What does conditioned reflex mean? Conditioned reflexes

Conditioned reflexes- these are reactions of the whole organism or any part of it to external or internal stimuli. They manifest themselves through the disappearance, weakening or strengthening of certain activities.

Conditioned reflexes are the body’s assistants, allowing it to quickly respond to any changes and adapt to them.

Story

The idea of ​​a conditioned reflex was first put forward by the French philosopher and scientist R. Descartes. Somewhat later, the Russian physiologist I. Sechenov created and experimentally proved new theory concerning the body's reactions. For the first time in the history of physiology, it was concluded that conditioned reflexes are a mechanism that is activated not only; the entire nervous system is involved in its work. This allows the body to maintain a connection with the environment.

Studied by Pavlov. This outstanding Russian scientist was able to explain the mechanism of action of the cerebral cortex and cerebral hemispheres. At the beginning of the 20th century, he created the theory of conditioned reflexes. The treatise became a real revolution in physiology. Scientists have proven that conditioned reflexes are reactions of the body that are acquired throughout life, based on unconditioned reflexes.

Instincts

Certain reflexes of the unconditional type are characteristic of each type of living organism. They are called instincts. Some of them are quite complex. An example of this would be bees making honeycombs or birds making nests. Thanks to the presence of instincts, the body is able to optimally adapt to environmental conditions.

They are congenital. They are inherited. In addition, they are classified as species, since they are characteristic of all representatives certain type. Instincts are permanent and persist throughout life. They manifest themselves in response to adequate stimuli that are applied to a specific single receptive field. Physiologically, unconditioned reflexes are closed in the brainstem and at the level of the spinal cord. They manifest themselves through anatomically expressed

As for monkeys and humans, the implementation of most of the complex unconditioned reflexes is impossible without the participation of the cerebral cortex. When its integrity is violated, pathological changes in unconditioned reflexes occur, and some of them simply disappear.

Classification of instincts

Unconditioned reflexes are very strong. Only under certain conditions, when their manifestation becomes unnecessary, can they disappear. For example, the canary, domesticated about three hundred years ago, currently does not have the instinct to build nests. The following types of unconditioned reflexes are distinguished:

Which is the body's reaction to a variety of physical or chemical stimuli. Such reflexes, in turn, can manifest locally (withdrawal of the hand) or be complex (flight from danger).
- Food instinct, which is caused by hunger and appetite. This unconditioned reflex includes a whole chain of sequential actions - from searching for prey to attacking it and further eating it.
- Parental and sexual instincts associated with the maintenance and reproduction of the species.

A comfortable instinct that serves to keep the body clean (bathing, scratching, shaking, etc.).
- Orienting instinct, when the eyes and head are turned towards the stimulus. This reflex is necessary to preserve life.
- The instinct of freedom, which is especially clearly expressed in the behavior of animals in captivity. They constantly want to break free and often die, refusing water and food.

The emergence of conditioned reflexes

During life, acquired reactions of the body are added to the inherited instincts. They are called conditioned reflexes. They are acquired by the body as a result of individual development. The basis for obtaining conditioned reflexes is life experience. Unlike instincts, these reactions are individual. They may be present in some members of the species and absent in others. In addition, a conditioned reflex is a reaction that may not persist throughout life. Under certain conditions, it is produced, consolidated, and disappears. Conditioned reflexes are reactions that can occur to various stimuli applied to different receptor fields. This is their difference from instincts.

The mechanism of the conditioned reflex closes at the level. If it is removed, then only instincts will remain.

The formation of conditioned reflexes occurs on the basis of unconditioned ones. To carry out this process, a certain condition must be met. However, any change external environment must be combined in time with the internal state of the body and perceived by the cerebral cortex with a simultaneously carried out unconditional reaction of the body. Only in this case does a conditioned stimulus or signal appear that contributes to the emergence of a conditioned reflex.

Examples

For the body’s reaction to occur, such as the release of saliva when knives and forks clink, as well as when an animal’s feeding cup is knocked (in humans and dogs, respectively), an indispensable condition is the repeated coincidence of these sounds with the process of providing food.

In the same way, the sound of a bell or the turning on of a light bulb will cause the dog's paw to flex if these phenomena have repeatedly occurred accompanied by electrical stimulation of the animal's leg, as a result of which an unconditioned type of flexion reflex appears.

The conditioned reflex is the child's hands being pulled away from the fire and subsequent crying. However, these phenomena will only occur if the type of fire, even once, coincides with a burn.

Reaction components

The body's reaction to irritation is a change in breathing, secretion, movement, etc. As a rule, unconditioned reflexes are quite complex reactions. That is why they contain several components at once. For example, the defensive reflex is accompanied not only by defensive movements, but also by increased breathing, accelerated activity of the heart muscle, and changes in blood composition. In this case, vocal reactions may also appear. As for the food reflex, there are also respiratory, secretory and cardiovascular components.

Conditioned reactions usually reproduce the structure of unconditioned ones. This occurs due to the stimulation of the same nerve centers by stimuli.

Classification of conditioned reflexes

The responses acquired by the body to various stimuli are divided into types. Some of the existing classifications are of great importance in solving not only theoretical, but also practical problems. One of the areas of application of this knowledge is sports activities.

Natural and artificial reactions of the body

There are conditioned reflexes that arise under the action of signals characteristic of the constant properties of unconditioned stimuli. An example of this is the sight and smell of food. Such conditioned reflexes are natural. They are characterized by rapid production and great durability. Natural reflexes, even in the absence of subsequent reinforcement, can be maintained throughout life. The importance of the conditioned reflex is especially great in the very first stages of an organism’s life, when it adapts to the environment.
However, reactions can also be developed to a variety of indifferent signals, such as smell, sound, temperature change, light, etc. natural conditions they are not irritants. It is precisely such reactions that are called artificial. They are developed slowly and, in the absence of reinforcement, quickly disappear. For example, artificial conditioned human reflexes are reactions to the sound of a bell, touching the skin, weakening or increasing lighting, etc.

First and highest order

There are types of conditioned reflexes that are formed on the basis of unconditioned ones. These are first order reactions. There are also higher categories. Thus, reactions that are developed on the basis of already existing conditioned reflexes are classified as higher-order reactions. How do they arise? When developing such conditioned reflexes, the indifferent signal is reinforced with well-learned conditioned stimuli.

For example, irritation in the form of a bell is constantly reinforced by food. In this case, a first-order conditioned reflex is developed. On its basis, a reaction to another stimulus, for example, to light, can be fixed. This will become a second-order conditioned reflex.

Positive and negative reactions

Conditioned reflexes can influence the activity of the body. Such reactions are considered positive. The manifestation of these conditioned reflexes can be secretory or motor functions. If there is no activity of the body, then the reactions are classified as negative. For the process of adaptation to constantly changing environmental conditions, both one and the second species are of great importance.

At the same time, there is a close relationship between them, since when one type of activity is manifested, the other is certainly suppressed. For example, when the command “Attention!” is heard, the muscles are in a certain position. At the same time, motor reactions (running, walking, etc.) are inhibited.

Education mechanism

Conditioned reflexes occur with the simultaneous action of a conditioned stimulus and an unconditioned reflex. In this case, certain conditions must be met:

The unconditioned reflex is biologically stronger;
- the manifestation of a conditioned stimulus is somewhat ahead of the action of instinct;
- the conditioned stimulus is necessarily reinforced by the influence of the unconditional;
- the body must be awake and healthy;
- the condition of the absence of extraneous stimuli producing a distracting effect is met.

The centers of conditioned reflexes located in the cerebral cortex establish a temporary connection (closure) with each other. In this case, the irritation is perceived by cortical neurons, which are part of the unconditioned reflex arc.

Inhibition of conditioned reactions

In order to ensure adequate behavior of the organism and for better adaptation to environmental conditions, the development of conditioned reflexes alone will not be enough. An action in the opposite direction will be required. This is the inhibition of conditioned reflexes. This is the process of eliminating those reactions of the body that are not necessary. According to the theory developed by Pavlov, certain types of cortical inhibition are distinguished. The first of these is unconditional. It appears as a response to the action of some extraneous stimulus. There is also internal inhibition. It is called conditional.

External braking

This reaction received this name due to the fact that its development is facilitated by processes taking place in those areas of the cortex that do not participate in reflex activity. For example, an extraneous smell, sound, or change in lighting before the onset of the food reflex can reduce it or contribute to its complete disappearance. A new stimulus acts as an inhibitor for a conditioned response.

Eating reflexes can also be eliminated by painful stimuli. Inhibition of the body's reaction is facilitated by bladder overflow, vomiting, internal inflammatory processes, etc. All of them inhibit food reflexes.

Internal inhibition

It occurs when the received signal is not reinforced by an unconditioned stimulus. Internal inhibition of conditioned reflexes occurs if, for example, an animal is periodically turned on an electric light bulb in front of its eyes during the day without bringing food. It has been experimentally proven that saliva production will decrease each time. As a result, the reaction will fade away completely. However, the reflex will not disappear without a trace. He will simply slow down. This has also been proven experimentally.

Conditioned inhibition of conditioned reflexes can be eliminated the very next day. However, if this is not done, then the body’s reaction to this stimulus will subsequently disappear forever.

Types of internal braking

Several types of elimination of the body's reaction to stimuli are classified. Thus, the basis for the disappearance of conditioned reflexes, which are simply not needed under given specific conditions, is extinctive inhibition. There is another type of this phenomenon. This is discriminative or differentiated inhibition. Thus, an animal can distinguish the number of metronome beats at which food will be brought to it. This happens when this conditioned reflex is previously developed. The animal distinguishes between stimuli. The basis of this reaction is internal inhibition.

The value of eliminating reactions

Conditioned inhibition plays a significant role in the life of the body. Thanks to it, the process of adaptation to the environment occurs much better. The ability to navigate in a variety of complex situations is provided by a combination of excitation and inhibition, which are two forms of a single nervous process.

Conclusion

There are an infinite number of conditioned reflexes. They are the factor that determines the behavior of a living organism. With the help of conditioned reflexes, animals and humans adapt to their environment.

There are many indirect signs of body reactions that have signaling value. For example, an animal, knowing in advance that danger is approaching, organizes its behavior in a certain way.

The process of developing conditioned reflexes, which belong to a higher order, is a synthesis of temporary connections.

The basic principles and patterns manifested in the formation of not only complex but also elementary reactions are the same for all living organisms. From this follows an important conclusion for philosophy and the natural sciences that it cannot but obey general laws biology. In this regard, it can be studied objectively. However, it is worth keeping in mind that the activity of the human brain is qualitatively specific and fundamentally different from the activity of the animal brain.

Higher nervous activity is a system that allows the human and animal body to adapt to variable environmental conditions. Evolutionarily, vertebrates have developed a number of innate reflexes, but their existence is not enough for successful development.

In the process of individual development, new adaptive reactions are formed - these are conditioned reflexes. Outstanding domestic scientist I.P. Pavlov is the founder of the doctrine of unconditioned and conditioned reflexes. He formed the conditioned reflex theory, which states that the acquisition of a conditioned reflex is possible through the action of a physiologically indifferent irritation on the body. As a result, a more complex system of reflex activity is formed.

I.P. Pavlov - the founder of the doctrine of unconditioned and conditioned reflexes

An example of this is Pavlov's study of dogs that salivated in response to a sound stimulus. Pavlov also showed that innate reflexes are formed at the level of subcortical structures, and new connections are formed in the cerebral cortex throughout the life of an individual under the influence of constant irritations.

Conditioned reflexes

Conditioned reflexes are formed on the basis of unconditional ones, in the process of individual development of the organism, against the background of a changing external environment.

Reflex arc The conditioned reflex consists of three components: afferent, intermediate (intercalary) and efferent. These links carry out the perception of irritation, the transmission of impulses to cortical structures and the formation of a response.

The reflex arc of the somatic reflex performs motor functions (for example, flexion movement) and has the following reflex arc:

The sensitive receptor perceives the stimulus, then the impulse goes to the dorsal horn of the spinal cord, where the interneuron is located. Through it, the impulse is transmitted to the motor fibers and the process ends with the formation of movement - flexion.

A necessary condition for the development of conditioned reflexes is:

• The presence of a signal that precedes the unconditional;
• the stimulus that will cause the catch reflex must be inferior in strength to the biologically significant effect;
• normal functioning of the cerebral cortex and the absence of distractions are mandatory.

Conditioned reflexes are not formed instantly. They are formed over a long period of time under constant observance of the above conditions. In the process of formation, the reaction either fades away, then resumes again, until stable reflex activity occurs.

An example of developing a conditioned reflex

Classification of conditioned reflexes:

1. A conditioned reflex formed on the basis of the interaction of unconditioned and conditioned stimuli is called first order reflex.
2. Based on the classical acquired reflex of the first order, it is developed second order reflex.

Thus, a third-order defensive reflex was formed in dogs, the fourth could not be developed, and the digestive reflex reached the second. In children, conditioned reflexes of the sixth order are formed, in an adult up to the twentieth.

The variability of the external environment leads to the constant formation of many new behaviors necessary for survival. Depending on the structure of the receptor that perceives the stimulus, conditioned reflexes are divided into:

• Exteroceptive– irritation is perceived by body receptors and predominates among reflex reactions (taste, tactile);
• intraceptive– caused by action on internal organs (changes in homeostasis, blood acidity, temperature);
• proprioceptive– are formed by stimulating the striated muscles of humans and animals, providing motor activity.

There are artificial and natural acquired reflexes:

Artificial occur under the influence of stimulation that has no connection with the unconditioned stimulus (sound signals, light stimulation).

Natural are formed in the presence of a stimulus similar to the unconditioned one (the smell and taste of food).

Unconditioned reflexes

These are innate mechanisms that ensure the preservation of the integrity of the body, the homeostasis of the internal environment and, most importantly, reproduction. Congenital reflex activity is formed in the spinal cord and cerebellum and is controlled by the cerebral cortex. Typically, they last a lifetime.

Reflex arcs hereditary reactions are laid down before a person is born. Some reactions are characteristic of a certain age and then disappear (for example, in small children - sucking, grasping, searching). Others do not manifest themselves at first, but appear (sexually) after a certain period of time.

Unconditioned reflexes are characterized by the following features:

• Occur regardless of the consciousness and will of a person;
• specific - manifested in all representatives (for example, coughing, salivation at the smell or sight of food);
• endowed with specificity - they appear when exposed to a receptor (the reaction of the pupil occurs when a beam of light is directed to photosensitive areas). This also includes salivation, secretion of mucous secretions and enzymes of the digestive system when food enters the mouth;
• flexibility - for example, different foods lead to the secretion of a certain amount and varied chemical composition of saliva;
• On the basis of unconditioned reflexes, conditioned ones are formed.

Unconditioned reflexes are needed to fulfill the needs of the body; they are constant, but as a result of illnesses or bad habits they can disappear. So, when the iris of the eye is diseased, when scars form on it, the reaction of the pupil to light exposure disappears.

Classification of unconditioned reflexes

Congenital reactions are classified into:

• Simple(quickly remove your hand from the hot object);
• complex(maintaining homeostasis in situations of increased CO 2 concentration in the blood by increasing the frequency of respiratory movements);
• the most complex(instinctive behavior).

Classification of unconditioned reflexes according to Pavlov

Pavlov divided innate reactions into food, sexual, protective, orientation, statokinetic, homeostatic.

TO food This includes the secretion of saliva at the sight of food and its entry into the digestive tract, the secretion of hydrochloric acid, gastrointestinal motility, sucking, swallowing, chewing.

Protective accompanied by contraction of muscle fibers in response to an irritating factor. Everyone is familiar with the situation when a hand reflexively withdraws from a hot iron or a sharp knife, sneezing, coughing, watery eyes.

Approximate occur when sudden changes occur in nature or in the body itself. For example, turning the head and body towards sounds, turning the head and eyes towards light stimuli.

Genital are associated with reproduction, preservation of the species, this also includes parental (feeding and caring for offspring).

Statokinetic provide upright posture, balance, and body movement.

Homeostatic– independent regulation of blood pressure, vascular tone, respiratory rate, heart rate.

Classification of unconditioned reflexes according to Simonov

Vital to maintain life (sleep, nutrition, saving energy) depend only on the individual.

Role-playing arise upon contact with other individuals (procreation, parental instinct).

The need for self-development(desire for individual growth, to discover new things).

Innate reflexes are activated when necessary due to a short-term violation of internal constancy or variability in the external environment.

Comparison table between conditioned and unconditioned reflexes

Comparison of the characteristics of conditioned (acquired) and unconditioned (innate) reflexes
Unconditional	Conditional
Congenital	Acquired during life
Present in all representatives of the species	Individual for each organism
Relatively constant	Appear and disappear with changes in the external environment
Formed at the level of the spinal cord and medulla oblongata	Carried out through the work of the brain
Laid in utero	Developed against the background of innate reflexes
Occurs when a stimulus acts on certain receptor areas	Manifest under the influence of any stimulus that is perceived by the individual

Higher nervous activity operates in the presence of two interrelated phenomena: excitation and inhibition (congenital or acquired).

Braking

External unconditional inhibition(congenital) is carried out by the action of a very strong irritant on the body. The termination of the conditioned reflex occurs due to the activation of nerve centers under the influence of a new stimulus (this is transcendental inhibition).

When the organism under study is exposed to several stimuli at the same time (light, sound, smell), the conditioned reflex fades, but over time the indicative reflex is activated and the inhibition disappears. This type of braking is called temporary.

Conditioned inhibition(acquired) does not arise on its own, it must be developed. There are 4 types of conditioned inhibition:

• Extinction (disappearance of a persistent conditioned reflex without constant reinforcement by the unconditioned);
• differentiation;
• conditional brake;
• delayed braking.

Inhibition is a necessary process in our life. In its absence, many unnecessary reactions would occur in the body that would not be beneficial.

Example of external inhibition (dog's reaction to a cat and the SIT command)

The meaning of conditioned and unconditioned reflexes

Unconditioned reflex activity is necessary for the survival and preservation of the species. A good example serves the birth of a child. In a new world for him, many dangers await him. Thanks to the presence of innate reactions, the cub can survive in these conditions. Activated immediately after birth respiratory system, the sucking reflex provides nutrients, touching sharp and hot objects is accompanied by an instant withdrawal of the hand (manifestation of defensive reactions).

For further development and existence, one has to adapt to the surrounding conditions; conditioned reflexes help with this. They ensure rapid adaptation of the body and can be formed throughout life.

The presence of conditioned reflexes in animals gives them the ability to quickly respond to the voice of a predator and save their lives. When a person sees food, he or she performs conditioned reflex activity, salivation begins, and gastric juice begins to be produced for rapid digestion of food. The sight and smell of some objects, on the contrary, signals danger: the red cap of the fly agaric, the smell of spoiled food.

The importance of conditioned reflexes in the everyday life of humans and animals is enormous. Reflexes help you navigate the terrain, get food, and escape from danger while saving your life.

Unconditioned reflexes- These are innate, hereditarily transmitted reactions of the body. Conditioned reflexes- these are reactions acquired by the body in the process of individual development on the basis of “life experience”.

Unconditioned reflexes are specific, that is, characteristic of all representatives of a given species. Conditioned reflexes are individual: some representatives of the same species may have them, while others may not.

Unconditioned reflexes are relatively constant; conditioned reflexes are not constant and, depending on certain conditions, they can be developed, consolidated or disappear; This is their property and is reflected in their very name.

Unconditioned reflexes are carried out in response to adequate stimulation applied to one specific receptive field. Conditioned reflexes can be formed to a wide variety of stimuli applied to various receptive fields.

In animals with a developed cerebral cortex, conditioned reflexes are a function of the cerebral cortex. After removing the cerebral cortex, the developed conditioned reflexes disappear and only unconditioned ones remain. This indicates that in the implementation of unconditioned reflexes, in contrast to conditioned ones, the leading role belongs to the lower parts of the central nervous system- subcortical nuclei, brain stem and spinal cord. It should be noted, however, that in humans and monkeys, who have a high degree of corticalization of functions, many complex unconditioned reflexes are carried out with the obligatory participation of the cerebral cortex. This is proven by the fact that its lesions in primates lead to pathological disorders of unconditioned reflexes and the disappearance of some of them.

It should also be emphasized that not all unconditioned reflexes appear immediately at the time of birth. Many unconditioned reflexes, for example, those associated with locomotion and sexual intercourse, arise in humans and animals a long time after birth, but they necessarily appear under the condition of normal development of the nervous system. Unconditioned reflexes are part of the fund of reflex reactions strengthened in the process of phylogenesis and hereditarily transmitted.

Conditioned reflexes are developed on the basis of unconditioned reflexes. For the formation of a conditioned reflex, it is necessary to combine in time some kind of change in the external environment or the internal state of the body, perceived by the cerebral cortex, with the implementation of one or another unconditioned reflex. Only under this condition does a change in the external environment or internal state of the body become a stimulus to a conditioned reflex - a conditioned stimulus, or signal. The irritation that causes an unconditioned reflex - unconditioned irritation - must, during the formation of a conditioned reflex, accompany the conditioned irritation and reinforce it.

In order for the clinking of knives and forks in the dining room or the knocking of a cup from which a dog is fed to cause salivation in the first case in a person, in the second case in a dog, it is necessary to re-coincidence of these sounds with food - reinforcement of stimuli that are initially indifferent to salivary secretion by feeding , i.e. unconditional irritation salivary glands. Likewise, the flashing of an electric light bulb in front of a dog’s eyes or the sound of a bell will only cause conditioned reflex flexion of the paw if they are repeatedly accompanied by electrical irritation of the skin of the leg, causing an unconditioned flexion reflex whenever it is used.

Similarly, a child’s crying and his hands pulling away from a burning candle will be observed only if the sight of the candle first coincided at least once with the feeling of a burn. In all the above examples, external agents that are initially relatively indifferent - the clinking of dishes, the sight of a burning candle, the flashing of an electric light bulb, the sound of a bell - become conditioned stimuli if they are reinforced by unconditioned stimuli. Only under this condition do the initially indifferent signals of the external world become stimuli for a certain type of activity.

For the formation of conditioned reflexes, it is necessary to create a temporary connection, a closure between the cortical cells that perceive conditioned stimulation and the cortical neurons that are part of the unconditioned reflex arc.

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 of animals and humans with the 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 occurs in in this case 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 the higher nervous activity of 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. It was previously assumed that the basis of literacy acquisition (learning to read and write) was the development special centers reading and writing. 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 is known, 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 of the text being read. 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 the student’s own oral speech. 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, one 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 long term the one who leaves him 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 foreign language, but then thoroughly forgot it due to lack of practice; undoubtedly, it is easier for such a person, with appropriate practice, to again master the language than for another who will be learning a 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 system, 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 analyzing 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 one or another area of ​​the cortex, which is associated with the active activity of coupling apparatuses (synapses) and the release chemical substances(mediators) 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 importance 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 unnecessary this moment connections contribute 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 rational 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 mental and speech activity In humans, 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 a 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 them under the influence of 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 the active work activity 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, which is witnessed at school, occurs gradually, as individual areas of the cortical mass are released 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 research showed that animals (dogs) react differently to external stimuli during this period. In this regard, special forms of phase states were identified. 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. Different kinds Sleep treatments and hypnosis became part of the therapeutic arsenal, especially in the clinic of nervous and mental illnesses.

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 is predominantly associated with in a given period of 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 occupies a dominant position 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 stimuli from the external and internal environment. Such alternation of points of excitation and inhibition, due to the mechanism of mutual induction, is accompanied 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, explaining to children the rules of division multi-digit numbers, such a teacher, at the moment of explanation, suddenly becomes distracted 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 constructing his scientific concept of 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, providing higher form 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 identified a central part at the cortical end of each analyzer - 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. The 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 various states basic nervous processes that 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 combination 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 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 of abstract thinking, a 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. Disturbance 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 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 insufficiency of general neurodynamics; in them, the mobility of nervous processes is disrupted, and stagnant inhibition occurs.” All this, in turn, is reflected in 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 whole organism, In the research 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 the entire internal structure of 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 stops”) or from the side. gastrointestinal tract and so on. 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.”

Conditioned reflexes are complex adaptive reactions of the body, carried out by the higher parts of the central nervous system by forming 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 constant environmental influences, 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 unstable and are acquired in the process of individual development of the organism. 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 the formation of a functional connection between the 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.

By studying the activity of single neurons of the central nervous system using the microelectrode method, it was established that both conditioned and unconditioned excitations come to one neuron (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. Determined that environment plays along with the time factor important role in animal behavior. 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 most perfectly navigate the changing conditions of existence.