Neuroplasticity: reshaping the brain. Why is running as important as reading? Structural neuroplasticity: a developmental constant

Norman Doidge

Brain plasticity

Amazing facts about how thoughts can change the structure and function of our brain

Dedicated to Eugene A. Goldberg, M.D., who said he might be interested in such a book

“Doidge's book is a wonderful and hopeful description of the limitless capacity of the human brain to adapt… Only a few decades ago, scientists believed that the brain was immutable and 'programmed' and that most forms of brain damage were incurable. Dr. Doidge, an eminent psychiatrist and researcher, was struck by the extent to which the transformations that occurred with his patients contradicted these ideas, so he began to study a new science - neuroplasticity. He was helped by communication with scientists standing at the origins of neurology, and patients who were helped by neurorehabilitation. In his fascinating book, written in the first person, he explains that our brain has an amazing ability to change its structure and compensate for even the most severe neurological diseases.

Oliver Sachs

“In bookstores, shelves of scientific books tend to be far enough away from self-improvement sections that hard facts end up on one shelf and speculative conclusions on another. However, Norman Doidge's fascinating overview of the revolution taking place in neuroscience today narrows this gap: as the possibilities of positive thinking gain more and more confidence in scientists, the age-old distinction between the brain and consciousness begins to blur. The book contains amazing, mind-blowing material that is of great significance... not only for patients suffering from neurological diseases but for all people, not to mention human culture, knowledge and history.

The New York Times

“A bright and extremely fascinating… informative and exciting book. It brings satisfaction to both the mind and the heart. Doidge manages to clearly and understandably explain the results latest research in the field of neurology. He talks about the ordeal that befell the patients he writes about - people deprived of part of the brain from birth; people with learning disabilities; stroke survivors - with amazing tact and brilliance. The main thing that unites the best books written by experts in the field of medicine - and the work of Doidge ... - is the courageous overcoming of the narrow bridge between the body and the soul.

Chicago Tribune

“Readers are sure to be tempted to read entire sections of the book aloud and pass it on to the person it can help. Combining tales of scientific experimentation with examples of personal triumph, Doidge evokes in the reader a sense of reverence for the brain and scientists' belief in its capabilities.

The Washington Post

“Doidge tells us one after the other fascinating stories that he learned while traveling the world and interacting with eminent scientists and their patients. Each of these stories is woven into an analysis of the latest advances in brain science, presented in a simple and engaging way. It may be difficult to imagine that a work containing a lot of scientific data can be fascinating, but this book is impossible to put down.

Jeff Zimman, Posit Science Email Newsletter

“In order to explain science in a clear and accessible way, one must have an extraordinary talent. Oliver Sacks does this very well. The same can be said about recent works Stephen Jay Gould. And now we have Norman Doidge. An amazing book. Reading it does not require special knowledge of neurosurgery - it is enough to have an inquisitive mind. Doidge is the best guide to this scientific field. His style is light and unpretentious, and he is able to explain complex concepts while communicating with readers as equals. Case studies are a typical genre of psychiatric literature, and Doidge excels at it.

The theory of neuroplasticity is of great interest because it upends our understanding of the brain. It tells us that the brain is not at all a set of specialized parts, each of which has a specific place and function, but is a dynamic organ that can reprogram and rebuild itself if necessary. This vision can benefit all of us. First of all, it is extremely important for people suffering from serious diseases - stroke, cerebral palsy, schizophrenia, learning disabilities, obsessive-compulsive disorder and others - but who wouldn't want to get a few extra points on an IQ test or improve their memory? Buy this book. Your brain will thank you."

The Globe & Mail (Toronto)

“To date, this is the most accessible and versatile book on the subject.”

Michael M. Merzenich, PhD, Professor, Center for Integrative Neurosciences. Keck University of California at San Francisco

"An expertly guided journey through the ever-expanding field of neuroplasticity research."

“Norman Doidge has written an excellent book that raises and illuminates the many neuropsychiatric issues that children and adults face. In the book, each syndrome is illustrated with specific case histories that read like great stories… so it feels almost like a science detective and keeps you bored… it also manages to make it more intimate and understandable ordinary people such a mysterious area as science. The book is aimed at the educated reader - however, you don't need to have a PhD to benefit from the knowledge it offers."

Barbara Milrod, MD, Psychiatrist, Weill College of Medicine

In a previous article, we identified several areas of the brain that are key to our cognitive abilities and plotted them on a brain map. Cognitive neuroscience reached its peak in the 1990s with the invention of brain imaging devices and focused on brain mapping. Different areas of the brain are responsible for different functions.

Opponents of brain mapping jokingly call it modern phrenology. Phrenologists, those nineteenth-century charlatans, judged people's abilities by the structure and shape of the skull. Attaching decisive importance to the shape of the head and skull, they not only cultivated pseudoscience, but also poured water on the mill of racial-biological teachings of the early 20th century.

Yet the comparison with phrenology somewhat simplifies the problem. Vernon Mountcastle, one of the foremost neurologists of the 20th century, although not involved in brain imaging himself, came out in part in defense of the phrenologists 86 . In his opinion, phrenology is based on two main postulates. The first one: various functions located in different areas of the brain. And second: the functions of the brain are reflected in the shape of the skull. The second postulate is absolute nonsense, but the first postulate can be considered correct and theoretically very important.

One of the first studies to show how brain functions are localized was done by the French neurologist Paul Broca. He came across a patient who was suddenly speechless. After the death of the patient, Broca examined his brain and found bleeding - in the lower part of the frontal lobe. This part of the brain is now known as Broca's area. However, at that time, Paul Broca still believed, according to traditional ideas, that this zone is symmetrical for both hemispheres. But then, relying on the data of numerous observations, he resolutely stated that the function of speech belongs to the left hemisphere. The discovery of the motor center of speech was the first anatomical evidence for the localization of brain function.

At the beginning of the 20th century, Korbinian Brodmann, on the basis of a huge comparative anatomical material, divided the surface of the cerebral hemispheres into many more or less autonomous sections, differing from one another in cellular structure and, consequently, in functions. He made one of the first maps of the brain, dividing it into 52 regions. By the way, this map is still used today 87 .

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) techniques have provided breakthroughs in brain mapping. Based on new knowledge, scientists over time abandoned the simplistic idea that one area of ​​the brain is responsible for a specific function. On the contrary, each function corresponds to a network of areas, and the same area can be included in many different networks. But fixation on the maps remained, and one way or another, traces of static thinking appear in such a systemic description. The cards represent something unchanging. Mountains and rivers are where they are. And only recently, science has paid attention to the fact that maps can change, moreover, in the most significant way.

How brain maps are redrawn

The brain is changing - and this is not news, but an indisputable scientific fact. If, for example, a schoolboy did not learn a lesson by Wednesday, but came home and worked out, and by Thursday he already knows what seed plants are, then his brain has changed. There is nowhere else to store information (with the exception of cheat sheets). We are primarily interested in when, where and how the brain changes.

We have already said that the functional maps of the brain are redrawn when the brain is deprived of an influx of information.

If a person, for example, has lost some organ or part of the body, and the sensory area of ​​​​the brain no longer receives information from there, the surrounding areas of the brain begin to encroach on this area. If the signals from the index finger stop coming to the brain, then this area narrows accordingly. But the neighboring area, which receives signals from the middle finger, on the contrary, expands.

This is not about neurons that migrate from one area of ​​the brain to another. A large number of of new neurons dies shortly after the end of migration. AT long term about 50 percent of the remaining cells also die. It is believed that the fate of new cells depends on the nature of the connections formed by them, and their elimination serves as a mechanism for maintaining the constancy of the number of neurons.

Of course, new neurons in certain areas of the brain are possible, but there is no evidence that they will be endowed with any functions in certain areas of the cerebral cortex. Changes are primarily observed in the structure of neurons, where some small processes die off and are replaced by others. On the processes are synapses that are in contact with other neurons. Changes in processes and synapses lead, in turn, to a change in the function of neurons. If we look at the brain from above, we see that the sensory area of ​​the brain, which first received signals from the index finger, then began to receive signals from the middle finger. Thus, the map of the brain is redrawn 88 .

Perhaps, due to the same mechanisms, the visual areas of the brain in the blind are activated when reading texts typed using the Braille method. But the fact that the visual areas are activated does not necessarily indicate that the blind are using them to analyze sensory information. It is not completely clear what processes take place in these zones. Perhaps the visual areas are activated by the mechanism of unconscious visualization.

The underlying question is how different parts of the brain change. Either they are initially programmed to perform a special task, or their functions depend on the nature of the stimuli received. What factor plays a primary role in this process - heredity or environment, nature or upbringing?

A significant contribution to the study of these mechanisms was made by a scientific group of researchers from the Massachusetts Institute of Technology under the leadership of Mriganka Sur (Massachusetts, USA). Scientists made ferrets surgical operation: both optic nerves were implanted in the thalamocortical pathways leading to the auditory sensory cortex 89 . The purpose of the experiment is to find out what structural and functional changes occur in the auditory zone when visual information is transmitted to it. This led to a restructuring of the auditory region, and in its structure it began to resemble the visual one more. The function of signals has also been reoriented. It turned out that the animals, moving, used the auditory region in order to see. None of the scientists believe that only nature or only nurture is "to blame" for this, but the results of Mriganka Sur confirm the importance of sensory stimulation for the organization of the brain, which in turn emphasizes the invaluable role of the environment 90 .

Stimulation effect

The above example shows how the brain map is redrawn when structural changes occur in the body, for example, a function stops working and the brain stops receiving information from a particular organ. Another type of change is caused by additional stimulation, such as training a special function. We do not know much about the phenomenon of plasticity. The first work in this direction was carried out in the 1990s.

For example, they trained monkeys - they developed the ability to distinguish the tone of sound. Monkeys master this skill. Having heard two sounds in succession, they determine whether they are of the same key, and then press the button. The study showed that at first, when the sounds were very different from each other, the monkeys successfully coped with the test. But they almost did not distinguish sounds close in tonality. A few weeks later, after hundreds of training sessions, the monkeys began to distinguish sounds that were very similar in tone. When the scientists set out to find out which auditory neurons fired during this task, they found that after a few weeks of training, the number of neurons fired increased. That is, the area that was activated during the tests expanded after training 91 .

A similar experiment was carried out on monkeys when they practiced a certain finger movement. After several weeks of training, the motor area responsible for the movement of this finger has increased. These experiments show that the map of the brain is highly subject to change 92 .

Music and juggling

The scientists found the most significant changes in connection with the improvement of motor skills. Researchers have studied the changes that occur in the brain during prolonged exercise on musical instruments. In musicians who play bowed instruments, the area that receives sensory input from the left hand is larger than the same area in non-musicians 93 .

Sarah Bengtsson and Fredrik Ullen (Karolinska Institute, Stockholm) also found that the pathways in the white matter of the brain that carry motor signals are more developed in pianists. Moreover, the differences turned out to be the more significant the longer the musicians practiced 94 .

But when exercising musical instrument We are talking about a very long-term effect on the brain. And how do people more short workouts? In one study, the subjects trained a specific skill - they flexed their fingers in a certain sequence: middle finger- little finger - ring finger- middle finger - forefinger and so on 95 . At first they made many mistakes. Ten days later, they had already mastered this exercise and began to perform it at a good pace and almost without errors. At the same time, there was an increase in activity in the main motor cortex, that is, in the area that controls the muscles.

The scientific literature often refers to the results of experiments with jugglers (which was already mentioned in the introduction) 96 . According to these studies, the area of ​​the occipital lobe increased as early as three months after the start of training. This study also demonstrates that short-term training can lead to changes so large that they can be seen even on magnetic resonance scans, which do not give very accurate readings. However, the fact that changes cannot always be fixed also demonstrates that plasticity is a double-edged sword; passivity also affects the brain.

What is use and what is it?

Data from experiments with jugglers and musicians convince neurophysiologists and psychologists of the immutability of the trivial truth “use it or lose it” (“use it, otherwise you will lose it”). Even if we agree that changes in the brain depend on what we do, this fact should not be overestimated. We must first ask ourselves, what does “use” mean in this context? Are all types vigorous activity are equivalent? After all, no one doubts the benefits active image life, everyone knows that training and exercise are very beneficial for physical health. When a cast is put on a leg after a fracture, it is very difficult for us to return to healthy lifestyle life - immobility and gypsum atrophy our muscles. In different situations, we give a different load on the musculoskeletal system. It's one thing to go to work and spend all day in the office, and another thing to train in the gym, giving a full load on all the muscles.

How intense and how long does the mental training need to be in order for us to feel the results? After all, between classes in a fitness club and professional strength training there are big difference.

It should also be remembered that "it" does not refer to the entire brain. "it" in this case appeals to specific functions and specific areas of the brain. If we begin to train to distinguish the tonality of sounds, then changes will occur in the auditory areas, and not in the frontal or occipital lobes. Again, a parallel can be drawn with physical training. If we bend and unbend the right arm, with a heavy dumbbell, then our biceps will develop precisely right hand provided that the dumbbell is heavy enough, that the exercises are carried out regularly, and that the training lasts for several weeks. But we can't generalize that "dumbbell exercise builds muscle" or "is good for physical health." It won't be quite correct.

Bowed instrument players have an enlarged sensory area, which is responsible for signals from the left hand, and not from the right hand. Juggling exercises develop coordination of movements and visual-spatial orientation.

So, the phrase "use it or lose it" can be interpreted extremely simplistically. For example, “It is good for the brain to do this and that…”. If a certain type of activity has an effect on the brain, this does not necessarily mean that we train the brain and improve intelligence. Specific functions help specific areas develop.

In the previous chapter, we tried to explain the paradox of how the intelligence of the Stone Age copes with the flow of information. Possible explanation This phenomenon is that the brain is likely to adapt to the environment and to the demands that it puts forward. In the same chapter, we have given many examples of how the brain can adapt to the environment and change in the process of training and exercise. Plasticity can be present in both the frontal and parietal lobes, including those key areas associated with working memory capacity. So in theory, working memory can be trained. Perhaps plasticity is the result of adaptation to the particular environment in which we find ourselves. And at the same time, the phenomenon of plasticity can be used quite purposefully, developing certain functions.

So, if we want to train our brain, we will have to choose a function and an area. The ability to juggle is hardly useful in everyday life, and probably does not special meaning develop this skill. It is better to spend time on the areas responsible for general functions. We already know that certain areas in the parietal and frontal lobes are polymodal, that is, not associated with any specific sensory stimulation, but are activated during both auditory and visual tasks. Training of the polymodal area would bring more benefit than training an area responsible, for example, only for hearing. These key areas are also related to our limited working memory.

If we train and develop these areas, it would benefit our intellectual functions. But is it real? If we could influence this bottleneck area through exercises, would we achieve significant results? In what life situations do we most often fail memory?

NOTES

86 For phrenology, see Mountcastle, V. The evolution of ideas concerning the function of the neocortex’, Cerebral Cortex, 1995, 5:289-295.
87 Brodmann, K. Vergleichende Lokalisationslehre der Grosshirnrinde. Leipzig: Barth. 1909.
88 For plasticity in sensory areas, see: Kaas, J.H., Merzenich, M.M. & Killackey, N.R. The reorganization of somatosensory cortex following peripheral nerve damage in adult and developing mammals, Annual Review of Neuroscience, 1983, 6:325-356; Kaas, J.H. Plasticity of sensory and motor maps in adult mammals. Annual Review of Neuroscience. 1991, 14:137-167.
89 About transplant optic nerve see: Sharma, J., Angelucci, A. & Sur, M. Induction of visual orientation modules in auditory cortex. Nature. 2000, 404:841-847.
90 For behavioral effects, see von Melchner, L., Pallas, S.L. & Sur, M. Visual behavior mediated by retinal projections directed to the auditory pathway. Nature. 2000, 404: 871-876.
91 On training and its effect on the auditory area, see: Recanzone, G.H., Schreiner, C.E. & Merzenich, M.M. Plasticity in the frequency representation of primary auditory cortex following discrimination training in adult owl monkeys. Journal of Neuroscience. 1993.13:87-103.
92 For motor training and its effects on the cerebral cortex, see Nudo, R.J., Milliken, G.W., Jenkins, W.M., & Merzenich, M.M. Use- dependent alterations of movement representations in primary motor cortex of adult squirrel monkeys. Journal of Neuroscience. 1996.16, 785-807.
93 See a study on stringed players: Elbert, T., Pantev, C., Wienbruch, C., Rockstroh, B. & Taub, E. Increased cortical representation of the fingers of the left hand in string players. Science. 1995, 270.
94 About the study white matter for pianists see: Bengtsson, S.L., Nagy, Z., Skare, S., Forsman, L., Forssberg, H. & Ullen, F. Extensive piano practicing has regionally specific effects on white matter development. nature neuroscience. 2005.8.
95 For a functional magnetic resonance study of finger movement learning, see: Kami, A., Meyer, G., Jezzard, P., Adams, M.M., Turner, R. & Ungerleider, L.G. Functional MRI evidence for adult motor cortex plasticity during motor skill learning. Nature. 1995, 377:155-158.
96 On juggling see: Draganski, B., Gaser, C., Busch, V., Schuierer, G., Bogdahn, U. & May, A. Neuroplasticity: changes in gray matter induced by training. Nature. 2004, 427: 311-312.

Thorkel Klingberg

It is assumed that new software products are able to "build" the baby's brain to order. How can parents benefit from modern science? What happens to a child's brain when we raise it?

The discovery of the nature and extent of brain plasticity has led to a huge breakthrough in our understanding of what happens to the brain during educational process, as well as the emergence of many software products that, according to manufacturers, increase the plasticity of the brain of developing children. Many products advertise the use of the vast possibilities of brain plasticity as a key benefit; along with this, the assertion that parents, with the help of these computer programs, can make the child's brain much "smarter" than others, is certainly extremely attractive. But what is "plasticity" and what do parents really need to do in order to use this aspect of their children's brain development?

Plasticity is the brain's inherent ability to form new synapses, connections between nerve cells, and even cut new neural pathways, building and strengthening connections in such a way that learning is accelerated, and the ability to access information and apply what has been learned becomes ever stronger. and more efficient.

The scientific study of plasticity has traced the change in the architectonics of the brain and the brain's "wiring" at the moment when it is exposed to unusual, non-standard situations. In this case, the term "brain wiring" refers to the axonal interconnections between areas of the brain and the activities that these areas perform (ie, in which they specialize). Just as an architect draws a wiring diagram for your home, indicating the route that the wires will take to the stove, refrigerator, air conditioner, and so on, the researchers drew wiring diagram for the brain. As a result, they found that the cerebral cortex is not a fixed, but a substance that is continuously modified as a result of learning. It turns out that the "wires" of the cerebral cortex are constantly forming new relationships and continue to do so, based on incoming data coming from the outside world.

Let's take a look at what happens to brain plasticity when a child first learns to read. Initially, no part of the brain is specifically tuned for reading. When a child learns to read, more and more brain cells and nerve circuits become involved in the task at hand. The brain uses plasticity when a child begins to recognize words and understand what they read. The word "ball", which the child already understands, is now associated with the letters M-Z-CH. Thus, learning to read is a form of neural plasticity.

The discovery of what developing brain can "wire" the process of letter recognition, and other amazing discoveries about neuronal plasticity are often embodied in commercial products touting the benefits of enhanced "brain fitness." But the fact that a scientific experiment shows that a particular activity activates brain plasticity does not mean that that particular activity, such as the ability to distinguish letters on a computer monitor, is necessary to achieve the effect, nor does it mean that such an activity is the only means. achieve plasticity.

Letter recognition classes on the computer really activate and train the character recognition centers in the visual cortex, using the plasticity of the brain. But you will achieve the same effect if you sit down and read a book with your child. This interactive parent-child approach is called "dialogical reading" (a way of reading that allows children to become more involved in the story). But the computer screen and applications train the brain to recognize only letters, not to understand the meaning of words consisting of these letters. In contrast, dialogic reading—intuitive and interactive—naturally uses neural plasticity to build axonal connections between the letter recognition centers and the language and thought centers of the brain.

Researchers have shown that normally developing children learn to distinguish speech sounds quite effectively with or without the help of special exercises to distinguish speech sounds or computer games. These speech-to-speech games are marketed as a specialty neuroplasticity-enhancing product and were developed by leading neuroscientists. In fact, children who have never been introduced to such exercises and games successfully develop a well-organized and flexible area of ​​​​the cerebral cortex responsible for

"Brain plasticity refers to the ability nervous system change its structure and functions throughout life in response to the diversity of the environment. This term is not so easy to define, even though it is currently widely used in psychology and neuroscience. It is used to refer to changes that occur at various levels of the nervous system: in molecular structures, changes in gene expression and behavior."

Neuroplasticity allows neurons to regenerate both anatomically and functionally, as well as to create new synaptic connections. neural plasticity is the ability of the brain to repair and restructure. This adaptive potential of the nervous system allows the brain to recover from injuries and disorders, and can also reduce the effects of structural changes caused by pathologies such as multiple sclerosis, Parkinson's disease, cognitive disorder, insomnia in children, etc.

Various groups of neuroscientists and cognitive psychologists studying the processes of synaptic plasticity and neurogenesis have concluded that the CogniFit battery of cognitive clinical exercises for brain stimulation and training promotes the creation of new synapses and neural circuits that help reorganize and restore the function of the damaged area and transfer of compensatory abilities. Studies have shown that brain plasticity is activated and strengthened by this clinical exercise program. In the figure below, you can see how the neural network develops as a result of constant and appropriate cognitive stimulation.

Neural networks before workoutsNeural networks after 2 weeks cognitive stimulationNeural networks after 2 months cognitive stimulation

Synaptic plasticity

When we learn or receive new experience, the brain sets the series neural connections. These neural networks are the pathways by which neurons exchange information with each other. These paths are formed in the brain during learning and practice, as, for example, a path is formed in the mountains if a shepherd walks along it daily with his flock. Neurons communicate with each other through connections called synapses, and these communication pathways can regenerate over a lifetime. Each time we acquire new knowledge (through constant practice), communication or synaptic transmission between the neurons involved in the process is enhanced. Improved communication between neurons means that electrical signals are more efficiently transmitted throughout the new path. For example, when you try to recognize what kind of bird is singing, new connections are formed between some neurons. So, the neurons of the visual cortex determine the color of the bird, the auditory cortex - its singing, and other neurons - the name of the bird. Thus, in order to identify a bird, you need to repeatedly compare its color, voice, name. With each new attempt, when returning to the neural circuit and restoring neural transmission between the neurons involved in the process, the efficiency of synaptic transmission increases. Thus, the communication between the corresponding neurons is improved, and the process of cognition is faster each time. Synaptic plasticity is the basis of human brain plasticity.

neurogenesis

Given that synaptic plasticity is achieved by improving synapse communication between existing neurons, neurogenesis refers to the birth and reproduction of new neurons in the brain. For a long time, the idea of ​​neuronal regeneration in the adult brain was considered almost heresy. Scientists believed that nerve cells die and do not regenerate. After 1944, and especially in last years, the existence of neurogenesis has been scientifically proven, and today we know what happens when stem cells ( special kind cells located in the dentate gyrus, hippocampus, and possibly in the prefrontal cortex) are divided into two cells: a stem cell and a cell that will turn into a full-fledged neuron, with axons and dendrites. After that, new neurons migrate to different areas (including distant from each other) of the brain, where they are needed, thereby maintaining the neuronal activity of the brain. It is known that both in animals and humans, sudden neuronal death (for example, after a hemorrhage) is a powerful stimulus for triggering the process of neurogenesis.

Functional Compensatory Plasticity

The neuroscience literature has covered the topic of cognitive decline with aging and explained why older people exhibit lower cognitive performance than younger people. Surprisingly, not all older people show poor performance: some perform just as well as younger people. These unexpectedly different results in a subgroup of people of the same age were scientifically investigated, as a result of which it was found that when processing new information, older people with greater cognitive performance use the same areas of the brain as young people, as well as other areas of the brain. , which are not used by either young or other older participants in the experiment. This phenomenon of overuse of the brain by the elderly has been investigated by scientists who concluded that the use of new cognitive resources occurs as part of a compensatory strategy. As a result of aging and a decrease in synaptic plasticity, the brain, demonstrating its plasticity, begins to restructure its neurocognitive networks. Research has shown that the brain arrives at this functional decision by activating other neural pathways, more often involving areas in both hemispheres (which is usually characteristic only for younger people).

Functioning and Behavior: Learning, Experience and Environment

We have considered that plasticity is the ability of the brain to change its biological, chemical and physical characteristics. However, not only the brain is changing - the behavior and functioning of the whole organism is also changing. In recent years, we have learned that genetic or synaptic brain disorders occur as a result of both aging and exposure to a huge number of environmental factors. Especially important are discoveries about the plasticity of the brain, as well as its vulnerability as a result of various disorders. The brain learns throughout our lives - at any time and for various reasons, we acquire new knowledge. For example, children acquire new knowledge in huge quantities, which provokes significant changes in brain structures during periods of intense learning. New knowledge can also be obtained as a result of neurological trauma experienced, for example, as a result of damage or hemorrhage, when the functions of the damaged part of the brain are impaired, and you need to learn anew. There are also people with a thirst for knowledge, for which it is necessary to constantly study. In connection with huge amount circumstances under which new learning may be required, we wonder if the brain changes every time? Researchers believe this is not the case. It appears that the brain acquires new knowledge and demonstrates its potential for plasticity if the new knowledge helps improve behavior. That is, for physiological changes brain requires that learning results in behavioral change. In other words, new knowledge must be needed. For example, knowledge about another way to survive. Probably, the degree of usefulness plays a role here. In particular, they help to develop brain plasticity. interactive games. This form of learning has been shown to increase the activity of the prefrontal cortex (PFC). In addition, it is useful to play with positive reinforcement and reward, which is traditionally used in teaching children.

Conditions for the implementation of brain plasticity

When, at what point in life is the brain most susceptible to changes under the influence of environmental factors? Brain plasticity seems to be age-dependent, and there are still many discoveries to be made about the influence of the environment on it depending on the age of the subject. However, we know that the mental activity of both healthy older people and older people with a neurodegenerative disease has a positive effect on neuroplasticity. The important thing is that the brain is subject to both positive and negative changes even before a person is born. Animal studies have shown that when mothers-to-be are surrounded by positive stimuli, babies form more synapses in certain areas of the brain. Conversely, when bright light was turned on during pregnancy, which introduced them into a state of stress, the number of neurons in the prefrontal cortex (PFC) of the fetus decreased. In addition, the PFC appears to be more sensitive to environmental influences than the rest of the brain. The results of these experiments are important in the nature versus environment debate, as they demonstrate that the environment can change neuronal gene expression. How does brain plasticity evolve over time, and what is the result of environmental influences on it? This question is the most important for therapy. Conducted genetic research animals have shown that some genes change even after a short exposure, others - as a result of more prolonged exposure, while there are also genes that could not be influenced in any way, and even if it was possible, as a result, they still returned to their original state. Although the term "plasticity" of the brain carries a positive connotation, in fact, by plasticity we also mean negative changes in the brain associated with dysfunctions and disorders. Cognitive training is very helpful in stimulating positive brain plasticity. With the help of systematic exercises, you can create new neural networks and improve synaptic connections between neurons. However, as we noted earlier, the brain does not learn effectively if learning is not rewarding. Therefore, when learning, it is important to set and achieve your personal goals.

1] Definition taken from: Kolb, B., Mohamed, A., & Gibb, R., Search for factors underlying brain plasticity in normal and damaged states, Revista de Trastornos de la Comunicación (2010), doi: 10.1016/ j.jcomdis.2011.04 0.007 This section is derived from Kolb, B., Mohamed, A., & Gibb, R., Finding the Factors Underlying Brain Plasticity in Normal and Damaged Conditions, Revista de Trastornos de la Comunicación (2010 ), doi: 10.1016/j. jcomdis.2011.04.007

Doctor of Biological Sciences E. P. Kharchenko, M. N. Klimenko

plasticity levels

At the beginning of this century, brain researchers abandoned traditional ideas about the structural stability of the adult brain and the impossibility of forming new neurons in it. It became clear that the plasticity of the adult brain also uses the processes of neurogenesis to a limited extent.

When talking about the plasticity of the brain, most often they mean its ability to change under the influence of learning or damage. The mechanisms responsible for plasticity are different, and its most perfect manifestation in brain damage is regeneration. The brain is an extremely complex network of neurons that communicate with each other through special formations - synapses. Therefore, we can distinguish two levels of plasticity: macro and micro levels. The macro level is associated with a change in the network structure of the brain, which provides communication between the hemispheres and between various areas within each hemisphere. At the micro level, molecular changes occur in the neurons themselves and in the synapses. At both levels, brain plasticity can manifest itself both quickly and slowly. In this article, we will focus mainly on plasticity at the macro level and on the prospects for research on brain regeneration.

There are three simple scenarios for brain plasticity. In the first, damage to the brain itself occurs: for example, a stroke in the motor cortex, as a result of which the muscles of the trunk and limbs lose control from the cortex and become paralyzed. The second scenario is the opposite of the first: the brain is intact, but an organ or section of the nervous system on the periphery is damaged: a sensory organ - an ear or an eye, a spinal cord, a limb is amputated. And since, at the same time, information ceases to flow into the corresponding parts of the brain, these parts become “unemployed”, they are not functionally involved. In both scenarios, the brain is reorganized, trying to fill the function of damaged areas with the help of undamaged ones, or to involve "unemployed" areas in the maintenance of other functions. As for the third scenario, it is different from the first two and is associated with mental disorders caused by various factors.

A bit of anatomy

On fig. 1 shows a simplified diagram of the location on the outer cortex of the left hemisphere of the fields described and numbered in the order of their study by the German anatomist Korbinian Brodmann.

Each Brodmann field is characterized by a special composition of neurons, their location (the neurons of the cortex form layers) and connections between them. For example, the fields of the sensory cortex, in which the primary processing of information from sensory organs, differ sharply in their architecture from the primary motor cortex, which is responsible for the formation of commands for voluntary muscle movements. The primary motor cortex is dominated by neurons resembling pyramids in shape, and the sensory cortex is represented mainly by neurons whose body shape resembles grains, or granules, which is why they are called granular.

Usually the brain is divided into anterior and posterior (Fig. 1). The areas of the cortex adjacent to the primary sensory fields in the hindbrain are called associative zones. They process information coming from primary sensory fields. The further away from them the associative zone, the more it is able to integrate information from different areas of the brain. The highest integrative capacity in the hindbrain is characteristic of the associative zone in the parietal lobe (not colored in Fig. 1).

AT forebrain the premotor cortex is adjacent to the motor cortex, where additional centers for regulating movement are located. At the frontal pole there is another extensive associative zone - the prefrontal cortex. In primates, this is the most developed part of the brain, responsible for the most complex mental processes. It is in the associative zones of the frontal, parietal and temporal lobes in adult monkeys that the inclusion of new granular neurons with a short lifespan of up to two weeks was revealed. This phenomenon is explained by the participation of these zones in the processes of learning and memory.

Within each hemisphere, nearby and distant regions interact with each other, but sensory regions within a hemisphere do not communicate directly with each other. Homotopic, that is, symmetrical, regions of different hemispheres are interconnected. The hemispheres are also connected with the underlying, evolutionarily older subcortical regions of the brain.

Brain reserves

Impressive evidence of brain plasticity is provided by neurology, especially in recent years, with the advent of visual methods for studying the brain: computer, magnetic resonance and positron emission tomography, magnetoencephalography. The images of the brain obtained with their help made it possible to make sure that in some cases a person is able to work and study, to be socially and biologically complete, even having lost a very significant part of the brain.

Perhaps the most paradoxical example of brain plasticity is the case of hydrocephalus in a mathematician, which led to the loss of almost 95% of the cortex and did not affect his high intellectual abilities. The journal Science published an article on this subject with the ironic title "Do we really need a brain?".

More often, however, significant brain damage leads to profound lifelong disability- its ability to restore lost functions is not unlimited. Common causes of brain damage in adults are cerebrovascular accidents (in the most severe manifestation - stroke), less often - trauma and brain tumors, infections and intoxications. In children, cases of impaired brain development are not uncommon, associated with both genetic factors and pathology of prenatal development.

Among the factors that determine the regenerative abilities of the brain, first of all, the age of the patient should be singled out. Unlike adults, in children, after the removal of one of the hemispheres, the other hemisphere compensates for the functions of the remote one, including language. (It is well known that in adults, the loss of the functions of one of the hemispheres is accompanied by speech disorders.) Not all children compensate equally quickly and completely, but a third of children at the age of 1 year with paresis of the arms and legs get rid of violations by the age of 7 years. motor activity. Up to 90% of children with neurological disorders in the neonatal period subsequently develop normally. Therefore, the immature brain is better able to cope with damage.

The second factor is the duration of exposure to the damaging agent. A slowly growing tumor deforms the parts of the brain closest to it, but it can reach an impressive size without disturbing the functions of the brain: compensatory mechanisms have time to turn on in it. However acute disorder the same scale is most often incompatible with life.

The third factor is the location of brain damage. Small in size, the damage may affect the area of ​​dense accumulation nerve fibers going to various parts of the body, and cause a serious illness. For example, through small areas of the brain called internal capsules (there are two of them, one in each hemisphere), fibers of the so-called pyramidal tract (Fig. 2) pass from the motor neurons of the cerebral cortex, which goes to the spinal cord and transmits commands to all the muscles of the body and limbs. So, a hemorrhage in the area of ​​​​the internal capsule can lead to paralysis of the muscles of the entire half of the body.

The fourth factor is the extent of the lesion. In general, the larger the lesion, the more loss of brain function. And since the basis of the structural organization of the brain is a network of neurons, the loss of one section of the network can affect the work of other, remote sections. That is why speech disorders are often noted when brain areas are affected that are located far from specialized areas of speech, such as Broca's center (fields 44-45 in Fig. 1).

Finally, in addition to these four factors, individual variations in the anatomical and functional connections of the brain are important.

How is the cortex reorganized

We have already said that the functional specialization of different areas of the cerebral cortex is determined by their architecture. This evolutionary specialization serves as one of the barriers to the manifestation of brain plasticity. For example, if the primary motor cortex is damaged in an adult, its functions cannot be taken over by the sensory areas located next to it, but the premotor zone of the same hemisphere adjacent to it can.

In right-handed people, when Broca's center associated with speech is disturbed in the left hemisphere, not only the areas adjacent to it are activated, but also the area homotopic to Broca's center in the right hemisphere. However, such a shift of functions from one hemisphere to another does not go unnoticed: overloading the area of ​​the cortex that helps the damaged area leads to a deterioration in the performance of its own tasks. In the case described, the transfer of speech functions to the right hemisphere is accompanied by a weakening of the patient's spatial-visual attention - for example, such a person may partially ignore (not perceive) the left side of space.