays pass through the body, they are absorbed or reflected at different levels. In the technique, a patient lies on a motorized platform while a computerized axial tomography (CAT) scanner rotates 360 degrees around the patient, taking X-ray images. A computer combines these images into a two-dimensional view of the scanned area, or "slice."

Since 1970, the development of more powerful computers and more sophisticated software has made CT scanning routine for many types of diagnostic evaluations. It is especially useful for soft tissue scanning, such as of the brain and the thoracic and abdominal viscera. Its level of detail is so precise that it can allow physicians to measure the size of a mass down to a millimeter. The main disadvantage of CT scanning is that it exposes patients to a dose of radiation many times higher than that of X-rays. In fact, children who undergo CT scans are at increased risk of developing cancer, as are adults who have multiple CT scans.

Interactive Link

A CT or CAT scan relies on a circling scanner that revolves around the patient's body. Watch this video to learn more about CT and CAT scans. What type of radiation does a CT scanner use?

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant (cancerous) tissue gave off different signals than normal body tissue. He applied for a patent for the first MRI scanning device, which was in use clinically by the early 1980s. The early MRI scanners were crude, but advances in digital computing and electronics led to their advancement over any other technique for precise imaging, especially to discover tumors. MRI also has the major advantage of not exposing patients to radiation.

Drawbacks of MRI scans include their much higher cost, and patient discomfort with the procedure. The MRI scanner subjects the patient to such powerful electromagnets that the scan room must be shielded. The patient must be enclosed in a metal tube-like device for the duration of the scan (see Figure 1.19 b), sometimes as long as thirty minutes, which can be uncomfortable and impractical for ill patients. The device is also so noisy that, even with earplugs, patients can become anxious or even fearful. These problems have been overcome somewhat with the development of "open" MRI scanning, which does not require the patient to be entirely enclosed in the metal tube. Patients with iron-containing metallic implants (internal sutures, some prosthetic devices, and so on) cannot undergo MRI scanning because it can dislodge these implants.

Functional MRIs (fMRIs), which detect the concentration of blood flow in certain parts of the body, are increasingly being used to study the activity in parts of the brain during various body activities. This has helped scientists learn more about the locations of different brain functions and more about brain abnormalities and diseases.

Interactive Link

A patient undergoing an MRI is surrounded by a tube-shaped scanner. Watch this video to learn more about MRIs. What is the function of magnets in an MRI?

Positron Emission Tomography

Positron emission tomography (PET) is a medical imaging technique involving the use of so-called radiopharmaceuticals, substances that emit radiation that is short-lived and therefore relatively safe to administer to the body. Although the first PET scanner was introduced in 1961, it took 15 more years before radiopharmaceuticals were combined with the technique and revolutionized its potential. The main advantage is that PET (see Figure 1.19 c) can illustrate physiologic activity-including nutrient metabolism and blood flow-of the organ or organs being targeted, whereas CT and MRI scans can only show static images. PET is widely used to diagnose a multitude of conditions, such as heart disease, the spread of cancer, certain forms of infection, brain abnormalities, bone disease, and thyroid disease.

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PET relies on radioactive substances administered several minutes before the scan. Watch this video to learn more about PET. How is PET used in chemotherapy?

Ultrasonography

Ultrasonography is an imaging technique that uses the transmission of high-frequency sound waves into the body to generate an echo signal that is converted by a computer into a real-time image of anatomy and physiology (see Figure 1.19 d). Ultrasonography is the least invasive of all imaging techniques, and it is therefore used more freely in sensitive situations such as pregnancy. The technology was first developed in the 1940s and 1950s. Ultrasonography is used to study heart function, blood flow in the neck or extremities, certain conditions such as gallbladder disease, and fetal growth and development. The main disadvantages of ultrasonography are that the image quality is heavily operator-dependent and that it is unable to penetrate bone and gas.

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1.7 Medical Imaging - Anatomy and Physiology 2e | OpenStax

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Learning Objectives By the end of this section, you will be able to: Discuss the uses and drawbacks of X-ray imaging Identify four modern medical imaging techniques and how they are used For thousands of years, fear of the dead and legal sanctions limited the ability of anatomists and physicians to study the internal structures of the human body.

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Basic structure and function of the nervous system

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Basic structure and function of the nervous system

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Learning Objectives

By the end of this section, you will be able to:

Identify the anatomical and functional divisions of the nervous system

Relate the functional and structural differences between gray matter and white matter structures of the nervous system to the structure of neurons

List the basic functions of the nervous system

The picture you have in your mind of the nervous system probably includes the brain, the nervous tissue contained within the cranium, and the spinal cord, the extension of nervous tissue within the vertebral column. That suggests it is made of two organs-and you may not even think of the spinal cord as an organ-but the nervous system is a very complex structure. Within the brain, many different and separate regions are responsible for many different and separate functions. It is as if the nervous system is composed of many organs that all look similar and can only be differentiated using tools such as the microscope or electrophysiology. In comparison, it is easy to see that the stomach is different than the esophagus or the liver, so you can imagine the digestive system as a collection of specific organs.

The Central and Peripheral Nervous Systems

The nervous system can be divided into two major regions: the central and peripheral nervous systems. The central nervous system (CNS) is the brain and spinal cord, and the peripheral nervous system (PNS) is everything else ( Figure 12.2). The brain is contained within the cranial cavity of the skull, and the spinal cord is contained within the vertebral cavity of the vertebral column. It is a bit of an oversimplification to say that the CNS is what is inside these two cavities and the peripheral nervous system is outside of them, but that is one way to start to think about it. In actuality, there are some elements of the peripheral nervous system that are within the cranial or vertebral cavities. The peripheral nervous system is so named because it is on the periphery-meaning beyond the brain and spinal cord. Depending on different aspects of the nervous system, the dividing line between central and peripheral is not necessarily universal.

Nervous tissue, present in both the CNS and PNS, contains two basic types of cells: neurons and glial cells. A glial cell is one of a variety of cells that provide a framework of tissue that supports the neurons and their activities. The neuron is the more functionally important of the two, in terms of the communicative function of the nervous system. To describe the functional divisions of the nervous system, it is important to understand the structure of a neuron. Neurons are cells and therefore have a soma, or cell body, but they also have extensions of the cell; each extension is generally referred to as a process. There is one important process that every neuron has called an axon, which is the fiber that connects a neuron with its target. Another type of process that branches off from the soma is the dendrite. Dendrites are responsible for receiving most of the input from other neurons. Looking at nervous tissue, there are regions that predominantly contain cell bodies and regions that are largely composed of just axons. These two regions within nervous system structures are often referred to as gray matter (the regions with many cell bodies and dendrites) or white matter (the regions with many axons). Figure 12.3 demonstrates the appearance of these regions in the brain and spinal cord. The colors ascribed to these regions are what would be seen in "fresh," or unstained, nervous tissue. Gray matter is not necessarily gray. It can be pinkish because of blood content, or even slightly tan, depending on how long the tissue has been preserved. But white matter is white because axons are insulated by a lipid-rich substance called myelin. Lipids can appear as white ("fatty") material, much like the fat on a raw piece of chicken or beef. Actually, gray matter may have that color ascribed to it because next to the white matter, it is just darker-hence, gray.

The distinction between gray matter and white matter is most often applied to central nervous tissue, which has large regions that can be seen with the unaided eye. When looking at peripheral structures, often a microscope is used and the tissue is stained with artificial colors. That is not to say that central nervous tissue cannot be stained and viewed under a microscope, but unstained tissue is most likely from the CNS-for example, a frontal section of the brain or cross section of the spinal cord.

Regardless of the appearance of stained or unstained tissue, the cell bodies of neurons or axons can be located in discrete anatomical structures that need to be named. Those names are specific to whether the structure is central or peripheral. A localized collection of neuron cell bodies in the CNS is referred to as a nucleus. In the PNS, a cluster of neuron cell bodies is referred to as a ganglion. Figure 12.4 indicates how the term nucleus has a few different meanings within anatomy and physiology. It is the center of an atom, where protons and neutrons are found; it is the center of a cell, where the DNA is found; and it is a center of some function in the CNS. There is also a potentially confusing use of the word ganglion (plural = ganglia) that has a historical explanation. In the central nervous system, there is a group of nuclei that are connected together and were once called the basal ganglia before "ganglion" became accepted as a description for a peripheral structure. Some sources refer to this group of nuclei as the "basal nuclei" to avoid confusion.

Terminology applied to bundles of axons also differs depending on location. A bundle of axons, or fibers, found in the CNS is called a tract whereas the same thing in the PNS would be called a nerve. There is an important point to make about these terms, which is that they can both be used to refer to the same bundle of axons. When those axons are in the PNS, the term is nerve, but if they are CNS, the term is tract. The most obvious example of this is the axons that project from the retina into the brain. Those axons are called the optic nerve as they leave the eye, but when they are inside the cranium, they are referred to as the optic tract. There is a specific place where the name changes, which is the optic chiasm, but they are still the same axons ( Figure 12.5). A similar situation outside of science can be described for some roads. Imagine a road called "Broad Street" in a town called "Anyville." The road leaves Anyville and goes to the next town over, called "Hometown." When the road crosses the line between the two towns and is in Hometown, its name changes to "Main Street." That is the idea behind the naming of the retinal axons. In the PNS, they are called the optic nerve, and in the CNS, they are the optic tract. Table 12.1 helps to clarify which of these terms apply to the central or peripheral nervous systems.

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Structures of the CNS and PNS

CNS

PNS

Group of Neuron Cell Bodies (i.e., gray matter)

Nucleus

Ganglion

Bundle of Axons (i.e., white matter)

Tract

Nerve

Functional Divisions of the Nervous System

The nervous system can also be divided on the basis of its functions, but anatomical divisions and functional divisions are different. The CNS and the PNS both contribute to the same functions, but those functions can be attributed to different regions of the brain (such as the cerebral cortex or the hypothalamus) or to different ganglia in the periphery. The problem with trying to fit functional differences into anatomical divisions is that sometimes the same structure can be part of several functions. For example, the optic nerve carries signals from the retina that are either used for the conscious perception of visual stimuli, which takes place in the cerebral cortex, or for the reflexive responses of smooth muscle tissue that are processed through the hypothalamus.

There are two ways to consider how the nervous system is divided functionally. First, the basic functions of the nervous system are sensation, integration, and response. Secondly, control of the body can be somatic or autonomic-divisions that are largely defined by the structures that are involved in the response. There is also a region of the peripheral nervous system that is called the enteric nervous system that is responsible for a specific set of the functions within the realm of autonomic control related to gastrointestinal functions.

Basic Functions

The nervous system is involved in receiving information about the environment around us (sensation) and generating responses to that information (motor responses). The nervous system can be divided into regions that are responsible for sensation (sensory functions) and for the response (motor functions). But there is a third function that needs to be included. Sensory input needs to be integrated with other sensations, as well as with memories, emotional state, or learning (cognition). Some regions of the nervous system are termed integration or association areas. The process of integration combines sensory perceptions and higher cognitive functions such as memories, learning, and emotion to produce a response.

Sensation. The first major function of the nervous system is sensation-receiving information about the environment to gain input about what is happening outside the body (or, sometimes, within the body). The sensory functions of the nervous system register the presence of a change from homeostasis or a particular event in the environment, known as a stimulus. The senses we think of most are the "big five": taste, smell, touch, sight, and hearing. The stimuli for taste and smell are both chemical substances (molecules, compounds, ions, etc.), touch is physical or mechanical stimuli that interact with the skin, sight is light stimuli, and hearing is the perception of sound, which is a physical stimulus similar to some aspects of touch. There are actually more senses than just those, but that list represents the major senses. Those five are all senses that receive stimuli from the outside world, and of which there is conscious perception. Additional sensory stimuli might be from the internal environment (inside the body), such as the stretch of an organ wall or the concentration of certain ions in the blood.

Response. The nervous system produces a response on the basis of the stimuli perceived by sensory structures. An obvious response would be the movement of muscles, such as withdrawing a hand from a hot stove, but there are broader uses of the term. The nervous system can cause the contraction of all three types of muscle tissue. For example, skeletal muscle contracts to move the skeleton, cardiac muscle is influenced as heart rate increases during exercise, and smooth muscle contracts as the digestive system moves food along the digestive tract. Responses also include the neural control of glands in the body as well, such as the production and secretion of sweat by the eccrine and merocrine sweat glands found in the skin to lower body temperature.

Responses can be divided into those that are voluntary or conscious (contraction of skeletal muscle) and those that are involuntary (contraction of smooth muscles, regulation of cardiac muscle, activation of glands). Voluntary responses are governed by the somatic nervous system and involuntary responses are governed by the autonomic nervous system, which are discussed in the next section.

Integration. Stimuli that are received by sensory structures are communicated to the nervous system where that information is processed. This is called integration. Stimuli are compared with, or integrated with, other stimuli, memories of previous stimuli, or the state of a person at a particular time. This leads to the specific response that will be generated. Seeing a baseball pitched to a batter will not automatically cause the batter to swing. The trajectory of the ball and its speed will need to be considered. Maybe the count is three balls and one strike, and the batter wants to let this pitch go by in the hope of getting a walk to first base. Or maybe the batter's team is so far ahead, it would be fun to just swing away.

Controlling the Body

The nervous system can be divided into two parts mostly on the basis of a functional difference in responses. The somatic nervous system (SNS) is responsible for conscious perception and voluntary motor responses. Voluntary motor response means the contraction of skeletal muscle, but those contractions are not always voluntary in the sense that you have to want to perform them. Some somatic motor responses are reflexes, and often happen without a conscious decision to perform them. If your friend jumps out from behind a corner and yells "Boo!" you will be startled and you might scream or leap back. You didn't decide to do that, and you may not have wanted to give your friend a reason to laugh at your expense, but it is a reflex involving skeletal muscle contractions. Other motor responses become automatic (in other words, unconscious) as a person learns motor skills (referred to as "habit learning" or "procedural memory").

The autonomic nervous system (ANS) is responsible for involuntary control of the body, usually for the sake of homeostasis (regulation of the internal environment). Sensory input for autonomic functions can be from sensory structures tuned to external or internal environmental stimuli. The motor output extends to smooth and cardiac muscle as well as glandular tissue. The role of the autonomic system is to regulate the organ systems of the body, which usually means to control homeostasis. Sweat glands, for example, are controlled by the autonomic system. When you are hot, sweating helps cool your body down. That is a homeostatic mechanism. But when you are nervous, you might start sweating also. That is not homeostatic, it is the physiological response to an emotional state.

There is another division of the nervous system that describes functional responses. The enteric nervous system (ENS) is responsible for controlling the smooth muscle and glandular tissue in your digestive system. It is a large part of the PNS, and is not dependent on the CNS. It is sometimes valid, however, to consider the enteric system to be a part of the autonomic system because the neural structures that make up the enteric system are a component of the autonomic output that regulates digestion. There are some differences between the two, but for our purposes here there will be a good bit of overlap. See Figure 12.6 for examples of where these divisions of the nervous system can be found.

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Everyday Connection

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12.1 Basic Structure and Function of the Nervous System - Anatomy and Physiology 2e | OpenStax

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Learning Objectives By the end of this section, you will be able to: Identify the anatomical and functional divisions of the nervous system Relate the functional and structural differences between gray matter and white matter structures of the nervous system to the structure of neurons List the basic functions of the nervous system The picture you have in your mind of the nervous system probably includes the brain, the nervous tissue contained within the cranium, and the spinal cord, the extension of nervous tissue within the vertebral column.

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Bond University Library APA Referencing Guide

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Bond University Library APA Referencing Guide

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Library Research Guides: APA Referencing Guide: Home

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This guide will help you discover how to reference a source in the APA style.

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The authority on APA Style and the 7th edition of the APA Publication Manual. Find tutorials, the APA Style Blog, how to format papers in APA Style, and other resources to help you improve your writing, master APA Style, and learn the conventions of scholarly publishing.

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Academic Writer Tutorial: Basics of Seventh Edition APA Style

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This page contains sample papers formatted in seventh edition APA Style. The sample papers show the format that authors should use to submit a manuscript for publication in a professional journal and that students should use to submit a paper to an instructor for a course assignment. You can download the Word files to use as templates and edit them as needed for the purposes of your own papers.

Most guidelines in the Publication Manual apply to both professional manuscripts and student papers. However, there are specific guidelines for professional papers versus student papers, including professional and student title page formats. All authors should check with the person or entity to whom they are submitting their paper (e.g., publisher or instructor) for guidelines that are different from or in addition to those specified by APA Style.

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Quantitative professional paper template: Adapted from "Fake News, Fast and Slow: Deliberation Reduces Belief in False (but Not True) News Headlines," by B. Bago, D. G. Rand, and G. Pennycook, 2020, Journal of Experimental Psychology: General, 149(8), pp. 1608-1613 ( https://doi.org/10.1037/xge0000729). Copyright 2020 by the American Psychological Association.

Qualitative professional paper template: Adapted from "'My Smartphone Is an Extension of Myself': A Holistic Qualitative Exploration of the Impact of Using a Smartphone," by L. J. Harkin and D. Kuss, 2020, Psychology of Popular Media, 10(1), pp. 28-38 ( https://doi.org/10.1037/ppm0000278). Copyright 2020 by the American Psychological Association.

Mixed methods professional paper template: Adapted from "'I Am a Change Agent': A Mixed Methods Analysis of Students' Social Justice Value Orientation in an Undergraduate Community Psychology Course," by D. X. Henderson, A. T. Majors, and M. Wright, 2019, Scholarship of Teaching and Learning in Psychology, 7(1), 68-80. ( https://doi.org/10.1037/stl0000171). Copyright 2019 by the American Psychological Association.

Literature review professional paper template: Adapted from "Rethinking Emotions in the Context of Infants' Prosocial Behavior: The Role of Interest and Positive Emotions," by S. I. Hammond and J. K. Drummond, 2019, Developmental Psychology, 55(9), pp. 1882-1888 ( https://doi.org/10.1037/dev0000685). Copyright 2019 by the American Psychological Association.

Review professional paper template: Adapted from "Joining the Conversation: Teaching Students to Think and Communicate Like Scholars," by E. L. Parks, 2022, Scholarship of Teaching and Learning in Psychology, 8(1), pp. 70-78 ( https://doi.org/10.1037/stl0000193). Copyright 2020 by the American Psychological Association.

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These sample papers formatted in seventh edition APA Style show the format that authors should use to submit a manuscript for publication in a professional journal and that students should use to submit a paper to an instructor for a course assignment.

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Paller, K. & Suzuki, S. (2023). Consciousness. In R. Biswas-Diener & E. Diener (Eds), Noba textbook series: Psychology. Champaign, IL: DEF publishers. http://noba.to/5ydq3tgk

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Contemplate the unique experience of being you at this moment! You, and only you, have direct knowledge of your own conscious experiences. At the same time, you cannot know consciousness from anyone else's inside view. How can we begin to understand this fantastic ability to have private, conscious experiences?

At the most basic level all of conscious experience is unique to each individual. [Image: Étienne Ljóni Poisson, https://goo.gl/mbo5VJ, CC BY-NC-SA 2.0, https://goo.gl/Toc0ZF]

In a sense, everything you know is from your own vantage point, with your own consciousness at the center. Yet the scientific study of consciousness confronts the challenge of producing general understanding that goes beyond what can be known from one individual's perspective.

To delve into this topic, some terminology must first be considered. The term consciousness can denote the ability of a person to generate a series of conscious experiences one after another. Here we include experiences of feeling and understanding sensory input, of a temporal sequence of autobiographical events, of imagination, of emotions and moods, of ideas, of memories-the whole range of mental contents open to an individual.

Consciousness can also refer to the state of an individual, as in a sharp or dull state of consciousness, a drug-induced state such as euphoria, or a diminished state due to drowsiness, sleep, neurological abnormality, or coma. In this module, we focus not on states of consciousness or on self-consciousness, but rather on the process that unfolds in the course of a conscious experience-a moment of awareness -the essential ingredient of consciousness.

Other Minds

You have probably experienced the sense of knowing exactly what a friend is thinking. Various signs can guide our inferences about consciousness in others. We can try to infer what's going on in someone else's mind by relying on the assumption that they feel what we imagine we would feel in the same situation. We might account for someone's actions or emotional expressions through our knowledge of that individual and our careful observations of their behavior. In this way, we often display substantial insight into what they are thinking. Other times we are completely wrong.

By measuring brain activity using various neuroscientific technologies, we can acquire additional information useful for deciphering another person's state of mind. In special circumstances such inferences can be highly accurate, but limitations on mind reading remain, highlighting the difficulty of understanding exactly how conscious experiences arise.

A Science of Consciousness

Attempts to understand consciousness have been pervasive throughout human history, mostly dominated by philosophical analyses focused on the first-person perspective. Now we have a wider set of approaches that includes philosophy, psychology, neuroscience, cognitive science, and contemplative science ( Blackmore, 2006; Koch, 2012; Zelazo, Moscovitch, & Thompson, 2007; Zeman, 2002).

Consciousness is a topic that has been addressed by religious scholars, philosophers, psychologists, and neuroscientists. [Image: CC0 Public Domain, https://goo.gl/m25gce]

The challenge for this combination of approaches is to give a comprehensive explanation of consciousness. That explanation would include describing the benefits of consciousness, particularly for behavioral capabilities that conscious experiences allow, that trump automatic behaviors. Subjective experiences also need to be described in a way that logically shows how they result from precursor events in the human brain. Moreover, a full account would describe how consciousness depends on biological, environmental, social, cultural, and developmental factors.

At the outset, a central question is how to conceive of consciousness relative to other things we know. Objects in our environment have a physical basis and are understood to be composed of constituents, such that they can be broken down into molecules, elements, atoms, particles, and so on. Yet we can also understand things relationally and conceptually. Sometimes a phenomenon can best be conceived as a process rather than a physical entity (e.g., digestion is a process whereby food is broken down). What, then, is the relationship between our conscious thoughts and the physical universe, and in particular, our brains?

Rene Descartes' position, dualism, was that mental and physical are, in essence, different substances. This view can be contrasted with reductionist views that mental phenomena can be explained via descriptions of physical phenomena. Although the dualism/reductionism debate continues, there are many ways in which mind can be shown to depend on brain.

A prominent orientation to the scientific study of consciousness is to seek understanding of these dependencies-to see how much light they can shed on consciousness. Significant advances in our knowledge about consciousness have thus been gained, as seen in the following examples.

Suppose you meet your friend at a crowded train station. You may notice a subtle smile on her face. At that moment you are probably unaware of many other things happening within your view. What makes you aware of some things but not others? You probably have your own intuitions about this, but experiments have proven wrong many common intuitions about what generates visual awareness.

For instance, you may think that if you attentively look at a bright spot, you must be aware of it. Not so. In a phenomenon known as motion-induced blindness, bright discs completely vanish from your awareness in full attention. To experience this for yourself, see this module's Outside Resource section for a demonstration of motion-induced blindness.

Are you really aware of everything that is going on around you? In the context of a crowded train station you may be visually aware of certain things while essentially being blind to many others that are right in front of you. [Image: Diego Torres Silvestre, https://goo.gl/ZkCWEC, CC BY 2.0, https://goo.gl/BRvSA7]

You may think that if you deeply analyze an image, decoding its meaning and making a decision about it, you must be aware of the image. Not necessarily. When a number is briefly flashed and rapidly replaced by a random pattern, you may have no awareness of it, despite the fact that your brain allows you to determine that the number is greater than 5, and then prepare your right hand for a key press if that is what you were instructed to do ( Dehaene et al., 1998).

Thus, neither the brightness of an image, paying full attention to it, nor deeply analyzing it guarantees that you will be aware of it. What, then, is the crucial ingredient of visual awareness?

A contemporary answer is that our awareness of a visual feature depends on a certain type of reciprocal exchange of information across multiple brain areas, particularly in the cerebral cortex. In support of this idea, directly activating your visual motion area (known as V5) with an externally applied magnetic field ( transcranial magnetic stimulation) will make you see moving dots. This is not surprising. What is surprising is that activating your visual motion area alone does not let you see motion. You will not see moving dots if the feedback signal from V5 to the primary visual cortex is disrupted by a further transcranial magnetic stimulation pulse ( Pascual-Leone & Walsh, 2001). The reverberating reciprocal exchange of information between higher-level visual areas and primary visual cortex appears to be essential for generating visual awareness.

This idea can also explain why people with certain types of brain damage lack visual awareness. Consider a patient with brain damage limited to primary visual cortex who claims not to see anything - a problem termed cortical blindness. Other areas of visual cortex may still receive visual input through projections from brain structures such as the thalamus and superior colliculus, and these networks may mediate some preserved visual abilities that take place without awareness. For example, a patient with cortical blindness might detect moving stimuli via V5 activation but still have no conscious experiences of the stimuli, because the reverberating reciprocal exchange of information cannot take place between V5 and the damaged primary visual cortex. The preserved ability to detect motion might be evident only when a guess is required ("guess whether something moved to the left or right")-otherwise the answer would be "I didn't see anything." This phenomenon of blindsight refers to blindness due to a neurological cause that preserves abilities to analyze and respond to visual stimuli that are not consciously experienced ( Lamme, 2001).

If exchanges of information across brain areas are crucial for generating visual awareness, neural synchronization must play an important role because it promotes neural communication. A neuron's excitability varies over time. Communication among neural populations is enhanced when their oscillatory cycles of excitability are synchronized. In this way, information transmitted from one population in its excitable phase is received by the target population when it is also in its excitable phase. Indeed, oscillatory neural synchronization in the beta- and gamma-band frequencies (identified according to the number of oscillations per second, 13-30 Hz and 30-100 Hz, respectively) appears to be closely associated with visual awareness. This idea is highlighted in the Global Neuronal Workspace Theory of Consciousness ( Dehaene & Changeux, 2011), in which sharing of information among prefrontal, inferior parietal, and occipital regions of the cerebral cortex is postulated to be especially important for generating awareness.

A related view, the Information Integration Theory of Consciousness, is that shared information itself constitutes consciousness ( Tononi, 2004). An organism would have minimal consciousness if the structure of shared information is simple, whereas it would have rich conscious experiences if the structure of shared information is complex. Roughly speaking, complexity is defined as the number of intricately interrelated informational units or ideas generated by a web of local and global sharing of information. The degree of consciousness in an organism (or a machine) would be high if numerous and diversely interrelated ideas arise, low if only a few ideas arise or if there are numerous ideas but they are random and unassociated. Computational analyses provide additional perspectives on such proposals. In particular, if every neuron is connected to every other neuron, all neurons would tend to activate together, generating few distinctive ideas. With a very low level of neuronal connectivity at the other extreme, all neurons would tend to activate independently, generating numerous but unassociated ideas. To promote a rich level of consciousness, then, a suitable mixture of short-, medium-, and long-range neural connections would be needed. The human cerebral cortex may indeed have such an optimum structure of neural connectivity. Given how consciousness is conceptualized in this theory as graded rather than all-or-none, a quantitative approach (e.g., Casali et al., 2013; Monti et al., 2013) could conceivably be used to estimate the level of consciousness in nonhuman species and artificial beings.

The pinnacle of conscious human memory functions is known as episodic recollection because it allows one to reexperience the past, to virtually relive an earlier event. People who suffer from amnesia due to neurological damage to certain critical brain areas have poor memory for events and facts. Their memory deficit disrupts the type of memory termed declarative memory and makes it difficult to consciously remember. However, amnesic insults typically spare a set of memory functions that do not involve conscious remembering. These other types of memory, which include various habits, motor skills, cognitive skills, and procedures, can be demonstrated when an individual executes various actions as a function of prior learning, but in these cases a conscious experience of remembering is not necessarily included.

Memory is one basis for conscious awareness. [Image: CC0 Public Domain, https://goo.gl/m25gce]

Research on amnesia has thus supported the proposal that conscious remembering requires a specific set of brain operations that depend on networks of neurons in the cerebral cortex. Some of the other types of memory involve only subcortical brain regions, but there are also notable exceptions. In particular, perceptual priming is a type of memory that does not entail the conscious experience of remembering and that is typically preserved in amnesia. Perceptual priming is thought to reflect a fluency of processing produced by a prior experience, even when the individual cannot remember that prior experience. For example, a word or face might be perceived more efficiently if it had been viewed minutes earlier than if it hadn't. Whereas a person with amnesia can demonstrate this item-specific fluency due to changes in corresponding cortical areas, they nevertheless would be impaired if asked to recognize the words or faces they previously experienced. A reasonable conclusion on the basis of this evidence is that remembering an episode is a conscious experience not merely due to the involvement of one portion of the cerebral cortex, but rather due to the specific configuration of cortical activity involved in the sharing or integration of information.

Further neuroscientific studies of memory retrieval have shed additional light on the necessary steps for conscious recollection. For example, storing memories for the events we experience each day appears to depend on connections among multiple cortical regions as well as on a brain structure known as the hippocampus. Memory storage becomes more secure due to interactions between the hippocampus and cerebral cortex that can transpire over extended time periods following the initial registration of information. Conscious retrieval thus depends on the activity of elaborate sets of networks in the cortex. Memory retrieval that does not include conscious recollection depends either on restricted portions of the cortex or on brain regions separate from the cortex.

The ways in which memory expressions that include the awareness of remembering differ from those that do not thus highlight the special nature of conscious memory experiences ( Paller, Voss, & Westerberg, 2009; Voss, Lucas, & Paller, 2012). Indeed, memory storage in the brain can be very complex for many different types of memory, but there are specific physiological prerequisites for the type of memory that coincides with conscious recollection.

The brain can generate body awareness by registering coincident sensations. For example, when you rub your arm, you see your hand rubbing your arm and simultaneously feel the rubbing sensation in both your hand and your arm. This simultaneity tells you that it is your hand and your arm. Infants use the same type of coincident sensations to initially develop the self/nonself distinction that is fundamental to our construal of the world.

The fact that your brain constructs body awareness in this way can be experienced via the rubber-hand illusion (see Outside Resource on this). If you see a rubber hand being rubbed and simultaneously feel the corresponding rubbing sensation on your own body out of view, you will momentarily feel a bizarre sensation-that the rubber hand is your own.

The construction of our body awareness appears to be mediated by specific brain mechanisms involving a region of the cortex known as the temporoparietal junction. Damage to this brain region can generate distorted body awareness, such as feeling a substantially elongated torso. Altered neural activity in this region through artificial stimulation can also produce an out-of-body experience (see this module's Outside Resources section), in which you feel like your body is in another location and you have a novel perspective on your body and the world, such as from the ceiling of the room.

Remarkably, comparable brain mechanisms may also generate the normal awareness of the sense of self and the sensation of being inside a body. In the context of virtual reality this sensation is known as presence (the compelling experience of actually being there). Our normal localization of the self may be equally artificial, in that it is not a given aspect of life but is constructed through a special brain mechanism.

A Social Neuroscience Theory of Consciousness ( Graziano & Kastner, 2011) ascribes an important role to our ability to localize our own sense of self. The main premise of the theory is that you fare better in a social environment to the extent that you can predict what people are going to do. So, the human brain has developed mechanisms to construct models of other people's attention and intention, and to localize those models in the corresponding people's heads to keep track of them. The proposal is that the same brain mechanism was adapted to construct a model of one's own attention and intention, which is then localized in one's own head and perceived as consciousness. If so, then the primary function of consciousness is to allow us to predict our own behavior. Research is needed to test the major predictions of this new theory, such as whether changes in consciousness (e.g., due to normal fluctuations, psychiatric disease, brain damage) are closely associated with changes in the brain mechanisms that allow us to model other people's attention and intention.

Choosing among multiple possible actions, the sense of volition, is closely associated with our subjective feeling of consciousness. When we make a lot of decisions, we may feel especially conscious and then feel exhausted, as if our mental energy has been drained.

When making a decision you might carefully consider your choices or simply "go with your gut". [Image: Daniel Lee, https://goo.gl/aJi3jx, CC BY-NC-SA 2.0, https://goo.gl/Toc0ZF]

We make decisions in two distinct ways. Sometimes we carefully analyze and weigh different factors to reach a decision, taking full advantage of the brain's conscious mode of information processing. Other times we make a gut decision, trusting the unconscious mode of information processing (although it still depends on the brain). The unconscious mode is adept at simultaneously considering numerous factors in parallel, which can yield an overall impression of the sum total of evidence. In this case, we have no awareness of the individual considerations. In the conscious mode, in contrast, we can carefully scrutinize each factor-although the act of focusing on a specific factor can interfere with weighing in other factors.

One might try to optimize decision making by taking into account these two strategies. A careful conscious decision should be effective when there are only a few known factors to consider. A gut decision should be effective when a large number of factors should be considered simultaneously. Gut decisions can indeed be accurate on occasion (e.g., guessing which of many teams will win a close competition), but only if you are well versed in the relevant domain ( Dane, Rockmann, & Pratt, 2012).

As we learn from our experiences, some of this gradual knowledge accrual is unconscious; we don't know we have it and we can use it without knowing it. On the other hand, consciously acquired information can be uniquely beneficial by allowing additional stages of control (d e Lange, van Gaal, Lamme, & Dehaene, 2011). It is often helpful to control which new knowledge we acquire and which stored information we retrieve in accordance with our conscious goals and beliefs.

Whether you choose to trust your gut or to carefully analyze the relevant factors, you feel that you freely reach your own decision. Is this feeling of free choice real? Contemporary experimental techniques fall short of answering this existential question. However, it is likely that at least the sense of immediacy of our decisions is an illusion.

In one experiment, people were asked to freely consider whether to press the right button or the left button, and to press it when they made the decision ( Soon, Brass, Heinze, & Haynes, 2008). Although they indicated that they made the decision immediately before pressing the button, their brain activity, measured using functional magnetic resonance imaging, predicted their decision as much as 10 seconds before they said they freely made the decision. In the same way, each conscious experience is likely preceded by precursor brain events that on their own do not entail consciousness but that culminate in a conscious experience.

In many situations, people generate a reason for an action that has nothing to do with the actual basis of the decision to act in a particular way. We all have a propensity to retrospectively produce a reasonable explanation for our behavior, yet our behavior is often the result of unconscious mental processing, not conscious volition.

Why do we feel that each of our actions is immediately preceded by our own decision to act? This illusion may help us distinguish our own actions from those of other agents. For example, while walking hand-in-hand with a friend, if you felt you made a decision to turn left immediately before you both turned left, then you know that you initiated the turn; otherwise, you would know that your friend did.

Even if some aspects of the decision-making process are illusory, to what extent are our decisions determined by prior conditions? It certainly seems that we can have full control of some decisions, such as when we create a conscious intention that leads to a specific action: You can decide to go left or go right. To evaluate such impressions, further research must develop a better understanding of the neurocognitive basis of volition, which is a tricky undertaking, given that decisions are conceivably influenced by unconscious processing, neural noise, and the unpredictability of a vast interactive network of neurons in the brain.

Yet belief in free choice has been shown to promote moral behavior, and it is the basis of human notions of justice. The sense of free choice may be a beneficial trait that became prevalent because it helped us flourish as social beings.

Our human consciousness unavoidably colors all of our observations and our attempts to gain understanding. Nonetheless, scientific inquiries have provided useful perspectives on consciousness. The advances described above should engender optimism about the various research strategies applied to date and about the prospects for further insight into consciousness in the future.

Because conscious experiences are inherently private, they have sometimes been taken to be outside the realm of scientific inquiry. This view idealizes science as an endeavor involving only observations that can be verified by multiple observers, relying entirely on the third-person perspective, or the view from nowhere (from no particular perspective). Yet conducting science is a human activity that depends, like other human activities, on individuals and their subjective experiences. A rational scientific account of the world cannot avoid the fact that people have subjective experiences.

Subjectivity thus has a place in science. Conscious experiences can be subjected to systematic analysis and empirical tests to yield progressive understanding. Many further questions remain to be addressed by scientists of the future. Is the first-person perspective of a conscious experience basically the same for all human beings, or do individuals differ fundamentally in their introspective experiences and capabilities? Should psychological science focus only on ordinary experiences of consciousness, or are extraordinary experiences also relevant? Can training in introspection lead to a specific sort of expertise with respect to conscious experience? An individual with training, such as through extensive meditation practice, might be able to describe their experiences in a more precise manner, which could then support improved characterizations of consciousness. Such a person might be able to understand subtleties of experience that other individuals fail to notice, and thereby move our understanding of consciousness significantly forward. These and other possibilities await future scientific inquiries into consciousness.

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Consciousness is the ultimate mystery. What is it and why do we have it? These questions are difficult to answer, even though consciousness is so fundamental to our existence. Perhaps the natural world could exist largely as it is without human consciousness; but taking away consciousness would essentially take away our humanity.

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Siegler, R. (2023). Cognitive development in childhood. In R. Biswas-Diener & E. Diener (Eds), Noba textbook series: Psychology. Champaign, IL: DEF publishers. http://noba.to/8uv4fn9h

This work is licensed under CC BY NC SA Creative Commons Attribution-Non-Commercial-ShareAlike 4.0 international license. You are free to share and adapt the work with an attribution.

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Robert Siegler
Carnegie Mellon University

This module examines what cognitive development is, major theories about how it occurs, the roles of nature and nurture, whether it is continuous or discontinuous, and how research in the area is being used to improve education.

Learning Objectives

Be able to identify and describe the main areas of cognitive development.

Be able to describe major theories of cognitive development and what distinguishes them.

Understand how nature and nurture work together to produce cognitive development.

Understand why cognitive development is sometimes viewed as discontinuous and sometimes as continuous.

Know some ways in which research on cognitive development is being used to improve education.

By the time you reach adulthood you have learned a few things about how the world works. You know, for instance, that you can't walk through walls or leap into the tops of trees. You know that although you cannot see your car keys they've got to be around here someplace. What's more, you know that if you want to communicate complex ideas like ordering a triple-shot soy vanilla latte with chocolate sprinkles it's better to use words with meanings attached to them rather than simply gesturing and grunting. People accumulate all this useful knowledge through the process of cognitive development, which involves a multitude of factors, both inherent and learned.

Cognitive development in childhood is about change. From birth to adolescence a young person's mind changes dramatically in many important ways. [Image: One Laptop per Child, https://goo.gl/L1eAsO, CC BY 2.0, https://goo.gl/9uSnqN]

Cognitive development refers to the development of thinking across the lifespan. Defining thinking can be problematic, because no clear boundaries separate thinking from other mental activities. Thinking obviously involves the higher mental processes: problem solving, reasoning, creating, conceptualizing, categorizing, remembering, planning, and so on. However, thinking also involves other mental processes that seem more basic and at which even toddlers are skilled-such as perceiving objects and events in the environment, acting skillfully on objects to obtain goals, and understanding and producing language. Yet other areas of human development that involve thinking are not usually associated with cognitive development, because thinking isn't a prominent feature of them-such as personality and temperament.

As the name suggests, cognitive development is about change. Children's thinking changes in dramatic and surprising ways. Consider DeVries's ( 1969) study of whether young children understand the difference between appearance and reality. To find out, she brought an unusually even-tempered cat named Maynard to a psychology laboratory and allowed the 3- to 6-year-old participants in the study to pet and play with him. DeVries then put a mask of a fierce dog on Maynard's head, and asked the children what Maynard was. Despite all of the children having identified Maynard previously as a cat, now most 3-year-olds said that he was a dog and claimed that he had a dog's bones and a dog's stomach. In contrast, the 6-year-olds weren't fooled; they had no doubt that Maynard remained a cat. Understanding how children's thinking changes so dramatically in just a few years is one of the fascinating challenges in studying cognitive development.

There are several main types of theories of child development. Stage theories, such as Piaget's stage theory, focus on whether children progress through qualitatively different stages of development. Sociocultural theories, such as that of Lev Vygotsky, emphasize how other people and the attitudes, values, and beliefs of the surrounding culture, influence children's development. Information processing theories, such as that of David Klahr, examine the mental processes that produce thinking at any one time and the transition processes that lead to growth in that thinking.

At the heart of all of these theories, and indeed of all research on cognitive development, are two main questions: (1) How do nature and nurture interact to produce cognitive development? (2) Does cognitive development progress through qualitatively distinct stages? In the remainder of this module, we examine the answers that are emerging regarding these questions, as well as ways in which cognitive developmental research is being used to improve education.

The most basic question about child development is how nature and nurture together shape development. Nature refers to our biological endowment, the genes we receive from our parents. Nurture refers to the environments, social as well as physical, that influence our development, everything from the womb in which we develop before birth to the homes in which we grow up, the schools we attend, and the many people with whom we interact.

The nature-nurture issue is often presented as an either-or question: Is our intelligence (for example) due to our genes or to the environments in which we live? In fact, however, every aspect of development is produced by the interaction of genes and environment. At the most basic level, without genes, there would be no child, and without an environment to provide nurture, there also would be no child.

The way in which nature and nurture work together can be seen in findings on visual development. Many people view vision as something that people either are born with or that is purely a matter of biological maturation, but it also depends on the right kind of experience at the right time. For example, development of depth perception, the ability to actively perceive the distance from oneself to objects in the environment, depends on seeing patterned light and having normal brain activity in response to the patterned light, in infancy ( Held, 1993). If no patterned light is received, for example when a baby has severe cataracts or blindness that is not surgically corrected until later in development, depth perception remains abnormal even after the surgery.

A child that is perceived to be attractive and calm may receive a different sort of care and attention from adults and as a result enjoy a developmental advantage. [Image: Cairn 111, https://goo.gl/6RpBVt, CC BY-NC-SA 2.0, https://goo.gl/HEXbAA]

Adding to the complexity of the nature-nurture interaction, children's genes lead to their eliciting different treatment from other people, which influences their cognitive development. For example, infants' physical attractiveness and temperament are influenced considerably by their genetic inheritance, but it is also the case that parents provide more sensitive and affectionate care to easygoing and attractive infants than to difficult and less attractive ones, which can contribute to the infants' later cognitive development ( Langlois et al., 1995; van den Boom & Hoeksma, 1994).

Also contributing to the complex interplay of nature and nurture is the role of children in shaping their own cognitive development. From the first days out of the womb, children actively choose to attend more to some things and less to others. For example, even 1-month-olds choose to look at their mother's face more than at the faces of other women of the same age and general level of attractiveness ( Bartrip, Morton, & de Schonen, 2001). Children's contributions to their own cognitive development grow larger as they grow older ( Scarr & McCartney, 1983). When children are young, their parents largely determine their experiences: whether they will attend day care, the children with whom they will have play dates, the books to which they have access, and so on. In contrast, older children and adolescents choose their environments to a larger degree. Their parents' preferences largely determine how 5-year-olds spend time, but 15-year-olds' own preferences largely determine when, if ever, they set foot in a library. Children's choices often have large consequences. To cite one example, the more that children choose to read, the more that their reading improves in future years ( Baker, Dreher, & Guthrie, 2000). Thus, the issue is not whether cognitive development is a product of nature or nurture; rather, the issue is how nature and nurture work together to produce cognitive development.

Some aspects of the development of living organisms, such as the growth of the width of a pine tree, involve quantitative changes, with the tree getting a little wider each year. Other changes, such as the life cycle of a ladybug, involve qualitative changes, with the creature becoming a totally different type of entity after a transition than before (Figure 1). The existence of both gradual, quantitative changes and relatively sudden, qualitative changes in the world has led researchers who study cognitive development to ask whether changes in children's thinking are gradual and continuous or sudden and discontinuous.

Figure 1: Continuous and discontinuous development. Some researchers see development as a continuous gradual process, much like a maple tree growing steadily in height and cross-sectional area. Other researchers see development as a progression of discontinuous stages, involving rapid discontinuous changes, such as those in the life cycle of a ladybug, separated by longer periods of slow, gradual change.

The great Swiss psychologist Jean Piaget proposed that children's thinking progresses through a series of four discrete stages. By "stages," he meant periods during which children reasoned similarly about many superficially different problems, with the stages occurring in a fixed order and the thinking within different stages differing in fundamental ways. The four stages that Piaget hypothesized were the sensorimotor stage (birth to 2 years), the preoperational reasoning stage (2 to 6 or 7 years), the concrete operational reasoning stage (6 or 7 to 11 or 12 years), and the formal operational reasoning stage (11 or 12 years and throughout the rest of life).

During the sensorimotor stage, children's thinking is largely realized through their perceptions of the world and their physical interactions with it. Their mental representations are very limited. Consider Piaget's object permanence task, which is one of his most famous problems. If an infant younger than 9 months of age is playing with a favorite toy, and another person removes the toy from view, for example by putting it under an opaque cover and not letting the infant immediately reach for it, the infant is very likely to make no effort to retrieve it and to show no emotional distress ( Piaget, 1954). This is not due to their being uninterested in the toy or unable to reach for it; if the same toy is put under a clear cover, infants below 9 months readily retrieve it (Munakata, McClelland, Johnson, & Siegler, 1997). Instead, Piaget claimed that infants less than 9 months do not understand that objects continue to exist even when out of sight.

During the preoperational stage, according to Piaget, children can solve not only this simple problem (which they actually can solve after 9 months) but show a wide variety of other symbolic-representation capabilities, such as those involved in drawing and using language. However, such 2- to 7-year-olds tend to focus on a single dimension, even when solving problems would require them to consider multiple dimensions. This is evident in Piaget's ( 1952) conservation problems. For example, if a glass of water is poured into a taller, thinner glass, children below age 7 generally say that there now is more water than before. Similarly, if a clay ball is reshaped into a long, thin sausage, they claim that there is now more clay, and if a row of coins is spread out, they claim that there are now more coins. In all cases, the children are focusing on one dimension, while ignoring the changes in other dimensions (for example, the greater width of the glass and the clay ball).

Piaget's Sensorimotor and Pre-operational Reasoning stages

Children overcome this tendency to focus on a single dimension during the concrete operations stage, and think logically in most situations. However, according to Piaget, they still cannot think in systematic scientific ways, even when such thinking would be useful. Thus, if asked to find out which variables influence the period that a pendulum takes to complete its arc, and given weights that they can attach to strings in order to do experiments with the pendulum to find out, most children younger than age 12, perform biased experiments from which no conclusion can be drawn, and then conclude that whatever they originally believed is correct. For example, if a boy believed that weight was the only variable that mattered, he might put the heaviest weight on the shortest string and push it the hardest, and then conclude that just as he thought, weight is the only variable that matters ( Inhelder & Piaget, 1958).

Finally, in the formal operations period, children attain the reasoning power of mature adults, which allows them to solve the pendulum problem and a wide range of other problems. However, this formal operations stage tends not to occur without exposure to formal education in scientific reasoning, and appears to be largely or completely absent from some societies that do not provide this type of education.

Although Piaget's theory has been very influential, it has not gone unchallenged. Many more recent researchers have obtained findings indicating that cognitive development is considerably more continuous than Piaget claimed. For example, Diamond ( 1985) found that on the object permanence task described above, infants show earlier knowledge if the waiting period is shorter. At age 6 months, they retrieve the hidden object if the wait is no longer than 2 seconds; at 7 months, they retrieve it if the wait is no longer than 4 seconds; and so on. Even earlier, at 3 or 4 months, infants show surprise in the form of longer looking times if objects suddenly appear to vanish with no obvious cause ( Baillargeon, 1987). Similarly, children's specific experiences can greatly influence when developmental changes occur. Children of pottery makers in Mexican villages, for example, know that reshaping clay does not change the amount of clay at much younger ages than children who do not have similar experiences (P rice-Williams, Gordon, & Ramirez, 1969).

Piaget's Concrete and Formal Operations stages

So, is cognitive development fundamentally continuous or fundamentally discontinuous? A reasonable answer seems to be, "It depends on how you look at it and how often you look." For example, under relatively facilitative circumstances, infants show early forms of object permanence by 3 or 4 months, and they gradually extend the range of times for which they can remember hidden objects as they grow older. However, on Piaget's original object permanence task, infants do quite quickly change toward the end of their first year from not reaching for hidden toys to reaching for them, even after they've experienced a substantial delay before being allowed to reach. Thus, the debate between those who emphasize discontinuous, stage-like changes in cognitive development and those who emphasize gradual continuous changes remains a lively one.

Understanding how children think and learn has proven useful for improving education. One example comes from the area of reading. Cognitive developmental research has shown that phonemic awareness-that is, awareness of the component sounds within words-is a crucial skill in learning to read. To measure awareness of the component sounds within words, researchers ask children to decide whether two words rhyme, to decide whether the words start with the same sound, to identify the component sounds within words, and to indicate what would be left if a given sound were removed from a word. Kindergartners' performance on these tasks is the strongest predictor of reading achievement in third and fourth grade, even stronger than IQ or social class background ( Nation, 2008). Moreover, teaching these skills to randomly chosen 4- and 5-year-olds results in their being better readers years later ( National Reading Panel, 2000).

Activities like playing games that involve working with numbers and spatial relationships can give young children a developmental advantage over peers who have less exposure to the same concepts. [Image: Ben Husmann, https://goo.gl/awOXSw, CC BY 2.0, https://goo.gl/9uSnqN]

Another educational application of cognitive developmental research involves the area of mathematics. Even before they enter kindergarten, the mathematical knowledge of children from low-income backgrounds lags far behind that of children from more affluent backgrounds. Ramani and Siegler ( 2008) hypothesized that this difference is due to the children in middle- and upper-income families engaging more frequently in numerical activities, for example playing numerical board games such as Chutes and Ladders. Chutes and Ladders is a game with a number in each square; children start at the number one and spin a spinner or throw a dice to determine how far to move their token. Playing this game seemed likely to teach children about numbers, because in it, larger numbers are associated with greater values on a variety of dimensions. In particular, the higher the number that a child's token reaches, the greater the distance the token will have traveled from the starting point, the greater the number of physical movements the child will have made in moving the token from one square to another, the greater the number of number-words the child will have said and heard, and the more time will have passed since the beginning of the game. These spatial, kinesthetic, verbal, and time-based cues provide a broad-based, multisensory foundation for knowledge of numerical magnitudes (the sizes of numbers), a type of knowledge that is closely related to mathematics achievement test scores ( Booth & Siegler, 2006).

Playing this numerical board game for roughly 1 hour, distributed over a 2-week period, improved low-income children's knowledge of numerical magnitudes, ability to read printed numbers, and skill at learning novel arithmetic problems. The gains lasted for months after the game-playing experience ( Ramani & Siegler, 2008; S iegler & Ramani, 2009). An advantage of this type of educational intervention is that it has minimal if any cost-a parent could just draw a game on a piece of paper.

Understanding of cognitive development is advancing on many different fronts. One exciting area is linking changes in brain activity to changes in children's thinking ( Nelson et al., 2006). Although many people believe that brain maturation is something that occurs before birth, the brain actually continues to change in large ways for many years thereafter. For example, a part of the brain called the prefrontal cortex, which is located at the front of the brain and is particularly involved with planning and flexible problem solving, continues to develop throughout adolescence ( Blakemore & Choudhury, 2006). Such new research domains, as well as enduring issues such as nature and nurture, continuity and discontinuity, and how to apply cognitive development research to education, insure that cognitive development will continue to be an exciting area of research in the coming years.

Research into cognitive development has shown us that minds don't just form according to a uniform blueprint or innate intellect, but through a combination of influencing factors. For instance, if we want our kids to have a strong grasp of language we could concentrate on phonemic awareness early on. If we want them to be good at math and science we could engage them in numerical games and activities early on. Perhaps most importantly, we no longer think of brains as empty vessels waiting to be filled up with knowledge but as adaptable organs that develop all the way through early adulthood.

Outside Resources

Book: Frye, D., Baroody, A., Burchinal, M., Carver, S. M., Jordan, N. C., & McDowell, J. (2013). Teaching math to young children: A practice guide. Washington, DC: National Center for Education Evaluation and Regional Assistance (NCEE), Institute of Education Sciences, U.S. Department of Education.

Book: Goswami, U. G. (2010). The Blackwell Handbook of Childhood Cognitive Development. New York: John Wiley and Sons.

Book: Kuhn, D., & Siegler, R. S. (Vol. Eds.). (2006). Volume 2: Cognition, perception, and language. In W. Damon & R. M. Lerner (Series Eds.), Handbook of child psychology (6th ed.). Hoboken, NJ: Wiley.

Book: Miller, P. H. (2011). Theories of developmental psychology (5th ed.). New York: Worth.

Book: Siegler, R. S., & Alibali, M. W. (2004). Children's thinking (4th ed.). Upper Saddle River, NJ: Prentice-Hall.

Discussion Questions

1. Why are there different theories of cognitive development? Why don't researchers agree on which theory is the right one?

2. Do children's natures differ, or do differences among children only reflect differences in their experiences?

3. Do you see development as more continuous or more discontinuous?

4. Can you think of ways other than those described in the module in which research on cognitive development could be used to improve education?

Vocabulary

Chutes and Ladders

A numerical board game that seems to be useful for building numerical knowledge.

Concrete operations stage

Piagetian stage between ages 7 and 12 when children can think logically about concrete situations but not engage in systematic scientific reasoning.

Conservation problems

Problems pioneered by Piaget in which physical transformation of an object or set of objects changes a perceptually salient dimension but not the quantity that is being asked about.

Continuous development

Ways in which development occurs in a gradual incremental manner, rather than through sudden jumps.

Depth perception

The ability to actively perceive the distance from oneself of objects in the environment.

Discontinuous development

Discontinuous development

Formal operations stage

Piagetian stage starting at age 12 years and continuing for the rest of life, in which adolescents may gain the reasoning powers of educated adults.

Information processing theories

Theories that focus on describing the cognitive processes that underlie thinking at any one age and cognitive growth over time.

Nature

The genes that children bring with them to life and that influence all aspects of their development.

Numerical magnitudes

The sizes of numbers.

Nurture

The environments, starting with the womb, that influence all aspects of children's development.

Object permanence task

The Piagetian task in which infants below about 9 months of age fail to search for an object that is removed from their sight and, if not allowed to search immediately for the object, act as if they do not know that it continues to exist.

Phonemic awareness

Awareness of the component sounds within words.

Piaget's theory

Theory that development occurs through a sequence of discontinuous stages: the sensorimotor, preoperational, concrete operational, and formal operational stages.

Preoperational reasoning stage

Period within Piagetian theory from age 2 to 7 years, in which children can represent objects through drawing and language but cannot solve logical reasoning problems, such as the conservation problems.

Qualitative changes

Large, fundamental change, as when a caterpillar changes into a butterfly; stage theories such as Piaget's posit that each stage reflects qualitative change relative to previous stages.

Quantitative changes

Gradual, incremental change, as in the growth of a pine tree's girth.

Sensorimotor stage

Period within Piagetian theory from birth to age 2 years, during which children come to represent the enduring reality of objects.

Sociocultural theories

Theory founded in large part by Lev Vygotsky that emphasizes how other people and the attitudes, values, and beliefs of the surrounding culture influence children's development.

References

Baillargeon, R. (1987). Object permanence in 3 1/2- and 4 1/2-month-old infants. Developmental Psychology, 23, 655-664.

Baker, L., Dreher, M. J., & Guthrie, J. T., (Eds.). (2000). Engaging young readers: Promoting achievement and motivation. New York: Guilford.

Bartrip, J., Morton, J., & De Schonen, S. (2001). Responses to mother's face in 3-week to 5-month old infants. British Journal of Developmental Psychology, 19, 219-232

Blakemore, S.-J., & Choudhury, S. (2006). Development of the adolescent brain: Implications for executive function and social cognition. Journal of Child Psychiatry and Psychology, 47, 296-312.

Booth, J. L., & Siegler, R. S. (2006). Developmental and individual differences in pure numerical estimation. Developmental Psychology, 41, 189-201.

DeVries, R. (1969). Constancy of genetic identity in the years three to six. Monographs of the Society for Research in Child Development, 34, 127.

Diamond, A. (1985). Development of the ability to use recall to guide action, as indicated by infants' performance on AB. Child Development, 56, 868-883.

Held, R. (1993). What can rates of development tell us about underlying mechanisms? In C. E. Granrud (Ed.), Visual perception and cognition in infancy (pp. 75-90). Hillsdale, NJ: Erlbaum.

Inhelder, B., & Piaget, J. (1958). The growth of logical thinking from childhood to adolescence. New York: Basic Books.

Langlois, J. H., Ritter, J. M., Casey, R. J., & Sawin, D. B. (1995). Infant attractiveness predicts maternal behaviors and attitudes. Developmental Psychology, 31, 464-472.

Munakata, Y., McClelland, J. L., Johnson, M. H., & Siegler, R. S. (1997). Rethinking infant knowledge: Toward an adaptive process account of successes and failures in object permanence tasks. Psychological Review, 104, 686 713.

Nation, K. (2008). Learning to read words. The Quarterly Journal of Experimental Psychology, 61, 1121 1133.

National Reading Panel (2000). Teaching children to read: An evidence-based assessment of the scientific research literature on reading and its implications for reading instruction. Washington, DC: National Institute of Child Health and Human Development.

Nelson, C. A., Thomas, K. M., & de Haan, M. (2006). Neural bases of cognitive development. In W. Damon & R. M. Lerner (Series Eds.) & D. Kuhn & R. S. Siegler (Vol. Eds.), Handbook of child psychology: Volume 2: Cognition, perception, and language (6th ed., pp. 3-57). Hoboken, NJ: Wiley.

Piaget, J. (1954). The construction of reality in the child. New York: BasicBooks.

Piaget, J. (1952). The child's concept of number. New York: W. W. Norton.

Price-Williams, D. R., Gordon, W., & Ramirez, M. (1969). Skill and conservation: A study of pottery making children. Developmental Psychology, 1, 769.

Ramani, G. B., & Siegler, R. S. (2008). Promoting broad and stable improvements in low-income children's numerical knowledge through playing number board games. Child Development, 79, 375-394.

Scarr, S., & McCartney, K. (1983). How people make their own environments: A theory of genotype-environment effects. Child Development, 54, 424-435.

Siegler, R. S., & Ramani, G. B. (2009). Playing linear number board games-but not circular ones-improves low-income preschoolers' numerical understanding. Journal of Educational Psychology, 101, 545-560.

van den Boom, D. C., & Hoeksma, J. B. (1994). The effect of infant irritability on mother-infant interaction: A growth curve analysis. Developmental Psychology, 30, 581-590.

Authors

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Dr Catherine N. Hall

What does the brain do?

All our thoughts and actions are biological structures and processes that work together to enable us to successfully exist and interact with the world, performing behaviours that keep us fed, watered and safe. In this chapter we will learn about the different parts of the nervous system that orchestrate these behaviours.

First, however, it is worth considering, on a very general level, what our brains and the nervous system do. They take in information from the outside world, and our bodies, and work out what is the best thing to do next. They then cause changes in our bodies to enable that thing to happen, whether that's running away from a lion, catching a ball, or going to sleep.

In this chapter, we are going to explore the structures, circuits and cells of the nervous system, in order to understand broadly how information flows into, through, and from the brain. You will learn a bit about how these structures and cells generate behaviours and internal responses that allow us to successfully adapt to and interact with what's going on around and inside us. You'll learn much more about this in following chapters of the book.

The nervous system as a computer

The nervous system is the network of neurons and supporting cells, termed glia, that do this job of detecting something, transmitting that information, integrating it with other information, and sending an instruction to other parts of our body to do something about it. In other words, our nervous system is like a computer. It takes an input, performs a computation on that input (using the programs running on that computer - these determine what computation is performed), and generates an output. In fact, every part of the nervous system does this same 'input - computation - output' job, but using different inputs, running different programs and generating different outputs. The whole nervous system might detect visual information that a lion is coming, compute that it would be a good idea to run away, and generate patterns of muscle contractions in your legs to make you run. On a microscopic scale, a single nerve cell, or neuron, might receive inputs carrying information about light falling on your retina in different locations, and integrate that information to conclude and output the information that the light falling on the retina was forming a vertical line. The program run by a given cell or structure in the nervous system is determined by how that cell or structure is connected to other cells or structures, and the biological rules that govern those connections and how they change over time. We'll learn much more about that throughout the next few chapters of this book.

First of all though, we need to learn our way around the nervous system. This chapter gives you an introduction to the anatomy of the nervous system. It should help you understand the organisation of the nervous system as well as introduce the function of some of its major components. You'll learn much more about how these structures perform their functions in later chapters.

Parts of the nervous system

The nervous system is made up of the central nervous system and the peripheral nervous system (Figure 2.1).

The central nervous system (CNS) comprises the brain and the spinal cord, while the peripheral nervous system (PNS) is the network of neurons and nerves that lie outside these two structures and connect the CNS with the rest of the body. It includes most of the cranial nerves, that connect to the brain as well as the spinal nerves that take information to and from the spinal cord. The PNS provides the input to the CNS, which computes what to do with that information, and sends outputs back to the body, via the PNS. Symmetry around the midline is a general feature of nervous system organisation.

The peripheral nervous system

The PNS can be subdivided into two parts: the somatic and autonom ic nervous systems. The autonomic nervous system can then be subdivided into three further divisions: the sympathetic, parasympathetic and enteric nervous systems.

The somatic nervous system

The somatic nervous system deals with interactions with the external environment: sensing the outside world via sensory neurons, and sending signals via motor neurons to control skeletal muscles to generate movements and behaviours that interact with that world. Many of these behaviours are voluntary, and are initiated by complex decision making processes in the brain. You hear a voice calling, you interpret the language, and turn towards the sound of your name. The somatic nervous system can also generate involuntary movements, however, via reflexes, in which a sensory input activates a motor response without voluntary control. The simplest of these reflexes involve only a single sensory neuron activating a single motor neuron. An example is the muscle stretch reflex, in which sensory neurons detect stretch in a muscle, causing motor neurons to activate the same muscle to contract it more and counter the stretch. So if you lean to one side, stretching core postural muscles, this reflex constricts those muscles, keeping you stable. Or if someone adds a heavy weight to something you're carrying, stretching your arm muscles, they then constrict so you don't drop the load. Even these simplest reflexes involve information transfer from PNS to CNS, as the connection or synapse between these two neurons occurs in the spinal cord - part of the CNS.

Indeed, there are no neurons that exist wholly in the peripheral somatic nervous system: somatic sensory neurons synapse for the first time in the CNS, while somatic motor neurons' cell bodies are found in the CNS, with their axons leaving the CNS to innervate muscles.

These afferents (carrying sensory information inwards to the CNS) and efferents (carrying motor information outwards from the CNS) form cranial nerves and spinal nerves. (Nerves are just bundles of axons - the long projections that each neuron has to carry electrical impulses). Cranial nerves innervate the head and carry information including about smell, taste, hearing, and control of facial muscles to and from their targets directly into the brainstem. Spinal nerves carry information to and from the skin and skeletal muscles to the spinal cord. There are 31 pairs of spinal nerves, which carry sensory and motor information from specific parts of the body into the spinal cord. The region of skin innervated by afferents from a given spinal nerve is called a dermatome, while the muscles contacted by efferents from a single nerve are called a myotome.

The sensory and motor parts of the nerve split apart at the spinal cord. Sensory afferents enter the dorsal root of the spinal cord, their cell bodies forming the dorsal root ganglion just outside the spinal cord. Motor neurons exit the spinal cord from the ventral root (Figure 2.3) before synapsing at neuromuscular junctions on skeletal muscle where they release acetylcholine to initiate muscle contraction (see the section Interacting with the world).

The autonomic nervous system

In contrast with the more voluntary control mediated by the somatic nervous system, the autonomic nervous system mediates interactions with the body's internal environment, for example regulating heart rate. These interactions are broadly involuntary reflexes, though modulated by the brain, and some of this regulation can be consciously done, for example people can train themselves to exert control over their heart rate. As in the somatic nervous system, sensory neurons provide information about the internal organs to the CNS, and motor neurons produce effects on the internal organs, often by modulating the tone of smooth muscle, for example to change blood vessel diameters. Outside the autonomic nervous system, non-neuronal pathways can also send information about the internal body state to the brain. For example, neurons in a brain region called the hypothalamus can detect increases in blood temperature, activating brain circuits that can then cause autonomic nervous system activation and increase blood vessel dilation in the skin as well as sweat gland activation.

The sympathetic, parasympathetic and enteric nervous systems

Now let's consider the different divisions of the autonomic nervous system:

The enteric nervous system is a large mesh of neurons which is embedded in the wall of the gastrointestinal system, from the oesophagus to the anus, and regulates motility and secretion of hormones. In humans, it contains around 500 million neurons, 0.5% of the number found in the brain and 5 times more than are found in the spinal cord. It can function without input from the brain, though can also be regulated by descending input.

The sympathetic and parasympathetic divisions of the autonomic nervous system are often thought of as the 'fight-and-flight' and 'rest-and-digest' systems, respectively, as they generate motor responses that broadly promote action or relaxation. For example, sympathetic activation increases heart rate, and increases blood flow to the brain, heart and skeletal muscles, priming the body for action. Conversely, activation of the parasympathetic nervous system reduces heart rate and blood flow to the brain, heart and skeletal muscles, instead directing blood flow to the gut and stimulating digestion.

While it is useful to think of the distinction between 'fight and flight' and 'rest and digest' functions of the two systems, the body doesn't switch in a binary manner between one or the other being active but rather the body's state depends on the balance of activity of the two systems at any one time. Furthermore, this balance is not uniform across the body, as is apparent from the need to independently regulate different organs, for example to control heart rate and bladder release.

The sympathetic preganglionic neurons leave the thoracic and lumbar spinal cord to synapse in either the sympathetic chain ganglia just outside the spinal cord, or in the prevertebral ganglia including the solar plexus or mesenteric ganglia within the abdomen. Preganglionic neurons use acetylcholine as their neurotransmitter. Postganglionic neurons - the motor neurons of the sympathetic division - use noradrenaline as their neurotransmitter, and often travel along the same nerves as the somatic nervous system [NB: Noradrenaline is called norepinephrine in the US, and adrenaline is called epinephrine].

Parasympathetic neurons leave the CNS via cranial nerves or via sacral regions of the spinal cord. These neurons synapse in ganglia that are generally very close to the organs to be contacted, so parasympathetic preganglionic neurons are much longer than the postganglionic neurons. The vast majority of parasympathetic fibres form the vagus nerve, which innervates most of the organs in the thorax and abdomen. Both pre and post-ganglionic parasympathetic neurons use acetylcholine as a neurotransmitter.

The Central Nervous System

Compass directions

The CNS comprises the brain and spinal cord. They, particularly the brain, are complex 3D structures, so before we explore them, it's useful to consider the language we can use to describe what exactly we are looking at and where different parts are located with respect to other regions.

We can look at the surface of the brain from different angles. In humans, if we look from the front, we are looking at the anterior surface, or from the back we are looking at the posterior surface. If we look at the top, we are looking at the superior surface or from below, the inferior surface. These words can also be used to describe relative positions of things within the brain too (e.g. visual cortex is posterior to auditory cortex).

To confuse matters, however, the front of the brain can also be referred to as rostral (meaning towards the nose), the back as caudal (meaning towards the tail), the top as dorsal (towards the back) and the bottom as ventral (towards the stomach).

In the brain these terms don't really make sense - dorsal regions are towards the top, not towards the back of the head. They make much more sense in the spinal cord - dorsal spinal cord really is towards the back, not the top. The reason for the confusion is that humans walk upright so our brain is angled relative to the spinal cord.

In most animals (e.g. think of mice), the brain continues in a straight line from the spinal cord, so the dorsal brain is aligned with the back of the animal. In humans, however, the top of our head points in a different direction to our back. All in all, this means we have lots of words we can use to describe whether we're looking at the front, back, top or bottom of the brain.

We don't just want to look at the brain from the outside surfaces, though, but to see inside at the many structures within. To do that we can virtually or physically slice through it, creating sagittal, coronal or horizontal/transverse slices. In doing so, we can notice that symmetry is a general feature of CNS organisation: the left and right halves of the brain and spinal cord are symmetrical around a midline. We can describe structures' locations with respect to this midline as being medial (closer to the midline) or lateral (closer to the side), as well as describing their anterior-posterior/rostral-caudal and superior-inferior/dorsal-ventral dimensions.

Fig 2.8. Anatomical slices allow us to visualise inside the brain

The spinal cord

The spinal cord can be divided into segments, each of which connects to a pair of sensory and motor nerves. Towards the head are 8 cervical segments, below which are 12 thoracic segments, 5 lumbar segments and 5 sacral segments (Figure 2.4).

The spinal cord carries afferent, somatosensory (touch) information up to the brain and efferent (motor) information to the muscles of the body. It comprises grey matter (neuronal cell bodies and short range connections) around a central canal, containing cerebrospinal fluid, surrounded by a number of white matter tracts containing myelinated and unmyelinated axons forming connections to other regions. Both the grey and white matter are organised. For example, the dorsal column of the white matter contains axons from somatosensory neurons whose cell bodies are located in the dorsal root ganglia, while the lateral corticospinal tract contains axons from motor neurons from the cerebral cortex which control voluntary movement of the limbs. The grey matter is where connections between different neurons form and contains cell bodies, dendrites and synapses as well as axons. Spinal cord grey matter can be divided into three 'horns' (Figure 2.9), the dorsal horn containing neurons carrying sensory information, the lateral horn largely containing sympathetic motor neurons, and the ventral horn containing cells conveying motor information.

The brain

The brain itself is made up of the brainstem, the cerebellum and the forebrain.

The brainstem

A lot of the volume of the brainstem contains white matter tracts carrying information up to the rest of the brain or down to the spinal cord, as well as to and from the cranial nerves that provide sensory and motor inputs to the face and neck. Within the medulla, the pyramids, so called for their shape, are prominent white matter bundles that carry descending motor axons to the spinal cord. On the ventral surface of the pons are the bridge-like wide mass of transverse fibres (perpendicular to the axis of the brain stem and spinal cord), from which the pons derives its name (pons is Latin for bridge). These fibres connect the brainstem to the cerebellum.

Nestled within the numerous white matter tracts passing through the brainstem are a number of grey matter nuclei (clusters of neuronal cell bodies). These nuclei include motor or sensory cranial nerve nuclei, containing cell bodies of neurons that project into or receive connections from the cranial nerves, as well as the dorsal column nuclei where many neurons carrying touch information from the spinal cord form their first connections. Also within the brainstem are nuclei that produce neuromodulators that are released over relatively large regions of forebrain and are involved in regulating arousal, attention, mood, movement, motivation and memory. Many of these neuromodulators are well known and will make several appearances elsewhere in this book: Dopamine is produced in neurons in the ventral tegmental area and substantial nigra pars compacta of the midbrain, serotonin from neurons in the Raphe nuclei that extend from the medulla to the midbrain, noradrenaline in neurons in locus coeruleus of the midbrain and the medial reticular zone of the pons, and acetylcholine in neurons of the pedunculopontine nucleus in the pons (as well as in the basal forebrain). Other brainstem nuclei, particularly in the medulla, regulate key functions for sustaining life, including breathing, heart rate, swallowing and consciousness. Brainstem damage can therefore be life-threatening, and can occur due to brain swelling compressing the brainstem against the skull.

Cerebellum

The cerebellum, or 'little brain', lies inferior to the occipital and temporal lobes of the cerebral cortex, and posterior to the pons.

Its cells are organised in clear layers - that is, it has a laminar structure - with a distinct connectivity that has made it a very interesting structure for neuroscientists to study. It receives inputs via 'mossy fibres' from nuclei in the pons, which in turn receive information from wide areas of the cerebral cortex, containing sensory and other information. These mossy fibres then synapse onto granule cells - small neurons which are packed together to form the granule cell layer. The human brain contains 50 billion granule cells - about 3/4 of the total number of neurons in the brain. The axons of these granule cells rise vertically from the granule cell layer into the molecular layer, where they split in two and send axons in opposite directions, forming a T shape. The axons of different granule cells are aligned parallel with each other, and are termed parallel fibres.

These parallel fibres synapse onto the highly branched, flat dendritic trees of Purkinje cells, the output cell of the cerebellum which sends connections to the deep cerebellar nuclei from which information is sent to the thalamus and onto the cerebral cortex. Purkinje cells also receive synaptic input from 'climbing fibres', axons of cells that originate in the medulla and carry information from across the brain, particularly information about ongoing motor processes.

Neuroscientists have been able to interrogate and understand how this highly organised circuitry mediates some of the key functions of the cerebellum, allowing us detailed insights into how the cerebellum performs some of its key functions. The cerebellum is important for bringing together diverse sensory information and using this to guide motor behaviours, making it important for balance and motor learning, such as learning to ride a bicycle, or your fingers learning to play a new tune on the piano. However, while the sensory-motor functions of the cerebellum are the best understood, it also receives many different sorts of information from across the brain. Functional imaging studies and other experiments have demonstrated cerebellar involvement in processes as diverse as language comprehension, autobiographical memory and attention.

Forebrain

The forebrain comprises the diencephalon and, surrounding it the cerebrum - two cerebral hemispheres containing an outer layer- the cerebral cortex and subcortical structures such as the hippocampus, basal ganglia and amygdala.The two cerebral hemispheres are connected to each other via the corpus callosum, a very large white matter tract, with many other white matter tracts connecting different parts of the forebrain to each other.

Diencephalon

Extending from the midbrain, the diencephalon's major components are the thalamus and the hypothalamus.

The thalamus is an information hub, relaying ascending and descending information from widespread brain areas. It is organised into functionally specialised nuclei which process information of certain modalities. For example the dorsal lateral geniculate nucleus of the thalamus receives visual information from the optic nerve and sends projections to primary visual cortex, while the medial geniculate nucleus receives auditory information from the inferior colliculus and projects to auditory cortex. Rather than simply relaying information in one direction, however, a key feature of thalamic processing is that nuclei also receive descending information from the cortex, forming circuits termed thalamocortical loops (or corticothalamic loops). These thalamocortical loops are not limited to sensory processing, but from higher order areas and motor areas as well, and can include additional structures in their circuitry.

For example, the anterior thalamus plays an important role in memory, receiving information from the hippocampus, mamillary bodies of the hypothalamus as well as the cerebral cortex, and projecting to cingulate cortex. Thalamocortical loops that incorporate the striatum and other nuclei of the basal ganglia are also important for motor control and motivated behaviour, via the ventrolateral, mediodorsal and anterior thalamic nuclei. These loops, and others like them we will hear about in other circuits, demonstrate that the 'input-computation-output' function of the nervous system is not simply in one direction - instead, outputs from a given region often feed back to structures providing inputs to that region, as well as sending outputs to 'upstream' brain areas.

The hypothalamus is located below the thalamus, above the pituitary gland. It consists of around 22 nuclei and is highly connected to the brainstem, the amygdala and the hippocampus. The hypothalamus is involved in regulation of many homeostatic processes, such as the control of eating and drinking, temperature regulation and circadian rhythms, as well as emotion and memory processing and sexual behaviour. Some hypothalamic nuclei are sexually dimorphic, being structurally and functionally different in males and females. The hypothalamus can effect changes on the body's physiology both by its projections via the brainstem to the autonomic nervous system, and by regulating hormone release via its connections with the adjacent pituitary gland. It is also involved in motivated behaviours such as defensive freezing or flight behaviours.

Cerebral cortex

Richly folded in humans, to maximise its surface area, the cerebral cortex is the outermost layer of the forebrain.

These folds form characteristic sulci (grooves) and gyri (ridges), the largest of which separate the cerebral cortex into 4 lobes, the frontal, temporal, parietal and occipital lobes. Most cerebral cortex is neocortex (new cortex) with 6 layers of neurons, containing different densities and types of neurons. Layer 1 has very few cell bodies and mostly contains the tips of dendrites and axons. Layers 2 and 3 contain cell bodies of neurons that receive and send projections to nearby cortical regions. Ascending inputs to the cerebral cortex from the thalamus arrive in layer 4, while cells that send descending projections to other brain areas are found in layers 5 and 6. These layers are different thicknesses across the cortex, varying with the function of that area. Sensory cortices receive lots of afferent inputs so have a thick layer 4, while motor regions send a lot of efferents to downstream regions, so have thick layers 5 and 6. There is more connectivity vertically through these layers than horizontally, so neurons in the same vertical 'column' of cortex tend to have the same response properties (i.e. they are all activated by the same sort of stimulus).

By studying the cytoarchitecture, or organisation of the cell layers across the cortex, in 1909 a German anatomist called Korbinian Brodmann divided the cerebral cortex into 52 different areas, now called Brodmann areas. Many of these have subsequently been subdivided into smaller regions. The different cellular organisation of these regions indicates differences in the circuitry and information processing within the region. Indeed many Brodmann areas have been shown to correspond with different functional specialisations. Area 17 is primary visual cortex, for example, and area 4 is primary motor cortex. Generally the functions of different cortical regions can be categorised as being sensory, motor or associative. Sensory information first enters primary sensory cortices, with further processing occurring in secondary sensory areas. Where multimodal information is processed within an area (e.g. both auditory and visual), that area is considered association cortex. These areas are important for a multitude of functions from understanding and generating language to spatial processing, abstract thinking, planning and memory. Conversely, primary motor cortex contains motor neurons that send their axons to the spinal cord to execute voluntary movements, while secondary or premotor areas project to primary motor cortex and help select or coordinate movements.

These functional areas as defined by cytoarchitecture can be further functionally subdivided. For example, primary sensory cortices are topographically organised: adjacent parts of the skin are represented by adjacent bits of somatosensory cortex - somatotopic organisation, and adjacent regions of the retina are represented by adjacent parts of primary visual cortex - retinotopic organisation. These representations can be even further subdivided into columns processing different stimuli (orientation of visual stimuli, for example).

While most brain areas are structurally symmetrical, there is lateralisation of some functions that are subserved by the cerebral cortex. Firstly, as mentioned above, sensory processing generally occurs in the opposite side of the body from where that sensory input is received (i.e. left somatosensory cortex processes stimuli applied to the right side of the body). Secondly, lesion studies reveal lateralisation in the function of information streams through each side of the brain. Lesions to the left hemisphere visual processing streams result in deficits in perceiving fine details, while lesions to the right hemisphere impair perception of the wider field of view, or 'big picture'. Finally, language production and comprehension are typically localised to the left hemisphere, particularly in right-handed people.

Neurons in the cerebral cortex project to a multitude of different brain areas as well as to the spinal cord, but the most common projection target for cortical neurons are other cortical neurons, and most of these projections are to nearby neurons. 80% of intracortical projections occur to neurons in the same area, while most connections between areas are also to nearby areas. Only 5% of intracortical connections are long range, to more distant cortical regions or across the corpus callous ( transcallosal), between the two hemispheres. These connections contribute to the formation of several large scale brain networks that contribute to different aspects of perceptual and cognitive function (see later).

Basal ganglia

The basal ganglia are a group of subcortical nuclei (i.e. they lie beneath the cerebral cortex). They comprise the dorsal striatum, which is made up of the caudate nucleus and the putamen, the ventral striatum, or nucleus accumbens and the external and internal global pallidus. Two other components of the basal ganglia circuitry are actually not in the cerebrum: the subthalamic nucleus is within the diencephalon and the substantial nigra is in the midbrain.

Information flows from widespread areas of the cerebral cortex, through the basal ganglia and thalamus, and back to cerebral cortex. These cortico-basal ganglia-thalamo-cortical loops are important for selecting motor actions, e.g. starting and stopping behaviours, and for aspects of motivated behaviour i.e. selecting actions based on whether they are likely to result in something good or bad happening to the individual. They include excitatory and inhibitory pathways, the balance of which is important for inhibiting or initiating motor outputs (see Interacting with the world).

Disruptions to this circuitry can cause an imbalance between these facilitatory and inhibitory effects, as is seen in a number of neurological conditions including Parkinson's disease and Huntingdon's disease, as well as schizophrenia, Tourette's syndrome, obsessive-compulsive disorder and addiction (see Dysfunctions of the nervous system).

Hippocampus

The hippocampus is an important structure involved in episodic memory, spatial processing and contextual learning.

Fig. 2.19. The hippocampus

It has a distinctly different laminar structure to the cerebral cortex. It is allocortex, with fewer cell layers than neocortex, with a densely packed layer of pyramidal cell bodies, above and below which are layers with only dendritic and axonal processes and much sparser inhibitory neurons. It is formed of two interlinked U-shaped folds, the dentate gyrus and the hippocampus 'proper', curved together into an elegant 3D shape, like a seahorse (hippocampus) or a ram's horn (Cornu ammonis) from which the hippocampal subfields CA1, CA2 and CA3 are named. The hippocampus receives most of its inputs from cortical or subcortical regions via the entorhinal cortex and most of its outputs are sent to cortical or subcortical regions via the subiculum. The fornix, another important output pathway, also connects the hippocampus, via CA3, to the mammillary bodies of the diencephalon.

Like the cerebellum, the hippocampus has a well-characterised neuronal circuitry that has provided useful insights into how it fulfils its function. From the entorhinal cortex, inputs via the perforant path synapse on granule cells in the dentate gyrus, which themselves send mossy fibres to CA3. CA3 pyramidal neurons send Schaffer collaterals (axon branches) to CA2 (which is small) and CA1, as well as recurrent collaterals - axon branches that synapse back onto CA3 cells. Changes, during learning, in the strength of connections in these subregions are thought to be important for particular aspects of memory formation and retrieval, particularly the ability to remember more of an event or stimulus when exposed to only part of it (pattern completion), and to remember events or stimuli as distinct from each other (pattern separation).

Damage to the hippocampus produces memory deficits and occurs early in Alzheimer's disease. Selective hippocampal damage and associated amnesia can also occur when the brain is deprived of oxygen, for example during birth. Because of its recurrent collateral connectivity, whereby excitatory neurons can excite themselves, the hippocampus is also a common focus of epileptic activity, where neuronal circuits are over activated, producing seizures.

Amygdala

The amygdala, named for its almond shape, sits adjacent to the hippocampus beneath the cerebral cortex within the temporal lobe (see Fig. 2.19).

It is important for processing of emotions and for the impact of emotions on learning and has been shown to be particularly involved in fear learning. It is made up of a complex of different nuclei, including the basolateral, corticomedial and centromedial nuclei. It receives inputs from wide regions of sensory and prefrontal cortex, then hippocampus and visceral information from brainstem nuclei, making it able to integrate information about the state of the body with contextual information. Its efferents go to cerebral cortex, particularly prefrontal and cingulate cortex, hippocampus, ventral striatum, thalamus and hypothalamus. This connectivity allows it to produce emotional responses appropriate to a given context; for example, when a stimulus appears that is associated with punishment, a fear response can be produced by altering hormone release via the hypothalamus, triggering freezing behaviours and activation of the sympathetic nervous system via the brainstem.

People with lesions to the amygdala display a reduction in emotional behaviour and a placidness or 'flatness of affect', and show reduced learning about emotional or frightening stimuli or situations.

Non-neuronal brain structures

In addition to these various brain regions, a number of other structures of the brain's anatomy are important to appreciate in order to understand the overall physiology of this organ.

Ventricles

Cerebrospinal fluid and meninges

Within the brain and spinal cord are a series of connected spaces containing cerebrospinal fluid (CSF). The central canal of the spinal cord extends into the brainstem before expanding in the region of the pons to form the fourth ventricle. At the top of the fourth ventricle another narrow channel, the cerebral aqueduct, connects to another broader chamber, the third ventricle, at the level of the diencephalon. From the third ventricle another two narrow channels connect to the large lateral ventricles that extend deep into the cerebrum. The CSF that fills the canals and ventricles is made by ependymal cells that line the ventricles in a specialised membrane structure called the choroid plexus. These ependymal cells surround capillaries of the vascular system and produce CSF by filtering the blood. CSF is similar in content to blood plasma, being mostly water but containing ions and glucose ( click here for a table with more information), though it has less protein content than plasma.

CSF flows from the fourth ventricle into the space between the membranes or meninges that cover the brain. There are three meninges; the pia is a delicate membrane that directly covers the brain and spinal cord. Above the pia is a fluid-filled space, then the arachnoid membrane, so called for its web-like strands that connect to the pia through this subarachnoid space. Above the arachnoid is the tough outer membrane - the dura - which supports large blood vessels that drain cerebral blood towards the heart. CSF flows from the ventricles into the subarachnoid space then circulates the brain, before draining into veins in the dural sinuses. CSF functions as a shock absorber for the brain, cushioning the brain from damage during knocks to the head, as well as clearing metabolic waste products from the brain into the blood.

Vasculature

The brain is an energetically demanding organ. It is only 2% of the body's mass, but uses 20% of its energy when the body is resting (i.e when muscles are not active). It relies on a constant supply of oxygen and glucose in the blood to sustain neurons, with disruption of blood flow to the brain leading to a loss of consciousness within 10 seconds. To deliver a constant flow of oxygenated blood, the brain has a complex and tightly regulated vasculature that directs blood to the most active brain regions. Four arteries feed the brain with oxygenated blood, forming a circle - the circle of Willis - that ensures that a reduction of blood flow to one artery can be compensated for by redistribution of flow from the others. Several large arteries branch off the circle of Willis to perfuse different regions of the brain. Branches of these major arteries form smaller and smaller arteries and arterioles that pass through the subarachnoid space before diving into the brain, before branching yet further to form a dense capillary network.

There are a mind-blowing 1 to 2 metres of capillaries in every cubic millimetre of brain tissue. These capillaries are less than 10 microns in diameter, though, so they only take up about 2% of the brain volume. This means that, in cerebral cortex, each neuron is only around 10-20 microns from its nearest capillary. This dense vascular network can therefore supply oxygen and glucose very close to active neurons.

Specialised mechanisms allow the blood supply to be fine-tuned to brain regions that need it most. Cells called smooth muscle cells or pericytes in blood vessel walls can dilate or constrict to regulate blood flowing through the vessel. Active neurons and astrocytes produce molecules that dilate smooth muscle cells and pericytes on local arterioles and capillaries, increasing blood flow to these regions of increased activity. In fact this increase in blood flow usually supplies more oxygen than is needed, so that blood oxygen levels increase in active brain regions. This increase in blood oxygen gives rise to the BOLD (blood oxygen level dependent) signal that can be detected using magnetic resonance imaging and is often used as a surrogate for neuronal activity in experiments studying the function of different brain regions.

Another specialised feature of the brain's vascular system is the blood-brain barrier (BBB). The endothelial cells lining blood vessels in the brain are very tightly joined together and express relatively few transporter proteins that allow molecules to be transported from the blood into the brain. This means that it is harder for molecules and cells to access the brain from the blood, protecting the brain from circulating toxins or immune cells.

The brain's vasculature can be impacted in several neurological conditions, leading to alterations in brain function. In ischaemic or haemorrhage stroke, there is a reduction in the blood supplied to the brain due to either a blockage or leakage in blood vessels feeding the brain. This reduces the oxygen available to the brain region fed by the lesioned vessel, damaging the neurons in that region and causing corresponding functional deficits. In other diseases there is a less severe decrease in blood flow. In Alzheimer's disease there is a decrease in brain blood flow many years before symptoms develop. It is not yet known what links this decrease in blood flow has with the development of Alzheimer's disease, but a decreased ability to clear toxic proteins from the brain, an increase in BBB permeability, or a chronic lack of oxygen supply may all be factors.

Overall in this chapter, you have learnt general principles about information flow in the brain, as well as some of the major neuronal and non-neuronal structures that mediate this transfer of information. Next we will explore the signalling and non-signalling cells of the nervous system to understand how they support information flow and computation.

References

Iturria-Medina, Y., Sotero, R. C., Toussaint, P. J., Mateos-Pérez, J. M., Evans, A. C., & The Alzheimer's Disease Neuroimaging Initiative. (2016). Early role of vascular dysregulation on late-onset Alzheimer's disease based on multifactorial data-driven analysis. Nature Communications 7, 11934. https://doi.org/10.1038/ncomms11934

Kwon, Diana. The mysterious, multifaceted cerebellum. (2020). Knowable Magazine. https://doi.org/10.1146/knowable-093020-2

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Dr Catherine N. Hall All our thoughts and actions are biological structures and processes that work together to enable us to successfully exist and interact with the world, performing behaviours that keep us fed, watered and safe. In this chapter we will learn about the different parts of the nervous system that orchestrate these behaviours.

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The brain is the most complex part of the human body. It is the center of consciousness and also controls all voluntary and involuntary movement and bodily functions. It communicates with each part of the body through the nervous system, a network of channels that carry electrochemical signals.