What is Neuroplasticity?

A dark-age of science. For four hundred years it was believed that brain anatomy was fixed. Norman Doidge M.D. in his book "The Brain that Changes Itself" puts it like this, "The common wisdom was that after childhood the brain changed only when it began the long process of decline; that when brain cells failed to develop properly, or were injured, or died, they could not be replaced. Nor could the brain ever alter its structure and find a new way to function if part of it was damaged. The theory of the unchanging brain decreed that people who were born with brain or mental limitations, or who sustained brain damage, would be limited or damaged for life." The analogy used to understand the body during that four hundred years was that of a machine. Even today people still tend to use that analogy, which leads to the idea that the brain is the processor, that the brain is hardware not software and that we speak of aspects of mind or brain as being hardwired, immutable.

Neurogenesis. While it was once thought that brain cells simply died off and no new cells were generated, it is now known that this is not the complete picture. Through the work of Joseph Altman, Michael Kaplan, Fernando Nottebohm and Elizabeth Gould, it is now known that at least one part of the brain, the hippocampus, continues to receive new cells throughout life, in a process called neurogenesis. It is now known that in the sub-ventricular part of the brain there is a reservoir of seed cells (also called stem cells) or undifferentiated cells. It is now held that these stem cells produce differentiating cells in this area in response to focused learning or dealing with totally new phenomena, which cannot be dealt with using previously learned actions. Where in fact totally new actions have to be learned. These seed cells divide and then half of them migrate to the area of the brain that is being used in the new learning. While doing this they change and differentiate into neurons of the type necessary for building up the area applied in the new learning. The old theory is dead. Although neurons cannot divide and grow like other cells in the body this is misleading. New brain cells could be formed and then could migrate to whatever area of the brain that they are needed in. This process of growth or regeneration in the brain is called neurogenesis.

It was found that novel and challenging environments would in all creatures including man stimulate the division of these stem cells and produce the required neurons. This in turn would prolong the average life of the animal and increase its brain power.

Although the work that brought neurogenesis to light happened over a period of time and includes the work of Joseph Altman, Michael Kaplan and Fernando Nottebohm, the person who brought the understanding of this concept into scientific acceptance was Elizabeth Gould. Most of her work has been done on animals specifically in the area of animal brains called the hippocampus. This area of the brain is understood to be concerned with memory which of course would require constant new neurons in forming links with the rest of the brain. The hippocampus is also the area of the brain where many stem cells in the process of changing into other cells were detected, although they appeared to have traveled there from the nearby sub-ventricular zone. All this seemed to indicate the possibility that any area of the brain might be able to accept new neurons if they could migrate that far. 

In October 1999, a study by Elizabeth Gould et. al., was published that investigated neurogenesis in the adult primate neocortex. Gould and the researchers reported that in adult macaque monkeys, new neurons are added to three neocortical association areas that are important in cognitive function: the prefrontal, inferior temporal and posterior parietal cortex. No neurons were detected in a fourth area, the striate cortex, a primary sensory area that processes visual information from the eyes. The new neurons appeared to originate in the sub-ventricular zone, where the stem cells that give rise to other cell types are located, and to migrate through the white matter to the neocortex, where they extend axons. Because these monkeys are very close genetically to humans, it is or should be now accepted that this process also probably goes on in humans. In the conclusions to her paper Gould had this to say:

"These results suggest that in the adult macaque brain, new cells originate in the svz [sub-ventricular zone] and migrate through the white matter to certain neocortical regions where they differentiate into mature neurons. At a short survival time (2 hours), BrdU-labeled cells were observed in the svz [sub-ventricular zone]. At longer survival times (1 to 3 weeks), BrdU-labeled cells that appeared to be migrating were observed in the white matter, and those with mature neuronal characteristics were found in the neocortex. In the adult rodent, the svz [sub-ventricular zone] produces new cells that migrate in the rostral migratory stream to the olfactory bulb, where they differentiate into neurons. Our results suggest that in the adult macaque, the svz [sub-ventricular zone] is the source of an additional population of new neurons that migrate through fiber tracts to neocortical regions."

Childhood, adolescence and the brain. It is now fairly well accepted that neurogenesis goes on at a fantastic rate as soon as we are born and that this gradually slows over time till we reach adulthood. In her book "Train Your Mind, Change Your Brain" Sharon Begley explains it as follows:

"... two groups of scientists, one at UCLA and one at NIH... Between the ages of ten and twelve or so, they discovered, the frontal lobes (the seat of such high level functions as judgment, emotion regulation, and self-control, organization, and planning) experience a growth spurt with grey matter proliferating almost as exuberantly as it did during gestation and infancy: the volume of grey matter increases noticeably, reflecting the formation of new connections and branches. And then, in a person's twenties, there is another reprise of neurological events of early childhood as unused synapses are eliminated so the networks that remain are more efficient. Other brain regions also remain under construction through adolescence. The parietal lobes, which assemble information that arrives from distant neighborhoods of the brain are works in progress through the mid-teens. They continue to add grey matter until age ten (in girls) or twelve (in boys), after which unused synapses are pruned as they are in early childhood. Similarly, the temporal lobes, which contain the regions responsible for language as well as emotional control, pack in grey matter until the age of sixteen and only then undergo pruning."

In terms of the number of synapses and the number of dendritic branchings does not begin to look adult until people are between twenty and twenty five.  The very interesting issue here is that we may be able to achieve some control over this process. It has been shown that this process can continue throughout the adult life of human beings, but if, and only if, we are willing to make an effort to learn new and novel things especially skills that require the use of body parts such as dance or a sport.

Depression. Depression, not surprisingly, is very much connected to this phenomenon of neurogenesis. It has been discovered that when the people or animals are in a state of depression the hippocampus area in the tends to shrink and become smaller as few new memory neurons are being constructed there. It has also been shown that this coincides with a reduction in the division of stem cells in the sub-ventricular zone. Likewise, it has been discovered that certain chemicals will increase the production of stem cells, and that they are the same ones that relieve depression. For the last 40 years, medical science has operated on the understanding that depression is caused by a lack of serotonin, a neurotransmitter that plays a role in just about everything the mind does, thinks or feels. The theory is appealingly simple: sadness is simply a shortage of chemical happiness. The typical antidepressant - like Prozac or Zoloft - works by increasing the brain’s access to serotonin. If depression is a hunger for neurotransmitter, then these little pills fill us up.

Unfortunately, the serotonergic hypothesis is mostly wrong. After all, within hours of swallowing an antidepressant, the brain is flushed with excess serotonin. Yet nothing happens; the patient is no less depressed. Weeks pass drearily by. Finally, after a month or two of this agony, the torpor begins to lift. But why the delay? If depression is simply a lack of serotonin, shouldn’t the effect of antidepressants be immediate? The paradox of the Prozac lag has been the guiding question of Dr. Ronald Duman’s career. Duman says, “Even as a graduate student, I was fascinated by how antidepressants work. I always thought that if I can just figure out their mechanism of action - and identify why there is this time-delay in their effect - then I will have had a productive career.”

In December 2000, Duman’s lab published a paper in the Journal of Neuroscience demonstrating that antidepressants increased neurogenesis in the adult rat brain. In fact, the two most effective treatments they looked at - electroconvulsive therapy and fluoxetine, the chemical name for Prozac - increased neurogenesis in the hippocampus by 75% and 50%, respectively. The time delay mentioned earlier is accounted for by the time it takes for stem cells to divide and migrate to their destination in the hippocampus in large numbers.

While these are important advances we must remember that neurogenesis is a double edged sword, the division of stem cells and their differentiation into neurons merely allows the brain to change more easily, but how it changes, depends on what is being learned.

Plasticity. Today the science of neuroscience has completely overturned the old view that brain cells do not change and we now understand that the brain far from being rigidly unchanging, is the most adaptable and changing part of the body. It has been discovered that the very fact that the brain changes accounts for learning. Scientists call this new idea brain plasticity or neuroplasticity. When Neuroscientists talk about plasticity of the brain they are not talking about polymers, they are talking about the ability of the brain to respond, adapt, and continually change i.e. that it is malleable and modifiable.

Norman Doidge became interested in the plasticity of the brain and began a series of travels to find out what had been discovered and what it means. He says, "...I met a scientist who enabled people who had been blind to see, another who had enabled the deaf to hear; I spoke with people who had strokes decades before and had been declared incurable, who were helped to recover with neuroplastic treatments; I met people whose learning disorders were cured and whose IQs were raised; I saw evidence that it is possible for eighty-year-olds to sharpen their memories to function the way they did when they were fifty-five. I saw people rewire their brains with their thoughts, to cure previously incurable obsessions and traumas." What he is saying is that he saw evidence that the brain can change itself, not if we do nothing, but if we are willing to make an effort. In what follows we will try to examine what is now known about the brain and how it learns. The evidence suggests that the positive psychologists like Martin Seligman were at least partly right and is especially supportive of the work of Carol Dweck and her work on self theories.

The brain can change itself by thought and activity. Doidge says, "The idea that the brain can change its own structure through thought and activity is, I believe, the most important alteration in our view of the brain since we first sketched out its basic anatomy and the workings of its basic component, the neuron."

The competitive nature of plasticity. Plasticity tells us a lot about learning and the brain. It turns out that the old saying of, "If you don't use it you will lose it", is truer of the brain than it is of an arm or a leg. It turns out that the 'brain maps' of the functional areas of the brain are not the rigid areas that people studying the brain previously thought. These areas, it turns out, are only similar because as human beings we tend to learn the same things the same way. In other words, the human brain is the way it is, because humans need to be able to process certain information, and various areas of the brain are specially adapted to processing various different types of information. But at the same time any area of the brain is capable of processing almost any type of information. The idea, that we use only a small part of the brain, is simply wrong. Any part of the brain that is not being used, will tend to be taken over for the processing of other information. It is no accident, that blind people have better, even remarkable, use of other senses. They have this, because the other senses tend to take over the brain real-estate that is normally used for the processing of visual input. Norman Doidge explains:

"The competitive nature of plasticity affects us all. There is an endless war of nerves going on inside each of our brains. If we stop exercising our mental skills, we do not just forget them: the brain map space for those skills is turned over to the other skills we practice instead. If you ever ask yourself, 'How often must I practice French, or guitar, or math to keep on top of it?' you are asking a question about competitive plasticity. You are asking how frequently you must practice one activity to make sure its brain map space is not lost to another." It is important to note however, that this is practice not in the sense of repetitive action but of practice in the sense of learning new and unique data and actions.  

Language, rigidity and plasticity. A second language tends to be much more difficult to learn than the first. While young children can learn their first language quite quickly, an adult who tries to learn a second language will find it difficult, it will take much longer, and it will never be as good. Norman Doidge explains:

"As we age, the more we use our native language, the more it comes to dominate our linguistic map space. Thus it is also because our brains is plastic - and because plasticity is competitive - that it is so hard to learn a new language and end the tyranny of the mother tongue." [In fact when a second language is learned it is normally processed in a brain area quite different to the linguistic area of the mother tongue.] "But why, if this is true, is it easier to learn a second language when we are young? Is there not competition then too? Not really. If two languages are learned at the same time, during the critical period, both get a foothold. Brain scans says [Michael] Merzenich, show that in a bilingual child all of the sounds of its two languages share a single large map, a library of sounds from both languages."

Changes in plasticity. Plasticity of the brain is greatest when we are young. During the period of infancy and on up into late teens the brain remains in a very plastic state, and during this time of high plasticity, there are many critical periods for learning all kinds of essential human activities. Learning to see, learning to hear, learning to use our other senses, learning to move intentionally the way we want are all very early critical periods. Learning to walk and learning to speak a native language come much later and learning to read comes much later again. Learning these things after these critical periods are finished makes them much more difficult but not impossible, especially if still within the childhood long period of plasticity.

Even after this period is over it may still be possible to learn or at least relearn these things. There is a story of a man who was blind with cataracts over his eyes from early childhood who was able to learn to see again after the cataracts had been removed although he eventually went blind again. His story was portrayed in the movie "At First Sight" staring Val Kilmer. It seems that we can learn these basic functions in later life but there are so many ifs and buts. On the other hand, plasticity does seem to decrease with age and with it the ability to learn and more especially the ability to unlearn. This process is linked to the dieing of neurons, which is with us while we are quite young and gradually increases. However, we are now fairly sure this massive decrease in plasticity is not inevitable.

Brain plasticity appears to be very much tied to the amount of learning that we do, and never disappears completely unless we allow it to. On the other, it appears that one of the reasons many tend to stop learning once they reach adulthood is because the brain has become much less plastic.  In fact, the plasticity of the brain falls during the entire period of the teenage years. Despite this, the human brain remains very plastic for nearly twenty years which is a staggering period of plasticity if compared with any other animal. After this period of plasticity, learning new things is much harder but not impossible as many people go on to learn throughout their lives.

Unlearning bad habits and plasticity. Norman Doidge continues:

"Competitive plasticity also explains why our bad habits are so difficult to break or 'unlearn'. Most of us think of the brain as a container and learning as putting something in it. When we try to break a bad habit, we think the solution is to put something new in the container. But when we learn a bad habit, it takes over a brain map, and each time we repeat it, it claims more control of that map and prevents the use of that space for 'good' habits." That is why 'unlearning' is often a lot harder than learning, and why early childhood education is so important - its best to get it right early before the 'bad habit' gets a competitive advantage.

Important. The above information is not only critical for understanding all types of learning but it is even more important to be clear about exactly what Doidge means.

In terms of actions or skills he clearly means that some activity that is repeated will become more and more fixed in one brain area for its processing. The more times an action is performed, the more variations of the action that are performed and the more complex the action is, the more of a brain area it will occupy. Likewise, the more an action is performed the more fixed in one area of the brain it will be and the larger that area will be. For instance if a person was to learn to type with two fingers it would be more difficult for them to learn to type with ten fingers than a person who started to learn ten fingers from the beginning. So what are some of the bad habits Doidge was talking about?

Well one bad habit witch affects almost all humans is that of jumping to conclusions when there is no need. When you are being chased by a tiger the first solution you come up with will be best because you have no time to come up with another. However most problems we have, do not require such instant judgment and we can afford to entertain other solutions, and to arrive at the best one. There are many bad habits humans tend to have because of our evolutionary heritage. In present day conditions these are counter productive. Perhaps the most counter productive habit humans have is to try and find the easiest way to do things the way that requires the least effort. In an environment where humans are in constant danger and are producing enormous effort most of the time, this may be effective. But with masses of leisure time and most of our work performed sitting in a chair this is not effective. Also the least effort does not always produce the best solution, which is the same as saying that the easiest solution is not the best solution. This does not dispute Occam's Razor which states that all things being equal the simplest solution is most likely to be correct. Simplest does not equal easiest. The most important thing we can learn is that doing stuff, or taking action, or effort is both pleasurable and promotes our health as human beings.   

Knowledge and the practical application of these ideas. At first glance one might be tempted to think that we need to be more careful about what we teach and only teach what is correct. In terms of this abstract knowledge Doidge is surely not asking us to teach only things that are correct, as that would be impossible with information changing as it does all the time. I believe what is implied in what he says is that information should be taught as theory (which is what it is) with all that theory implies. While clearly some information has been verified in many experiments over many years and is held by the community (scientific or otherwise) to be accepted, it is nevertheless still only theory and some part of it, or some analogy we use to understand it may be disproved at any moment. We should, therefore, commend knowledge simply as practical and useful tool to use until some better more accurate theory is produced. In doing this, we are in a sense, saying to the brain, this mapped area of the brain is not finished, we are still accepting information in this area and will continue to do so.

In terms of body parts what Doidge implies is quite simple. If you loose a limb or say a finger the area devoted to it in the brain will be invaded by the function of whatever is left nearby. In the case of a finger the closest other finger will tend to take over that area. In the case of a poor monkey who had two of his fingers sown together the areas in the brain devoted to the two fingers grew together into an undifferentiated whole.

Learning and plasticity. When we compare the brain activity of primitive peoples with modern day instruments we find that not only are they are processing different information but they are processing it in areas of the brain that people who are technologically sophisticated use to process other skills. People in highly scientific jobs are processing very different information (and are processing it differently) in the same areas of the brain than say ordinary laborers. Likewise peoples of different cultures process different information differently. It is only because these groups interbreed that our brain maps end up looking a bit similar. In her book "The Creative Brain" Nancy C. Andreasen puts it like this:

"Neuroscience adds a new dimension: it makes us aware that experiences throughout life change the brain throughout life. We are literally remaking our brains - who we are and how we think, with all our actions, reactions, perceptions, postures, and positions - every minute of the day and every day of the week and every month and year of our entire lives.

During infancy, childhood, adolescence, young adulthood, middle age, and  late life we all accumulate a trove of experiences and memories. These shape our minds and brains, and mightily so. We literally become what we have seen, heard, smelled, touched, done, read, and remembered. Some of us have smelled cookies freshly baking and have tuned our brains to be to feel both soothed and hungry at the sent.

Those of us that grew up in 'radio days' have different memories and probably different auditory and imaging skills, from those of us exposed to the graphic visual images that flicker across a television screen. Those of us that grew up doing arithmetic 'in our heads' in the pre-calculator and pre-computer era may have greater skills at doing various mental manipulations, yet we watch in awe and even envy as five-year-olds swiftly navigate their way through icon-driven menus on any one of the myriad handheld or desktop computerized devices that currently surround us. Differences in the environment to which their brains have been exposed have produced very different brains from a those of a sixty-year-old."

Culture and the brain. Norman Doidge in his book "The Brain that Changes Itself" points out much the same thing, except to make clear that all these activities mental or physical that affect the development of the brain are not just a consequence of the environment, but are the work of culture. He says:

"Neuroplastic research has shown us that every sustained activity ever mapped - including physical activities, sensory activities, learning, thinking and imagining - changes the brain as well as the mind. Cultural ideas and activities are no exception. Our brains are modified by the cultural activities we do - be they reading, studying music, or learning new languages. We all have what might be called a culturally modified brain, and as cultures evolve, they continually lead to new changes in the brain As Merzenich puts it, 'Our brains are vastly different in fine detail from the brains of our ancestors...In each stage of cultural development...the average human had to learn complex new skills and abilities that all involve massive brain change...Each one of us can actually learn an incredibly elaborate set of ancestrally developed skills and abilities in our lifetimes, in a sense generating a re-creation of this history of cultural evolution via brain plasticity.' So a neuroplastically informed view of culture and the brain implies a two way street: the brain and genetics produce culture, but culture also shapes the brain."

Doidge points out for instance, that musicians tend to build very large brain map areas concerned with whatever is involved with the playing of their instrument. Playing a violin might involve building a large area that is concerned with movements of the person's right hand. A study of London taxi drivers reveals that the longer they have been building up a map of London in their heads the larger their hippocampus tended to be. The hippocampus is the part of the brain that normally deals with spatial relationships and memory. Also, we should be aware that changes in our circumstances can quickly cause the brain to adapt to those circumstances. For instance people who for the sake of an experiment wear prism inversion glasses, which turn the world upside down, after a short while are able to see the world the right way up. The wiring in the brain changes and flips the information so they see the world the right way up.

This is all very interesting but the work with brain injured people had shown that if one area of the brain was damaged another area could be used to compensate. People were starting to wonder if the brain maps that had been drawn up were truly wedded to the functions they usually performed. For instance does the visual experience arise out of intrinsic properties of the tissue in the visual cortex or is it instructed by the eyes to become the visual processor?

An eye for an ear. Helen Neville was one of those asking this question and she decided to do something about it. "What if," she wondered, "the kind of input a brain receives matters...and matters as much as the instructions it receives from the genes? ...What if, instead, environmental inputs and thus experiences a person has, shape the development and specialization of the brain's regions and circuits?" In 1983 Neville began a series of experiments on deaf people using fMRI scans to monitor brain activity in deaf people.

People deaf from birth or early childhood were compared with people who had normal hearing. The subjects were told to look straight ahead and were subjected to flashes of light at the side of their heads. The response to he flashes proved to be 2  or 3 times as great for deaf people as for normal people. More interesting, however, was the fact that, although normal people registered the flashes in their visual cortex, the deaf people registered the flashes in the area of their auditory cortex. Further experiment reveled that while color and shape information was being processed in the visual cortex of the deaf people, information about location and movement was being diverted to the auditory cortex for processing, where it was being processed considerably better than for people with hearing.

Peripheral vision in deaf people was not only far better, more accurate and sensitive, but was being processed in the part of the brain that would normally be used for hearing. Instead of the auditory cortex withering away through disuse it was being used for something else. It seems the that in deaf people the brain compensates for the lack of hearing by tinkering with the circuits that handle particular aspects of vision namely peripheral vision and object change of place or motion.    

An ear for an eye. Blind people are supposed in folk-law to have magically superior abilities with their other senses but science had found little evidence of this. Helen Neville set off to see if she could find evidence of this based on what she had learned about the deaf. It occurred to her that there may be an equivalent of peripheral vision a kind of peripheral hearing. In an experiment where speakers had been placed in four different locations it was found that both sighted and unsighted people could register changes in tone in the speaker directly in front of them.

But although all had difficulty registering sound at the periphery or the side the blind people were considerably better at it. They were faster at detecting the changes in tone and the brain activity associated with this was more easily returned to a rested, ready state. In sighted people the response to peripheral sound was in the auditory cortex as you would expect. But in blind people, the response occurred in the visual cortex. The sharper and more directional hearing was being processed in the part of the blind people's minds that had been thought to be reserved for processing vision.    

Reading with a finger. Brail is a code in which any language may be written. Each cipher is composed of two columns of 3 possible raised dots allowing for 63 possible variations. They are small. Each dot is only 2.29 millimeters apart. An ordinary person can brush his fingers over brail and understand only that there are some raised dots there. With help from a local association for the blind Pascual-Leone found a group of brail experts willing to volunteer for his research.

Pascual-Leone's initial finding was that the brain map of the blind readers fingers was very different to a normal group of people who were also studied. The thumb and the middle finger got crowded out of their usual place in the somatosensory cortex. The somatosensory cortex was not, it turned out, that strongly wedded to how it represents the body. The brail reading finger (index finger) region in the brail reader's brains was, however, much expanded to fill the space left by their thumbs and middle fingers. Their brains had expanded this region in response to the demands of learning brail.

Norihiro Sadato a Japanese scientist working in Maryland was endeavoring to build on Pascual-Leone's findings decided to use PET (Positron Emission Tomography) to look at the brains of brail readers while they were reading brail. What he found was most unexpected. He found that the visual cortex was activated when the brail readers were reading brail. The finding was confirmed by using fMRI. Then a process was used to temporally disable the visual cortex in the brail readers to see if it interfered with their reading. It did. They could still feel the dots like a normal sighted person but they could no longer understand what the brail was saying. They had temporally lost the ability to process the dots into language.

People who have been blind from birth or early childhood understand brail with their visual cortex. The neurons that process visual images into sight in sighted people find a use in reading the raised dots of brail. Indeed a woman who had been blind from an early age and who had become proficient at reading brail suffered a stroke in her visual cortex and could no longer read brail.    

Recalling and language. Amir Amedi started working with plasticity while he was still a student at Hebrew University in Jerusalem. He conducted a number of experiments on blind volunteers. When he began to test verbal memory it produced a surprise. The blind people were asked to read from a brail document a list of words and their visual cortex lit up as expected. But when asked to recall as many of the words as they could their visual cortex's lit up again. This showed that the brain not only had altered the place for processing sensory input signals but had reshaped the brain in the processing the sophisticated cognitive function of recall. Also the memory of the blind people appeared to be far better than a group of sighted controls who read the same list of words normally. To make sure that the lit up area was doing the work in the visual cortex Amedi temporarily knocked out the visual cortex's of the subjects with magnetic stimulation. The sighted people were able to perform verbal activities normally but the blind people were no longer able to perform verbal operations.  

The blind artist. Esref Armagan was blind from birth, color and perspective are properties he has learned from what others have told him. He never learned brail but he paints pictures of recognizable objects in vibrant colors and uses 3 point perspective. He is a professional artist painting the sort of images one would expect are only possible with vision.

When scientists analyzed the fMRI scans of Armagan when he was painting and drawing they were surprised to find that his visual cortex was lit up. Not only that, but when he was visualizing something before he went to work, his visual cortex lit up in a way indistinguishable from how it would look when normal people were seeing something. In sighted people visualization produces similar activity in the visual cortex but the activity is much quieter than when seeing something. 

Learning redefined. With this new neuroscience knowledge we can redefine learning as the act of eternally recreating the brain. We even have some idea as to how this learning (knowledge) is stored in the brain thanks to neuroscience. The current theory is that new knowledge is initially stored by strengthening existing synapses which allow one part of the brain to connect to another part of the brain. This is said to be short term memory. If lots of these connections are involved the brain activates various chemicals in the brain that cause new (connections) synapses to form and grow along with other connecting brain elements to become separate unique storage bundles. Thus short term memory becomes long term memory. In her book "The Creative Brain" Nancy C. Andreasen continues:

"In this particular case, when the neuron is stimulated to a sufficient degree to create a memory that needs to be preserved, a variety of chemical messages are sent to the cell nucleus, where in turn genes are expressed and send messages back out to the synapse that say: 'build more synapses and create new synaptic connections so that you can keep this information for a long time."

Totally new unique memories, especially those involving new skills, it is thought likely, may require the formation of totally new neurons, which are known to form in the hippocampus and connect to various parts of the cortex of the brain. Memory may even require the formation of new neurons in the outer neocortical layers as would be consistent with the recent work of Elizabeth Gould.

Are the learning associationists correct? The idea of association is discussed elsewhere in this site and is the backbone of the behaviorist ideas. The answer to the question at the beginning of this paragraph is yes and no. Yes, pleasure can be bonded with almost any activity. But this is only really effective when the brain is in a special state.

Falling in love and pleasure. The pleasure centers are part of the brain's reward system. Found in the part of the limbic system called the septal region, the pleasure centers do not really provide pleasure when they fire. The pleasure centers rather enable any sort of external input to be experienced as pleasure. Drugs like cocaine have the effect of making any sort of action or sensory input pleasurable because it lowers the threshold at which our pleasure centers fire. Similarly falling in love or maybe bonding with a child can cause the threshold to be lowered and the pleasure centers to fire.

Pleasure, associations and firing together. When the threshold is lowered a person enters an enthusiastic and optimistic state, where anticipation of gaining his desire is high. This state has been shown to occur in controlled tests when a person takes cocaine, when a person is becoming manic, and when a person is in love. During this state people are sensitive to anything that might give pleasure such as flowers, a thoughtful gesture or fresh air. This is called 'Globalization'. Globalization not only allows us to feel pleasure more intensely but also makes it harder for us to experience pain or be unhappy. Globalization also creates an opportunity for us to develop tastes in what we find attractive. An unattractive pock mark on a girls face can suddenly become a beauty spot. Doidge explains it as follows, "Neurons that fire together wire together, and feeling such pleasure in the presence of this normally unappealing pockmark causes it to get wired into the brain as a source of delight." This explains how associations can build but only at times when this threshold has been lowered in some manner.

Learned nonuse and the use of plasticity in treating disabilities. The idea of learned nonuse comes from the work of Edward Taub. Taub although originally a behaviorist has done most to show scientifically that action is initiated in the brain and is not just a reflex. This arose out of an experiment by Sherrington where the sensory nerves in a monkey's arm was cut before it reached the brain. The monkey who had this done simply stopped moving their arm. From this it was theorized that movement must entail sensory input to initialize activity. Later the behaviorists generalized this to all activity. Initially Taub tried to duplicate the experiment that originally gave rise to the idea that all activity is reflexes. The following is from "The Brain that Changes Itself" by Norman Doidge:

"Taub working with a neurosurgeon, A. J. Berman, wanted to see if he could replicate Sherrington's experiment on a number of monkeys, and he expected to get Sherrington's result. Going a step further than Sherrington he decided not only to deafferent one of the monkey's arms but to put the monkey's good arm in a sling to restrain it. It had occurred to Taub that the monkeys might not be using their deafferented arms because they could use their good ones more easily. Putting the good one in a sling might force a monkey to use a deafferented arm to feed itself and move around. It worked. The monkeys, unable to use their good arms, started using their deafferented arms."

Taub realized that his finding had major implications, if the monkeys could move their arms without feeling. All his teachers were wrong. This really overthrew the behaviorist ideas and caused Taub some trepidation, but with some encouragement by a mentor he eventually arrived at his theory of nonuse. Taub supposed that people were unable to use parts of their bodies simply because they stopped trying and were able to continue with their normal activities some other way. Taub believed the reason movement was so difficult was not just muscle atrophy, but brain atrophy, where the area of the brain devoted to the limb was taken over by other functions.

Taub reasoned, as in his experiment, he might be able to get people who had lost the use of their limbs to regain use of them. The first thing he tried was to put the good arm of a stroke victim in a sling as in the experiment. This worked very well and he was soon getting very good results with useless arms. He realized that this should be applicable to any kind failure in the brain if only he could figure out how to stop the person coping some other way. This therapy is called constraint-induced therapy or CI.

In his early work with monkeys Taub had tried behaviorist conditioning and discovered it was ineffective but found another technique called 'shaping' to be very effective. Shaping differed in that a deafferented animal would get a reward not only for successfully reaching for food but making the first, most modest gesture toward it. Doidge continues, "Taub has discovered a number of training principles:

training is more effective if the skill closely relates to everyday life;

training should be done in increments;

and work should be concentrated into a short time, a technique Taub calls 'massed practice' which he found more effective than long term but less frequent training.

Many of the same principles are used in 'immersion' learning of a foreign language. How many of us have taken language courses over years and not learned as much as when we went to the country and immersed ourselves in the language for a far shorter period of time."

Taub's work has been effective in dealing with stroke victims who have not moved their limb for ten and more years, it has been effective in dealing with children who had suffered from cerebral palsy, and it has been effective in helping brain injured people.

The use of plasticity in treating OCD. If we add up figures all day long, if we count items all day long, we must expect some consequences, such as the almost automatic counting of any objects you come in contact with. Not stepping on the cracks in the pavement, which starts off as a child's game, can often become part of an obsessive compulsive's disorder, as are things that are religiously drummed into us like cleanliness. What is neuroscience saying about this? It is saying that when we do something that involves the new, the novel, and requires learning the area of the brain allocated to that activity grows and become more healthy. If however, we use that area of the brain less the area shrinks. But if we use the area in a repetitive manner, doing the same things over and over, we tend to create a closed circuit in the brain which repeats as a kind of reflex. This repetitiveness can get lose from voluntary control. When these repetitions occur involuntarily they are called obsessive compulsive.

The work of Jeffrey M. Schwartz was with OCD (Obsessive Compulsive Disorder). Using knowledge gained from neuroscience about plasticity Schwartz developed a successful treatment for Obsessive Compulsive Disorder. Standard treatment for OCD was that of desensitization or cognitive self confrontation and logic. Schwartz's take was quite different. He first advised sufferers to recognize that the content of the obsession was irrelevant. If they were obsessional about germs, he advised them to think, "yes I have a serious problem" but it is not a problem of germs it is rather an episode of OCD.

The second part of the treatment, was for the sufferer, as soon as an OCD episode started, to focus on something pleasant like listening to music or working on a hobby or playing a game. The idea was to shift gears, to stop going through the OCD ritual and do something else instead. Like everything in the brain he theorized, the more you do it the more it becomes entrenched. Doidge explains about compulsions. "With obsessions and compulsions, the more you do it, the more you want to do it; the less you do it, the less you want to do it....it is not what you feel while applying the technique that counts, it is what you do." The other techniques actually induce OCD episodes in order to deal with them. But this is counter productive as they increases the number of OCD episodes. The idea with Schwartz's technique was to lower the number of episodes. This follows from two key bits of knowledge about plasticity:

"Neurons that fire together wire together."

"Neurons that fire apart wire apart."

Doidge gave a very good bit of advice to a friend who was having trouble leaving the house because she kept rechecking whether she had turned things off and locked the door. This is a well known symptom of OCD, but it is something perhaps most people do to some extent. Here is Doidge's advice. "...often we check and recheck appliances without really concentrating. I suggest you check once, and once only, with the utmost care."

The plastic paradox. The plastic paradox is considered by Doidge to be the most important conclusion of his book and it is as follows: The same neuroplastic properties that allow us to change our brains and produce flexible behavior can also allow us to produce more ridged ones. Doidge continues; "All people start out with plastic potential. Some of us develop into increasingly flexible children and stay that way throughout their adult lives. For others of us the spontaneity, creativity and unpredictability of childhood gives way to a routinized existence that repeats the same behavior and turns us into rigid caricatures of ourselves. Anything that involves unvaried repetition - our careers, cultural activities, skills and neuroses - can lead to rigidity. Indeed, it is because we have a neuroplastic brain that we can develop these rigid behaviors in the first place. As Pascual-Leone's metaphor illustrates, neuroplasticity is like pliable snow on a hill. When we go down the hill on a sled, we can be flexible because we have the option of taking different paths through the soft snow each time. But should we choose the same path the second time or the third time, tracks will start to develop, and soon we will get stuck in a rut. - our route will now be quite rigid as neural circuits, once established, tend to become self-sustaining."

Please note how this tends to explain the work of Carol Dweck on mindsets. It is easy to see people who believe that things are unchanging and can't be changed, are ridged caricatures and people who believe that things can be changed by effort have flexible brains.

It is not surprising that our brains have developed in a way that provides more and more brain area for abilities that we use all the time. It is also not surprising that we convert brain area not in use to become available for frequently used functions. However, this enables the possibility that skills, thoughts, routine etc. can become more and more entrenched till we can no longer change them, and our ability to modify our own model of reality becomes atrophied. The thing is, skills, no matter how good, can always be improved. We need new things to occupy our minds, we need to continue learning and to think new thoughts. There is no need for a routine. Doing things the same way all the time may seem easier, but the brain and the body, for that matter, are not constructed to be always in harmony. They are constructed to replace old information with new information, to solve problems, to change and to grow.

Language learning where there are learning problems. The work of Michael Meizenich with the help of Paula Tallal sent research down new avenues looking for ways of overcoming mental impairments in children. They set up a company called "Fast Forward" for the purpose of teaching children, and then adults, skills that could not be helped by restraint of the body as in Taub's work. They were interested in the learning or relearning of language. The idea was to set up ways of exercising those areas of the brain concerned with language function. In the case of dyslexia they conceived a theory that the problems children with certain words might be the result of being unable to distinguish certain sounds. Very short sounds like 'd', 'p', & 'b' they conjectured might be difficult to distinguish from each other because the brain is dealing with such a small amount of information for such a short time. If the brain had not built up structures for processing this when they were very young it might be very difficult later on.

The scientific team approached this problem with special computer software that could slow down just these particular sounds. The phonemes still sounded like spoken English, but stretched out the duration of 'b' before 'aaa' for example. To normal people it sounded like someone shouting under water but for the dyslexic children it was an opportunity to distinguish a group of new sounds. This they did and quickly. Once a child had learned to tell the difference between b and p in the stretched version the software began shortening the sound by a couple of dozen milliseconds at a time. The software waited for the children to distinguish between each sound before progressing. The software continued to do this till the sounds reached normal speed and length. The results were remarkable. After a period of only twenty to forty hours of training all the children could distinguish the fast phonemes. They were no longer dyslexic.

The brain, learning and volition. This site has always maintained that real learning can only be truly accomplished if the person is interested in learning, and so is intentionally active in trying to learn. Neuroscience has now bought to light an indication that this may be true in terms of neurogenesis. In other words, neuroscience seems to indicate that new neurons are formed in the brain only when the organism is volitionally engaged in learning, and that the so called learning that is done under duress is not really learning at all.

Fred 'Rusty' Gage, became interested in the role of learning and exercise in promoting neurogenesis as mentioned earlier and had installed running wheels in the cages of a sample of his mice.

Gage then considered the running wheels and the fact that the rats could enter and leave the wheel at will and wondered what would happen if rats were forced to exercise. He set about placing some test mice in wheels where they were prevented from leaving the wheel, and had to run or be thrown off the back like a rag doll. The outcome was as he suspected, the rats who where forced to exercise had produced far fewer new neurons than the rats that had exercised voluntarily.

While there are other possible explanations of the decrease in neuron production such as the stress involved in not being able to escape the wheel, it seems likely that voluntary character of the action could have been a factor. If we connect this up with the idea that the voluntary exercise was a form of learning, then there is a possibility, that only voluntary learning produces easily recalled long term memory, as would be indicated by new neurons in the hippocampus connecting to the cortex.

Neural Migration. The brain seems to go through a massive reorganization as we get older. Young people seem to perform most activities and process incoming data with their temporal lobes while old people who had continued learning throughout life seemed to process the same functions in the frontal lobes and more so the more they had continued to learn. Young people also seem to use the different sides of their brains for different functions while old people seem to use both sides of the brain for a single function. As one side of the brain seems to deteriorate the other side seems to compensate for the lack. The brain seems to restructure itself in response to its own inefficiencies.

Half a brain. Just how good the brain is at compensating for its own inefficiencies was made clear by the remarkable story of Michelle Mack, who although seeming fairly normal was born with only half a brain or rather a single hemisphere. Although she had certain inabilities, she nevertheless managed to learn to speak. She learned to speak normally quite a bit later than normal children and although she learned to do almost everything more slowly than normal people she was still able to become a fully functioning person. Doidge puts it like this, "Her life is a demonstration that the whole is more than the sum of its parts and that half a brain does not make for half a mind." Although Michelle is unique in being born with a single hemisphere of brain this idea of near normalcy of children growing up with half a brain has other examples. By the mid 1980s a radical operation called hemispherectomy had become the operation of choice for children suffering with uncontrollable, life-threatening seizures. They found that, as long as the operation was performed before the child is 4 years old, the child will still learn to talk, read and write. The worst a child typically suffers from losing half a brain, is some impairment of peripheral vision and fine motor skills on one side of the body, the opposite side of the surgery.  

Four methods of compensation. Thanks to the work of Jordan Graphman, we now have some idea of how the brain manages to compensate for its own inefficiencies or damage. He was particularly interested in loss of memory and loss of understanding of words. He theorized that memory and understanding were subject to the same 'use it or lose it' rule of the brain. He figured the more we use a word (in different contexts) the more easily we would be able to access it and recognize it or understand it. The memory he theorized was probably the firing of neurons in different parts of the brain that were connected together. The meaning of a word might be mapped in one sector of the brain while the visual appearance of letters might be stored in another sector. Its sound might be mapped to yet another sector. Doidge explains it like this: "Each sector is bound together in a network, so that when we encounter a word, we can see it hear it and understand it. Neurons from each sector have to be activated at the same time - coactivated - for us to see, hear and understand at once."  Graphman also theorizes that the brain compensates in four different ways.

1. Map expansion. The boundaries of brain map areas for various functions are constantly changing. The more we use some function the more it grows and encroaches on nearby areas. Minute by minute our brain area maps are impinging on each other at their boundaries, becoming larger or smaller depending on the amount of use they are given.
2. Sensory reassignment. This is where, if one sense is blocked, as in a blind person, the area assigned to that perception, (in this case the visual cortex) is commandeered by the other senses such as touch. Brain space is never unused or empty, it is always being used for something. In this way people who have lost one sense or say a limb will find they have greater control over those remaining.
3. Compensatory masquerade. This is like the brain's redundancy system. There is often more than one way for a brain to approach a task. Some people use visual landmarks to get from place to place, while others have a good sense of direction. If one of these brain areas is lost to injury the brain can resort to the other. In this way a function that is damaged will hardly seem to be missing because another function is compensating for it so well.
4. Mirror region takeover.  To some extent the two hemispheres of the brain are duplicate areas of function. Unfortunately the brain needs to be so complex that the different sides of the brain have over time developed different functions. However, if part of one hemisphere fails, the mirror region in the opposite hemisphere adapts, taking over its mental functions as best it can. This is a kind of redundancy system that has been cooped by evolution to do ever more complex things. It still works but it can of course cause problems in whatever that part of the brain was previously being used for.

Plasticity and life long, learning. The plasticity of the brain requires us to review how we understand human potential, and brings into question whether potential exists at all in terms of talent. If potential exists, it must be able to change over time. The potential of a new born baby, cannot be the same as the same person when he or she is a fully grown adult. Our abilities may be the outcome of various influences that seek to change us. The efforts of our parents, the efforts of our extended family, the efforts of our teachers, the efforts of our community the efforts of our society and the efforts of our culture may all be involved. More importantly we are changed by our own efforts to change ourselves. Other important factors are the observation of and interaction with skilled role models. Ultimately, it can be said, that we are subject to two great forces of change. Our genes and a random environment make of us what they will, but we also make ourselves through our own efforts.

This whole process of lifelong learning, it turns out, has the amazing bonus of making people mentally healthier. What has become clear is that people who continue to learn throughout their lives are better protected against mental decline. The best thing we can do to keep our brains healthy is to keep using them as much as possible throughout our lives. We should remain learners throughout our lives, continue to try and solve problems throughout our lives, and we should immerse ourselves in new and novel sensory experiences. If we do all this there will be many benefits. We will live longer, our brains will remain healthier, and we can remain more like we were in our youth, than was ever thought possible. This is not easy to do, but that it can become easy, if we learn to love the experience of the new and novel and love learning. If children can be exposed to an optimum learning environment they may all live full productive, important and great lives. If we as a species are willing to provide our children with such an optimum environment, we may be able to solve the problems that have plagued us since our beginnings, the problems of our genetic inheritance. If we so wish, we may be able to change ourselves into something better. By making our brains better we can make ourselves better.

Science, is as yet not certain, why all this seems to be the case, but it is likely that the effort of learning new actions and memorizing material may trigger neurogenesis, or assist the brain in compensating (through neural migration) for its own breakdown or inefficiencies.