How the nervous system can regenerate and change after a stroke and other serious illnesses. Ugryumov M

Until recently, scientists could not see the brain and measure its components. The nature of the brain, neatly packaged in the cranium, was hidden. Scientists who have not had the opportunity to observe how the brain functions have been trying for many centuries to create models and theories that explain its enormous potential.

old concept

The brain has been likened to a chest of drawers with many compartments, to a filing cabinet with folders that can be opened and closed, and to a supercomputer continuously performing operations on its electrical circuits. All these analogies are connected with inorganic, mechanical objects. They are non-living - and do not grow and do not change.

Most scientists considered the brain as such an object, with the exception of childhood, which was considered as the only period in a person's life when the brain is able to develop and adapt. The child absorbs signals coming from the internal and external environment; while his brain, for better or worse, adapts to it.

In the case recounted by Antonio Battro in his book Half a Brain Is Enough: The Story of Nico, doctors removed the boy's right cortex to treat his epilepsy. Despite the fact that Niko lost an important part of his brain tissue, he developed with little or no disturbance.

He developed not only the functions associated with the left hemisphere of the brain, but also musical and mathematical abilities, which are usually the responsibility of the right hemisphere of the brain. The only explanation for how the boy's brain was able to compensate for the missing functions after half of the brain tissue was removed, Battro said, is that the brain continues to develop into adulthood.

Previously, it was believed that such a deep compensation for brain disorders or injuries is possible(although it happens extremely rarely) only when the child is still growing, and when he reaches the age of puberty, the brain becomes unchanged and no external influence can affect this. No more development, no more adaptation. If the brain gets damaged at this stage, the latter is practically irreparable.

Here is an example from the field of psychology: if a child is raised by indifferent adults who do not understand his needs, his brain is formed that generates a behavior pattern that reflects a sense of hopelessness.

According to the old concept of brain development, the only chance to save such a child is careful intervention in the process of forming his brain at an early stage. Without this, the emotional fate of the child is sealed. Other physical and emotional traumas can also take their toll on a young brain.

In keeping with the "brain-as-hardware" metaphor, it was believed that the brain was destined to break down. As a result of overcoming those blows that fall on the brain in Everyday life, its components gradually fail. Or a major catastrophe can occur when large components of the brain shut down due to an accident, infection, or stroke. According to this view, the cells of the central nervous system are like fragments of an antique porcelain service; if you break one object, you will have no choice but to sweep away the fragments and be content with what is left.

No one believed that brain cells could regenerate or form new connections with each other. This disappointing neurological "fact" had serious consequences for people who have been injured or have had diseases that affect the brain.

Until about fifteen years ago, it was standard practice in rehabilitation centers to actively treat patients during the first few weeks or months after an injury, but once the swelling of the brain subsided and the improvement process ceased, it was believed that nothing more could be done. After that, rehabilitation was reduced to finding options to compensate for the violations that had arisen.

If you damaged your visual cortex (the area of ​​the brain associated with vision), you would have cortical blindness, period.

If your left hand stopped functioning, you had to come to terms with the idea that it would forever remain inactive. Rehabilitation specialists will teach you how to move around without seeing anything, or how to bring groceries into the house with just your right hand.

And if you had a difficult childhood, it was supposed to leave an indelible mark on your ability to make and maintain connections with other people.

New concept

Fortunately, this concept of brain development can be consigned to the archives of medical history, along with other obsolete ideas such as bloodletting or black bile (a fluid that Hippocrates believed causes cancer and other diseases). Brain cells do need protection, which is why I don't recommend exposing the brain to physical abuse.

However, the brain is not at all the immutable fragile object that we used to think it was. There are certain brain change rules, which can be used to solve problems, restore neural pathways C.A.R.E . and strengthening relationships with others.

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 that provides communication between the hemispheres and between different 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, 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).

In the 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?"

However, more often significant damage to the brain leads to a deep life-long 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, one should single out patient's age. 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 motor activity disorders by the age of 7. 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, an acute disturbance of the same scale is most often incompatible with life.

The third factor is the location of brain damage. Small in size, damage can affect the area of ​​​​dense accumulation of 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 pass from the motor neurons of the cerebral cortex ( fig. 2), which goes to the spinal cord and transmits commands to all muscles of the trunk 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.

Fourth factor- the extent of the lesion. In general, the larger the lesion, the more loss of brain function. And since the basis structural organization The brain makes up 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 in lesions of brain regions 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.

It is noteworthy that interhemispheric transfer of functions is possible in some cases, but not in others. Apparently, this means that the homotopic zones in both hemispheres are loaded differently. Perhaps that is why in the treatment of stroke by transcranial microelectrostimulation (we will talk about it in more detail below), speech improvement is more often observed and more successful than the restoration of motor activity of the hand.

Compensatory restoration of function, as a rule, does not occur due to any one mechanism. Almost every function of the brain is realized with the participation of its various areas, both cortical and subcortical. For example, in the regulation of motor activity, in addition to the primary motor cortex, several additional motor cortical centers are involved, which have their own connections with near and distant areas of the brain and their own pathways that go through the brainstem to the spinal cord. When the primary motor cortex is damaged, the activation of these centers improves motor functions.

In addition, the organization of the pyramidal tract itself - the longest conducting path, which consists of many millions of axons ("abductor" processes) of motor neurons of the cortex and follows the neurons of the anterior horns of the spinal cord (Fig. 2) - provides another possibility. In the medulla oblongata, the pyramidal tract splits into two bundles: thick and thin. The thick bundles cross each other, and as a result, the thick bundle of the right hemisphere in the spinal cord follows on the left, and the thick bundle of the left hemisphere, respectively, on the right. The motor neurons of the cortex of the left hemisphere innervate the muscles of the right half of the body, and vice versa. Thin beams do not intersect, they lead from the right hemisphere to the right side, from the left to the left.

In an adult, the activity of motor neurons of the cortex, the axons of which pass through thin bundles, is practically not detected. However, if, for example, the right hemisphere is damaged, when the motor activity of the muscles of the neck and trunk of the left side is disturbed, it is these motor neurons that are activated in the left hemisphere, with axons in a thin bundle. As a result, muscle activity is partially restored. It can be assumed that this mechanism is also involved in the treatment of strokes in the acute stage by transcranial microelectrostimulation.

A remarkable manifestation of brain plasticity is the reorganization of the damaged cortex even many years after the injury occurred. American researcher Edward Taub (now working at the University of Alabama) and his colleagues from Germany, Wolfgang Mitner and Thomas Elbert, proposed a simple scheme for the rehabilitation of motor activity in stroke patients. The duration of brain damage among their patients ranged from six months to 17 years. The essence of the two-week therapy was to develop the movements of the paralyzed hand using various exercises, while the healthy hand was motionless (fixed). The peculiarity of this therapy is the intensity of the load: the patients exercised for six hours daily! When the brains of patients whose motor activity of the hand was restored were examined using functional magnetic resonance imaging, it turned out that many areas of both hemispheres were involved in the performance of movements with this hand. (Normal - with an unaffected brain - if a person moves right hand, his left hemisphere is predominantly activated, and the right hemisphere is responsible for the movement of the left hand.)

The reactivation of a paralyzed hand 17 years after a stroke is an undeniably exciting achievement and a prime example of cortical reorganization. However, this achievement was realized at a high price - the complicity of a large number of areas of the cortex and, moreover, of both hemispheres.

The principle of the brain is such that at any given moment one or another area of ​​the cortex can participate in only one function. The involvement of many areas of the cortex at once in the control of hand movements limits the possibility of parallel (simultaneous) performance of different tasks by the brain. Imagine a child on a two-wheeled bicycle: he sits on a saddle, pedals with his feet, traces his route, fixes the steering wheel with his right hand and her index finger presses the bell, and holds a cookie with his left hand, biting it off. The implementation of such a simple program of quickly switching from one action to another is beyond the power of not only the affected, but also the reorganized brain. Without belittling the importance of the proposed method of rehabilitation of stroke patients, I would like to note that it cannot be perfect. The ideal option seems to be the restoration of function not due to the reorganization of the affected brain, but due to its regeneration.

Departure from the rules

Let us now turn to the second scenario: the brain is intact, but damaged peripheral organs more specifically hearing or vision. It is in this situation that people who are born blind or deaf find themselves. It has long been observed that the blind discriminate auditory information and perceive speech faster than the sighted. When people who were blind from birth (and who lost their sight in early childhood) were examined by positron emission tomography of the brain while they were reading texts typed in Braille, it turned out that when they read with their fingers, not only the somatosensory cortex responsible for tactile sensitivity is activated. but also the visual cortex. Why is this happening? After all, the visual cortex of the blind does not receive information from the visual receptors! Similar results were obtained when studying the brain of the deaf: they perceived the sign language (gestures) used by them for communication, including the auditory cortex.

Rice. 3. Operation of replanting the optic tract to the medial geniculate body of the thalamus. On the left, the normal course of the nerve pathways from the eyes and ears is shown; on the right, their location after surgery. (The nerve pathways carrying auditory information were cut off from the medial geniculate bodies and the endings of the optic nerves, separated from the lateral geniculate bodies of the thalamus, were planted in their places. The lower colliculus in the midbrain, where part of the nerve pathways from the ear to the auditory cortex (not shown in the diagram): 1 - optic tract, 2 - auditory tract, 3 - lateral geniculate bodies of the thalamus, 4 - medial geniculate bodies of the thalamus, 5 - thalamocortical pathways to the visual cortex, 6 - thalamocortical pathways to the auditory cortex.

As already noted, sensory zones are not directly connected with each other in the cortex, but interact only with associative areas. It can be assumed that the redirection of somatosensory information in the blind to the visual cortex and visual information in the deaf to the auditory occurs with the participation of subcortical structures. This redirection appears to be economical. When information is transmitted from a sensory organ to the sensory area of ​​the cortex, the signal switches several times from one neuron to another in the subcortical formations of the brain. One of these switches occurs in the thalamus (thalamus) of the diencephalon. The switching points of the nerve pathways from different sensory organs are closely adjacent (Fig. 3, left).

If any sensory organ (or the nerve pathway leading from it) is damaged, its switching point is occupied by the nerve pathways of another sensory organ. Therefore, the sensory areas of the cortex, which turned out to be cut off from the usual sources of information, are involved in the work due to the redirection of other information to them. But what happens then to the neurons of the sensory cortex themselves, which process information that is alien to them?

Researchers from Massachusetts Institute of Technology In the USA, Jitendra Sharma, Alessandra Angelucci and Mriganka Sur took ferrets at the age of one day and performed a surgical operation on the animals: they planted both optic nerves to the thalamocortical pathways leading to the auditory sensory cortex (Fig. 3). The purpose of the experiment was to find out whether the auditory cortex is transformed structurally and functionally when visual information is transmitted to it. (Recall again that each type of cortex is characterized by a specific architecture of neurons.) Indeed, this happened: the auditory cortex became morphologically and functionally similar to the visual one!

Researchers Diane Cann and Lee Krubitzer from the University of California did otherwise. Opossums had both eyes removed on the fourth day after birth, and after 8–12 months, the primary sensory areas of the cortex and the association zone adjacent to them were studied in mature animals. As expected, in all the blinded animals, the visual cortex was reorganized: it greatly decreased in size. But, to the surprise of the researchers, a structurally new area X was adjacent directly to the visual cortex. Both the visual cortex and area X contained neurons that perceived auditory, somatosensory, or both information. In the visual cortex, there remained an insignificant number of areas that did not perceive either one or the other sensory modality - that is, they retained, probably, their original purpose: the perception of visual information.

Surprisingly, the reorganization of the cortex affected not only the visual cortex, but also the somatosensory and auditory ones. In one of the animals, the somatosensory cortex contained neurons that responded to either the auditory or somatosensory or both modalities, and the auditory cortex neurons responded either to auditory signals or to auditory and somatosensory. In normal brain development, this mixing of sensory modalities occurs only in higher-order association areas, not in primary sensory areas.

The development of the brain is determined by two factors: internal - the genetic program and external - information coming from outside. Until recently, the evaluation of the influence of an external factor has been an intractable experimental problem. The studies that we have just described have made it possible to establish how important the nature of information entering the brain is for the structural and functional formation of the cortex. They deepened our understanding of brain plasticity.

Why does the brain regenerate poorly

The goal of regenerative biology and medicine is to block healing by scarring in case of damage to an organ and to identify the possibilities of reprogramming the damaged organ to restore structure and function. This task involves the restoration in the damaged organ of a state characteristic of embryogenesis, and the presence in it of the so-called stem cells capable of multiplying and differentiating into Various types cells.

In the tissues of an adult organism, cells often have a very limited ability to divide and strictly adhere to “specialization”: epithelial cells cannot turn into muscle fiber cells and vice versa. However, the data accumulated to date allow us to state with certainty that cells are renewed in almost all organs of mammals. But the update speed is different. Regeneration of blood cells and intestinal epithelium, hair and nail growth proceed at a constant pace throughout a person's life. The liver, skin or bones have a remarkable regenerative ability, and regeneration requires the participation of a large number of regulatory molecules. various origins. In other words, the homeostasis (balance) of these organs is under systemic supervision, so that their ability to regenerate is awakened every time any damage disturbs the balance.

The muscle cells of the heart are renewed, albeit slowly: it is easy to calculate that during a human life, the cellular composition of the heart is completely renewed at least once. Moreover, a line of mice was found in which the heart affected by a heart attack almost completely regenerates. What are the prospects for brain regenerative therapy?

Neurons are updated in the brain of an adult. In the olfactory bulbs of the brain and the dentate gyrus of the hippocampus, located on inner surface temporal lobe of the brain, there is a continuous renewal of neurons. Stem cells have been isolated from the brain of an adult human and have been shown under laboratory conditions to be able to differentiate into cells of other organs. As already mentioned, in the associative areas of the frontal, temporal, and parietal lobes in adult monkeys, new granular neurons with a short (about two weeks) lifespan are formed. Primates have also shown neurogenesis in a vast area covering the inner and lower surfaces of the temporal lobe of the brain. But these processes are of a limited nature - otherwise they would come into conflict with the evolutionarily formed mechanisms of the brain.

It is difficult to imagine how man and his younger brothers would exist in nature with a rapid cellular renewal of the brain. It would be impossible to keep in memory the accumulated experience, information about the world around us, the necessary skills. Moreover, the mechanisms responsible for the combinatorial manipulation of mental representations of objects and processes of the past, present or future would be impossible - everything that underlies consciousness, thinking, memory, language, etc.

Researchers agree that the limited regeneration of the adult brain cannot be explained by any one factor and therefore cannot be removed by any single impact. Today, several dozen different molecules are known that block (or induce) the regeneration of long processes of neurons - axons. Although some progress has already been made in stimulating the growth of damaged axons, the problem of regeneration of the neurons themselves is still far from being solved. However, in these days, when the complexity of the brain has ceased to frighten researchers, this problem is increasingly attracting attention. But we must not forget what was said in the previous paragraph. Recovery of a damaged brain will not mean a complete restoration of the former personality: the death of neurons is an irreparable loss of past experience and memory.

What is MES

The complexity of the mechanisms of brain regeneration gave impetus to the search for such systemic effects that would cause the movement of molecules in the neurons themselves and in their environment, transferring the brain to a new state. Synergetics - the science of collective interactions - states that a new state in a system can be created by mixing its elements. Since most molecules in living organisms carry a charge, such a perturbation in the brain could be caused by external weak pulsed currents, approaching in their characteristics to the biocurrents of the brain itself. We tried to put this idea into practice.

The decisive factor for us was the slow-wave (0.5-6 hertz) bioactivity of the brain of young children. Since the characteristics of the brain are self-consistent at each developmental stage, we hypothesized that it is this activity that maintains the ability of the child's brain to restore function. Could slow-wave micro-electrostimulation with weak currents (MES) induce similar mechanisms in an adult?

Difference in electrical resistance of cellular elements and intercellular fluid of the nervous tissue is enormous - in cells it is 10 3–10 4 times higher. Therefore, during MES, molecular shifts are more likely to occur in the intercellular fluid and on the cell surface. The scenario of changes can be as follows: small molecules in the intercellular fluid will begin to vibrate most strongly, low-molecular regulatory factors that are weakly bound to cell receptors will break away from them, ion flows from cells and into the cell will change, etc. Therefore, MES can cause immediate perturbation intercellular environment in the lesion, change pathological homeostasis and induce a transition to new functional relationships in the brain tissue. As a result, the clinical picture of the disease will quickly improve, neurodeficiency will decrease. Note that the MES procedure is harmless, painless and short: the patient is simply placed on certain areas of the head with a pair of electrodes connected to a current source.

To test the validity of our assumptions, we, in collaboration with specialists from several clinics and hospitals in St. Petersburg, selected patients with the following lesions of the central nervous system: acute stage of stroke, trigeminal neuralgia, opium withdrawal syndrome and cerebral palsy. These diseases differ in their origin and mechanisms of development, however, in each case, MES caused rapid or immediate therapeutic effects (rapid and immediate are not the same thing: an immediate effect occurs immediately after exposure or very soon).

Such impressive results give reason to believe that MES changes the functioning of the network structure of the brain through various mechanisms. As for the effects of MES that are fast and increasing from procedure to procedure in patients in the acute stage of stroke, in addition to the mechanisms discussed above, they can be associated with the restoration of neurons suppressed by intoxication, with the prevention of apoptosis - the programmed death of neurons in the affected area, as well as with activation of regeneration. The latter assumption is supported by the fact that MES accelerates the recovery of hand function after the ends of damaged peripheral nerves are surgically reconnected in it, and also by the fact that delayed therapeutic effects were observed in patients in our study.

In opium withdrawal syndrome, the third of the brain plasticity scenarios we are considering is realized. This is a mental disorder associated with repeated drug use. On the early stages violations are not yet associated with noticeable structural changes in the brain, as in cerebral palsy, but are largely due to processes occurring at the microlevel. The rapidity and multiplicity of effects of MES in this syndrome and in other mental disorders confirms our assumption that MES affects many different molecules at once.

Treatment with MES was received in total more than 300 patients, and the main criterion for evaluating the action of MES was therapeutic effects. In the future, it seems to us necessary not so much to elucidate the mechanism of MES action as to achieve maximum brain plasticity in each disease. One way or another, it would apparently be incorrect to reduce the explanation of the action of MES to some individual molecules or cellular signaling systems.

An important advantage of microelectrostimulation with weak currents is that, unlike the currently popular methods of cell and gene replacement therapy, it triggers endogenous, own mechanisms of brain plasticity. The main problem of substitution therapy is not even to accumulate the necessary mass of cells for transplantation and introduce them into the affected organ, but to ensure that the organ accepts these cells so that they can live and work in it. Up to 97% of cells transplanted into the brain die! Therefore, further study of MES in the induction of brain regeneration processes seems promising.

Conclusion

We have considered only some examples of brain plasticity associated with damage repair. Other manifestations of it are related to the development of the brain, more precisely, to the mechanisms responsible for memory, learning and other processes. Perhaps here we are waiting for new exciting discoveries. (A probable harbinger of them is neooneurogenesis in the associative zones of the frontal, parietal, and temporal lobes of adult monkeys.)

However, brain plasticity also has its downsides. Its negative effects determine many diseases of the brain (for example, diseases of growth and aging, mental disorders). Reviews of numerous brain imaging data agree that the frontal cortex is often reduced in schizophrenia. But changes in the cortex in other areas of the brain are also not uncommon. Consequently, the number of neurons and contacts between the neurons of the affected area decreases, as well as the number of its connections with other parts of the brain. Does this change the nature of the processing of information entering them and the content of the information "at the output"? Disturbances in perception, thinking, behavior and language in patients with schizophrenia allow us to answer this question in the affirmative.

We see that the mechanisms responsible for brain plasticity play an important role in its functioning: in compensation for damage and in the development of diseases, in the processes of learning and memory formation, etc. It would not be a big exaggeration to attribute plasticity to the fundamental features of the brain.

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

Chemistry and Life, 2004, N6

In cases where there is a "breakdown" of any mechanism of the brain, the process of development and learning is disrupted. "Breakdown" can occur on different levels: information input, its reception, processing, etc. may be violated. For example, damage to the inner ear with the development of hearing loss causes a decrease in the flow of sound information. This leads, on the one hand, to functional and then to structural underdevelopment of the central (cortical) section of the auditory analyzer, on the other hand, to underdevelopment of connections between the auditory cortex and the motor zone of the speech muscles, between the auditory and other analyzers. Under these conditions, phonemic hearing and the phonetic formation of speech are disturbed. Not only the speech, but also the intellectual development of the child is disturbed. As a result, the process of his training and education becomes much more difficult.

Thus, underdevelopment or violation of one of the functions leads to underdevelopment of another or even several functions. However, the brain has significant compensatory capabilities. We have already noted that the unlimited possibilities of associative connections in the nervous system, the absence of a narrow specialization of the neurons of the cerebral cortex, the formation of complex “ensembles of neurons” form the basis of the great compensatory possibilities of the cerebral cortex.

The reserves of compensatory possibilities of the brain are truly grandiose. According to modern calculations, the human brain can hold approximately 1020 units of information; this means that each of us is able to remember all the information contained in the millions of volumes of the library. Of the 15 billion cells in the brain, humans use only 4%. The potential capabilities of the brain can be judged by the extraordinary development of any function in talented people and the ability to compensate for impaired function at the expense of other functional systems. In the history of various times and peoples, it is known big number people with phenomenal memory. The great commander Alexander the Great knew by name all his soldiers, of whom there were several tens of thousands in his army. A. V. Suvorov possessed the same memory for faces. Giuseppe Mezzofanti, the chief custodian of the library in the Vatican, was striking in his phenomenal memory. He was fluent in 57 languages. Mozart had a unique musical memory. At the age of 14 in the Cathedral of St. Peter, he heard church music. The notes of this work were the secret of the papal court and were kept in the strictest confidence. The young Mozart “stole” this secret in a very simple way: when he came home, he wrote down the score from memory. When, many years later, it was possible to compare Mozart's notes with the original, there was not a single mistake in them. The artists Levitan and Aivazovsky had exceptional visual memory.

A large number of people are known who have an original ability to memorize and reproduce a long series of numbers, words, etc.

These examples clearly demonstrate the unlimited possibilities of the human brain. In the book “From Dream to Discovery”, G. Selye notes that as much mental energy is contained in the human cerebral cortex as physical energy is contained in the atomic nucleus.

Large reserve capabilities of the nervous system are used in the process of rehabilitation of persons with certain developmental disabilities. With the help of special techniques, a defectologist can compensate for impaired functions at the expense of intact ones. So, in the case of congenital deafness or hearing loss, a child can be taught visual perception oral speech, i.e. lip reading. Tactile speech can be used as a temporary substitute for oral speech. If the left temporal region is damaged, a person loses the ability to understand speech addressed to him. This ability can be gradually restored through the use of visual, tactile and other types of perception of speech components.

Thus, defectology bases its methods of work on the habilitation and rehabilitation of patients with lesions of the nervous system on the use of the enormous reserve capabilities of the brain.

“Nerve cells do not recover” - everyone knows this phrase. But not everyone knows that this is actually not true. Nature has given the brain all the possibilities for reparation. The Fleming project tells how nerve cells change their purpose, why a person needs a second hemisphere and how a stroke will be treated in the near future.

Path to change

To the question "Is it possible to restore the nervous tissue?" doctors and scientists from all over the world for a long time with one voice firmly answered "No". However, some enthusiasts did not give up hope to prove the opposite. In 1962, American professor Joseph Altman set up an experiment on the restoration of nervous tissue in a rat. In 1980, the Soviet physiologist and neuroendocrinologist Andrey Polenov discovered in amphibians neuronal stem cells in the walls of the cerebral ventricles, which begin to divide when the nervous tissue is damaged. In the 1990s, Professor Fred Gage used bromdioxyuridine, which accumulated in cells of dividing tissues, to treat brain tumors. Subsequently, traces of this drug were found throughout the cerebral cortex, which allowed him to conclude that there is neurogenesis in the human brain. Today, science has enough data to allow it to assert that the growth and renewal of the functions of nerve cells is possible.

The nervous system is designed to provide communication between the body and the outside world. From the point of view of the structure, the nervous tissue is divided into the nervous tissue proper and neuroglia - a set of cells that ensure the isolation of the parts of the nervous system, their nutrition and protection. Neuroglia also plays a role in the formation of the blood-brain barrier. The blood-brain barrier protects nerve cells from external influences, in particular, it prevents the occurrence of autoimmune reactions directed against one's own cells. In turn, the nervous tissue itself is represented by neurons that have two types of processes: numerous dendrites and a single axon. Approaching, these processes form synapses - the places where the signal passes from one cell to another, and the signal is always transmitted from the axon of one cell to the dendrite of another. The nervous tissue is very sensitive to the influence of the external environment, the supply of nutrients in the neurons themselves is close to zero, therefore, a constant supply of glucose and oxygen is necessary to provide the cells with energy, otherwise degeneration and death of neurons occurs.

Subacute cerebral infarction

Back in 1850, the English physician August Waller studied degenerative processes in injured peripheral nerves and discovered the possibility of restoring nerve function by comparing the ends of the nerve. Waller noticed that damaged cells are engulfed by macrophages, and axons from one side of the damaged nerve begin to grow towards the other end. If axons collide with an obstacle, their growth stops and a neuroma is formed - a tumor of nerve cells that causes unbearable pain. However, if the ends of the nerve are very accurately compared, it is possible to completely restore its function, for example, with traumatic amputation of limbs. Thanks to this, microsurgeons now sew cut off legs and arms, which, in case of successful treatment, completely restore their function.

The situation is more complicated with our brain. If in the peripheral nerves the impulse transmission goes in one direction, then in the central organs of the nervous system, neurons form nerve centers, each of which is responsible for a specific, unique function of the body. In the brain and spinal cord, these centers are interconnected and combined into pathways. This feature allows a person to perform complex actions and even combine them into complexes, ensure their synchronism and accuracy.

The key difference between the central nervous system and the peripheral one is the stability of the internal environment provided by glia. Glia prevents the penetration of growth factors and macrophages, and the substances secreted by it inhibit (slow down) cell growth. Thus, axons cannot grow freely, because nerve cells simply do not have the conditions for growth and division, which, even normally, can lead to serious disorders. On top of that, neuroglial cells form a glial scar that prevents axons from sprouting, as is the case with peripheral nerves.

Hit

Stroke, acute stage

Damage to the nervous tissue occurs not only in the periphery. According to the US Centers for Disease Control, more than 800,000 Americans are hospitalized with a diagnosis of stroke, and one patient dies from this disease every 4 minutes. According to Rosstat, in 2014 in Russia, stroke was the direct cause of death in more than 107,000 people.

A stroke is an acute violation of cerebral circulation resulting from hemorrhage with subsequent compression of the brain substance ( hemorrhagic stroke) or poor blood supply to areas of the brain resulting from blockage or narrowing of the vessel ( cerebral infarction, ischemic stroke). Regardless of the nature of a stroke, it leads to a violation of various sensory and motor functions. By what functions are impaired, the doctor can determine the localization of the focus of the stroke and begin treatment and subsequent recovery in the near future. The doctor, focusing on the nature of the stroke, prescribes therapy that ensures the normalization of blood circulation and, thereby, minimizes the consequences of the disease, but even with adequate and timely therapy, less than 1/3 of patients recover.

Retrained Neurons

In the brain, the restoration of nervous tissue can occur in different ways. The first is the formation of new connections in the area of ​​the brain next to the injury. First of all, the area around the directly damaged tissue is restored - it is called the diaschisis zone. With the constant input of external signals normally processed by the affected area, neighboring cells begin to form new synapses and take over the functions of the damaged area. For example, in an experiment with monkeys, when the motor cortex was damaged, the premotor zone took over its role.

In the first months after a stroke, the presence of a second hemisphere in a person also plays a special role. It turned out that in the early stages after brain damage, part of the functions of the damaged hemisphere is taken over by the opposite side. For example, when you try to move a limb on the affected side, that hemisphere is activated, which is normally not responsible for this half of the body. In the cortex, a restructuring of pyramidal cells is observed - they form connections with the axons of motor neurons from the damaged side. This process is active in the acute phase of a stroke; later on, this compensation mechanism comes to naught and some of the connections are broken.

There are also areas in the adult brain where stem cells are active. This is the so-called. dentate gyrus of the hippocampus and subventricular zone. The activity of stem cells in adults, of course, is not the same as in the embryonic period, but nevertheless, cells from these zones migrate to the olfactory bulbs and there they become new neurons or neuroglia cells. In an animal experiment, some cells left their usual migration route and reached the damaged area of ​​the cerebral cortex. There are no reliable data on such migration in humans, due to the fact that this process can be hidden by other phenomena of brain recovery.

brain transplant

Stroke, acute phase

In the absence of natural cell migration, neurophysiologists have proposed artificially replacing damaged areas of the brain with embryonic stem cells. In this case, the cells must differentiate into neurons, and the immune system will not be able to destroy them due to the blood-brain barrier. According to one hypothesis, neurons fuse with stem cells, forming binuclear synkaryons; The "old" nucleus subsequently dies, and the new one continues to control the cell, prolonging its life by pushing the limit of cell divisions further.

Experimental operations carried out by an international team of scientists led by the French neurosurgeon Anna-Catherine Baschou-Levy from the Henry Mondor Hospital have already shown the effectiveness of this method in the treatment of Huntington's chorea (a genetic disease that causes degenerative changes in the brain). Unfortunately, in the situation with Huntington's chorea, a functioning graft introduced for replacement purposes cannot resist the progress of neurodegeneration in general, since the cause of the disease is a hereditary genetic defect. However, the autopsy material showed that transplanted nerve cells survive for a long time and do not undergo changes characteristic of Huntington's disease. Thus, intracerebral transplantation of embryonic nervous tissue in patients with Huntington's disease, according to preliminary data, can provide a period of improvement and long-term stabilization during the course of the disease. A positive effect can be obtained only in a number of patients, so careful selection and development of criteria for transplantation is necessary. As in oncology, neurologists and their patients in the future will have to choose between the degree and duration of the expected therapeutic effect and the risks associated with surgery, the use of immunosuppressants, and so on. Similar operations are also performed in the USA, but American surgeons use purified xenografts (taken from organisms of a different species) and are still facing the problem of the occurrence of malignant tumors (30-40% of all operations of this kind).

It turns out that the future of neurotransplantology is not far off: although existing methods do not provide a full recovery and are only experimental in nature, they significantly improve the quality of life, but this is still only the future.

The brain is an incredibly plastic structure that adapts even to damage such as a stroke. In the near future, we will stop waiting for the tissue to rebuild itself and start helping it, which will make the rehabilitation of patients an even faster process.

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Currently, the interaction of the cerebral hemispheres is understood as complementary, mutually compensating in the implementation of various functions of the central nervous system.

Although each hemisphere performs a number of functions specific to it, it must be borne in mind that any brain function performed by the left hemisphere can also be performed by the right hemisphere. It's about only about how successfully, quickly, reliably, and fully this function is performed.

Apparently, we should talk about the dominance of the hemisphere in the performance of a particular task, but not about the complete distribution of functions between them.

This representation most accurately reflects the importance of the cerebral hemispheres in compensatory processes.

The dissection of the commissures of the brain in humans according to clinical indications, in animals for experimental purposes, showed that in this case the integral, integrative activity of the brain is disturbed, the processes of formation of a temporary connection are hampered, as well as the performance of functions that are considered specific only for this hemisphere.

After dissection of the commissures of the brain, for example, visual ones, the recognition of objects is first disturbed if they are addressed only to the left hemisphere. In this case, the person does not recognize the object, but it is worth giving this object to his hand, as identification occurs. In this case, the function is compensated by a hint from another analyzer.

If the image of an object is addressed only to the right hemisphere, then the patient recognizes the object, but cannot name it. However, he can perform actions that are normally performed using this item. After the separation of the cerebral hemispheres, compensatory processes become more difficult.

Studies of the brain with field 17 of the visual cortex removed in one hemisphere showed that in the symmetrical, preserved area of ​​this field of the other hemisphere, the background activity of neurons increased, and the percentage of background-active neurons increased. At the same time, the synchronization of neuronal activity increased, which was manifested by an increase in the amplitude of the positive and negative phases of evoked potentials to the use of single light stimuli*

that the removal of the 17th field of the cortex of one hemisphere led to an increase in the number of neurons that respond to heterosensory stimuli, i.e. the number of polysensory neurons increased.

An increase in the background activity of neurons in the preserved symmetrical zone of the visual cortex, an increase in the synchronization of their activity can be attributed to intrasystemic compensation. The increase in the number of polysensory, polymodal neurons is associated with intersystem compensation, since in this case conditions are created for new relationships between different analyzer structures.

Fundamentally, the same picture is observed with damage to other projection zones of the cortex of one hemisphere.

Reorganizations of the compensatory plan occur somewhat differently in the associative parietal cortex with a one-hemispheric removal of the visual projection zone. The associative cortex is essential in the processes of organizing intersystem compensation.

After damage to the visual cortex, the amplitude of evoked activity and the frequency of impulse activity increased.

In the case when the conditioning stimulus was stimuli applied to the parietal associative cortex of the hemisphere in which the projection cortex was damaged, and activity was removed from the symmetrical point of the parietal cortex of the opposite hemisphere, it turned out that damage to the projection cortex led to an increase in the amplitude of evoked potentials as conditioning and test transcallosal stimuli.

Consequently, damage to the projection zones of the cortex increases functional activity in association with

ciative parietal zone of the brain, containing a large number of polysensory neurons. Such a reaction of the associative cortex is regarded as an intersystem regulation of compensatory processes in case of dysfunction of the projection areas of the brain and can be used for clinical purposes.

The following data also testify to the intersystem nature of the processes taking place here. Somatic electrocutaneous stimulation elicits a evoked response in the sensorimotor cortex and S-1 area of ​​the opposite hemisphere. This response is slightly modulated in amplitude and latency during pre-light stimulation.

In the case when transcallosal activation serves as a conditioning stimulus, then a light stimulus is given and only after that somatic electrocutaneous activation, the evoked response to the somatic stimulus sharply increases in amplitude, the latent periods of its occurrence are shortened.

Therefore, interhemispheric interaction, enhanced by pre-stimulation through the trans-callosal system, facilitates intersystemic, in this case, visual-sensory-motor interaction.

Carrying out the same experiments after the destruction of interhemispheric connections between the symmetrical points of the sensorimotor cortex of the hemispheres showed the absence of facilitating interaction between the cerebral hemispheres. It also turned out that the uncoupling of the hemispheres led to a decrease in the activity of the sensorimotor cortex in response to visual stimuli. This is direct evidence that interhemispheric interaction contributes to intersystem compensation of impaired functions.

Thus, unilateral dysfunction of the cerebral cortex is accompanied by increased

the functional activity of the area symmetrical to the damaged zone. It should be noted that with damage to the projection areas of the cortex, increased functional activity is also observed in the associative areas of the brain, which is expressed by an increase in the number of polysensory neurons, an increase in the average frequency of their discharges, and a decrease in the activation thresholds of these zones.

14.9. Compensatory processes in the spinal cord

In those cases when the flow of information to the spinal cord, its motor neurons, is limited along the reticulospinal pathway from the reticular nucleus of the pons or the giant cell nucleus of the medulla oblongata, the body of motor neurons, the total length of their dendrites increases. The orientation of the dendritic tree, when the inflow of information along the reticulospinal pathway is limited, changes in the direction of increased contacts with the medial reticulospinal pathway and the anterior commissure. In parallel, the number of dendrites oriented towards the lateral reticulospinal pathway, which has predominant connections with the giant cell nucleus of the medulla oblongata, decreases.

Consequently, there is a compensatory restructuring of functional descending connections due to an increase in the dendritic tree, which receives information from the preserved reticulospinal system.

When one limb is amputated in dogs, there is an increase in the bodies and nuclei of neurons of the posterior and anterior horns of the spinal cord, hypertrophy of processes is noted, motor neurons become multinucleated and multinucleolar, i.e. expanding nuclear-protoplasmic relations. Last testimonial

This is about hypertrophy of neuronal functions, which is accompanied by an increase in the diameter of the capillaries suitable for the neurons of the anterior and posterior horns of the spinal cord of the opposite half, relative to the amputated limb. Around the neurons of this half of the spinal cord, there is an increase in the number of glial elements.

An analysis of the recovery of movements in experimental animals after transection of various sections of the spinal cord led to the conclusion that the appearance of motor coordinated acts is based on the formation of temporary connections that are fixed during training and learning.

Compensation for impaired functions in spinal cord injury is realized due to the polysensory function of the brain, which ensures the interchangeability of one analyzer with another, for example, deep vision sensitivity, etc. Some functions of the spinal cord in regulating the work of internal organs are well compensated by the autonomic nervous system. So, even with gross violations of the spinal cord, the regulation of the activity of organs is restored. abdominal cavity, pelvic organs (intersystem compensation).

Thus, after the onset of the pathology of the spinal cord and the removal of spinal shock, the phase of exaltation of neurons begins, and this is accompanied by an increase in muscle tone, an increase in deep reflexes, restoration of spinal automation, and hyperesthesia for various types of sensitivity. Later, a restructuring of the coordinating relationships between the symmetrical structures of the spinal cord segments occurs. At the same time, synergistic reactions are enhanced, the activity of symmetrical muscles increases, and a distortion of antagonistic muscles is observed.

relationships. In the future, the mechanisms associated with learning are connected, i.e. intersystem compensation mechanisms are used.

14.10. compensatory processes,

ensuring the preservation of a temporary connection

After damage to various structures of the central nervous system, behavioral disorders occur, which are gradually restored. This recovery may not be complete, but it is quite effective and, with constant training, it reaches such a high level that deviations are not detected without special provocative methods.

Apparently, at the heart of the compensatory processes of higher nervous activity lies described by M.N. Livanov is a phenomenon, which lies in the fact that during training, the similarity of the states of many brain structures increases.

So, during the formation of a food-procuring conditioned reflex in monkeys, the activity of: pre- and postcentral, auditory, visual, associative parietal, lower temporal cortex, dentate fascia, cerebellum, caudate nucleus, shell, pale ball, pillow, reticular formation changes.

In these structures, in the dynamics of the development of the food conditioned reflex, one can register the gradual formation of a specific evoked potential with the presence of a late positive wave in it. With a strengthened reflex, this positive wave is registered only in the structures that are directly interested in the realization of the reflex. However, in those cases when there were difficulties in the functioning of the signal perception zone or the zone of its implementation, a late positive wave reappeared.

feces in multiple leads. Consequently, compensation was provided by the entire system that was involved in training.

Thus, traces of memory are recorded not only in structures interested in the perception and implementation of a response to a signal, but also in other structures involved in the formation of a temporal connection. In the case of pathology, these structures are able to replace each other and ensure the normal implementation of the conditioned reflex.

However, other mechanisms also lie in the compensation of violations of the functions of the temporal connection. Thus, it is known that the same cortical neuron can participate in the implementation of a conditioned reflex with different types of reinforcement, i.e. the polyfunctionality of the neuron makes it possible to compensate for dysfunctions arising from the use of other pathways of the nervous system.

Finally, compensation for violations of conditioned reflex processes can be provided by the establishment of new intercentral relationships between cortical structures, the cortex and subcortical formations. New intercentral relationships also arise in the event of damage to various formations of the limbic system. So, simultaneous, unihemispheric damage to the dorsal and ventral regions of the hippocampus, the nuclei of the medial septal region, the basolateral part of the amygdala, the nuclei of the posterior and lateral parts of the hypothalamus causes only a short-term, up to two weeks, specific, for one of these structures, a violation of conditioned reflex activity.

In those cases when, on the side of damage to the limbic structure, the cortex of the cerebral hemispheres was functionally switched off

brain, violations of conditioned reflex activity persisted for a long time. Consequently, the most optimal compensatory mechanisms of conditioned reflex processes are implemented with the participation of the cerebral cortex.

Compensation for disorders of higher nervous activity due to inter-hemispheric connections is most successfully manifested in case of damage to certain areas of the cerebral cortex after the development of a conditioned reflex.

Experimental verification of this kind of compensation can be demonstrated by the following experiments. A cat develops a defensive conditioned reflex of hitting a target with its paw. The conditioned signal is light stimulation, the unconditioned reinforcement is electrocutaneous stimulation. A paw strike on a target stops pain irritation or prevents it. After the strengthening of such a reflex, the sensorimotor cortex of one hemisphere is removed, or in the same way it is removed in one hemisphere, but only the visual cortex.

Damage to the sensorimotor cortex, as a rule, leads to incompleteness of the motor response to the signal, inaccuracy of the reaction, and the appearance of uncoordinated movements in response to the signal stimulus.

Damage to the visual cortex causes the cat to react to the signal, but misses when trying to hit the target. Such disorders after damage to the sensorimotor or visual cortex are recorded no more than two weeks. After this period, the conditioned reflex activity of animals is almost completely restored.

In order to make sure that this compensation is due to interhemispheric mechanisms, after the restoration of the conditioned reflex activity

in animals dissect the corpus callosum, thereby separating the cortical interhemispheric connections.

Dissection of the corpus callosum restores dysfunctions of conditioned reflex behavior - precisely of the nature that occurs in the initial stages after removal of the cortex in one of the hemispheres.

Such experiments show a direct dependence of compensation for the deficit of the cortical function on interhemispheric connections. These connections form new system between the intact hemisphere and scattered elements of the cortex, polysensory neurons of the damaged hemisphere, which allows compensating for impaired function.

In addition to the noted way of compensation through interhemispheric cortical connections, the brain also has other possibilities for compensating conditioned reflex behavior. So, if it is difficult to perform a movement with one limb, the desired reaction can be performed by another.

Consequently, the compensatory mechanisms of conditioned reflex activity make it possible to organize a behavioral response in various ways. This is especially easy when the output structure of the cortex, which was originally trained for this function, suffers.

Such a way of compensation is provided primarily by rearrangements of activity in a point of the cortex of the other hemisphere that is symmetrical with respect to damage. Normally, stimulation of the cortex causes local activation of neurons in a symmetrical area. Around this zone, a braking environment is formed, as a rule, twice as large. After damage to a section of the cortex in a point symmetrical to it, the number of background-active neurons, the number of polysensory neurons increases, the average frequency increases.

discharges of neurons. Such a reaction of the cortex indicates that it has great opportunities to participate in compensation processes.

The structures of the associative system of the brain play a significant role in compensating the processes of higher nervous activity.

Such systems include associative reticular formations of the brain stem, associative nuclei of the thalamus, associative fields of the cerebral cortex and associative structures of the projection zones of the cerebral cortex. In humans, the associative areas of the brain are dominant in size.

Animal studies have shown that destruction of the posterior pituitary gland or the entire pituitary gland disrupted conditioned reflex activity. This violation was eliminated by the introduction of extracts from the pituitary gland or vasopressin, intermedin, ACTH. Systematic administration of vasopressin completely restored conditioned reflex activity. In intact animals, vasopressin accelerated the formation of a temporary bond. In animals with depression of the neo-striatum, which causes disturbances in the production and reproduction of previously fixed conditioned conditioned reflexes, the administration of vasopressin also restores normal conditioned reflex activity.

It also turned out that vasopressin optimizes conditioned reflex sexual behavior. For example, the conditioned reflex run of a male rat to a female through a maze after the introduction of vasopressin was developed much faster than under normal conditions.

Vasopressin causes different effects depending on the route of administration. Subcutaneous injection normalizes water-salt metabolism without affecting the conditioned reflex activity. The introduction of the same

The drug directly into the ventricles of the brain eliminates learning and memory disorders and does not affect the processes of water-salt metabolism.

In the same way, when administered subcutaneously, oxytocin has an inhibitory effect on conditioned reflex activity, and its introduction into the ventricles of the brain improves long-term memory and facilitates the formation of reflexes.

Vasopressin impairs short-term memory and improves long-term memory. The introduction of this substance before the start of learning makes memorization difficult, or even makes learning impossible. An injection of the same drug after learning facilitates the reproduction of memory traces.

Currently, there is an idea that vasopressin is involved in the regulation of the processes of memorization and reproduction, and oxytocin in the processes of forgetting. The use of vasopressin, as already mentioned, improves the processes of memory and conditioned reflex activity, but active conditioned reflex activity also increases the concentration of vasopressin in the blood in the brain.

Consequently, the more actively the brain is involved in the conditioned reflex process, the more vasopressin it contains and the more successful the processes of maintaining new temporary connections. This is especially important during destructive processes in the central nervous system, since at this time it is possible to form new temporary connections that compensate for the developing pathology.

The introduction of vasopressin reduces the dependence of animals on drugs, the injection of antibodies to vasopressin increases drug consumption.

In humans, intranasal administration of vasopressin improves attention, memory, mental performance, different kinds intellectual activity.

14.11. Hemodynamic mechanisms

compensation of disturbed functions of structures

nervous system

One-fifth of the blood ejected by the heart passes through the brain, and the brain consumes one-fifth of the oxygen that enters the body at rest. In this regard, any changes in cerebral circulation affect the functioning of the brain.

Sensory activation of the brain changes the nature of the blood flow of its individual structures; motor activity, in addition to the nonspecific reaction of the brain vessels, causes rearrangements of blood flow in the motor areas of the brain. In the dynamics of mental activity: during the period of development, the period of optimal performance, with fatigue, monotony, with the current correction of fatigue, in conditions of post-labor rehabilitation, the blood supply to the brain changes significantly, optimizing the blood flow in the most loaded brain structures.

Correlation of vascular blood flow in the brain under various loads on its structures is carried out at the level of pial vessels. It is the pial vessels that form a network of collateral circulation, ensuring the reliability of blood flow to individual brain structures.

The pial arterioles, being the "faucets" of the vascular bed, provide the necessary volume of blood flow to this brain formation. Regulation of pial arterioles is largely carried out by bio feedback from the structure, which is provided by the blood of the pool of this pial vessel.

These changes in pial blood flow do not depend on the value of systemic arterial pressure, i.e. they are associated only with an increase in the functional activity of the corresponding area of ​​the brain. Unila-

lateral delivery of a visual or auditory signal increases vascular blood flow in the hemisphere contralateral to stimulation.

The analysis of compensatory processes of vascular blood flow in the associative and projection areas of the cortex is most conveniently studied when the functioning of their symmetrical areas of the brain changes. It is known that in the case of destruction or ischemia of one of the symmetrical areas of the brain, the other part takes part in compensating for the deficiency resulting from the pathology that has arisen.

Experiments on animals in which the parietal or somatosensory cortex of the left hemisphere was functionally switched off under anesthesia and simultaneously controlled the vascular bed of the pial system over symmetrical brain regions showed the following.

In symmetrical areas, the response to functional shutdown of the activity of one hemisphere (hemodynamic changes) proceeds in two phases. In the first phase, which lasts up to 15 minutes, blood flow decreases. Then comes the second phase, during which the blood flow is restored and gradually increases compared to the norm. Moreover, an increase in blood flow occurs not only in the somatosensory cortex, which is symmetrical to the exclusion, but also in the parietal cortex of the opposite hemisphere.

Fundamentally the same pattern of increased blood flow is observed in studies on awake animals. The only difference is that when the cortical region of one hemisphere was functionally switched off, the changes in hemodynamics in the first phase - the decrease in blood flow - lasted less and lasted no more than 10 minutes, then the restoration of blood flow began and its increase compared to the norm.

The hemodynamics of the somatosensory cortex, a symmetrical point relative to the off one, changed more dynamically compared to the hemodynamics of the parietal cortex, the restoration of the vascular bed occurred more quickly and its hyperactivity lasted longer. a short time. The inertness of hemodynamic changes in the associative areas, the long-term preservation of changes in them indicate that these areas play a decisive role in providing compensation for impaired functions in the structures of the central nervous system.

14.12. bioreverse connection in the compensation of disorders of the functions of the nervous system

Activation of the natural reserves of the body with the help of biofeedback is a common mechanism for compensating for violations of the functions of the central nervous system.

Feedback biofeedback is a form of learning that allows you to implement involuntary functions based on monitoring the results of your activities.

An example of the use of biofeedback is given by N. Miller (1977). He talks about a basketball player who adjusts his movements according to the luck or bad luck of hitting the ball into the basket. Feedback is the result observed visually. With a successful result, the posture, muscle tension, force of the push, etc. are automatically remembered, which are subsequently used unconsciously during the second throw.

Biofeedback is often used in psychology to regulate a certain mental state based on the registration and presentation of the level of expression of the alpha rhythm in the activity of the cerebral cortex to the subjects.

In the clinic, biofeedback is used to control brain activity, muscles, temperature, heart rate, breathing rate and depth, blood pressure, for the treatment of bronchial asthma, hypertension, insomnia, stuttering, anxiety after a cerebral stroke, epilepsy, etc.

Biofeedback compensation is the training of a person in a new activity that is not voluntarily controlled.

The principle scheme for generating compensation based on biofeedback using the example of epilepsy is as follows.

As you know, epilepsy is accompanied by a specific character of the electroencephalogram with special signs in the form of a high-amplitude negative oscillation, immediately after which a low-amplitude slow wave occurs - the “peak wave”.

The patient is located in comfortable chair for EEG registration. Electrodes are applied to him, and the activity diverted from certain areas of the brain is shown to the patient on the monitor. It is explained that this disease is characterized by activity in the form of a “peak wave” in the EEG, that most of these fluctuations remain beyond the visibility on the screen, but it is recorded using a computer and its presence is indicated by the appearance of a green strip on the monitor screen: the more the peak-wave activity is expressed, the wider the green band. The patient's task is to find such a state in which the green strip has a minimum latitude, i.e. the amount of peak-wave activity is minimized or it does not occur at all.

As a result of training in patients who previously did not have an aura, it appeared, i.e. was developed with

the ability to feel the harbingers of an attack, a slower onset of a paroxysmal attack was observed, the phase of loss of consciousness was shortened upon the onset of an attack, and post-attack amnesia often did not develop. In some patients, large convulsive seizures were replaced by small, local, abortive ones. In some cases, there was a cessation or decrease in the frequency of occurrence of convulsive seizures for a period of two weeks to a year.

As a result of the training, the patient, when an aura appeared, used seizure prevention techniques, as he did during training, reducing the number of paroxysmal peak-wave discharges.

In the EEG, after learning to suppress peak-wave activity using biofeedback, the occurrence of paroxysmal activity decreased.

Thus, in the dynamics of treatment with the help of biofeedback, a new functional state of the brain was formed, preventing the development of paroxysmal activity. This functional state is recorded in long-term memory.

Quite successfully, biofeedback can be used to compensate for violations of motor functions, dyskinesia different etiology.

Dyskinesias can be characterized by redundancy or deficiency.

Excessive dyskinesia causes the attention of others, which injures the patient's psyche, causes negative emotional reactions and leads to increased dyskinesia - a positive biofeedback, leading in this case to a deterioration in the patient's condition.

Treatment of dyskinesias with drugs makes the patient pharmaco-dependent. Surgical

which stereotaxic treatment has adverse long-term effects.

Of the dyskinesias in the form of hyperkinesias, the most successful use of biofeedback for compensation purposes in parkinsonism and writing spasm.

Parkinsonism occurs as a result of dysfunction of the pallido-nigro-reticular structures, which leads to disruption of the mechanisms of self-regulation and feedback between the subcortical and cortical structures of the extrapyramidal system. At the same time, parkinsonian symptoms are subject to a daily rhythm and are affected by the emotional state of the patient, therefore, they depend on the functional state of the brain, i.e. can be managed.

Writing spasm appears in persons of a certain profession and leads to a violation of professional activity, and this, in turn, to emotional negative reactions. The latter cannot but affect the strengthening of the disease.

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