✚ Basics of brain development. Neuropsychiatric Clinic of Professor Minutko. Article No. 4626

The human brain is called the main computer: the life support of the body and the fate of a person depend on its activity. There have been numerous studies by quantum biologists and geneticists who have proven: the brain is a receiver that emits a sound wave, because the cells in the body are alive, they move and vibrate. The wave that is created by vibration is considered a “router” or “router” - it builds a route. It turns out that if the brain is sufficiently developed, it emits better signals, and a person lives a richer and more interesting life.

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What to do to improve the functioning of the brain, and what the consequences will be if left unattended, says Olga Burlakova, health specialist, naturopath, author of the “Conscious Health System - CO2” method.

1. Developmental plasticity: formation of neural connections

[…] “The human brain,” says Jean-Pierre Changer, “appears to us as a gigantic assembly of tens of billions of neural “webs” entangled with each other, where thousands of electrical impulses “chirp” and spread, here and there intercepted by a wide range of chemical signals." These “webs,” also called “ramifications,” are neural connections that gradually form as an individual develops. When they talk about plasticity, it is this neurogenesis that is characterized. The brain essentially shapes itself. “A person is born with a brain that weighs 300 grams, that is, five times less than an adult brain... One of the main features of the development of the human brain is that it continues for a long time after birth... approximately fifteen years.”

So it all starts with making connections, then multiplying them and making them more complex. The increase in brain mass coincides with the growth of axons and dendrites, the formation of synapses, and the development of myelin sheaths around the axons. This development is subject to strict genetic determinism. In their origin and structure, “all human brains are similar to each other,” says Marc Jeanreau. Of course, the connections that make up the anatomy of the mature brain are not a matter of chance or spontaneous organization. The migration of nerve cells and their adaptation to final goals are programmed. “We’ll give just one example,” the author continues. - In all people, the fibers emanating from the retina and carrying visual information complete their path in the visual part of the cerebral cortex, that is, in the occipital lobe, located in the back of the brain; in all people, this visual part forms connections with other areas located in the parietal, temporal lobe, etc. Consequently, the adult brain reflects the existence of a pre-established plan, which ensures the invariance of anatomy from one individual to another.”

If neurogenesis follows a “preset plan,” why even talk about plasticity to characterize this development? For two significant reasons related to 1) the aforementioned process of connection establishment and 2) their formation (which is different from modulation of synaptic effectiveness). In both cases, the execution of the program acts as plastic. There is, so to speak, a plastic art of the brain, which explains the use of the term “plasticity” in this context. It is here that the narrowed or “closed” meaning of this concept—sculpture of a predetermined form—comes to the fore.

In the process of making connections, a sculptor's chisel can be compared to a phenomenon called apoptosis, or cell death. This death is a normal occurrence. It again corresponds to the execution of a genetic program, which leads to the elimination of useless connections and the gradual formation of the final form of the system by targeting nerve fibers to target cells. In the human brain, neuronal death begins at the end of the fetal period and continues through at least the first six months of life. In an adult, its dynamics slow down significantly. As Jean-Pierre Changet writes: “The destruction of neurons is part of normal development. It constitutes one of its decisive stages.” In a book with the eloquent title “The Sculpture of the Living,” biologist Jean-Claude Amaisen emphasizes the fact that the brain, far from being, as has long been assumed, a fully formed organ at birth, is an institution that simultaneously takes and gives itself its own form. “Cell death,” he writes, “is ... a tool that allows the embryo to develop its form by a method of elimination, which makes it similar to sculpture.”

Meanwhile, as Marc Genreau explains, from this stage of development and as soon as the system takes on a complete sculptural form, “genetic determinism weakens.” “After birth, the topographic network, formed during embryogenesis and stabilized through the death of neurons and the elimination of connections, begins to function under the influence of external factors. This functioning entails a new phase of joint formation.” The environment plays a fundamental role here.

Much of the development of the human brain occurs in open space, in contact with stimuli from the world, which directly affect the growth and volume of connections.

For example, the visual system is not fully functional at birth. The synapses that connect fibers emanating from the retina to neurons in the visual cortex are not yet fully formed. And it is information received from the outside that activates these synapses and promotes their maturation. It is in this vein that it is customary to talk about the formation of synapses or the mechanism of synaptic plasticity (as we see, still associated with the genetic program) in the second phase of development.

The process of brain formation during these two phases - the establishment of connections and their maturation under the influence of the environment - thus reveals plasticity in the execution of the program. In both cases, the brain appears as formed - gradually sculpted, stabilized, divided into different regions - and at the same time as a formative authority: little by little, as the volume of connections increases, the identity of the individual is drawn. And the further we go, the more this “first plasticity” loses its inexorable determinism. The sculptor gradually begins to improvise. Our own activity plays an increasingly important role in shaping connections: “Our brain, shaped by our own activities, our interactions with the outside world, as well as the influences we experience during our upbringing, knows our history and life path. From this proximity is born a deep identity of the functioning of our brain and our understanding of the world, one might even say an identity of views.”

In fact, the first level of plasticity is closely related to the second, since the influence of the environment gradually replaces epigenetic “sculpting” and becomes more and more pronounced. The narrowed or “closed” meaning of plasticity very soon comes across its “open” meaning - “freedom”, in which determinism and uncertainty surprisingly converge. And indeed, we see that brain morphogenesis does not lead to the establishment of a rigid and finally fixed structure, but to the formation of what can be called a template. It is then honed (sculpted) during development and then - to a lesser extent, but with no less efficiency - throughout life. The neural activity of pre-established circuits thus replaces the sculptured activity of apoptosis. From now on, the role of morphogenic factors is played by the environment of the brain as an organ (formation of connections), and then by its external environment (synaptic modulation under the influence of the environment).

Source: Svetlana Mokrova / istockphoto.com

How to develop your brain

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The brain needs to be developed from early childhood. A child is born with an immature brain, and the development process continues until at least seven years of age. Until this age, connections are built between the right and left hemispheres. Injuries also affect brain development: the structure of cells is disrupted if there have been blows to the head, falls, or concussions.

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Brain development is influenced by movements, often diagonal ones. It is important that from childhood a child has a lot of fine motor skills and diagonal movements, for example, crawling, where the right leg and left arm, or the left leg and right arm are alternately involved. Dynamic gymnastics and swimming are also suitable for babies: cross movements of arms and legs help brain cells actively develop. Therefore, it is important for children not only to read books, but also to constantly move.

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Active learning for children begins at the age of seven: it is not recommended to study logic, mathematics, reading and writing before this age. Otherwise, the right hemisphere is suppressed, which is responsible for the ability to find a way out of non-standard, difficult life circumstances. In other words: you can close the way to a successful, happy life if you force your child to learn at too early an age.

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At seven years old, the left hemisphere begins to develop, and with it logic, attention, perseverance, and you can study school subjects. At this age, it is useful to try yourself in different types of activities. Therefore, parents should not worry if the child went to tennis for a month, then went to gymnastics, then to clay modeling. If he is comfortable, let him experience different things.

In addition to studying and physical activity, it is important to pay attention to good nutrition, which includes fats and glucose. The brain uses a lot of glucose, so children often crave sweets. It is better to choose high-quality dark chocolate or fruit.

At a more mature age, you need to learn poetry, train memory and attention, solve logical problems, engage in erudition, watch difficult-to-understand films, read scientific literature, and study foreign languages. The main thing is to get plenty of rest: if you don't relax, your brain will enter a state of hyperactivity and function will deteriorate.

Modulation plasticity: the brain and its history

At this point we immediately encounter the second field of action of neuroplasticity - the modification of neural connections through modulation of synaptic effectiveness. Undoubtedly, it is at this level that plasticity manifests itself with the greatest brightness and strength, and it is here that it “reveals” its meaning. In fact, there is a kind of neural “creativity” that does not depend on anything other than the individual’s experience, life and interactions with the environment. This “creativity” is not assigned exclusively to the human brain, but is already characteristic of the most rudimentary nervous systems.

This plasticity, which consists of giving shape to branches and modulating synaptic effectiveness, was first identified by the Canadian neurologist Donald Olding Hebb. Donald Olding Hebb (1904–1985) is the author of the work “Organization of Behavior: A Neuropsychological Theory” (1949). The term “plasticity” was first proposed by the outstanding Polish neurologist Jerzy (Yuri) Konorski, whose vision of synaptic functioning was quite close to Hebb’s views (Konorski J. Conditioned Reflexes and Neuron Organization. Cambridge: Cambridge University Press, 1948; Konorski J. Integrative activity of the brain. M.: Mir, 1970).. At the end of the 1930s, various experimental observations forced him to move away from the concept of rigid localization of memory chains in accordance with Pavlov’s reflex arc model. In his opinion, one should rather talk about the existence of “plastic synapses” capable of adapting their transmission efficiency. Hebb formulated the hypothesis of neural circuits capable of self-organization, that is, modification of their connections during the activities necessary for perception and learning. The synapse is the primary site where neural activity can leave a trace that can displace, change, or transform itself through the repetition of past actions.

The ability of synapses to modulate their effectiveness and modify the intensity of their branches under the influence of experience occurs in two directions. Either the effectiveness of the synapse (its ability to transmit signals from neuron to neuron) increases - this is “long-term potentiation (LTP or LTP)”; or it decreases - this is “long-term depression (LTD or LTD).” This can already be seen in the example of such an animal as Aplysia. Its central nervous system is simple and consists of eight pairs of ganglia located around the esophagus and a large abdominal ganglion. Aplysia has a meager set of behavioral stereotypes, among which a number of defensive maneuvers can be distinguished, such as retracting the siphon or gills. At the same time, the strength of her protective reflex is modulated by experience. Repeating non-hazardous stimulation on the mantle causes a decrease in the reflex (habituation), which is expressed in a decrease in the amplitude of retreat movements. Habituation is accompanied by suppression of synaptic activity and a proportional decrease in the amount of neurotransmitter released at the level of the sensory-motor synapse. Neurotransmitters (acetylcholine, adrenaline, etc.) ensure the transfer of nerve impulses from one side of the synaptic cleft to the other. Here, electricity is replaced by chemistry (the principle of nerve signal transmission is electrical/chemical/electrical)..

The phenomena of long-term potentiation and depression are even more clearly expressed in the processes of adaptation, learning and memory in birds. For example, the black-capped chickadee stores food in pantries, which it then unerringly finds. Researchers were able to establish that the size of the brain zone (hippocampus) Since the hippocampal formation and parahippocampal gyrus play a primary role in the memorization process. The key to brain and behavioral plasticity is the ability to learn and remember. And the hippocampus is precisely the zone primarily responsible for these operations. Its damage has especially severe and most often irreversible consequences for cognitive activity and memory, which are involved in this process, in this bird more than in others that do not have experience in storing food. Therefore, species that practice storage have a significantly larger hippocampus in comparison with others. This change is a consequence of the accumulation of new neurons, decreased cell death (apoptosis), and increased connections between hippocampal neurons. The latter thus demonstrates amazing structural plasticity.

Potentiation and depression are not simply synaptic processes during which one or more stimulations produce immediate excitation. These are also long-term modifications that can transform the form (changes in the size of a certain brain area, varying the permeability of a regularly excited area) and remove a trace in order to reapply it (lability of the memory trace). Indeed, it has been observed that some neural networks become more productive when they “suppress” synapses that were involved in tasks that led to errors in motor learning. In the human brain, this feature is clearly evident during all learning processes. For example, when learning to play the piano, a mechanism for suppressing input signals corresponding to erroneous movements (“misses”) makes it possible to learn correct movements. In the case of potentiated connections, synapses increase the area of contact, their permeability increases, and nerve conduction accelerates. Conversely, a synapse that is underused or "suppressed" tends to become less productive. Neurons store stimulation impulses in some way. It is as if the stabilization of memories occurred solely under the condition of a potential destabilization of the overall landscape of memory.

So, long-term potentiation is structurally related to long-term depression. If synapses, and especially hippocampal synapses, did nothing but strengthen under the influence of LTP, they would soon all reach the maximum degree of efficiency and, therefore, the encoding of new information would be impossible, and this connection would be impossible. constitutes a differentiating, or rather, transdifferentiating force of neuroplasticity. If we use the analogy with the formation of stem cells, we can assume that, due to their plasticity, neural connections are always able to change a difference, perceive an imprint or get rid of it, and transform their program.

Hence,

The fact that synapses show increased or decreased effectiveness as a function of experience suggests that, although the anatomy of the brain is the same in all people, no brain is identical in history to another.

This is directly evidenced by the phenomena of learning and memory. Repetition and habit play an essential role, which means that the neural chain never has a clearly fixed response. Plasticity combines the role of the sculptor with the functions of the artist and educator of freedom and autonomy. In a sense, it is plausible to say that synapses represent the brain's reserves for the future. They are not fixed and do not serve as mere transmitters of neural information, but they have the power to shape or reform that information itself. Marc Genreau writes: “The effectiveness of synapses varies depending on the flow of information that passes through them: each of us, in childhood and throughout our lives, experiences a unique configuration of environmental influences that is reflected in the shape and function of our brain networks.”

This once again calls into question the old dogma that the adult brain tends to lose its plasticity - it is, of course, able to accumulate new information, but there is no change in its learning, memory functions and global structure, except perhaps to the side. decline or degeneration. On the contrary, we see that there is a constant restructuring of neural morphology.

Environmental factors influence brain development

The structure of the adult brain and the division of various functions between the hemispheres is already well understood. However, information about the developing brain of newborns is still limited, although understanding this normal developmental process is important. By understanding this process in future studies, effects that may be influenced by environmental factors, such as maternal prenatal conditions, on the infant's brain can be easily detected.

“The developing brain is most sensitive to environmental factors during pregnancy, and these factors can dramatically alter the course of development,”
says study author Satu Lehtola, an employee at the University of Turku.

3. Restorative plasticity: the brain and its regeneration

Here we come to consider the third field of action of plasticity - restoration. The term "restorative plasticity" actually refers to two different processes: neuronal renewal, or secondary neurogenesis, and the brain's ability to repair some types of damage caused by injury.

What is meant by “neuronal renewal” or “secondary neurogenesis”? From what we have just said, it appears that the first plasticity, morphogenetic, is followed by modulation plasticity, which modifies synaptic effectiveness but does not affect the anatomical stability of the brain, as if it were operating, so to speak, within a closed system. According to Heather Cameron: “Some scientists still adhere to the stable brain hypothesis, according to which there is no anatomical plasticity of the adult brain, and especially the cerebral cortex; They believe that the functional plasticity underlying learning mechanisms involves changes in the “power” of synapses produced by modification of receptors or the intercellular environment of neurons at the molecular level." Heather Cameron is a researcher in the laboratory of molecular biology of the National Institute of Neurological Disorders and Stroke (NINDS / NIH) in Bethesda, USA. We quote her article: Cameron H. Naissance des neurones et mort d'un dogme // La Recherche, No. 329, Mars 2000. P. 35.. However, this dogma of a stable brain is not entirely true. Indeed, the author continues,

“We now know that individual neurons in areas important for learning are constantly being updated—and this amounts to relatively significant anatomical changes.”

Even if the role of stem cells in the adult brain and their localization are still poorly understood, and even if there is a possibility that secondary neurogenesis does not affect all regions of the brain, it is undeniable that nerve cells are renewed in adulthood. This opens up unprecedented prospects for brain restoration and changes our understanding of its functioning.

A recent study of the primate neocortex revealed the presence of new neurons in three regions of the association cortex: the prefrontal, inferior temporal, and parietal areas. “This result is particularly interesting because the association cortex plays an important role in high-level cognitive functions, while the striate cortex [which does not show updating] is involved in processing visual information. This difference suggests that while neurogenesis plays a key role in functions that are inherently plastic, it is not beneficial for lower-level functions such as sensory processing, which are typically stable throughout life.”

The production of new neurons is thus not simply about replacing dying cells. It plays a role in the plasticity of modulation and, because of this, further expands the concept of plasticity - to the point of shaking the concept of stability. Again: the statue comes to life, the program becomes animated. Where, as it seems to us, there is only pure mechanics, we find a complex interweaving of different types of plasticity, contradicting the usual ideas about the brain as a machine. As Alain Proshyants states: “It must be said that one of the main characteristics of the nervous system, of course, lies in its plasticity. The brain cannot be viewed as a network of finally laid cables, and brain aging cannot be viewed as the disconnection of an ever-increasing number of elements of this chain from the network. Even though this has only been formally proven in a few experimental models, we have the right to assume that nerve fibers grow daily, that some synapses disintegrate, while others, new ones, are formed. These changes in the neural landscape... are a testament to our adaptability, our ability to learn, and our potential for improvement, which continues into old age and, in fact, until death.”

In a paper titled “The Unusual Distribution of New Neurons,” the researchers state: “…observations of secondary neurogenesis clearly show that the adaptive capabilities of the nervous systems of birds and adult mammals do not arise solely from variability in synaptic connections. They also rely on the production or renewal of distinct populations of neurons in several highly defined regions, the common property of which is to perform functions responsible for learning and/or memory. In this light, it appears that secondary neurogenesis similarly allows the subject's personal experiences to leave their mark on neural networks in the form of regular morphological and functional rearrangements. This means that adult neurogenesis, as the ultimate mechanism of plasticity, largely controlled by the subject’s personal experience and its interactions with the environment, apparently constitutes an additional mechanism of individuation. With the significant difference that it lasts throughout life.”

The idea of cellular renewal, regeneration, resource as an aid to synaptic plasticity sheds light on the power of healing - healing, healing, compensation, restoration, the brain's ability to create natural "prostheses". The plastic art of the brain gives birth to a statue capable of healing itself. The functioning of the brain, as we know, can be impaired due to many pathologies, the most famous of which are traumatic brain injuries, cerebrovascular accidents, encephalitis, neurodegenerative diseases (Parkinson's disease, Alzheimer's disease). At the same time, after such injuries and illnesses, the nervous system invariably shows plasticity, regardless of whether its efforts are crowned with success or not: the affected structures and functions try to modify themselves in order to compensate for the deficiency or form a new organizational pattern that simultaneously deviates from the norm and restores it .

Restorative plasticity obviously does not compensate for all deficits. Some lesions, as we know, are irreversible. But at first, the brain always tries to reorganize the affected function with greater or less effectiveness, efficiency and reliability. As an example of this phenomenon, Marc Janreau cites “paralysis of the left arm caused by damage to the motor cortex on the right due to a stroke. At first, no movement is possible, the hand is motionless and lethargic. After some time, muscle strength returns and mobility of the elbow and wrist is restored. How is this possible if the neurons responsible for controlling these movements are destroyed?... Here functional neuroimaging comes to the rescue: it shows that when the patient tries to move the paralyzed arm, it is the unaffected motor cortex on the left that is activated. The patient, either by himself or through rehabilitation, learns to use neural pathways that normally do not exist. Such a reorganization of motor function once again indicates the plasticity of cerebral mechanisms.” Another example is what happens in the early stages of Alzheimer's disease. The onset of amnesia is partially compensated by the ability to restore stored information. The deactivation of some regions (hippocampus) is balanced by the metabolic activation of others (frontal). Thus,

damage to individual circuits is followed by a change in information processing strategies, which also indicates functional plasticity of the brain.

So, the human brain has functions responsible for reorganization after damage. These phenomena are also observed in some transplants. In January 2000, staff at the Edouard Herriot Hospital in Lyon performed the first hand transplant on thirty-three-year-old Denis Chatelier, who had suffered an amputation after an accidental explosion three years earlier. The question was: even if it is possible to establish anatomical continuity between the donor's hands and the recipient's forearms, can the same continuity be achieved at the psychological and neurological levels? The case of D. Sh. proved that yes. His phantom pain disappeared, and the motor progress he made suggested that his brain had successfully integrated the transplanted arms. “When the motor cortex reorganizes, the synapses are modified. They change their influence and “weight” in the local functioning of the network of neurons... After transplantation, [such] changes in neural connections could lead to the restoration of the representation of the hand.” Another proof of the amazing adaptability of our brain.

In the “Open Reading” section we publish excerpts from books in the form in which publishers provide them. Minor abbreviations are indicated by ellipses in square brackets. The author's opinion may not coincide with the opinion of the editors.