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The Brain

The brain is the single most important structure in our bodies. As far as we can tell, the brain controls most of human thought and emotion. When you sit and think about it, the brain is also the coolest thing about you. Every time you think about anything- it is your brain. When you feel pain of pleasure- it comes from your brain. Its all about the brain!!!

The brain is made up of neurons and glial cells. I call my wife my glial cell. Glial cells support nerve cells in the brain by providing food and support. Although the brain is made up of millions of densely packed neurons, it actually feels no pain. If I stuck a knife into your head, you would feel pain from the skin, scalp and skull being pierced, but once the knife reached the brain, pain stops (but the other stuff still hurts). It was commonly believed that once you damage brain cells (through drinking, smoking, hitting your head or just holding your breath for a REALLY long time) they would never grow back. There is some research now that points to the contrary.

If you happen to suffer from some brain damage, do not despair. Some of our brain functions are flexible and if one part goes out, others will try to compensate and continue to function. The concept that some of our brain will attempt to reroute itself if damaged is called Brain Plasticity. It does this by rerouting connections to avoid damaged dendrites. Picture Brad Pitt or Angelina Jolie (take your pick or fill in your own fantasy) invites you over for nookie. If the highway you were going to take to their house flooded, would you give up? No way, you would use Mapquest to get directions using local streets. That is essentially what our brains try to do when damaged. Unfortunately, as we age the ability of brain plasticity working decreases. The lesson here, if you are going to damage your brain, do it at a very young age.

Before we talk about brain structures, lets quickly go over some of the ways scientists learn about the brain.

Ways to study the Brain
Accidents
Every so often someone gets smacked in the head REALLY hard and from their injury we learn about the brain. The most famous case occurred in 1848 to a fellow named Phineas Gage. Phineas was working on the railroad when a iron pole shot through his head.

Unbelievably, he survived the accident. But his personality and behavior changed drastically after the catastrophe. He became violent, angry and unpredictable (not just because a four foot pole shot through his head). Phineas's accident first led scientists to believe that various parts of the brain control different parts of who we are.
Lesions
A lesion is the removal or destruction of part of the brain. Doctors will lesion a patients brain during brain surgery (usually to remove some type of tumor). By removing parts of the brain we were able to learn what different parts of the brain do.

Below is a lesion of a rat's brain

For example, if a doctor removed a tumor in your left temporal lobe of the brain and you were then unable to speak, we could assume that speech comes from that area of the brain. Brain lesions were commonly used in the mid 1900s to control mentally unstable patients. Part of the frontal lobe was removed (frontal lobotomy) and drastic behavioral changes occurred after surgery (we learned that our personalities are strongly centered in the front of our brains).
EEG (Electroencephalogram)
The brain is just like an electrical battery (remember the Matrix). An EEG machine measures brain waves. If you are awake it measures what we call alpha waves (short active waves) and when you are asleep it measures other waves like delta waves (long inactive waves). If the EEG measures no activity then you are either brain dead or watching Jerry Springer. It is used commonly in sleep research.

CAT Scan (Computerized Axial Tomography)
A CAT scan is just a really sophisticated x-ray of the brain. It gives us a 3D picture of the brain which is great for locating tumors, but it does NOT show brain activity or function.

MRI (Magnetic Resonance Imaging)
An MRI gives us the most detailed picture of the brain. It uses magnetic fields to knock electrons of their orbit and takes a picture by seeing them run back to their orbits (kind of). There is no radiation so the procedure is safe, but once again it only gives us an idea of structure and not function.

PET Scan (Positron Emission Tomography)

A PET scan is the best way for us to see activity in the brain. The patient will usually swallow a substance (like glucose) and the PET scan will see what parts of the brain are using the substance. If a patient seems to be using alot of the substance in a certain part of the brain, we can tell what part of the brain is working.
Functional MRI
This is essentially a combination of the PET scan and the MRI. The fMRI can give us the best picture of the brain while showing use blood flow information. The Yankees of brain technology.
Piece of cake, now on to the heart of this unit: Brain Anatomy and Function.

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The Brain The brain is the single most important structure in our bodies. As far as we can tell, the brain controls most of human thought and emotion. When you sit and think about it, the brain is also the coolest thing about you. Every time you think about anything- it is your brain.

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Evaluation of ways of investigating the brain

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The problem a patient displays during their lifetime (e.g. an inability to speak) may not be linked to the deficits found in the brain (e.g. a damaged Broca's area)= could have been the result of another illness TF= unable to conclude that the deficit is caused by the damage found in the brain.

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ERP/EEG

EEG stands for "electroencephalography". Break the word down and you get "electrical-brain-writing". This is a technique for recording "brain waves", or more technically the electrical activity produced by the brain. EEG does this using electrodes that are placed on the scalp. Measuring electrical activity from the brain is useful because the brain uses electrical impulses to operate - electrical signals travel along brain cells (neurons). The basic way that information is processed by the brain is by very complex connections (networks) of neurons communicating with each other using electricity.

ERP stands for "event-related potentials". This is a specific use of EEG in which we look at brain waves that are generated in response to particular events, such as seeing a word or picture on a computer screen. Within the first second of seeing a stimulus, like a word or a picture, the brain generates a series of "blips" in the ERP brain wave that indicate the activity of different brain systems that are involved in perceiving and making sense of that stimulus. By looking at the timing of these blips (technically called "components") we can gain a better understanding of how different types of information are processed, and when. One of the biggest advantages to EEG/ERP is the ability to see brain activity as it unfolds in real time, at the level of milliseconds (thousandths of a second).

One of the big disadvantages of EEG/ERP is that it's hard to figure out where in the brain the electrical activity is coming from. By putting lots of electrodes all over the scalp (in our lab we use 64 or 128 electrodes), we can get some idea of where the ERP components are strongest. This doesn't really tell us where in the brain the signals are coming from, but it can be useful in telling us whether two ERP components come from the same place or not. For example, let's say we want to know if different parts of the brain are used when you see a picture of an apple, and when you read the word "apple". Maybe the ERP components to the picture and the word are biggest at the same time, but they are biggest over different parts of the head. This would tell us that different parts of the brain were being used.

Modern analysis techniques can give us a better clue to where in the brain ERP signals are coming from. Using lots of electrodes and complex models of the shape of the head and the brain, these techniques allow us to make a guess as to where in the brain the components are generated. However, this is still a "best guess" and lots more work is needed to improve these techniques.

A better way of seeing inside the brain is using MRI.

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EEG stands for "electroencephalography". Break the word down and you get "electrical-brain-writing". This is a technique for recording "brain waves", or more technically the electrical activity produced by the brain. EEG does this using electrodes that are placed on the scalp.

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What Are the Advantages and Disadvantages of fMRI? - Advantages and Disadvantages of fMRI | HowStuffWorks

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The big advantage of fMRI is that it doesn't use radiation like X-rays, computed tomography (CT) and positron emission tomography (PET) scans. If done correctly, fMRI has virtually no risks. It can evaluate brain function safely, noninvasively and effectively. fMRI is easy to use, and the images it produces are very high resolution (as detailed as 1 millimeter). Also, compared to the traditional questionnaire methods of psychological evaluation, fMRI is far more objective.

Yet fMRI also has its disadvantages. First, it's expensive. Second, it can only capture a clear image if the person being scanned stays completely still. And third, researchers still don't completely understand how it works.

The biggest complaint from researchers is that fMRI can only look at blood flow in the brain. It can't home in on the activities of individual nerve cells ( neurons), which are critical to mental function. Each area of the brain studied in fMRI is made up of thousands of individual neurons, each of which might have a unique story to tell. Because certain areas of the brain that "light up" on fMRI may represent a number of different functions, it's hard to tell exactly what kind of brain activity is being represented on the scan.

In addition, the results of an fMRI scan can be difficult to interpret. For example, in one UCLA study by researcher Marco Iacoboni, when swing voters were shown the words "Democrat," "Republican" and "independent," an area of their brain called the amygdala was activated, indicating feelings of anxiety and disgust. But the three terms also elicited activity in areas of the brain associated with reward, desire and connectedness. So how did those political terms make the subjects feel -- disgusted or connected? It was difficult for researchers to tell with any certainty [source: Scientific American].

Because of these drawbacks, some critics argue that fMRI is nothing more than a high-tech version of phrenology, the 19th-century pseudo-science that claimed to divulge a person's character based solely on the shape of his or her skull. In the future, researchers hope to make fMRI more "scientific" and improve its accuracy by focusing on individual neurons. They think that by recording the electrical activity in neurons, they will get a more complete and precise picture of brain activity.

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The big advantage of fMRI is that it doesn't use radiation like X-rays, computed tomography (CT) and positron emission tomography (PET) scans. If done correctly, fMRI has virtually no risks. It can evaluate brain function safely, noninvasively and effectively. fMRI is easy to use, and the images it produces are very high resolution (as detailed as 1 millimeter).

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Biopsychology: Studying the Brain - Evaluation of EEG & ERP | tutor2u Psychology

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We've just flicked the switch on moving all our digital resources to instant digital download - via our new subject stores. For every subject you can now access each digital resource as soon as it is ordered. This will always be the latest edition of each resource too (and we'll update you automatically if there is an upgraded version to use).

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An electroencephalogram (EEG) works on the premise that information is processed in the brain as electrical activity in the form of action potentials or nerve impulses, transmitted along neurons. EEG measure this electrical activity through electrodes attached to the scalp. Small electrical charges that are detected by the electrodes are graphed over a period of time, indicating the level of activity in the brain.

Event-Related Potentials (ERP) use similar equipment to EEG, i.e. electrodes attached to the scalp. However, the key difference is that a stimulus is presented to a participant (for example a picture/sound) and the researcher looks for activity related to that stimulus.

Electroencephalogram (EEG)

An electroencephalogram (EEG) works on the premise that information is processed in the brain as electrical activity in the form of action potentials or nerve impulses, transmitted along neurons. EEG scanners measure this electrical activity through electrodes attached to the scalp. Small electrical charges detected by the electrodes are graphed over a period of time, indicating the level of activity in the brain. There are four types of EEG patterns including alpha waves, beta waves, theta waves and delta waves. Each of these patterns has two basic properties that psychologists can examine:

Amplitude: the intensity or size of the activity

Frequency: the speed or quantity of activity

Also, EEG patterns produce two distinctive states: synchronised and desynchronized patterns. A synchronised pattern is where a recognised waveform (alpha, beta, delta and theta) can be detected, whereas a desynchronized is where no pattern can be detected.

Fast desynchronized patterns are usually found when awake and synchronised patterns are typically found during sleep (alpha waves are associated with light sleep, and theta/delta waves are associated with deep sleep). Furthermore, EEG scanning was responsible for developing our understanding of REM (dream) sleep, which is associated with a fast, desynchronized activity, indicative of dreaming.

EEG can also be used to detect illnesses like epilepsy and sleep disorders, and to diagnose other disorders that affect brain activity, like Alzheimer's disease.

Event-Related Potentials (ERP)

Event-Related Potentials (ERP) use similar equipment to EEG, electrodes attached to the scalp. However, the key difference is that a stimulus is presented to a participant (for example a picture/sound) and the researcher looks for activity related to that stimulus. However, as ERPs are difficult to separate from all of the background EEG data, the stimulus is present many times (usually hundreds), and an average response is graphed. This procedure, which is called 'averaging', reduces any extraneous neural activity which makes the specific response to the stimulus stand out.

The time or interval between the presentation of the stimulus and the response is referred to as latency. ERPs have a very short latency and can be divided into two broad categories. Waves (responses) that occur within 100 milliseconds following the presentation of a stimulus are referred to as sensory ERPs, as they reflect a sensory response to the stimulus. ERPs that occur after 100 milliseconds are referred to as cognitive ERPs, as they demonstrate some information processing.

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Biopsychology: Studying the Brain - Electroencephalogram & Event-Related Potentials Electroencephalogram

# data[].attributes.attachment_link.description
An electroencephalogram (EEG) works on the premise that information is processed in the brain as electrical activity in the form of action potentials or nerve impulses, transmitted along neurons. EEG measure this electrical activity through electrodes attached to the scalp.

# data[].attributes.body
x Low spatial resolution
x (EEG) electrical activity often detected in several regions of brain simultaneously- hard to pinpoint exact area/region of activity, making it difficult for researchers to draw accurate conclusions.
x (ERP) must eliminate all background noise / EVs - difficult

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+ High temporal resolution
+ Non-invasive
+ Cheaper than other techniques
+ Used for diagnosis
+ (ERP) more specific than EEG- makes use a more experimentally robust method as it can eliminate extraneous neutral activity, which other scanning techniques (and EEG) struggle to do.
+ Can use more natural environment and wider range of stimuli.
+ (EEG) good for sleep studies & (ERP) good for diagnosis e.g. epilepsy

# data[].attributes.body
-Event related potentials are a specified version of EEG.
-The ppt will be repeatedly exposed to a stimulus rand, using a statistical averaging technique, psychologists can single out the specific wave patterns caused by that stimulus.

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Introduction
A post-mortem examination, also known as an autopsy, is the examination of a body after death. The aim of a post-mortem is to determine the cause of death.
Post-mortems are carried out by pathologists (doctors who specialise in understanding the nature and causes of disease).

The Royal College of Pathologists and the Human Tissue Authority (HTA) set the standards pathologists work to.

Post-mortems provide useful information about how, when and why someone died, and they enable pathologists to obtain a better understanding of how diseases spread.

Learning more about illnesses and medical conditions benefits patients too, because it means they'll receive more effective treatment in the future.

If your child, partner or relative has died and a post-mortem is to be carried out, hospital bereavement officers can offer you support and advice. They also act as the main point of contact between you and the staff carrying out the post-mortem.

When post-mortems are carried out

A post-mortem examination will be carried out if it's been requested by:

a coroner - because the cause of death is unknown, or following a sudden, violent or unexpected death

a hospital doctor - to find out more about an illness or the cause of death, or to further medical research and understanding

The two different types of post-mortem are discussed below.

Coroner's post-mortem examination

A coroner is a judicial officer responsible for investigating deaths in certain situations (see below). Coroners are usually lawyers or doctors with a minimum of five years' experience.

In most cases, a doctor or the police refer a death to the coroner. A death will be referred to the coroner if:

it's unexpected, such as the sudden death of a baby (cot death)

it's violent, unnatural or suspicious, such as a suicide or drug overdose

it's the result of an accident or injury

it occurred during or soon after a hospital procedure, such as surgery

the cause of death is unknown

The main aim of a post-mortem requested by a coroner is to find out how someone died and decide whether an inquest is needed. An inquest is a legal investigation into the circumstances surrounding a person's death.

If someone related to you has died and their death has been referred to a coroner, you won't be asked to give consent (permission) for a post-mortem to take place. This is because the coroner is required by law to carry out a post-mortem when a death is suspicious, sudden or unnatural.

A coroner may decide to hold an inquest after a post-mortem has been completed. Samples of organs and tissues may need to be retained until after the inquest has finished.

If the death occurred in suspicious circumstances, samples may also need to be kept by the police, as evidence, for a longer period. In some cases, samples may need to be kept for a number of months or even years.

The coroner's office will discuss the situation with you if, following an inquest, tissue samples need to be retained for a certain length of time.

Hospital post-mortem examination

Post-mortems are sometimes requested by hospital doctors to provide more information about an illness or the cause of death, or to further medical research.

Sometimes, the partner or relative of the deceased person will request a hospital post-mortem to find out more about the cause of death.

Hospital post-mortems can only be carried out with consent. Sometimes, a person may have given their consent before they died. If this isn't the case, a person who is close to the deceased can give their consent for a post-mortem to take place.

Hospital post-mortems may be limited to particular areas of the body, such as the head, chest or abdomen. When you're asked to give your consent, this will be discussed with you. During the post-mortem, only the organs or tissue that you've agreed to can be removed for examination.

The HTA recommends that you should be given at least 24 hours to consider your decision about the post-mortem examination. You should also be given the details of someone to contact in case you change your mind.

What happens during a post-mortem

A post-mortem will be carried out as soon as possible, usually within two to three working days of a person's death. In some cases, it may be possible for it to take place within 24 hours. Depending upon when the examination is due to take place, you may be able to see the body before the post-mortem is carried out.

The post-mortem takes place in an examination room that looks similar to an operating theatre. The examination room will be licensed and inspected by the HTA.

During the procedure, the deceased person's body is opened and the organs removed for examination. A diagnosis can sometimes be made by looking at the organs.

Some organs need to be examined in close detail during a post-mortem and these investigations can take several weeks to complete.

The pathologist will return the organs to the body after the post-mortem has been completed. If you wish, you'll usually be able to view the body after the examination.

Once release papers have been issued, the undertakers you've appointed will be able to collect the body from the mortuary in preparation for the funeral.

What happens after a post-mortem

After a post-mortem, the pathologist writes a report of the findings.

If the post-mortem was requested by the coroner, the coroner or coroner's officer will let you know the cause of death determined by the pathologist.

If you want a full copy of the pathologist's report, you can request this from the coroner's office, but there may be a fee. In some cases, the report may be sent to a hospital doctor or GP so they can discuss it with you.

If the post-mortem was requested by a hospital doctor, you'll have to request the results from the hospital where the post-mortem took place. You may be charged a small fee for this.

You can arrange to discuss the results with the doctor in charge of the deceased person's care while they were in hospital (if applicable), or with your GP.

The HTA has produced a leaflet providing further information about what happens before, during and after the examination - Post-mortem examination: Your choices about organs and tissue (PDF, 68kb).

The Human Tissue Authority

The Human Tissue Authority (HTA) ensures that human tissue is used safely, ethically and with proper consent.

It regulates organisations that remove, store and use tissue for research, medical treatment, post-mortem examination, teaching and public display.

All premises where post-mortems are carried out must be licensed by the HTA.

Bereavement support

For many people, understanding the reason for a loved one's death helps them come to terms with their loss.

Talking and sharing your feelings with someone can also help. Some people find that relying on the support of family and friends is the best way to cope.

Your GP will be able to put you in touch with bereavement services in your area. You can also contact the national Cruse helpline on 0844 477 9400 or a local Cruse centre.

Read more about bereavement and coming to terms with the death of a loved one.

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A post-mortem examination, also known as an autopsy, is the examination of a body after death. The aim of a post-mortem is to determine the cause of death. Post-mortems are carried out by pathologists (doctors who specialise in understanding the nature and causes of disease).

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x Can't establish cause and effect- can't be sure that lesion in the brain caused abnormal beahviour when living or if the abnormal behaviour caused the lesion.
x Person is dead so cannot benefit them
x Ethical issues with consent
x Many extraneous factors that can affect the results/conclusions of post-mortem examinations.

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+ Provide a detailed examination of the anatomical structure and neurochemical aspects of the brain that is not possible with other scanning techniques (e.g. EEG, ERP and fMRI)
+While post-mortem examinations are ‘invasive’, this is not an issue because the patient is dead.
+ Broca and Wernicke and other early psychologists relied on this method to build the foundations of cognitive neuroscience
+ Brown (1986) found that schizophrenic patients had larger vesicles in the brain

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Functional magnetic resonance imaging, or fMRI, is a technique for measuring brain activity. It works by detecting the changes in blood oxygenation and flow that occur in response to neural activity - when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow increases to the active area. fMRI can be used to produce activation maps showing which parts of the brain are involved in a particular mental process.

The development of FMRI in the 1990s, generally credited to Seiji Ogawa and Ken Kwong, is the latest in long line of innovations, including positron emission tomography (PET) and near infrared spectroscopy (NIRS), which use blood flow and oxygen metabolism to infer brain activity. As a brain imaging technique FMRI has several significant advantages:

1. It is non-invasive and doesn't involve radiation, making it safe for the subject.
2. It has excellent spatial and good temporal resolution.
3. It is easy for the experimenter to use.

The attractions of FMRI have made it a popular tool for imaging normal brain function - especially for psychologists. Over the last decade it has provided new insight to the investigation of how memories are formed, language, pain, learning and emotion to name but a few areas of research. FMRI is also being applied in clinical and commercial settings.

How Does an fMRI Work?

The cylindrical tube of an MRI scanner houses a very powerful electro-magnet. A typical research scanner has a field strength of 3 teslas (T), about 50,000 times greater than the Earth's field. The magnetic field inside the scanner affects the magnetic nuclei of atoms. Normally atomic nuclei are randomly oriented but under the influence of a magnetic field the nuclei become aligned with the direction of the field. The stronger the field the greater the degree of alignment. When pointing in the same direction, the tiny magnetic signals from individual nuclei add up coherently resulting in a signal that is large enough to measure. In fMRI it is the magnetic signal from hydrogen nuclei in water (H2O) that is detected.

The key to MRI is that the signal from hydrogen nuclei varies in strength depending on the surroundings. This provides a means of discriminating between gray matter, white matter and cerebral spinal fluid in structural images of the brain.

Oxygen is delivered to neurons by hemoglobin in capillary red blood cells. When neuronal activity increases there is an increased demand for oxygen and the local response is an increase in blood flow to regions of increased neural activity.

Hemoglobin is diamagnetic when oxygenated but paramagnetic when deoxygenated. This difference in magnetic properties leads to small differences in the MR signal of blood depending on the degree of oxygenation. Since blood oxygenation varies according to the levels of neural activity these differences can be used to detect brain activity. This form of MRI is known as blood oxygenation level dependent (BOLD) imaging.

One point to note is the direction of oxygenation change with increased activity. You might expect blood oxygenation to decrease with activation, but the reality is a little more complex. There is a momentary decrease in blood oxygenation immediately after neural activity increases, known as the "initial dip" in the hemodynamic response. This is followed by a period where the blood flow increases, not just to a level where oxygen demand is met, but overcompensating for the increased demand. This means the blood oxygenation actually increases following neural activation. The blood flow peaks after around 6 seconds and then falls back to baseline, often accompanied by a "post-stimulus undershoot".

What Does an fMRI Scan Look Like?

The image shown is the result of the simplest kind of fMRI experiment. While lying in the MRI scanner the subject watched a screen which alternated between showing a visual stimulus and being dark every 30 second. Meanwhile the MRI scanner tracked the signal throughout the brain. In brain areas responding to the visual stimulus you would expect the signal to go up and down as the stimulus is turned on and off, albeit blurred slightly by the delay in the blood flow response.

Researchers look at activity on a scan in voxels - or volume pixels, the smallest distinguishable box-shaped part of a three-dimensional image. The activity in a voxel is defined as how closely the time-course of the signal from that voxel matches the expected time-course. Voxels whose signal corresponds tightly are given a high activation score, voxels showing no correlation have a low score and voxels showing the opposite (deactivation) are given a negative score. These can then be translated into activation maps.

This article is courtesy of FMRIB Centre, Department of Clinical Neurology, University of Oxford. It was written by Hannah Devlin, with additional contributions by Irene Tracey, Heidi Johansen-Berg and Stuart Clare. Copyright © 2005-2008 FMRIB Centre.

What is Functional Magnetic Resonance Imaging (fMRI)?

Related Articles

# data[].attributes.attachment_link.title
What is Functional Magnetic Resonance Imaging (fMRI)?

# data[].attributes.attachment_link.description
Functional magnetic resonance imaging, or fMRI, is a technique for measuring brain activity. It works by detecting the changes in blood oxygenation and flow that occur in response to neural activity - when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow increases to the active area.

# data[].attributes.body
x Poor temporal resolution
x Expensive
x Need to lie VERY still for a long period of time
x Doesn't measure electrical activity of neurons, just blood flow
x Small space- could be uncomfortable

# data[].attributes.body
+ Great spatial resolution (1-2mm)
+ Can be used for diagnosis
+ non-invasive and virtually risk free

# data[].attributes.body
-EEG is a method which studies the general electrical activity of the brain.
-It involves the ppt using a skull cap covered in electrodes to pick up signals of neurons firing together.
-This produces a pattern of waves that represent different levels of arousal.

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-This method involves studying the internal structure of the brain of someone deceased.
-Generally the person had a very rare disease or suffered from an unknown death.
-It's though that any deficits/abnormalities found in the brain may have been linked to the deficits that the person suffered from when they were living.

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Another method of investigating the brain is post-mortem examination, where researchers will study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage.

An example of this technique is the work of Broca, who examined the brain of a man who displayed speech problems when he was alive. It was subsequently discovered that he had a lesion in the area of the brain important for speech production. This later became known as Broca's area. Similarly, Wernicke discovered a region in the left temporal lobe, which is important for language comprehension and processing, which is now known as Wernicke's area.

This method of investigation has successfully contributed to the understanding of many disorders. Iverson examined the brains of deceased schizophrenic patients and found that they all had a higher concentration of dopamine, especially in the limbic system, compared with brains of people without schizophrenia, highlighting the importance of such investigations.

Furthermore, post-mortem studies allow for a more detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other techniques. They also enable researchers to examine deeper regions of the brain such as the hypothalamus and hippocampus, something that is not as easy with other methods of investigation.

Evaluation of Post-Mortem Examination

Causation: One of the main limitations of post-mortem examination is the issue of causation. The deficit a patient displays during their lifetime (e.g. an inability to speak) may not be linked to the deficits found in the brain (e.g. a damaged Broca's area). The deficits reported could have been the result of another illness, and therefore psychologists are unable to conclude that the deficit is caused by the damage found in the brain.

Another issue is that there are many extraneous factors that can affect the results/conclusions of post-mortem examinations. For example, people die at different stages of their life and for a variety of different reasons. Furthermore, any medication a person may have been taking, their age, and the length of time between death and post-mortem examination, are all confounding factors that make the conclusions of such research questionable.

However, one strength of post-mortem examinations is that they provide a detailed examination of the anatomical structure and neurochemical aspects of the brain that is not possible with other scanning techniques (e.g. EEG, ERP and fMRI). Post-mortem examinations can access areas like the hypothalamus and hippocampus, which other scanning techniques cannot, and therefore provide researchers with an insight into these deeper brain regions, which often provide a useful basis for further research. For example, Iverson found a higher concentration of dopamine in the limbic system of patients with schizophrenia which has prompted a whole area of research looking into the neural correlates of this disorder.

While post-mortem examinations are 'invasive', this is not an issue because the patient is dead. However, there are ethical issues in relation to informed consent and whether or not a patient provides consent before his/her death. Furthermore, many post-mortem examinations are carried out on patients with severe psychological deficits (e.g. patient HM who suffered from severe amnesia) who would be unable to provide fully informed consent, and yet a post-mortem examination has been conducted on his brain. This raises severe ethical questions surrounding the nature of such investigations.

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Biopsychology: Studying the Brain - Post-Mortem Examination | tutor2u Psychology

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Another method of investigating the brain is post-mortem examination, where researchers will study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage. An example of this technique is the work of Broca, who examined the brain of a man who displayed speech problems when he was alive.

# data[].attributes.body
-This is a method of studying the brain that looks at blood flow.
-When an area of the brain is more active then it requires a larger amount of Oxygen.
-This therefore means that a larger flow of blood will travel to that particular area (haemodynamic response).
-When the oxyhaemoglobin loses its oxygen, the deoxygenated blood has a different magnetic quality to oxygenated.
-It's this that we can use to form a 3D active map of the brain.
-Therefore areas of the brain that are illuminated during a specific task are those suggested to be involved in the task!

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Functional magnetic resonance imaging (fMRI) is a brain-scanning technique that measures blood flow in the brain when a person performs a task. fMRI works on the premise that neurons in the brain that are the most active during a task use the most energy.

Energy requires glucose and oxygen. Oxygen is carried in the bloodstream attached to haemoglobin (found in red blood cells) and is released for use by these active neurons, at which point the haemoglobin becomes deoxygenated.

Deoxygenated haemoglobin has a different magnetic quality from oxygenated haemoglobin. An fMRI can detect these different magnetic qualities and can be used to create a dynamic (moving) 3D map of the brain, highlighting which areas are involved in different neural activities. fMRI images show activity approximately 1-4 seconds after it occurs and are thought to be accurate within 1-2 mm. An increase in blood flow is a response to the need for more oxygen in that area of the brain when it becomes active, suggesting an increase in neural activity.

Evaluation of fMRI

Invasive or Non-Invasive: An advantage of fMRI is that is non-invasive. Unlike other scanning techniques, for example Positron Emission Tomography (PET), fMRI does not use radiation or involve inserting instruments directly into the brain, and is therefore virtually risk-free. Consequently, this should allow more patients/participants to undertake fMRI scans which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of localisation of function.

Spatial Resolution: fMRI scans have good spatial resolution. Spatial resolution refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. fMRI scans have a spatial resolution of approximately 1-2 mm which is significantly greater than the other techniques (EEG, ERP, etc.) Consequently, psychologists can determine the activity of different brain regions with greater accuracy when using fMRI, in comparison to when using EEG and/or ERP.

Temporal Resolution: fMRI scans have poor temporal resolution. Temporal resolution refers to the accuracy of the scanner in relation of time: or how quickly the scanner can detect changes in brain activity. fMRI scans have a temporal resolution of 1-4 seconds which is worse than other techniques (e.g. EEG/ERP which have a temporal resolution of 1-10 milliseconds). Consequently, psychologists are unable to predict with a high degree of accuracy the onset of brain activity.

Causation: fMRI scans do not provide a direct measure of neural activity. fMRI scans simply measure changes in blood flow and therefore it is impossible to infer causation (at a neural level). While any change in blood flow may indicate activity within a certain brain area, psychologists are unable to conclude whether this brain region is associated with a particular function.

In addition, some psychologists argue that fMRI scans can only show localisation of function within a particular area of the brain, but are limited in showing the communication that takes place among the different areas of the brain, which might be critical to neural functioning.

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Biopsychology: Studying the Brain - Functional Magnetic Resonance Imaging (fMRI)

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Functional magnetic resonance imaging (fMRI) is a brain-scanning technique that measures blood flow in the brain when a person performs a task. fMRI works on the premise that neurons in the brain that are the most active during a task use the most energy.