“If the animal were not... accurately adapted to the outside world, then it would soon or slowly cease to exist... It should react to the outside world in such a way that its existence would be ensured by all its response activity.”
I.P. Pavlov.

The adaptation of animals and humans to changing conditions of existence in the external environment is ensured by the activities nervous system and is realized through reflex activity. In the process of evolution, hereditarily fixed reactions arose (without conditioned reflexes), which combine and coordinate the functions of various organs, carry out adaptation of the body. In humans and higher animals, in the process of individual life, qualitatively new reflex reactions arise, which I. P. Pavlov called conditioned reflexes, considering them the most perfect form of adaptation.

While relatively simple shapes nervous activity determine the reflex regulation of homeostasis and vegetative functions of the body, the highest nervous activity(VND) provides complex individual forms of behavior in changing living conditions. GNI is realized due to the dominant influence of the cortex on all underlying structures of the central nervous system. The main processes that dynamically replace each other in the central nervous system are the processes of excitation and inhibition. Depending on their ratio, strength and localization, the control influences of the cortex are built. The functional unit of the GNI is the conditioned reflex.

Higher nervous activity is a set of unconditioned and conditioned reflexes, as well as higher mental functions that ensure adequate behavior in changing natural and social conditions. For the first time, the assumption about the reflex nature of the activity of the higher parts of the brain was made by I.M. Sechenov, which made it possible to extend the reflex principle to human mental activity. The ideas of I.M. Sechenov received experimental confirmation in the works of I.P. Pavlov, who developed a method for objective assessment of the functions of the higher parts of the brain - the method of conditioned reflexes.

I.P. Pavlov showed that all reflex reactions can be divided into two groups: unconditioned and conditioned.

Unconditioned reflexes	Conditioned reflexes
1. Congenital, hereditary reactions, most of them begin to function immediately after birth.	1. Reactions acquired in the process of individual life.
2. They are specific, i.e. characteristic of all representatives of this species.	2. Individual.
3. Permanent and maintained throughout life.	3. Impermanent - they can appear and disappear.
4. Carried out by the lower parts of the central nervous system ( subcortical nuclei, brainstem, spinal cord).	4. They are primarily a function of the cerebral cortex.
5. They arise in response to adequate stimulation acting on a specific receptive field.	5. Occurs in response to any stimuli acting on different receptive fields.

Unconditioned reflexes can be simple or complex. Complex innate unconditional reflex reactions are called instincts. Their characteristic feature is the chain nature of the reactions.

Conditioned reflex is a complex multicomponent reaction that is developed on the basis of unconditioned reflexes using a previous indifferent stimulus. It has a signaling character, and the body meets the impact of an unconditioned stimulus prepared. For example, in the pre-launch period, blood is redistributed, breathing and blood circulation are increased, and when the muscle load begins, the body is already prepared for it.

To develop a conditioned reflex it is necessary:

1) the presence of two stimuli, one of which is unconditioned (food, painful stimulus, etc.), causing an unconditioned reflex reaction, and the other is conditioned (signal), signaling the upcoming unconditional stimulus (light, sound, type of food, etc. .);
2) multiple combinations of conditioned and unconditioned stimuli (although the formation of a conditioned reflex is possible with their single combination);
3) the conditioned stimulus must precede the action of the unconditional;
4) any stimulus from the external or internal environment can be used as a conditioned stimulus, which should be as indifferent as possible, not cause a defensive reaction, not have excessive force and be able to attract attention;
5) the unconditioned stimulus must be strong enough, otherwise a temporary connection will not be formed;
6) arousal from an unconditioned stimulus should be stronger than from a conditioned one;
7) it is necessary to eliminate extraneous stimuli, as they can cause inhibition of the conditioned reflex;
8) the animal in which the conditioned reflex is developed must be healthy;
9) when developing a conditioned reflex, motivation must be expressed, for example, when developing a food salivary reflex, the animal must be hungry, but in a well-fed animal, this reflex is not developed.

Conditioned reflexes are easier to develop in response to environmentally similar influences for a given animal. In this regard, conditioned reflexes are divided into natural and artificial. Natural conditioned reflexes are developed to agents that, under natural conditions, act together with a stimulus that causes an unconditioned reflex (for example, the type of food, its smell, etc.). All other conditioned reflexes are artificial, i.e. are produced in response to agents that are not normally associated with the action of an unconditioned stimulus, for example, the food salivary reflex to a bell.

The physiological basis for the emergence of conditioned reflexes is the formation of functional temporary connections in the higher parts of the central nervous system.

Temporary connection is a set of neurophysiological, biochemical and ultrastructural changes in the brain that arise during the combined action of conditioned and unconditioned stimuli. I.P. Pavlov suggested that during the development of a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - the cortical representations of the conditioned and unconditioned reflexes. Excitation from the center of the conditioned reflex can be transmitted to the center of the unconditioned reflex from neuron to neuron.

Consequently, the first way of forming a temporary connection between the cortical representations of the conditioned and unconditioned reflexes is intracortical. However, when the cortical representation of the conditioned reflex is destroyed, the developed conditioned reflex is preserved. Apparently, the formation of a temporary connection occurs between the subcortical center of the conditioned reflex and the cortical center of the unconditioned reflex. When the cortical representation of the unconditioned reflex is destroyed, the conditioned reflex is also preserved. Consequently, the development of a temporary connection can occur between the cortical center of the conditioned reflex and the subcortical center of the unconditioned reflex.

Separation of the cortical centers of the conditioned and unconditioned reflexes by crossing the cerebral cortex does not prevent the formation of the conditioned reflex.

This indicates that a temporary connection can be formed between the cortical center of the conditioned reflex, the subcortical center of the unconditioned reflex and the cortical center of the unconditioned reflex.

There are different opinions on the issue of the mechanisms for the formation of temporary connections. Perhaps the formation of a temporary connection occurs according to the dominant principle. The source of excitation from an unconditioned stimulus is always stronger than from a conditioned one, since the unconditioned stimulus is always biologically more significant for the animal. This focus of excitation is dominant, therefore attracts excitation from the focus of conditioned stimulation. If the excitation has passed along some nerve circuits, then next time it will pass along these paths much easier (the phenomenon of “blazing a path”). This is based on: the summation of excitations, a long-term increase in the excitability of synaptic formations, an increase in the amount of mediator in synapses, and an increase in the formation of new synapses. All this creates structural prerequisites for facilitating the movement of excitation along certain neural circuits.

Another idea about the mechanism of formation of a temporary connection is the convergent theory. It is based on the ability of neurons to respond to stimulation of different modalities. According to P.K. Anokhin, conditioned and unconditioned stimuli cause widespread activation of cortical neurons due to the inclusion of the reticular formation. As a result, the ascending signals (conditioned and unconditioned stimuli) overlap, i.e. these excitations meet on the same cortical neurons. As a result of the convergence of excitations, temporary connections arise and stabilize between the cortical representations of the conditioned and unconditioned stimuli.

Reflex– the body’s response is not an external or internal irritation, carried out and controlled by the central nervous system. The development of ideas about human behavior, which has always been a mystery, was achieved in the works of Russian scientists I. P. Pavlov and I. M. Sechenov.

Reflexes unconditioned and conditioned.

Unconditioned reflexes- These are innate reflexes that are inherited by offspring from their parents and persist throughout a person’s life. The arcs of unconditioned reflexes pass through the spinal cord or brain stem. The cerebral cortex is not involved in their formation. Unconditioned reflexes are provided only to those environmental changes that have often been encountered by many generations of a given species.

These include:

Food (salivation, sucking, swallowing);
Defensive (coughing, sneezing, blinking, withdrawing your hand from a hot object);
Approximate (squinting eyes, turns);
Sexual (reflexes associated with reproduction and care of offspring).
The importance of unconditioned reflexes lies in the fact that thanks to them the integrity of the body is preserved, constancy is maintained and reproduction occurs. Already in a newborn child the simplest unconditioned reflexes.
The most important of these is the sucking reflex. The stimulus of the sucking reflex is the touching of an object to the child’s lips (mother’s breast, pacifier, toy, finger). The sucking reflex is an unconditioned food reflex. In addition, the newborn already has some protective unconditioned reflexes: blinking, which occurs if a foreign body approaches the eye or touches the cornea, constriction of the pupil when exposed to strong light on the eyes.

Particularly pronounced unconditioned reflexes in various animals. Not only individual reflexes can be innate, but also more complex forms of behavior, which are called instincts.

Conditioned reflexes– these are reflexes that are easily acquired by the body throughout life and are formed on the basis of an unconditioned reflex under the action of a conditioned stimulus (light, knock, time, etc.). I.P. Pavlov studied the formation of conditioned reflexes in dogs and developed a method for obtaining them. To develop a conditioned reflex, a stimulus is needed - a signal that triggers the conditioned reflex; repeated repetition of the action of the stimulus allows you to develop a conditioned reflex. During the formation of conditioned reflexes, a temporary connection arises between the centers and the centers of the unconditioned reflex. Now this unconditioned reflex is not carried out under the influence of completely new external signals. These stimuli from the surrounding world, to which we were indifferent, can now acquire vital significance. Throughout life, many conditioned reflexes are developed that form the basis of our life experience. But this life experience has meaning only for a given individual and is not inherited by its descendants.

In a separate category conditioned reflexes distinguish motor conditioned reflexes developed during our lives, i.e. skills or automated actions. The meaning of these conditioned reflexes is to master new motor skills and develop new forms of movements. During his life, a person masters many special motor skills related to his profession. Skills are the basis of our behavior. Consciousness, thinking, attention are freed from performing those operations that have become automated and become skills everyday life. The most successful way to master skills is through systematic exercises, correcting errors noticed in time, and knowing the ultimate goal of each exercise.

If you do not reinforce the conditioned stimulus with the unconditioned stimulus for some time, then inhibition of the conditioned stimulus occurs. But it doesn't disappear completely. When the experience is repeated, the reflex is restored very quickly. Inhibition is also observed when exposed to another stimulus of greater strength.

The body responds to the action of a stimulus, which is carried out with the participation of the nervous system and is controlled by it. According to Pavlov's ideas, the main principle of the nervous system is the reflex principle, and the material basis is the reflex arc. Reflexes are conditioned and unconditioned.

Reflexes are conditioned and unconditioned. - These are reflexes that are inherited and passed on from generation to generation. By the time a person is born, the almost reflex arc of unconditioned reflexes is fully formed, with the exception of sexual reflexes. Unconditioned reflexes are species-specific, that is, they are characteristic of individuals of a given species.

Conditioned reflexes(UR) is an individually acquired reaction of the body to a previously indifferent stimulus ( stimulus– any material agent, external or internal, conscious or unconscious, acting as a condition for subsequent states of the organism. Signal stimulus (also indifferent) is a stimulus that has not previously caused a corresponding reaction, but under certain conditions of formation begins to cause it), reproducing an unconditioned reflex. SDs are formed throughout life and are associated with the accumulation of life. They are individual for each person or animal. Able to fade away if not reinforced. Extinguished conditioned reflexes do not disappear completely, that is, they are capable of recovery.

The physiological basis of the conditioned reflex is the formation of new or modification of existing neural connections, occurring under the influence of changes in the external and internal environment. These are temporary connections (in belt connection- this is a set of neurophysiological, biochemical and ultrastructural changes in the brain that arise in the process of combining conditioned and unconditioned stimuli and form certain relationships between various brain formations), which are inhibited when the situation is canceled or changed.

General properties of conditioned reflexes. Despite certain differences, conditioned reflexes are characterized by the following general properties (features):

• All conditioned reflexes represent one of the forms of adaptive reactions of the body to changing environmental conditions.
• SDs are acquired and canceled during the individual life of each individual.
• All SDs are formed with the participation of.
• SDs are formed on the basis of unconditioned reflexes; Without reinforcement, conditioned reflexes are weakened and suppressed over time.
• All types of conditioned reflex activity are of a warning signal nature. Those. precede and prevent the subsequent occurrence of BD. They prepare the body for any biologically targeted activity. UR is a reaction to a future event. SDs are formed due to the plasticity of the NS.

The biological role of UR is to expand the range of adaptive capabilities of the organism. SD complements BR and allows subtle and flexible adaptation to a wide variety of environmental conditions.

Differences between conditioned reflexes and unconditioned ones

Unconditioned reflexes	Conditioned reflexes
Congenital, reflect the specific characteristics of the organism	Acquired throughout life and reflect the individual characteristics of the body
Relatively constant throughout the life of an individual	Formed, changed and canceled when they become inadequate to living conditions
Implemented along anatomical pathways determined genetically	Implemented through functionally organized temporary (closing) connections
Characteristic of all levels of the central nervous system and carried out mainly by its lower sections (stem, subcortical nuclei)	For their formation and implementation, they require the integrity of the cerebral cortex, especially in higher mammals
Each reflex has its own specific receptive field and specific	Reflexes can be formed from any receptive field to a wide variety of stimuli
React to a present stimulus that can no longer be avoided	They adapt the body to an action that has yet to be experienced, that is, they have a warning, signaling value.

1. Unconditioned reactions are innate, hereditary reactions; they are formed on the basis of hereditary factors and most of them begin to function immediately after birth. Conditioned reflexes are acquired reactions in the process of individual life.
2. Unconditioned reflexes are species-specific, that is, these reflexes are characteristic of all representatives of a given species. Conditioned reflexes are individual; some animals may develop certain conditioned reflexes, while others may develop others.
3. Unconditioned reflexes are constant; they persist throughout the life of the organism. Conditioned reflexes are not constant; they can arise, become established and disappear.
4. Unconditioned reflexes are carried out due to the lower parts of the central nervous system (subcortical nuclei,). Conditioned reflexes are primarily a function of the higher parts of the central nervous system - the cerebral cortex.
5. Unconditioned reflexes are always carried out in response to adequate stimulation acting on a specific receptive field, i.e. they are structurally fixed. Conditioned reflexes can be formed to any stimuli, from any receptive field.
6. Unconditioned reflexes are reactions to direct irritations (food, being in the oral cavity, causes salivation). Conditioned reflex - a reaction to the properties (signs) of a stimulus (food, the type of food causes salivation). Conditioned reactions are always signaling in nature. They signal the upcoming action of the stimulus, and the body meets the influence of the unconditioned stimulus when all responses have already been included, ensuring the body is balanced by the factors causing this unconditioned reflex. So, for example, food entering the oral cavity encounters saliva there, released conditionally (at the sight of food, at its smell); muscle work begins when the conditioned reflexes developed to it have already caused a redistribution of blood, increased breathing and blood circulation, etc. This reveals the highest adaptive nature of conditioned reflexes.
7. Conditioned reflexes are developed on the basis of unconditioned ones.
8. A conditioned reflex is a complex multicomponent reaction.
9. Conditioned reflexes can be developed in real life and in laboratory conditions.

Conditioned reflexes are complex adaptive reactions of the body, carried out by the higher parts of the central nervous system through the formation of a temporary connection between a signal stimulus and an unconditioned reflex act that reinforces this stimulus. Based on an analysis of the patterns of formation of conditioned reflexes, the school created the doctrine of higher nervous activity (see). Unlike unconditioned reflexes (see), which ensure the body’s adaptation to permanent influences external environment, conditioned reflexes enable the body to adapt to changing environmental conditions. Conditioned reflexes are formed on the basis of unconditioned reflexes, which requires the coincidence in time of some stimulus from the external environment (conditioned stimulus) with the implementation of one or another unconditioned reflex. The conditioned stimulus becomes a signal of a dangerous or favorable situation, allowing the body to respond with an adaptive reaction.

Conditioned reflexes are not permanent and are acquired in the process individual development body. Conditioned reflexes are divided into natural and artificial. The first ones arise in response to natural stimuli in natural conditions of existence: a puppy, having received meat for the first time, sniffs it for a long time and timidly eats it, and this act of eating is accompanied by. In the future, only the sight and smell of meat causes the puppy to lick and eliminate. Artificial conditioned reflexes are developed in an experimental setting, when the conditioned stimulus for an animal is an influence that is not related to unconditioned reactions in the animals’ natural habitat (for example, flickering light, the sound of a metronome, sound clicks).

Conditioned reflexes are divided into food, defensive, sexual, orienting, depending on the unconditional reaction that reinforces the conditioned stimulus. Conditioned reflexes can be named depending on the registered response of the body: motor, secretory, vegetative, excretory, and can also be designated by the type of conditioned stimulus - light, sound, etc.

To develop conditioned reflexes in an experiment, a number of conditions are necessary: ​​1) the conditioned stimulus must always precede the unconditioned stimulus in time; 2) the conditioned stimulus should not be strong so as not to cause the body’s own reaction; 3) a conditioned stimulus is taken that is usually found in the environmental conditions of the given animal or person; 4) the animal or person must be healthy, cheerful and have sufficient motivation (see).

There are also conditioned reflexes of various orders. When a conditioned stimulus is reinforced by an unconditioned stimulus, a first-order conditioned reflex is developed. If some stimulus is reinforced by a conditioned stimulus to which a conditioned reflex has already been developed, then a second-order conditioned reflex is developed to the first stimulus. Conditioned reflexes of higher orders are developed with difficulty, which depends on the level of organization of the living organism.

A dog can develop conditioned reflexes of up to 5-6 orders, in a monkey - up to 10-12 orders, in humans - up to 50-100 orders.

The work of I. P. Pavlov and his students established that in the mechanism of the emergence of conditioned reflexes the leading role belongs to education functional connection between foci of excitation from conditioned and unconditioned stimuli. An important role was assigned to the cerebral cortex, where conditioned and unconditioned stimuli, creating foci of excitation, began to interact with each other, creating temporary connections. Subsequently, using electrophysiological research methods, it was established that the interaction between conditioned and unconditioned excitations can first occur at the level of subcortical structures of the brain, and at the level of the cerebral cortex, the formation of integral conditioned reflex activity takes place.

However, the cerebral cortex always controls the activity of subcortical formations.

Studies of the activity of single neurons of the central nervous system using the microelectrode method have established that one neuron receives both conditioned and unconditioned excitations (sensory-biological convergence). It is especially clearly expressed in the neurons of the cerebral cortex. These data forced us to abandon the idea of ​​the presence of foci of conditioned and unconditioned excitation in the cerebral cortex and create the theory of convergent closure of the conditioned reflex. According to this theory, a temporary connection between conditioned and unconditioned excitation arises in the form of a chain of biochemical reactions in the protoplasm of the nerve cell of the cerebral cortex.

Modern ideas about conditioned reflexes have expanded and deepened significantly thanks to the study of the higher nervous activity of animals in conditions of their free natural behavior. It has been established that the environment, along with the time factor, plays an important role in the behavior of the animal. Any stimulus from the external environment can become conditioned, allowing the body to adapt to environmental conditions. As a result of the formation of conditioned reflexes, the body reacts some time before the impact of unconditioned stimulation. Consequently, conditioned reflexes contribute to the successful finding of food by animals, help to avoid danger in advance and to most perfectly navigate the changing conditions of existence.

Unconditioned and conditioned reflexes.

An element of higher nervous activity is a conditioned reflex. The path of any reflex forms a kind of arc, consisting of three main parts. The first part of this arc, which includes the receptor, sensory nerve and brain cell, is called the analyzer. This part perceives and distinguishes the entire complex of various external influences entering the body.

The cerebral cortex (according to Pavlov) is a collection of the brain ends of various analyzers. Stimuli from the external world arrive here, as well as impulses from the internal environment of the body, which causes the formation of numerous foci of excitation in the cortex, which, as a result of induction, cause points of inhibition. Thus, a kind of mosaic arises, consisting of alternating points of excitation and inhibition. This is accompanied by the formation of numerous conditioned connections (reflexes), both positive and negative. As a result, a certain functional dynamic system of conditioned reflexes is formed, which is the physiological basis of the psyche.

Two main mechanisms carry out higher nervous activity: conditioned reflexes and analyzers.

Each animal organism can exist only if it is constantly balanced (interacts) with the external environment. This interaction is carried out through certain connections (reflexes). I.P. Pavlov identified constant connections, or unconditioned reflexes. An animal or a person will be born with these connections - these are ready-made, constant, stereotypical reflexes. Unconditioned reflexes, such as the reflex for urination, defecation, sucking reflex in a newborn, salivation, are various forms of simple defensive reactions. Such reactions are constriction of the pupil to light, squinting of the eyelid, withdrawal of the hand during sudden irritation, etc. Complex unconditioned reflexes in humans include instincts: food, sexual, orientation, parental, etc. Both simple and complex unconditioned reflexes are innate mechanisms; they operate even at the lowest levels of development of the animal world. So, for example, the weaving of a web by a spider, the construction of honeycombs by bees, the nesting of birds, sexual desire - all these acts do not arise as a result of individual experience or learning, but are innate mechanisms.

However, the complex interaction between animals and humans environment requires the activity of a more complex mechanism.

In the process of adaptation to living conditions, another type of connections with the external environment is formed in the cerebral cortex - temporary connections, or conditioned reflexes. A conditioned reflex, according to Pavlov, is an acquired reflex, developed under certain conditions, and is subject to fluctuations. If not reinforced, it can weaken and lose its direction. Therefore, these conditioned reflexes are called temporary connections.

The main conditions for the formation of a conditioned reflex in its elementary form in animals are, firstly, the combination of a conditioned stimulus with unconditioned reinforcement and, secondly, the conditioned stimulus preceding the action of the unconditioned reflex. Conditioned reflexes are developed on the basis of unconditioned or on the basis of well-developed conditioned reflexes. In this case, they are called conditioned or conditioned reflexes of the second order. The material basis of unconditioned reflexes is the lower levels of the brain, as well as the spinal cord. Conditioned reflexes in higher animals and humans are formed in the cerebral cortex. Of course, in every nervous act it is impossible to clearly distinguish between the actions of unconditioned and conditioned reflexes: undoubtedly, they represent a system, although the nature of their formation is different. The conditioned reflex, being generalized at first, is then refined and differentiated. Conditioned reflexes as neurodynamic formations enter into certain functional relationships with each other, forming various functional systems, and are thus the physiological basis of thinking,

knowledge, skills, labor abilities.

To understand the mechanism of formation of a conditioned reflex in its elementary form in a dog, the well-known experience of I.P. Pavlov and his students (Fig. 56).

The essence of the experience is as follows. It is known that during the act of feeding, animals (in particular dogs) begin to secrete saliva and gastric juice. These are natural manifestations of the unconditioned food reflex. In the same way, when acid is poured into a dog’s mouth, saliva is released abundantly, washing away acid particles that irritate it from the mucous membranes of the mouth. This is also a natural manifestation of the defensive reflex, which in this case occurs through the salivary center in the medulla oblongata. However, under certain conditions, it is possible to force a dog to salivate to an indifferent stimulus, for example, the light of a light bulb, the sound of a horn, a musical tone, etc. To do this, before giving the dog food, light a lamp or ring a bell. If you combine this technique one or several times, and then use only one conditioned stimulus, without accompanying it with food, you can cause the dog to salivate in response to the action of an indifferent stimulus. What explains this? In the dog’s brain, during the period of action of a conditioned and unconditioned stimulus (light and food), certain areas of the brain come into a state of excitation, in particular the visual center and the center of the salivary gland (in the medulla oblongata). The food center, which is in a state of excitation, forms an excitation point in the cortex as a cortical representation of the center of the unconditioned reflex. Repeated combination of indifferent and unconditioned stimuli leads to the formation of an easier, “trodden” path. Between these points of excitation a chain is formed in which a number of irritated points are closed. In the future, it is enough to irritate only one link in a closed chain, in particular the visual center, and the entire developed connection will be activated, which will be accompanied by a secretory effect. Thus, a new connection was established in the dog’s brain - a conditioned reflex. The arc of this reflex closes between the cortical foci of excitation that arise as a result of the action of an indifferent stimulus and the cortical representations of the centers of unconditioned reflexes. However, this connection is temporary. Experiments have shown that for some time the dog will salivate only to the action of a conditioned stimulus (light, sound, etc.), but soon this reaction will stop. This will indicate that the connection has faded; True, it does not disappear without a trace, but only slows down. It can be restored again by combining feeding with the action of a conditioned stimulus; again it is possible to obtain salivation only in response to the action of light. This experience is elementary, but it is of fundamental importance.

The point is that the reflex mechanism is the main physiological mechanism in the brain not only of animals, but also of humans. However, the ways of formation of conditioned reflexes in animals and humans are not the same. The fact is that the formation of conditioned reflexes in humans is regulated by a special, uniquely human, second signaling system, which does not exist in the brain even of higher animals. The real expression of this second signaling system is the word, speech. Hence, the mechanical transfer of all laws obtained in animals to explain all higher nervous activity in humans will not be justified. I.P. Pavlov suggested observing “the greatest caution” in this matter. However, in general view the reflex principle and a number of basic laws of higher nervous activity in animals retain their significance for humans.

Students of I.P. Pavlova N.I. Krasnogorsky, A.G. Ivanov - Smolensky, N.I. Protopopov and others did a lot of research on conditioned reflexes in people, in particular in children. Therefore, material has now accumulated that allows us to make an assumption about the characteristics of higher nervous activity in various acts of behavior. For example, in the second signaling system, conditioned connections can be formed quickly and more firmly held in the cerebral cortex.

Let’s take for example a process that is close to us, such as teaching children to read and write. Previously, it was assumed that the basis of literacy acquisition (learning to read and write) was the development of special reading and writing centers. Now science denies the existence in the cerebral cortex of any local areas, anatomical centers, as if specialized in the area of ​​these functions. In the brains of people who have not mastered literacy, such centers do not naturally exist. However, how do these skills develop? What are the functional mechanisms of such completely new and real manifestations in the mental activity of a child who has mastered literacy? This is where the most correct idea would be that the physiological mechanism of literacy skills is the neural connections that form specialized systems of conditioned reflexes. These connections are not inherent in nature; they are formed as a result of the interaction of the student’s nervous system with the external environment. In this case, such an environment will be a classroom - a literacy lesson. The teacher, starting to teach literacy, shows the students on the appropriate tables or writes individual letters on the board, and the students copy them in their notebooks. The teacher not only shows letters (visual perception), but also pronounces certain sounds (auditory perception). As you know, writing is carried out by a certain movement of the hand, which is associated with the activity of the motor-kinesthetic analyzer. When reading, there is also a movement of the eyeball, which moves in the direction of the lines readable text. Thus, during the period of learning to read and write, the child’s cerebral cortex receives numerous irritations signaling the optical, acoustic and motor appearance of letters. This whole mass of irritation leaves nerve traces in the cortex, which are gradually balanced, reinforced by the teacher’s speech and one’s own orally student. As a result, a specialized system of conditional connections is formed, reflecting sound-letters and their combinations in various verbal complexes. This system - a dynamic stereotype - is the physiological basis of school literacy skills. It can be assumed that the formation of various labor skills is a consequence of the formation of neural connections that arise in the process of learning skills - through vision, hearing, tactile and motor receptors. At the same time, we must keep in mind the importance of innate inclinations, on which the nature and results of the development of a particular ability depend. All these connections, arising as a result of nervous stimulation, enter into complex relationships and form functional-dynamic systems, which are also the physiological basis of labor skills.

As is known from elementary laboratory experiments, a conditioned reflex that is not reinforced by food fades away, but does not disappear completely. We see something similar in people's lives. There are known facts when a person who learned to read and write, but then, due to life circumstances, did not have to deal with a book, largely lost the literacy skills he had once acquired. Who does not know such facts when the acquired skill in the field of theoretical knowledge or work skills, not supported by systematic work, is weakened. However, it does not disappear completely, and a person who has studied this or that skill, but then leaves it for a long period of time, only feels very insecure at first if he again has to return to his previous profession. However, it will relatively quickly restore the lost quality. The same can be said about people who once studied a foreign language, but then completely forgot it due to lack of practice; undoubtedly, it is easier for such a person, with appropriate practice, to regain mastery of the language than for another who will study new language for the first time.

All this suggests that traces of past irritations remain in the cerebral cortex, but, not reinforced by exercise, they fade away (inhibited).

Analyzers

By analyzers we mean formations that carry out knowledge of the external and internal environment of the body. These are, first of all, taste, skin, and olfactory analyzers. Some of them are called distant (visual, auditory, olfactory) because they can perceive stimuli at a distance. The internal environment of the body also sends constant impulses to the cerebral cortex.

1-7 – receptors (visual, auditory, skin, olfactory, gustatory, motor apparatus, internal organs). I – area of ​​the spinal cord or medulla oblongata where afferent fibers enter (A); impulses from which are transmitted to the neurons located here, forming the ascending pathways; the axons of the latter go to the area of ​​the optic hillocks (II); the axons of the nerve cells of the visual thalamus ascend into the cerebral cortex (III). At the top (III) the location of the nuclear parts of the cortical sections of various analyzers is outlined (for the internal, gustatory and olfactory analyzers, this location has not yet been precisely established); The scattered cells of each analyzer scattered throughout the cortex are also indicated (according to Bykov)

One of these analyzers is the motor analyzer, which receives impulses from skeletal muscles, joints, ligaments and reports to the cortex about the nature and direction of movement. There are other internal analyzers - interoceptors, which signal to the cortex about the state of the internal organs.

Each analyzer consists of three parts (Fig. 57). The peripheral end, i.e. receptor directly facing the external environment. These are the retina of the eye, the cochlear apparatus of the ear, sensitive devices of the skin, etc., which connect through the conducting nerves to the brain end, i.e. specific area of ​​the cerebral cortex. Hence, the occipital cortex is the cerebral end of the visual, the temporal – the auditory, the parietal – the cutaneous and muscular-articular analyzers, etc. In turn, the cerebral end, already in the cerebral cortex, is divided into a nucleus, where the most subtle analysis and synthesis of certain stimuli is carried out, and secondary elements located around the main nucleus and representing the analyzer periphery. The boundaries of these secondary elements between individual analyzers are fuzzy and overlap. In the analyzer periphery, similar analysis and synthesis are carried out only in the most elementary form. The motor area of ​​the cortex is the same analyzer of the skeletal-motor energy of the body, but its peripheral end faces the internal environment of the body. It is characteristic that the analyzing apparatus acts as an integral formation. Thus, the cortex, including numerous analyzers, itself is a grandiose analyzer of the external world and the internal environment of the body. Irritations entering certain cells of the cortex through the peripheral ends of the analyzers produce excitation in the corresponding cellular elements, which is associated with the formation of temporary nerve connections - conditioned reflexes.

Excitation and inhibition of nervous processes

The formation of conditioned reflexes is possible only when the cerebral cortex is in an active state. This activity is determined by the occurrence of basic nervous processes in the cortex - excitation and inhibition.

Excitation is an active process that occurs in the cellular elements of the cortex when it is exposed to certain stimuli from the external and internal environment through analyzers. The process of excitation is accompanied by a special state of nerve cells in a particular area of ​​the cortex, which is associated with the active activity of coupling devices (synapses) and the release of chemicals (transmitters) such as acetylcholine. In the area where foci of excitation occur, increased formation of nerve connections occurs - here a so-called active working field is formed.

Braking(detention) is also not a passive, but an active process. This process seems to forcibly restrain excitement. Braking is characterized to varying degrees intensity. I.P. Pavlov attached great value the inhibitory process, which regulates the activity of excitation, “holds it in its fist.” He identified and studied several types, or forms, of the inhibitory process.

External inhibition is an innate mechanism, which is based on unconditioned reflexes, acts immediately (from the spot) and can suppress conditioned reflex activity. An example illustrating the effect of external inhibition was a fact, not uncommon in the laboratory, when the established conditioned reflex activity in dogs in response to the action of a conditioned stimulus (for example, salivation towards light) suddenly stopped as a result of some extraneous strong sounds, the appearance of a new face, etc. d. The indicative unconditioned reflex to novelty that arose in the dog inhibited the course of the developed conditioned reflex. In people's lives, we can often encounter similar facts, when intense mental activity associated with the performance of a particular work may be disrupted due to the appearance of some extra stimuli, for example, the appearance of new faces, loud conversation, some sudden noises and etc. External inhibition is called fading, because if the action of external stimuli is repeated many times, then the animal already “gets used” to them and they lose their inhibitory effect. These facts are well known in human practice. So, for example, some people get used to working in a difficult environment, where there are many external stimuli (work in noisy workshops, work as cashiers in large stores, etc.), causing the newcomer to feel confused.

Internal inhibition is an acquired mechanism based on the action of conditioned reflexes. It is formed in the process of life, education, work. This type of active inhibition is inherent only in the cerebral cortex. Internal inhibition has a twofold character. During the day, when the cerebral cortex is active, it is directly involved in the regulation of the excitatory process, is fractional in nature and, mixing with foci of excitation, forms the basis of the physiological activity of the brain. At night, this same inhibition radiates through the cerebral cortex and causes sleep. I.P. Pavlov in his work “Sleep and internal inhibition are the same process” emphasized this feature of internal inhibition, which, participating in the active work of the brain during the day, delays the activity of individual cells, and at night, spreading, irradiating throughout the cortex, causes inhibition of the entire cerebral cortex , which determines the development of physiological normal sleep.

Internal inhibition, in turn, is divided into extinction, delayed and differentiation. In well-known experiments on dogs, the mechanism of extinctive inhibition causes a weakening of the effect of a developed conditioned reflex when it is reinforced. However, the reflex does not disappear completely; it can reappear after some time and is especially easy with appropriate reinforcement, for example, food.

In humans, the process of forgetting is caused by a certain physiological mechanism - extinctive inhibition. This type of inhibition is very significant, since the inhibition of currently unnecessary connections contributes to the emergence of new ones. Thus, the desired sequence is created. If all formed connections, both old and new, were at the same optimal level, then intelligent mental activity would be impossible.

Delayed inhibition is caused by a change in the order of stimuli. Usually in experience a conditioned stimulus (light, sound, etc.) somewhat precedes an unconditioned stimulus, for example food. If you leave the conditioned stimulus aside for some time, i.e. lengthen the time of its action before giving the unconditioned stimulus (food), then as a result of such a change in the regime, the conditioned salivary reaction to light will be delayed by approximately the time for which the conditioned stimulus was left.

What causes the delay in the appearance of a conditioned reaction and the development of delay inhibition? The mechanism of delayed inhibition underlies such properties of human behavior as endurance, the ability to restrain one or another type of mental reactions that are inappropriate in the sense of reasonable behavior.

Differential inhibition is extremely important in the functioning of the cerebral cortex. This inhibition can dissect conditional connections down to the smallest detail. Thus, dogs developed a salivary conditioned reflex to 1/4 of a musical tone, which was reinforced with food. When they tried to give 1/8 of the musical tone (the difference in acoustic terms is extremely insignificant), the dog did not salivate. Undoubtedly, in the complex and subtle processes of human mental and speech activity, which have chains of conditioned reflexes as their physiological basis, all types of cortical inhibition are of great importance, and among them, differentiation should be especially emphasized. The development of the finest differentiations of the conditioned reflex determines the formation of higher forms of mental activity - logical thinking, articulate speech and complex work skills.

Protective (extraordinary) inhibition. Internal inhibition has various forms of manifestation. During the day it is fractional in nature and, mixing with foci of excitation, takes an active part in the activity of the cerebral cortex. At night, irradiating, it causes diffuse inhibition - sleep. Sometimes the cortex can be exposed to extremely strong stimuli, when the cells work to the limit and their further intense activity can lead to their complete exhaustion and even death. In such cases, it is advisable to turn off weakened and exhausted cells from work. This role is played by a special biological reaction of the nerve cells of the cortex, expressed in the development of an inhibitory process in those areas of the cortex whose cells have been weakened by super-strong stimuli. This type of active inhibition is called healing-protective or transcendental and is predominantly innate in nature. During the period when certain areas of the cortex are covered by extreme protective inhibition, weakened cells are switched off from active activity, and restoration processes occur in them. As the diseased areas normalize, the inhibition is removed, and those functions that were localized in these areas of the cortex can be restored. The concept of protective inhibition created by I.P. Pavlov, explains the mechanism of a number of complex disorders that occur in various nervous and mental diseases.

“We are talking about inhibition, which protects the cells of the cerebral cortex from the danger of further damage, or even death, and prevents the serious threat that arises when the cells are overexcited, in cases where they are forced to perform impossible tasks, in catastrophic situations, in exhaustion and weakening they are influenced various factors. In these cases, inhibition occurs not in order to coordinate the activity of the cells of this higher part of the nervous system, but in order to protect and protect them" (E.A. Asratyan, 1951).

In cases observed in the practice of defectologists, such causative factors are toxic processes (neuroinfections) or skull injuries that cause weakening of nerve cells due to their exhaustion. A weakened nervous system is favorable soil for the development of protective inhibition in it. “Such a nervous system,” wrote I.P. Pavlov, “when encountering difficulties... or after unbearable excitement inevitably goes into a state of exhaustion. And exhaustion is one of the most important physiological impulses for the emergence of an inhibitory process as a protective process.”

Disciples and followers of I.P. Pavlova – A.G. Ivanov-Smolensky, E.A. Asratyan, A.O. Dolin, S.N. Davydenko, E.A. Popov and others attached great importance to further scientific developments related to clarifying the role of healing and protective inhibition in various forms ah nervous pathology, noted for the first time by I.P. Pavlov in the physiological analysis of schizophrenia and some other neuropsychiatric diseases.

Based on a number of experimental works carried out in his laboratories, E.A. Asratyan formulated three main provisions characterizing the significance of healing-protective inhibition as a protective reaction of nervous tissue under various harmful influences:

1) healing-protective inhibition belongs to the category of universal coordination properties of all nervous elements, to the category of general biological properties of all excitable tissues;

2) the process of protective inhibition plays the role of a healing factor not only in the cerebral cortex, but throughout the entire central nervous system;

3) the process of protective inhibition plays this role not only in functional, but also in organic lesions of the nervous system.

The concept of the role of healing-protective inhibition is particularly fruitful for the clinical and physiological analysis of various forms of nervous pathology. This concept makes it possible to more clearly imagine some complex clinical symptom complexes, the nature of which long time was a mystery.

Undoubtedly, the role of protective-healing inhibition in the complex system of brain compensation is great. It is one of the active physiological components that contribute to the development of compensatory processes.

The duration of the existence of healing-protective inhibition in individual areas of the cortex in the residual stage of the disease, apparently, can have different periods. In some cases it does not last long. This mainly depends on the ability of the affected cortical elements to recover. E.A. Asratyan points out that in such cases a peculiar combination of pathology and physiology occurs. In fact, on the one hand, the protective inhibitory process is healing, since turning off a group of cells from active work gives them the opportunity to “heal their wounds.” At the same time, the loss of a certain mass of nerve cells operating at a reduced level from the general cortical activity leads to a weakening of the performance of the cortex, to a decrease in individual abilities, and to peculiar forms of cerebral asthenia.

Applying this position to our cases, we can assume that some forms of undeveloped individual abilities in students who have suffered from a brain disease, for example, reading, writing, counting, as well as some types of speech deficiencies, weakening of memory, shifts in the emotional sphere are based on the presence stagnant inhibitory process, causing a violation of the mobility of general neurodynamics. Improvement in development, activation of weakened abilities, as witnessed by the school, occurs gradually, as the individual areas cortical mass from inhibition. However, it would be an attempt to simplify to explain the noticeable improvements that occur in the condition of children who have suffered trauma, encephalitis, only by the gradual removal of protective inhibition.

Based on the very nature of this type of healing process, which is a unique form of self-medication of the body, it should be assumed that the removal of protective inhibition from certain areas of the cerebral cortex is associated with the simultaneous development of a whole complex of restorative processes (resorption of foci of hemorrhage, normalization of blood circulation, reduction of hypertension and a number of others ).

It is known that sleep usually does not occur immediately. Between sleep and wakefulness there are transitional periods, the so-called phase states, which cause drowsiness, which is some kind of threshold to sleep. Normally, these phases can be very short-lived, but in pathological conditions they are fixed for a long time.

Laboratory studies have shown that animals (dogs) react differently to external stimuli during this period. In this regard, it was highlighted special forms phase states. The equalizing phase is characterized by the same reaction to both strong and weak stimuli; during the paradoxical phase, weak stimuli produce a noticeable effect, and strong ones – an insignificant one, and during the ultraparadoxical phase, positive stimuli have no effect at all, and negative ones cause a positive effect. Thus, a dog in an ultraparadoxical phase turns away from food offered to it, but when the food is removed, it reaches for it.

Patients with certain forms of schizophrenia sometimes do not answer the questions of others asked in a normal voice, but they give an answer to a question addressed to them, asked in a whisper. The occurrence of phase states is explained by the gradual spread of the inhibitory process throughout the cerebral cortex, as well as the strength and depth of its effect on the cortical mass.

Natural sleep in the physiological sense is a diffuse inhibition in the cerebral cortex, extending to some of the subcortical formations. However, inhibition may be incomplete, then sleep will be partial. This phenomenon can be observed during hypnosis. Hypnosis is a partial sleep in which certain areas of the cortex remain excited, which determines the special contact between the doctor and the person being hypnotized. Various types of sleep treatments and hypnosis have become part of the therapeutic arsenal, especially in the clinic of nervous and mental diseases.

Irradiation, concentration and mutual induction of nerves

processes

Excitation and inhibition (retention) have special properties that naturally arise during the implementation of these processes. Irradiation is the ability of excitation or inhibition to spread, spread across the cerebral cortex. Concentration is the opposite property, i.e. the ability of nervous processes to gather and concentrate at any one point. The nature of irradiation and concentration depends on the strength of the stimulus. I.P. Pavlov pointed out that with weak irritation, irradiation of both irritating and inhibitory processes occurs, with irritants of medium strength - concentration, and with strong ones - irradiation again.

By mutual induction of nervous processes we mean the closest connection of these processes with each other. They constantly interact, conditioning each other. Emphasizing this connection, Pavlov figuratively said that excitation will give rise to inhibition, and inhibition will give rise to excitation. There are positive and negative induction.

These properties of the basic nervous processes are distinguished by a certain constancy of action, which is why they are called the laws of higher nervous activity. What do these laws established in animals provide for understanding the physiological activity of the human brain? I.P. Pavlov pointed out that it can hardly be disputed that the most general foundations of higher nervous activity, confined to the cerebral hemispheres, are the same in both higher animals and humans, and therefore the elementary phenomena of this activity should be the same in both . Undoubtedly, the application of these laws, adjusted for that special specific superstructure that is characteristic only of humans, namely the second signaling system, will help in the future to better understand the basic physiological patterns that operate in the human cerebral cortex.

The cerebral cortex is integrally involved in certain nervous acts. However, the degree of intensity of this participation in certain parts of the cortex is not the same and depends on which analyzer the person’s active activity in this segment time. So, for example, if this activity for a given period is primarily associated with the visual analyzer in nature, then the leading focus (working field) will be localized in the region of the brain end of the visual analyzer. However, this does not mean that during this period only the visual center will work, and all other areas of the cortex will be turned off from activity. Everyday life observations prove that if a person is engaged in an activity primarily related to the visual process, such as reading, then he simultaneously hears sounds coming to him, the conversation of others, etc. However, this other activity - let's call it secondary - is carried out inactively, as if in the background. The areas of the cortex that are associated with side activities are, as it were, covered with a “haze of inhibition”; the formation of new conditioned reflexes there is limited for some time. When moving to an activity associated with another analyzer (for example, listening to a radio broadcast), the active field, the dominant focus, moves from the visual analyzer to the auditory one in the cerebral cortex, etc. More often, several active foci are simultaneously formed in the cortex, caused by external and internal stimuli of different nature. At the same time, these foci enter into interaction with each other, which may not be established immediately (“struggle of centers”). The active centers that have entered into interaction form a so-called “constellation of centers” or a functional-dynamic system, which for a certain period will be the dominant system (dominant, according to Ukhtomsky). When activity changes this system is inhibited, and in other areas of the cortex another system is activated, which takes the position of a dominant, in order to again give way to other functional-dynamic formations that have replaced them, again associated with new activity caused by the entry into the cortex of new irritations from the external and internal environment. This alternation of points of excitation and inhibition, caused by the mechanism of mutual induction, is accompanied by the formation of numerous chains of conditioned reflexes and represents the basic mechanisms of brain physiology. The dominant focus, the dominant, is the physiological mechanism of our consciousness. However, this point does not remain in one place, but moves along the cerebral cortex depending on the nature of human activity, mediated by the influence of external and internal stimuli.

Systematicity in the cerebral cortex

(dynamic stereotype)

The various irritations acting on the cortex are diverse in the nature of their influence: some have only an approximate value, others form neural connections, which are initially in a somewhat chaotic state, then are balanced by the inhibitory process, refined and form certain functional-dynamic systems. The stability of these systems depends on certain conditions of their formation. If the complex of acting irritations acquires some periodicity and the irritations arrive in a certain order over a certain time, then the developed system of conditioned reflexes is more stable. I.P. Pavlov called this system a dynamic stereotype.

Thus, a dynamic stereotype is a developed
a balanced system of conditioned reflexes that perform

specialized functions. The development of a stereotype is always associated with a certain nervous labor. However, after the formation of a certain dynamic system, the performance of functions is greatly facilitated.

The significance of the developed functional-dynamic system (stereotype) is well known in the practice of life. All our habits, skills, and sometimes certain forms of behavior are determined by the developed system of nervous connections. Any change or violation of a stereotype is always painful. Everyone knows from life how difficult it is sometimes to perceive a change in lifestyle, habitual forms of behavior (breaking a stereotype), especially for older people.

The use of systematic cortical functions is extremely important in the upbringing and education of children. Reasonable, but steady and systematic presentation of a number of specific requirements to the child determines the strong formation of a number of general cultural, sanitary-hygienic and labor skills.

The question of the strength of knowledge is sometimes a sore point for schools. The teacher’s knowledge of the conditions under which a more stable system of conditioned reflexes is formed also ensures the students’ strong knowledge.

It is often necessary to observe how an inexperienced teacher, not taking into account the possibilities that the higher nervous activity of students, especially in special schools, has, leads the lesson incorrectly. When forming any school skill, it gives too many new irritations, and chaotically, without the necessary sequence, without dosing the material and without making the necessary repetitions.

So, for example, while explaining to children the rules for dividing multi-digit numbers, such a teacher suddenly gets distracted at the moment of explanation and remembers that this or that student did not bring a certificate of illness. Such inappropriate words, by their nature, are a kind of extra-irritant: they interfere with the correct formation of specialized systems of connections, which then turn out to be unstable and are quickly erased by time.

Dynamic localization of functions in the cortex

hemispheres

In building your scientific concept localization of functions in the cerebral cortex I.P. Pavlov proceeded from the basic principles of reflex theory. He believed that neurodynamic physiological processes occurring in the cortex necessarily have a root cause in the external or internal environment of the body, i.e. they are always deterministic. All nervous processes are distributed among the structures and systems of the brain. The leading mechanism of nervous activity is analysis and synthesis, which provide the highest form of adaptation of the body to environmental conditions.

Without denying the different functional significance of individual areas of the cortex, I.P. Pavlov substantiated a broader interpretation of the concept of “center”. On this occasion, he wrote: “And now it is still possible to remain within the limits of previous ideas about the so-called centers in the central nervous system. To do this, it would only be necessary to add a physiological point of view to the exclusive, as before, anatomical point of view, allowing for unification through a special well-trodden connections and paths of different parts of the central nervous system to perform a certain reflex act.”

The essence of the new additions made by I.P. Pavlov’s teaching on the localization of functions was, first of all, that he considered the main centers not only as local areas of the cortex, on which the performance of various functions, including mental ones, depends. The formation of centers (analyzers, according to Pavlov) is much more complicated. The anatomical region of the cortex, characterized by a unique structure, represents only a special background, the basis on which certain physiological activities develop, caused by the influence of various irritations of the external world and the internal environment of the body. As a result of this influence, nervous connections (conditioned reflexes) arise, which, gradually balancing, form certain specialized systems - visual, auditory, olfactory, gustatory, etc. Thus, the formation of the main centers occurs according to the mechanism of conditioned reflexes formed as a result of the interaction of the organism with the external environment.

The importance of the external environment in the formation of receptors has long been noted by evolutionary scientists. Thus, it was known that some animals living underground, where the sun’s rays do not reach, had underdevelopment of the visual organs, for example, moles, shrews, etc. The mechanical concept of the center as a narrow-local area in the new physiology was replaced by the concept of an analyzer - a complex device, providing cognitive activity. This device combines both anatomical and physiological components, and its formation is due to the indispensable participation of the external environment. As mentioned above, I.P. Pavlov isolated at the cortical end of each analyzer central part– the nucleus, where the accumulation of receptor elements of this analyzer is especially dense and which correlates with a certain area of ​​the cortex.

The core of each analyzer is surrounded by an analyzer periphery, the boundaries of which with neighboring analyzers are unclear and may overlap each other. Analyzers are closely interconnected by numerous connections that determine the closure of conditioned reflexes due to alternating phases of excitation and inhibition. Thus, the entire complex cycle of neurodynamics, proceeding according to certain patterns, represents a tuphysiological “canvas” on which a “pattern” of mental functions arises. In this regard, Pavlov denied the presence in the cortex of so-called mental centers (attention, memory, character, will, etc.), as if connected with certain local areas in the cerebral cortex. The basis of these mental functions are different states of the basic nervous processes, which also determine the different nature of conditioned reflex activity. So, for example, attention is a manifestation of the concentration of the excitatory process, in connection with which the formation of the so-called active or working field occurs. However, this center is dynamic, it moves depending on the nature of human activity, hence visual, auditory attention, etc. Memory, which usually means the ability of our cortex to store past experience, is also determined not by the presence of an anatomical center (memory center), but represents a totality numerous nerve traces (trace reflexes) that arose in the cortex as a result of stimuli received from the external environment. Due to constantly changing phases of excitation and inhibition, these connections can be activated, and then the necessary images appear in consciousness, which are inhibited when unnecessary. The same should be said about the so-called “supreme” functions, which usually included the intellect. This complex function of the brain was previously exclusively correlated with the frontal lobe, which was considered to be the only carrier of mental functions (the center of the mind).

In the 17th century the frontal lobes were seen as a thought factory. In the 19th century the frontal brain was recognized as an organ abstract thinking, the center of spiritual concentration.

Intelligence, a complex integral function, arises as a result of the analytical and synthetic activity of the cortex as a whole and, of course, cannot depend on individual anatomical centers in the frontal lobe. However, clinical observations are known when damage to the frontal lobe causes sluggishness of mental processes, apathy, and motor initiative suffers (according to Lhermit). The tracts observed in clinical practice led to views on the frontal lobe as the main center for the localization of intellectual functions. However, analysis of these phenomena in the aspect of modern physiology leads to other conclusions. The essence of the pathological changes in the psyche observed in the clinic with damage to the frontal lobes is not due to the presence of special “mental centers” affected as a result of the disease. This is about something else. Mental phenomena have a certain physiological basis. This is a conditioned reflex activity that occurs as a result of alternating phases of excitatory and inhibitory processes. In the frontal lobe there is a motor analyzer, which is presented in the form of a nucleus and scattered periphery. The importance of the motor analyzer is extremely important. It regulates motor movements. Disruption of the motor analyzer due to various reasons (deterioration of blood supply, skull injury, brain tumor, etc.) may be accompanied by the development of a kind of pathological inertia in the formation of motor reflexes, and in severe cases, their complete blocking, which leads to various movement disorders (paralysis, lack of motor coordination ). Disorders of conditioned reflex activity are based on a lack of general neurodynamics, in which the mobility of nervous processes is disrupted and stagnant inhibition occurs.” All this, in turn, affects the nature of thinking, the physiological basis of which is conditioned reflexes. A kind of rigidity of thinking, lethargy, lack of initiative arises - in a word, the whole complex of mental changes that were observed in the clinic in patients with damage to the frontal lobe and which were previously interpreted as the result of a disease of individual local points that carry “supreme” functions. The same should be said about the essence of speech centers. The lower parts of the frontal region of the dominant hemisphere, which regulate the activity of the speech organs, are separated into the speech motor analyzer. However, this analyzer also cannot be mechanically considered as a narrow local center of motor speech. Here only the highest analysis and synthesis of all speech reflexes coming from all other analyzers is carried out.

It is known that I.P. Pavlov emphasized the unity of the somatic and mental in the whole organism. In the studies of academician K.M. Bykov, the connection between the cortex and internal organs was experimentally confirmed. Currently, the so-called interoreceptor analyzer is located in the cerebral cortex, which receives signals about the state of internal organs. This area of ​​the cortex is conditionally - reflexively connected with everything internal structure our body. Facts from everyday life confirm this connection. Who does not know such facts when mental experiences are accompanied by various sensations from the internal organs? So, with excitement or fear, a person usually turns pale, often experiences an unpleasant sensation from the heart (“the heart sinks”) or from the gastrointestinal tract, etc. Corticovisceral connections have bilateral information. Hence, the primarily impaired activity of internal organs, in turn, can have a depressing effect on the psyche, causing anxiety, lowering mood, and limiting ability to work. The establishment of corticovisceral connections is one of the important achievements of modern physiology and is of great importance for clinical medicine.

Centers and activities can be considered in the same aspect
which were usually associated with the management of individual skills and labor
skills, such as writing, reading, counting, etc. These centers in the past also
were interpreted as local areas of the cortex with which graphical
and lexical functions. However, this idea from the standpoint of modern
physiology also cannot be accepted. In humans, as mentioned above, from
birth, there are no special cortical centers for writing and reading formed by specialized elements. These acts are specialized systems of conditioned reflexes that are gradually formed during the learning process.

However, how can we understand the facts that at first glance may confirm the presence of local cortical centers for reading and writing in the cortex? We are talking about observations of writing and reading disorders with damage to certain areas of the parietal lobe cortex. For example, dysgraphia (writing disorder) more often occurs when field 40 is affected, and dyslexia (reading disorder) most often occurs when field 39 is affected (see Fig. 32). However, it is wrong to believe that these fields are the direct centers of the described functions. The modern interpretation of this issue is much more complicated. The writing center is not only a group of cellular elements on which the specified function depends. The skill of writing is based on a developed system of neural connections. The formation of this specialized system of conditioned reflexes, which represent the physiological basis of the writing skill, occurs in those areas of the cortex where the corresponding junction of pathways occurs that connect a number of analyzers involved in the formation of this function. For example, to perform the function of writing, the participation of at least three receptor components is necessary - visual, auditory, kinesthetic and motor. Obviously, at certain points in the cortex of the parietal lobe, the closest combination of associative fibers occurs, connecting a number of analyzers involved in the act of writing. It is here that the closure of neural connections occurs, forming a functional system - a dynamic stereotype, which is the physiological basis of this skill. The same applies to field 39, associated with the reading function. As is known, the destruction of this area is often accompanied by alexia.

Thus, the reading and writing centers are not anatomical centers in a narrow local sense, but dynamic (physiological), although they arise in certain cortical structures. Under pathological conditions, during inflammatory, traumatic and other processes, systems of conditioned connections can quickly disintegrate. We are talking about aphasic, lexical and graphic disorders that develop after brain disorders, as well as the breakdown of complex movements.

In cases of optimal excitability of a particular point, the latter becomes dominant for some time and other points that are in a state of less activity are attracted to it. Between them, paths are paved and a unique dynamic system of working centers (dominant) is formed, performing one or another reflex act, as mentioned above.

It is characteristic that the modern doctrine of the localization of functions in the cerebral cortex is based on anatomical and physiological correlations. Now the idea that the entire cerebral cortex is divided into many isolated anatomical centers that are associated with the performance of motor, sensory and even mental functions will seem naive. On the other hand, it is also undeniable that all these elements are combined at any given moment into a system where each of the elements interacts with all the others.

Thus, the principle of functional unification of centers into certain working systems, in contrast to narrow static localization, is a new characteristic addition to the old doctrine of localization, which is why it received the name dynamic localization of functions.

A number of attempts have been made to develop the provisions expressed by I.P. Pavlov, in connection with the question of dynamic localization of functions. The physiological nature of the reticular formation as a tonic apparatus for cortical processes was clarified. Finally, and most importantly, ways were identified to explain the connections that exist between higher mental processes (as a complex product of socio-historical development) and their physiological basis, which was reflected in the works of L.S. Vygotsky, A.N. Leontyeva, A.R. Luria et al. “If higher mental functions are complexly organized functional systems, social in their genesis, then any attempt to localize them in special narrowly limited areas of the cerebral cortex, or centers, is even more unjustified than” an attempt to look for narrowly limited “centers” “for biological functional systems... Therefore, we can assume that the material basis of higher mental processes is the entire brain as a whole, but as a highly differentiated system, the parts of which provide different aspects of the whole.”