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Language acquisition does not require extensive use of conscious grammatical rules, and does not require tedious drill.

Acquisition requires meaningful interaction in the target language - natural communication - in which speakers are concerned not with the form of their utterances but with the messages they are conveying and understanding.

... 'comprehensible input' is the crucial and necessary ingredient for the acquisition of language.

The best methods are therefore those that supply 'comprehensible input' in low anxiety situations, containing messages that students really want to hear. These methods do not force early production in the second language, but allow students to produce when they are 'ready', recognizing that improvement comes from supplying communicative and comprehensible input, and not from forcing and correcting production.

In the real world, conversations with sympathetic native speakers who are willing to help the acquirer understand are very helpful.

Stephen Krashen

Introduction

Stephen Krashen (University of Southern California) is an expert in the field of linguistics, specializing in theories of language acquisition and development. Much of his recent research has involved the study of non-English and bilingual language acquisition. Since 1980, he has published well over 100 books and articles and has been invited to deliver over 300 lectures at universities throughout the United States and Canada.

This is a brief description of Krashen's widely known and well-accepted theory of second language acquisition, which has had a large impact in all areas of second language research and teaching.

The 5 hypotheses of Krashen's Theory of Second Language Acquisition

Krashen's theory of second language acquisition consists of five main hypotheses:

the Acquisition-Learning hypothesis;

the Monitor hypothesis;

the Input hypothesis;

and the Affective Filter hypothesis;

the Natural Order hypothesis.

The Acquisition-Learning distinction is the most fundamental of the five hypotheses in Krashen's theory and the most widely known among linguists and language teachers. According to Krashen there are two independent systems of foreign language performance: 'the acquired system' and 'the learned system'. The 'acquired system' or ' acquisition' is the product of a subconscious process very similar to the process children undergo when they acquire their first language. It requires meaningful interaction in the target language - natural communication - in which speakers are concentrated not in the form of their utterances, but in the communicative act.

The "learned system" or " learning" is the product of formal instruction and it comprises a conscious process which results in conscious knowledge 'about' the language, for example knowledge of grammar rules. A deductive approach in a teacher-centered setting produces " learning", while an inductive approach in a student-centered setting leads to " acquisition".

According to Krashen 'learning' is less important than 'acquisition'. (See here our in-depth analysis of the Acquisition/Learning hypothesis and its implications).

The Monitor hypothesis explains the relationship between acquisition and learning and defines the influence of the latter on the former. The monitoring function is the practical result of the learned grammar. According to Krashen, the acquisition system is the utterance initiator, while the learning system performs the role of the 'monitor' or the 'editor'. The 'monitor' acts in a planning, editing and correcting function when three specific conditions are met:

The second language learner has sufficient time at their disposal.

They focus on form or think about correctness.

They know the rule.

It appears that the role of conscious learning is somewhat limited in second language performance. According to Krashen, the role of the monitor is minor, being used only to correct deviations from "normal" speech and to give speech a more 'polished' appearance.

Krashen also suggests that there is individual variation among language learners with regard to 'monitor' use. He distinguishes those learners that use the 'monitor' all the time (over-users); those learners who have not learned or who prefer not to use their conscious knowledge (under-users); and those learners that use the 'monitor' appropriately (optimal users). An evaluation of the person's psychological profile can help to determine to what group they belong. Usually extroverts are under-users, while introverts and perfectionists are over-users. Lack of self-confidence is frequently related to the over-use of the "monitor".

The Input hypothesis is Krashen's attempt to explain how the learner acquires a second language - how second language acquisition takes place. The Input hypothesis is only concerned with 'acquisition', not 'learning'. According to this hypothesis, the learner improves and progresses along the 'natural order' when he/she receives second language 'input' that is one step beyond his/her current stage of linguistic competence. For example, if a learner is at a stage 'i', then acquisition takes place when he/she is exposed to 'Comprehensible Input' that belongs to level 'i + 1'. Since not all of the learners can be at the same level of linguistic competence at the same time, Krashen suggests that natural communicative input is the key to designing a syllabus, ensuring in this way that each learner will receive some 'i + 1' input that is appropriate for his/her current stage of linguistic competence.

See here an enlightening video by Krashen about comprehensible input.
Your browser does not support the video tag.

The Affective Filter hypothesis embodies Krashen's view that a number of 'affective variables' play a facilitative, but non-causal, role in second language acquisition. These variables include: motivation, self-confidence, anxiety and personality traits. Krashen claims that learners with high motivation, self-confidence, a good self-image, a low level of anxiety and extroversion are better equipped for success in second language acquisition. Low motivation, low self-esteem, anxiety, introversion and inhibition can raise the affective filter and form a 'mental block' that prevents comprehensible input from being used for acquisition. In other words, when the filter is 'up' it impedes language acquisition. On the other hand, positive affect is necessary, but not sufficient on its own, for acquisition to take place.

Finally, the less important Natural Order hypothesis is based on research findings (Dulay & Burt, 1974; Fathman, 1975; Makino, 1980 cited in Krashen, 1987) which suggested that the acquisition of grammatical structures follows a 'natural order' which is predictable. For a given language, some grammatical structures tend to be acquired early while others late. This order seemed to be independent of the learners' age, L1 background, conditions of exposure, and although the agreement between individual acquirers was not always 100% in the studies, there were statistically significant similarities that reinforced the existence of a Natural Order of language acquisition. Krashen however points out that the implication of the natural order hypothesis is not that a language program syllabus should be based on the order found in the studies. In fact, he rejects grammatical sequencing when the goal is language acquisition.

The Role of Grammar in Krashen's View

According to Krashen, the study of the structure of the language can have general educational advantages and values that high schools and colleges may want to include in their language programs. Any benefit, however, will greatly depend on the learner being already familiar with the language. It should also be clear that analizing the language, formulating rules, setting irregularities apart, and teaching complex facts about the target language is not language teaching, but rather is "language appreciation" or linguistics, which does not lead to communicative proficiency.

The only instance in which the teaching of grammar can result in language acquisition (and proficiency) is when the students are interested in the subject and the target language is used as a medium of instruction. Very often, when this occurs, both teachers and students are convinced that the study of formal grammar is essential for second language acquisition, and the teacher is skillful enough to present explanations in the target language so that the students understand. In other words, the teacher talk meets the requirements for comprehensible input and perhaps, with the students' participation, the classroom becomes an environment suitable for acquisition. Also, the filter is low in regard to the language of explanation, as the students' conscious efforts are usually on the subject matter, on what is being talked about, and not the medium.

This is a subtle point. In effect, both teachers and students are deceiving themselves. They believe that it is the subject matter itself, the study of grammar, that is responsible for the students progress, but in reality their progress is coming from the medium and not the message. Any subject matter that held their interest would do just as well.

References

Crystal, David The Cambridge Encyclopedia of Language. Cambridge University Press, 1997.

Krashen, Stephen D. Principles and Practice in Second Language Acquisition. Prentice-Hall International, 1987.

Krashen, Stephen D. Second Language Acquisition and Second Language Learning. Prentice-Hall International, 1988.

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Schütz, Ricardo E. "Stephen Krashen's Theory of Second Language Acquisition"English Made in Brazil <https://www.sk.com.br/sk-krash-english.html>. Online.(data do acesso).

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Stephen Krashen's Theory of Second Language Acquisition

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Página inicial Portuguese version Language acquisition does not require extensive use of conscious grammatical rules, and does not require tedious drill. Acquisition requires meaningful interaction in the target language - natural communication - in which speakers are concerned not with the form of their utterances but with the messages they are conveying and understanding.

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English Language Learners / Dual Language Learners / Multicultural Education Support - Language Lizard Blog | Supporting Dual Language Learners Bringing Multiculturalism to the Classroom!

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by guest blogger Karen Nemeth EdM
Cognates are pairs of words that sound alike and have the same meaning in two different languages. They are useful first steps in learning a new language.
How Do Cognates Work?

In English we say "elephant" and in Spanish we say "elefante." English and Spanish speakers can easily make the connection between these cognates to learn and remember the animal's name. In English, we say "frog" but in Spanish we say "rana." Frog and rana are not cognates, and the lack of connection means learners will find those words harder to use and remember. We know that people need to use their new language to really learn it. Cognates make it possible for language learners at any age to use their new words right away. By starting with the cognate words, a learner can build their vocabulary and gain the confidence to add more words in their new language.

Find Cognates in Your Target Language

Spanish and English share hundreds of cognates and have borrowed from each other for centuries. There are also many cognates that connect German to English, such as "mouse" and "maus". Other languages, like Chinese and Arabic, have fewer cognates with English words. Lists of cognate words in different languages can be found online. I created a resource for Spanish-English cognates in preschool and kindergarten called . Language Castle Cognate Guide. It has user-friendly lists of simple cognates in the different educational domains to support early learning. Other cognate resources can be found at colorincolorado.org Bilingual children's books, or matching books in two or more languages, can also be great resources to find vocabulary connections.

Learning Activities Using Cognates

Research shows that teachers and families can help children learn a new language successfully when they use cognates to explain the meanings of words in conversations and stories. Look for examples of cognates to support the language learners you work with. Use the pairs of words to help children understand the characters, stories and facts in books. Plan activities around the cognates you have found. Add cognates to familiar songs. Use cognates in puppet shows or pretend play to give children more opportunities to practice and use the words. Highlight cognates on word walls or classroom dictionaries. Plan science and math lessons that use cognates to strengthen children's comprehension. Building connections through cognates is a sure path to success.

Read more about what experts are saying about the importance of using cognates to build second language learning:

August, D., Carlo, M., Dressler, C. and Snow, C. (2005) The Critical Role of Vocabulary Development for English Language Learners. Learning Disabilities Research & Practice, 20: 50-57

Collins, M.F. (2010) ELL preschoolers' English vocabulary acquisition from storybook reading, Early Childhood Research Quarterly, 25(1), 84-97

Gillanders, C. & Castro, D.C. (2011) Storybook reading for young dual language learners, Young Children, January 2011, 91-95

Lugo-Neris, M.J., Jackson, C.W., Goldstein, H (2008) Facilitating Vocabulary Acquisition of Young English Language Learners, Language, Speech, and Hearing Services in Schools, 41, 314-327

Pérez, A.M., Peña, E.D., & Bedore, L.M. (2010) Cognates facilitate young Spanish-English bilinguals' test performance, Early Childhood Services, 4(1), 55-67

Wallace, Christopher, (2007) Vocabulary: The Key to Teaching English Language Learners to Read, Reading Improvement, 44.4 , 189-193
Be sure to check out languagecastle.com, Karen Nemeth's website that offers a wealth of resources for anyone who teaches young children who speak different languages.
This blog post is linked with the monthly Creative Kids Culture Blog Hop. Be sure to check out other bloggers' tips, teaching strategies, and resources!

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USING COGNATES TO SUPPORT SECOND LANGUAGE AND LITERACY LEARNING

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by guest blogger Karen Nemeth EdM Cognates are pairs of words that sound alike and have the same meaning in two different languages. They are useful first steps in learning a new language. How Do Cognates Work? In English we say "elephant" and in Spanish we say "elefante."

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Total Physical Response (TPR) is a method of teaching language or vocabulary concepts by using physical movement to react to verbal input. The process mimics the way that infants learn their first language, and it reduces student inhibitions and lowers stress.

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Brain Hack: 6 secrets to learning faster, backed by neuroscience | Lila Landowski | TEDxHobart

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White matter, the insulation around our neural wiring, plays a critical role in acquiring knowledge

By R. Douglas Fields

Our concepts of how the two and a half pounds of flabby flesh between our ears accomplish learning date to Ivan Pavlov's classic experiments, where he found that dogs could learn to salivate at the sound of a bell. In 1949 psychologist Donald Hebb adapted Pavlov's "associative learning rule" to explain how brain cells might acquire knowledge. Hebb proposed that when two neurons fire together, sending off impulses simultaneously, the connections between them-the synapses-grow stronger. When this happens, learning has taken place. In the dogs' case, it would mean the brain now knows that the sound of a bell is followed immediately by the presence of food. This idea gave rise to an oft-quoted axiom: "Synapses that fire together wire together."

The theory proved sound, and the molecular details of how synapses change during learning have been described in depth. But not everything we remember results from reward or punishment, and in fact, most experiences are forgotten. Even when synapses do fire together, they sometimes do not wire together. What we retain depends on our emotional response to an experience, how novel it is, where and when the event occurred and our level of attention and motivation during the event, and we process these thoughts and feelings while asleep. A narrow focus on the synapse has given us a mere stick-figure conception of how learning and the memories it engenders work.

It turns out that strengthening a synapse cannot produce a memory on its own, except for the most elementary reflexes in simple circuits. Vast changes throughout the expanse of the brain are necessary to create a coherent memory. Whether you are recalling last night's conversation with dinner guests or using an acquired skill such as riding a bike, the activity of millions of neurons in many different regions of your brain must become linked to produce a coherent memory that interweaves emotions, sights, sounds, smells, event sequences and other stored experiences. Because learning encompasses so many elements of our experiences, it must incorporate different cellular mechanisms beyond the changes that occur in synapses. This recognition has led to a search for new ways to understand how information is transmitted, processed and stored in the brain to bring about learning. In the past 10 years neuroscientists have come to realize that the iconic "gray matter" that makes up the brain's outer surface-familiar from graphic illustrations found everywhere from textbooks to children's cartoons-is not the only part of the organ involved in the inscription of a permanent record of facts and events for later recall and replay. It turns out that areas below the deeply folded, gray-colored surface also play a pivotal role in learning. In just the past few years a series of studies from my laboratory and others has elucidated these processes, which could point to new ways of treating psychiatric and developmental disorders that occur when learning impairments arise.

If synaptic changes alone do not suffice, what does happen inside your brain when you learn something new? Magnetic resonance imaging methods now enable researchers to see through a person's skull and examine the brain's structure. In scrutinizing MRI scans, investigators began to notice differences in the brain structure of individuals with specific highly developed skills. Musicians, for example, have thicker regions of auditory cortex than nonmusicians. At first, researchers presumed that these subtle differences must have predisposed clarinetists and pianists to excel at their given skills. But subsequent research found that learning changes the structure of the brain.

The kind of learning that leads to alterations in brain tissue is not limited to repetitive sensorimotor skills such as playing a musical instrument. Neuroscientist Bogdan Draganski, currently at the University of Lausanne in Switzerland, and his colleagues witnessed increases in the volume of gray matter in medical students' brains after they studied for an examination. Many different cellular changes could expand gray matter volume, including the birth of new neurons and of nonneuronal cells called glia. Vascular changes and the sprouting and pruning of axons and dendrites that extend from the main body of a neuron could also do the same. Remarkably, physical changes in the brain can happen much faster during learning than might be expected. Yaniv Assaf of Tel Aviv University and his colleagues showed that 16 laps around a race track in a computerized video game were enough to cause changes in new players' hippocampal brain region. Structural alterations in the hippocampus in these gamers make sense because this brain region is critical for spatial learning for navigation. In other studies, Assaf and, separately, Heidi Johansen-Berg of the University of Oxford were surprised to find changes in unexpected parts of the brain, including regions that have no neurons or synapses-areas known as white matter.

Deep Learning

Consciousness arises from the cerebral cortex, the three-millimeter-thick outer layer of the human brain, so this gray matter layer is where most researchers expected to find learning-induced modifications. But below the surface layer, billions of tightly packed bundles of axons (nerve fibers), much like tightly wound fibers under the leather skin of a baseball, connect neurons in the gray matter into circuits.

These fiber bundles are white because the axons are coated with a fatty substance called myelin, which acts as electrical insulation and boosts the speed of transmission by 50 to 100 times. White matter injury and disease are important areas of research, but until recently little attention had been given in these investigations to a possible role of myelin in information processing and learning.

In the past 10 or so years studies have begun to find differences in white matter in brain scans of experts with a variety of skills, including people with high proficiency in reading and arithmetic. Expert golfers and trained jugglers also show differences in white matter compared with novices, and white matter volume has even been associated with IQ. If information processing and learning arise from the strengthening of synaptic connections between neurons in gray matter, why does learning affect the brain's subsurface cabling?

A possible answer began to emerge from cellular studies in my lab investigating how synapses-but also other brain areas-change during learning. The reason for looking beyond the synapse was that most of the drugs we have for treating neurological and psychological disorders work by altering synaptic transmission, and there is a pressing need for more effective agents. The present focus on synaptic transmission might cost us opportunities for better treatments for dementia, depression, schizophrenia or post-traumatic stress disorder (PTSD).

In the early 1990s my lab at the National Institutes of Health and others began to explore the possibility that glia might be able to sense information flowing through neural networks and alter it to improve performance. Experimental evidence that has accumulated since then shows that all types of glial cells respond to neural activity and can modify information transmission in the brain. One of the most surprising of these new findings involves myelin.

Myelin insulation is formed by layers of cell membrane wrapped around axons like electrical tape. In the brain and spinal cord, octopus-shaped glial cells (oligodendrocytes) do the wrapping. In the limbs and trunk, sausage-shaped glial cells (Schwann cells) perform the same task. Many oligodendrocytes grip an axon and wrap layers of myelin around it in segments, like the stacked hands of baseball players gripping a bat to determine which team bats first. The tiny gap between two myelin segments exposes a one-micron section of bare axon where ion channels that generate electrical impulses become concentrated. These spaces, known as the nodes of Ranvier, act like bioelectric repeaters to relay an electrical impulse from node to node down the axon. The speed of impulse transmission increases as more layers of myelin are wrapped around the axon, protecting it better against voltage loss. Also, as a node of Ranvier becomes squeezed more tightly by the adjoining myelin segments, an electrical impulse is initiated more rapidly because it takes less time to charge the smaller amount of nodal membrane to the voltage that triggers ion channels to open and generate an impulse.

Disorders that damage myelin, such as multiple sclerosis and Guillain-Barré syndrome, can cause serious disability because neural impulse transmission fails when the insulation is damaged. But until recently, the idea that myelin might be modified routinely by neural impulses was not widely accepted. And even if myelin structure changed, how and why would this improve performance and learning?

The explanation was hiding in plain sight. It loops back to the old maxim about neurons firing and wiring together. In any complex information or transportation network, the time of arrival at network relay points is critical-think of missing a connection because your flight arrives too late.

How, then, does the transmission speed in every link in the human brain get timed appropriately so that an impulse arrives just when needed? We know that electrical signals shuffle along at the pace of a slow walk in some axons but blaze away at the speed of a race car in others. Signals from two axons that converge on neurons that act as relay points will not arrive together unless the travel time from their input source is optimized to compensate for differences in the lengths of the two axons and the speed at which impulses travel along each link.

Because myelin is the most effective means of speeding impulse transmission, axon myelination promotes optimal information transmission through a network. If oligodendrocytes sense and respond to the information traffic flowing through neural circuits, then myelin formation and the way it adjusts impulse-transmission speed could be controlled by feedback from the axon. But how can myelinating glia detect neural impulses flowing through axons?

Signal Transmission

Over the past two decades our research and that of other labs has succeeded in identifying many neurotransmitters and other signaling molecules that convey to glia the presence of electrical activity in the axon to stimulate myelination. Our experiments have shown that when a neuron fires, neurotransmitters are released not only at synapses but also all along the axon. We found that the "tentacles" of the octopuslike oligodendrocytes probe bare sections of axons in search of neurotransmitters being released from axons firing. When a single tentacle touches an axon that is firing, it forms a "spot weld" contact, which enables communication between the axon and the oligodendrocyte. The oligodendrocyte begins to synthesize myelin at that spot and wrap it around the axon.

When we gave oligodendrocytes in cell culture the choice of myelinating electrically active axons or ones treated with botulinum toxin to prevent the release of neurotransmitters, the oligodendrocytes opted for the electrically active axons over the silent ones by a factor of eight to one. So it may be that as a person learns to play "Für Elise" on the piano, bare axons are wrapped with myelin or the volume of existing sheaths is increased in circuits that are activated repetitively during practice, which speeds information flow through brain networks. New myelin then shows up on an MRI as changes in white matter tracts in parts of the brain that are necessary for musical performance.

Several labs have verified that action potentials, signals coursing the length of axons, stimulate myelination of these exposed areas of neural wiring. In 2014 Michelle Monje's lab at Stanford University showed that optogenetic stimulation (using lasers to make neurons fire) increased myelination in the mouse brain. That same year William Richardson's lab at University College London demonstrated that when the formation of new myelin is prevented, mice are slower to learn how to run on a wheel with some of its rungs removed. In studies where they used a confocal microscope to watch myelin form in live zebra fish, researchers in David Lyons's lab at the University of Edinburgh and in Bruce Appel's lab at the University of Colorado Denver observed that when the release of small sacs containing neurotransmitters from axons is inhibited, often the first few wraps of myelin slip off, and the oligodendrocyte aborts the entire process.

In 2018, working with our colleagues, including Daisuke Kato and others from various institutions in Japan, we showed how myelin promotes learning by ensuring that various spiking electrical signals traveling along axons arrive at the same time in the motor cortex, the brain region that controls movement. Using genetically modified mice with impaired myelination that had been trained to pull a lever to receive a reward, we found that learning this task increased myelination in the motor cortex.

By using electrodes to record neural impulses, we found that action potentials were less synchronized in the motor cortices of mice with faulty myelination. We then boosted the synchronization of spike arrivals in the motor cortex by using optogenetics to make neurons fire at the appropriate time. The mice with impaired myelination then performed the learned task proficiently. Eventually less invasive forms of brain stimulation may become effective therapy to treat neurological and psychological disorders caused by disrupted myelination.

Oligodendrocyte (green) prepares to coat an axon (purple) with myelin. Credit: R. Douglas Fields National Institutes of Health and NICHD

Despite these recent advances, stimulation to increase axon myelination is not always enough to enable new learning, because we cannot synchronize the arrival of spikes at critical relay points in neural networks simply by making the impulses travel as rapidly as possible. There must also be a way to slow the speed of impulses from inputs that arrive at those points too soon.

The myelin that has already formed on axons has to be thickened or thinned in a controlled way to speed or slow signal transmission. Prior to our findings, there was no known explanation for how the myelin sheath could be thinned to slow signals, aside from disease damage. Our research revealed another type of glial cell involved in these "plastic" nervous system changes.

Surrounding the node of Ranvier is a glial cell called an astrocyte. Astrocytes have many functions, but most neuroscientists have largely ignored them because they do not communicate with other cells through electrical impulses. Surprisingly, research in the past decade has shown that astrocytes positioned close to the synapse between two neurons can regulate synaptic transmission during learning by releasing or taking up neurotransmitters there. But until fairly recently, myelin biologists tended to ignore the unique type of astrocyte that contacts an axon at a node of Ranvier.

What exactly do these so-called perinodal astrocytes do to thin the myelin sheath? Just as one would begin when remodeling a garment, these cells assist in cutting the "seams." The myelin sheath is attached to the axon by a spiral junction flanking the node of Ranvier. Under an electron microscope these junctions appear as spirals of stitches between the axon and the myelin, and the threads that form each stitch are composed of a complex of three cell adhesion molecules. Our analysis of the molecular composition of these stitch points showed that one of these molecules, neurofascin 155, has a site that can be cleaved by a specific enzyme, thrombin, to thin the myelin.

Thrombin is made by neurons, but it also can enter the brain from the vascular system. As the myelin lifts off the axon, the amount of bare axon at the node of Ranvier increases. The outer layer of myelin is attached to the axon adjacent to the perinodal astrocytes. When the myelin is detached from the axon, the outer layer withdraws into an oligodendrocyte, thinning the sheath. Both widening of the nodal gap and thinning of the myelin sheath slow the speed of impulse transmission.

We found that the enzyme's snipping of these threads that stitch myelin to the axon can be controlled by the perinodal astrocyte's release of an inhibitor of thrombin. We carried out experiments on genetically modified mice in which astrocytes released less of this thrombin inhibitor. When we looked at their neurons with an electron microscope, we could see that the myelin had thinned and that the nodal gap had increased. By using electronic amplifiers to detect neural impulses and measure their speed of transmission, we found that after the myelin thickness decreased in this way, the speed of impulse transmission in the optic nerve slowed by about 20 percent and the animals' vision declined. We were able to reverse all these changes by injecting thrombin inhibitors, which are approved for treating vascular disorders.

Our experiments support a new hypothesis: the myelin sheath's changes in thickness represent a new form of nervous system plasticity governed by the addition and subtraction of myelin. Additional layers of myelin are not added to axons as one would wrap tape around a wire, because this would tie the legs of the oligodendrocytes in knots. Instead new insulation is affixed through the construction of a new inner layer that spirals around the axon like a snake below the overlying myelin. Meanwhile the outer layer of myelin can be detached by the perinodal astrocyte to thin the sheath. The thickness of the myelin sheath is not fixed; instead it reflects a dynamic balance between the addition of layers next to the axon and removal of the outer layer under control of the astrocyte.

Brainy Waves

The optimal timing of action potentials at relay points is critical for strengthening synapses by adjusting their timing to allow them to fire together. But myelin plasticity can contribute to neural circuit function and learning in another way-by tuning the frequency of brain-wave oscillations. Not all neural activity in the brain arises from sensory inputs. Much of it takes place because of what goes on in the brain itself at both conscious and unconscious levels. This self-generated activity consists of oscillating waves of different frequencies that sweep through the brain, just as the vibration of a car engine at a certain speed will set different parts of the automobile rattling together at resonant frequencies.

These brain waves, or oscillations, are believed to be a key mechanism for coupling neurons across distant regions of the brain, which may be important for sorting and transmitting neural information. Oscillations, for example, tie together neural activity in the prefrontal cortex, which provides contextual meaning, and in the hippocampus (responsible for encoding spatial information). This oscillatory coupling enables a person to quickly recognize a familiar face at work, but it also makes it more difficult to identify the same co-worker in an unfamiliar place.

More important, the various stages of sleep, critical for storing long-term memories, can be identified by brain waves oscillating at different frequencies. Our experiences accumulated during the day are replayed during sleep and sorted for storage or deletion based on how they relate to other memories and emotions, which can mark them as potentially useful (or not) in the future. Appropriate brain-wave oscillations are believed to be pivotal in this process of memory consolidation. But the speed of impulse transmission is critical in synchronizing brain waves.

Just as two toddlers must precisely time their leg movements to drive the up-and-down motion of a teeter-totter, the transmission delays between two populations of oscillating neurons must be timed so that coupled neurons oscillate in synchrony across long distances in the brain. Myelin plasticity is important for brain waves because the proper conduction velocity is necessary to sustain oscillations that couple two regions of the brain at the same frequency.

This conclusion is based on mathematical modeling of the fundamental physics of wave propagation done by me, together with my NIH colleagues Sinisa Pajevic and Peter Basser. In 2020 a study by Patrick Steadman and his colleagues in Paul Frankland's lab at the University of Toronto provided convincing experimental support for the idea. Using genetically modified mice in which myelination could be temporarily halted, the researchers found that the ability to learn to fear an unsafe environment and to remember safe locations depends on the formation of new myelin. Moreover, they found that in this type of learning, brain-wave activity during sleep becomes coupled between the hippocampus and the prefrontal cortex. The prevention of new myelin formation also weakened connections and resulted in a type of impaired recall often found in people who have difficulty associating fear after a traumatic event with the appropriate context.

Learning and performing any complex task involves the coordinated operation of many different neurons in diverse brain regions and requires that signals proceed through large neural networks at an optimal speed. The myelin sheath is crucial for optimal transmission, but people begin to lose myelin in the cerebral cortex in their senior years. This gradual degradation is one of the reasons for cognitive slowing and the increasing difficulty of learning new things as we age.

Consider how transmission delays disrupt long-distance communication by telephone. Similarly, lags in the brain can cause cognitive difficulties and disorganized thinking in individuals with psychological disorders such as schizophrenia. Indeed, differences in brain-wave oscillations are seen in many neurological and psychiatric disorders. Alzheimer's disease, for instance, is associated with changes in white matter.

Drugs that control myelin production could provide new approaches to treating these problems. Indeed, Fei Wang and his colleagues at the Third Military Medical University in China, in collaboration with Jonah Chan of the University of California, San Francisco, reported in 2020 that the myelination-promoting drug clemastine given to mice with a gene deletion that impairs development of oligodendrocytes improved learning tested in a water maze. Because myelination is influenced by many forms of neural activity, a number of techniques-for example, cognitive training, neurofeedback and physical therapy-may be helpful in treating age-related cognitive decline and other disorders. A 2018 study of older adults by Jung-Hae Youn and his colleagues in South Korea indicated that 10 weeks of memory-training exercises increased recall. Brain imaging before and after training revealed increased integrity of white matter tracts connecting to the frontal lobe in the group of seniors who undertook the memory-training sessions.

These novel concepts have begun to change the way we think about how the brain works as a system. Myelin, long considered inert insulation on axons, is now seen as making a contribution to learning by controlling the speed at which signals travel along neural wiring. In venturing beyond the synapse, we are beginning to fill out the stick-figure skeleton of synaptic plasticity to create a fuller picture of what happens in our brain when we learn.

R. Douglas Fields is a senior investigator at the National Institutes of Health's Section on Nervous System Development and Plasticity. He is author of Electric Brain: How the New Science of Brainwaves Reads Minds, Tells Us How We Learn, and Helps Us Change for the Better (BenBella Books, 2020).

More by R. Douglas Fields

This article was originally published with the title "The Brain Learns in Unexpected Ways" in Scientific American Magazine Vol. 322 No. 3 (), p. 48
doi:10.1038/scientificamerican0320-74

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We are the first generation to develop a deep understanding of how the brain learns, works, changes, and thrives. Yet, schools have changed so little as a result of what we have learned. What if we could change that? What if we took the most promising research- and evidence- backed strategies and trained every educator-from those in training to enter schools to those who are already leading classrooms, schools, and districts? Every educator would have a toolbox of strategies informed by the best of what we know works as well as the skill and confidence to adapt them to their particular context. We teach in the classroom every day and benefit from being in a school that has, for the past 12 years, been systematically using research evidence to improve all aspects of teaching, learning, and the whole child's school experience. We can confidently say that we are exponentially better in how we design each of our classes and work with each of our students because of our own training in the science of teaching and learning.

Three Grounding Principles

In order to support the commitment to continuously train all of its faculty and administration in how the brain learns best, our school launched the Center for Transformative Teaching and Learning (CTTL) in 2011, the first Mind, Brain, and Education (MBE) research center based in a pre-collegiate school. In addition to serving its own teachers, the CTTL works with educators around the world to help translate brain research into everyday classroom and school practices. These educators often ask us: What should all teachers and leaders know about the learning brain? We start by saying that teachers should be experts in the subject areas and developmental levels of the students they teach. Further, our work with schools around the world suggests that the following three principles from Mind, Brain, and Education science are the foundation that needs to be in place before educators can translate research into everyday actions.

All Brains Are Neuroplastic

Our brains alter over time in reaction to our environment and experiences. Brains are never "set"; neurons are always being formed, connected, and pruned throughout our lives. The discovery of neuroplasticity is possibly the most important research-to-classroom instruction contribution from neuroscience. It means that all teachers must see themselves as "brain changers" and that every student, regardless of race, class, or gender, can learn through deliberate practice, scaffolded support, and positive relationships in school.

Emotion and Cognition Are Intertwined

Students bring their emotions, identities, and whole mental and physical selves to learning. For example, the emotional center of the brain, the amygdala, is part of the brain's limbic system, which also includes the hippocampus, one of the key memory centers. The limbic system is also the pathway for information to pass through to the prefrontal cortex, the brain's higher order thinking region. When students experience trauma, toxic stress, or even episodic stress, the fight, flight, or freeze response makes learning difficult to impossible. Teachers can recruit students' emotions in support of learning by first cultivating a sense of belonging in their classrooms and school. Without this emotional connection, students will be less likely to engage in challenging work or see the relevance of their learning.

Neuromyths Are Detrimental to Pedagogy

One of the barriers to creating learning environments that align with current research in Mind, Brain, and Education science is the persistence of neuromyths; for example "learning styles." Taking time to define a student's learning style, let's say as a visual learner, and designing lessons and assessments targeted to the learning style does not lead to higher achievement and can even make things worse. The idea that students fall into learning-style categories contradicts what we know about neuroplasticity and leads teachers, students, and even parents to have a fixed mindset about how students learn. Instead of falling for this neuromyth, teachers should design lessons using multiple modalities, choosing them based on what works best for the content to be taught. Students, in turn, must learn to judiciously apply learning strategies from a toolbox of options.

Bringing Mind, Brain, Education to Scale

Research suggests that increasing a teacher's understanding of the science behind how the brain learns leads to enhanced teacher efficacy and instructional variation, as well as enhanced student efficacy (Hardiman et al., 2013). And yet, in educator prep and school-based professional development, teachers and leaders are largely not required to have a foundational understanding of how the brain best learns. This lack might be the greatest irony in education. It is equivalent to going for a visit to your cardiologist and having them say "I want to make you healthier, but I have never studied the heart." In the case of too many educators, they might say, "I want to help you achieve more, but I have never studied the learning brain." Transforming the design and delivery of educator PD is essential if we are to capitalize on the benefits of neuroscience in the classroom.

Fortunately, organizations like researchED and Deans for Impact are working to bridge the gap between research and classroom practice. Turnaround for Children has "building blocks" to address the traumatic experiences that get in the way of learning for so many kids. Books like Why Students Don't Like School?, Rosenshine's Principles in Practice, and Neuroteach are written in a teacher-friendly way. The Learning Scientists and the Learning Agency are producing resources and podcasts for teacher consumption and "next day" application. MBE microcredentials are now available through Digital Promise. And with the support of the Chan Zuckerberg Initiative, the CTTL launched Neuroteach Global, a novel microlearning experience that uses the science of teaching and learning to teach the science of teaching and learning.

The Work Ahead

When we survey the teachers and leaders we work with through the Center for Transformative Teaching and Learning, only about a quarter say they have a foundational knowledge of how the brain best learns. Closing this gap by using the science of teaching and learning to teach the science of teaching and learning is thus one of the great opportunities and challenges that we face. We must be willing to transform how we traditionally deliver professional learning experiences. Research-based strategies around novelty, choice, metacognition, play, memory, cognitive load, executive function, and sleep that are being used to help elevate K-12 student achievement should also be applied to the redesign of professional learning experiences for teachers. Our students deserve better. Our adult learners deserve better. Leveraging how much more we know about the student and adult learning brain provides a pathway to help all children, and their teachers, meet their full potential in classrooms, schools, and districts throughout the world.

References

Hardiman, M., JohnBull, R. M., &amp; Rinne, L. (2013). Professional development effects on teacher efficacy: Exploring how knowledge of neuro- and cognitive sciences changes beliefs and practice. Paper presented at the American Educational Research Association Conference, San Francisco.

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Every Educator Needs to Know How the Brain Learns

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You have 0 free articles left this month. Create an account and get additional free articles. We are the first generation to develop a deep understanding of how the brain learns, works, changes, and thrives. Yet, schools have changed so little as a result of what we have learned.

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Putting Neuroscience in the Classroom: How the Brain Changes As We Learn

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The more we know about how the developing brain changes as we learn, the better we can support young learners.

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TPR = Total Physical Response According to the website http://www2.vobs.at/ludescher/total_physical_response.htm , “Total Physical Response (TPR) is a language teaching method built around the…