The outstanding Russian physiologist I.M. Sechenov was the first to express the idea of ​​a connection between human consciousness and thinking and the reflex activity of his brain. This idea was developed and convincingly confirmed in numerous experiments by I.P. Pavlova. Therefore I.P. Pavlov is considered the creator of the doctrine of higher nervous activity.

Higher nervous activity- these are the functions of the cerebral cortex and the nearest subcortical formations, where temporary nerve connections (conditioned reflexes) are developed anew, ensuring the most subtle and perfect individual adaptation of the body to changing environmental conditions.

UNCONDITIONED AND CONDITIONED REFLEXES

Higher nervous activity is reflexive in nature. Higher animals and humans have unconditioned and conditioned reflexes. Their specificity is as follows.

Unconditioned reflexes ensuring the maintenance of vital functions in relatively constant environmental conditions, are inherent in a person from birth. These include food (sucking, swallowing, salivation, etc.), defensive (coughing, blinking, withdrawing a hand, etc.), reproduction (feeding and caring for offspring), respiratory, etc.

Conditioned reflexes are developed on the basis of unconditioned ones under the influence of a conditioned stimulus. They provide a more perfect adaptation of the body to changing environmental conditions. They help to find food by smell, avoid danger, navigate, etc.

Meaning of the word. In humans, conditioned reflexes can be formed not only as in animals, on the basis of the first signal system, when the conditioned stimuli are directly objects of the external world, but also on the basis of the second (speech) signal system, when the conditioned stimuli are words expressing concepts about objects and phenomena . Conditioned reflexes are the physiological basis of technical processes, the basis of thinking. The word is a kind of irritant for many conditioned reflexes. For example, just talking about food or describing it can cause a person to salivate.

Features of conditioned and unconditioned reflexes

Unconditioned reflexes	Conditioned reflexes (temporary connections)
Congenital, hereditary reflex reactions of this type	Acquired in the process of individual development on the basis of unconditioned reflexes
Reflex centers are located in the subcortical nuclei, brain stem and spinal cord	Reflex centers are located in the cerebral cortex
Racks. They persist throughout life. Their number is limited	Changeable. New reflexes arise, and old ones fade away when environmental conditions change. Quantity is unlimited
Carry out the relationship between parts of the body, reflex self-regulation and maintaining the constancy of the internal environment	Carry out a reflex reaction of the body to a stimulus (conditioned), signaling the upcoming action of an unconditioned stimulus

Human consciousness is associated with the activity of the cerebral cortex. This has been convincingly proven by numerous experiments by I.P. Pavlov, as well as by the study of diseases and dysfunctions of the brain.

The teachings of I. P. Pavlov on the higher nervous activity of man convincingly proved the inconsistency and anti-scientific nature of religious ideas about the “soul”.

Inhibition of conditioned reflexes. When environmental conditions change, previously developed conditioned reflexes fade away and new ones are formed. I.P. Pavlov distinguished two types of inhibition of conditioned reflexes.

External braking occurs when the body is exposed to an irritant that is stronger than the previous one. At the same time, a new focus of excitation is formed in the cerebral cortex. For example, in a dog, the conditioned salivary reflex developed in response to light (see “Digestion”) is inhibited under experimental conditions by a stronger stimulus - the sound of a bell. The latter causes strong stimulation in the auditory zone of the cerebral cortex. Initially, it generates inhibition of neighboring areas, and then spreads to the visual area. Therefore, excitation cannot be carried out through the neurons located in it and the arc of the previous conditioned reflex is interrupted.

Internal inhibition occurs in the arc of a conditioned reflex when the conditioned stimulus ceases to receive reinforcement from the unconditioned stimulus and the temporary connections formed in the cortex are gradually inhibited. When conditioned reflexes are repeated in the same sequence, dynamic stereotypes are formed that make up habits and skills.

Hygiene of physical and mental work. The activity of the body depends on the state of the central nervous system. Overwork leads to disruption of the vital functions of the body, reduces perception, attention, memory and performance.

During monotonous physical labor, only one muscle group works and only one part of the central nervous system is excited, which leads to its fatigue.

To avoid overwork, it is useful to perform industrial exercises during breaks, which involve other muscles. This, in turn, leads to the excitation of new areas of the cerebral cortex, inhibition of previously working areas, their rest and restoration of performance.

Mental work also causes fatigue in the central nervous system. The best rest for this is gymnastics or other physical activity.

The daily routine is of great importance in the formation of conditioned reflexes. When followed, a person develops many important conditioned reflexes that stimulate the better functioning of various organ systems and prevent their overwork.

The alternation of physical and mental labor, rationalization of work, adherence to a daily routine, and active rest are of paramount importance to protect the central nervous system from overwork.

Sleep gives the most complete rest to the central nervous system. The alternation of sleep and wakefulness is a necessary condition for human existence. I.P. Pavlov experimentally proved that sleep is an inhibition that involves the cerebral cortex and other parts of the brain. During sleep, metabolism, hearing, smell, and the intensity of activity of a number of organ systems decrease, muscle tone decreases, and thinking turns off. Sleep is a protective device against overwork of the nervous system. Infants sleep 20-22 hours, schoolchildren - 9-11 hours, adults - 7-8 hours. With lack of sleep, a person loses his ability to work. In order for the body to receive the most complete rest during sleep, it is necessary to go to bed at the same time, eliminate bright light, noise, ventilate the room, etc.

Conditioned and unconditioned reflexes are characteristic of the entire animal world.

In biology, they are considered as the result of a long evolutionary process and represent the response of the central nervous system to external environmental influences.

They provide a very quick response to a particular stimulus, thereby significantly saving the resources of the nervous system.

Classification of reflexes

In modern science, such reactions are described using several classifications that describe their features in different ways.

So, they come in the following types:

1. Conditional and unconditional - depending on how they are formed.
2. Exteroceptive (from “extra” - external) - reactions of external receptors of the skin, hearing, smell and vision. Interoreceptive (from “intero” - inside) - reactions of internal organs and systems. Proprioceptive (from “proprio” - special) - reactions associated with the sensation of one’s own body in space and formed by the interaction of muscles, tendons and joints. This is a classification based on receptor type.
3. Based on the type of effectors (zones of reflex response to information collected by receptors), they are divided into: motor and autonomic.
4. Classification based on specific biological role. There are species aimed at protection, nutrition, orientation in the environment and reproduction.
5. Monosynaptic and polysynaptic - depending on the complexity of the neural structure.
6. Based on the type of influence, excitatory and inhibitory reflexes are distinguished.
7. And based on where the reflex arcs are located, they are divided into cerebral (various parts of the brain are included) and spinal (neurons of the spinal cord are included).

What is a conditioned reflex

This is a term denoting a reflex formed as a result of the fact that simultaneously for a long time a stimulus that does not cause any reaction is presented with a stimulus that causes some specific unconditioned reflex. That is, the reflex response eventually extends to an initially indifferent stimulus.

Where are the centers of conditioned reflexes located?

Since this is a more complex product of the nervous system, the central part of the neural arc of conditioned reflexes is located in the brain, specifically in the cerebral cortex.

Examples of conditioned reflexes

The most striking and classic example is Pavlov’s dog. The dogs were presented with a piece of meat (this caused the secretion of gastric juice and salivation) along with the inclusion of a lamp. As a result, after a while, the process of activating digestion started when the lamp was turned on.

A familiar example from life is the feeling of cheerfulness from the smell of coffee. Caffeine does not yet have a direct effect on the nervous system. He is outside the body - in a circle. But the feeling of vigor is triggered only by the smell.

Many mechanical actions and habits are also examples. We rearranged the furniture in the room, and the hand reaches in the direction where the closet used to be. Or a cat who runs to the bowl when he hears the rustling of a box of food.

The difference between unconditioned reflexes and conditioned ones

They differ in that unconditional ones are innate. They are the same for all animals of one species or another, as they are inherited. They are quite unchanged throughout the life of a person or animal. From birth and always occur in response to receptor irritation, and are not produced.

Conditional ones are acquired throughout life, with experience in interaction with the environment. Therefore, they are quite individual - depending on the conditions under which it was formed. They are unstable throughout life and can fade away if they do not receive reinforcement.

Conditioned and unconditioned reflexes - comparison table

The difference between instincts and unconditioned reflexes

Instinct, like reflex, is a biologically significant form of animal behavior. Only the second is a simple short response to a stimulus, and instinct is a more complex activity that has a specific biological goal.

The unconditioned reflex is always triggered. But instinct is only in a state of biological readiness of the body to trigger this or that behavior. For example, mating behavior in birds is triggered only during a certain period of the year when chick survival may be maximum.

What is not typical for unconditioned reflexes?

In short, they cannot change during life. They do not differ between different animals of the same species. They cannot disappear or stop appearing in response to a stimulus.

When conditioned reflexes fade

Extinction occurs as a result of the fact that the stimulus (stimulus) ceases to coincide in time of presentation with the stimulus that caused the reaction. Need reinforcements. Otherwise, without reinforcement, they lose their biological significance and fade away.

Unconditioned reflexes of the brain

These include the following types: blinking, swallowing, vomiting, orientation, maintaining balance associated with hunger and satiety, braking movement in inertia (for example, during a push).

The disruption or disappearance of any type of these reflexes can be a signal of serious disturbances in the functioning of the brain.

Pulling your hand away from a hot object is an example of which reflex

An example of a painful reaction is pulling your hand away from a hot kettle. This is an unconditional look, the body's response to dangerous environmental influences.

Blink reflex - conditioned or unconditioned

The blink reaction is an unconditional type. It occurs as a result of dry eye and to protect against mechanical damage. All animals and humans have it.

Salivation in a person at the sight of a lemon - what is the reflex?

This is a conditional view. It is formed due to the fact that the rich taste of lemon provokes salivation so often and strongly that simply looking at it (and even remembering it) triggers a response.

How to develop a conditioned reflex in a person

In humans, unlike animals, the conditioned appearance is developed faster. But for all, the mechanism is the same - joint presentation of stimuli. One, causing an unconditioned reflex, and the other, an indifferent one.

For example, for a teenager who falls off a bicycle while listening to some specific music, later unpleasant feelings that arise while listening to the same music can become the acquisition of a conditioned reflex.

What is the role of conditioned reflexes in the life of an animal

They enable an animal with rigid, unchanging unconditioned reactions and instincts to adapt to conditions that are constantly changing.

At the level of the entire species, this is the ability to live in the largest possible areas with different weather conditions, with different levels of food supply. In general, they provide the ability to react flexibly and adapt to the environment.

Conclusion

Unconditioned and conditioned responses are extremely important for the survival of the animal. But it is in interaction that they allow us to adapt, reproduce and raise the healthiest offspring possible.

Differences between conditioned reflexes and unconditioned ones. Unconditioned reflexes are innate reactions of the body; they were formed and consolidated in the process of evolution and are inherited. Conditioned reflexes arise, become consolidated, and fade away throughout life and are individual. Unconditioned reflexes are specific, i.e. they are found in all individuals of a given species. Conditioned reflexes may be developed in some individuals of a given species, but absent in others; they are individual. Unconditioned reflexes do not require special conditions for their occurrence; they necessarily arise if adequate stimuli act on certain receptors. Conditioned reflexes require special conditions for their formation; they can be formed in response to any stimuli (of optimal strength and duration) from any receptive field. Unconditioned reflexes are relatively constant, persistent, unchanging and persist throughout life. Conditioned reflexes are changeable and more mobile.

Unconditioned reflexes can occur at the level of the spinal cord and brain stem. Conditioned reflexes can be formed in response to any signals perceived by the body and are primarily a function of the cerebral cortex, realized with the participation of subcortical structures.

Unconditioned reflexes can ensure the existence of an organism only at the very early stage of life. The body's adaptation to constantly changing environmental conditions is ensured by conditioned reflexes developed throughout life. Conditioned reflexes are changeable. In the process of life, some conditioned reflexes, losing their meaning, fade away, while others are developed.

Biological significance of conditioned reflexes. The body is born with a certain fund of unconditioned reflexes. They provide him with the maintenance of vital functions in relatively constant conditions of existence. These include unconditioned reflexes: food (chewing, sucking, swallowing, secretion of saliva, gastric juice, etc.), defensive (pulling a hand away from a hot object, coughing, sneezing, blinking when a stream of air enters the eye, etc.), sexual reflexes (reflexes associated with sexual intercourse, feeding and caring for offspring), thermoregulatory, respiratory, cardiac, vascular reflexes that maintain the constancy of the internal environment of the body (homeostasis), etc.

Conditioned reflexes provide a more perfect adaptation of the body to changing living conditions. They help to find food by smell, timely escape from danger, and orientation in time and space. The conditioned reflex separation of saliva, gastric and pancreatic juices by sight, smell, and meal times creates better conditions for digesting food even before it enters the body. Enhancing gas exchange and increasing pulmonary ventilation before starting work, only when seeing the environment in which the work is being done, contributes to greater endurance and better performance of the body during muscular activity.

When a conditioned signal is applied, the cerebral cortex provides the body with preliminary preparation for responding to those environmental stimuli that will subsequently have an impact. Therefore, the activity of the cerebral cortex is signaling.

Conditions for the formation of a conditioned reflex. Conditioned reflexes are developed on the basis of unconditioned ones. The conditioned reflex was so named by I.P. Pavlov because certain conditions are needed for its formation. First of all, you need a conditioned stimulus, or signal. A conditioned stimulus can be any stimulus from the external environment or a certain change in the internal state of the body. In the laboratory of I.P. Pavlov, the flashing of an electric light bulb, the bell, the gurgling of water, skin irritation, taste, olfactory stimuli, the clinking of dishes, the sight of a burning candle, etc. were used as conditioned stimuli. Conditioned reflexes are temporarily developed in a person by observing a work regime, eating at the same time, consistent with bedtime.

A conditioned reflex can be developed by combining an indifferent stimulus with a previously developed conditioned reflex. In this way, conditioned reflexes of the second order are formed, then the indifferent stimulus must be reinforced with a conditioned stimulus of the first order. It was possible to form conditioned reflexes of the third and fourth orders in the experiment. These reflexes are usually unstable. Children managed to develop sixth-order reflexes.

The possibility of developing conditioned reflexes is hampered or completely eliminated by strong extraneous stimuli, illness, etc.

In order to develop a conditioned reflex, the conditioned stimulus must be reinforced with an unconditioned stimulus, that is, one that evokes an unconditioned reflex. The clinking of knives in the dining room will cause a person to salivate only if this clinking has been reinforced with food one or more times. The clinking of knives and forks in our case is a conditioned stimulus, and the unconditioned stimulus that causes the salivary unconditioned reflex is food. The sight of a burning candle can become a signal for a child to withdraw his hand only if at least once the sight of a candle coincides with pain from a burn. When a conditioned reflex is formed, the conditioned stimulus must precede the action of the unconditioned stimulus (usually by 1-5 s).

The mechanism of formation of a conditioned reflex. According to the ideas of I.P. Pavlov, the formation of a conditioned reflex is associated with the establishment of a temporary connection between two groups of cortical cells: between those who perceive conditioned and those who perceive unconditional stimulation. This connection becomes stronger the more often both areas of the cortex are simultaneously excited. After several combinations, the connection turns out to be so strong that under the influence of only one conditioned stimulus, excitation also occurs in the second focus (Fig. 15).

Initially, an indifferent stimulus, if it is new and unexpected, causes a general generalized reaction of the body - an orienting reflex, which I. P. Pavlov called the exploratory or “what is it?” reflex. Any stimulus, if used for the first time, causes a motor reaction (general shudder, turning the eyes and ears towards the stimulus), increased breathing, heartbeat, generalized changes in the electrical activity of the brain - the alpha rhythm is replaced by rapid oscillations (beta rhythm). These reactions reflect generalized generalized arousal. When a stimulus is repeated, if it does not become a signal for a specific activity, the orienting reflex fades away. For example, if a dog hears a bell for the first time, it will give a general approximate reaction to it, but will not produce saliva. Now let's back up the sound of the bell with food. In this case, two foci of excitation will appear in the cerebral cortex - one in the auditory zone, and the other in the food center (these are areas of the cortex that are excited under the influence of the smell and taste of food). After several reinforcements of the bell with food, a temporary connection will arise (close) in the cerebral cortex between the two foci of excitation.

In the course of further research, facts were obtained indicating that the closure of the temporary connection occurs not only along horizontal fibers (bark - bark). Cuts in the gray matter separated different areas of the cortex in dogs, but this did not prevent the formation of temporary connections between the cells of these areas. This gave reason to believe that the cortex-subcortex-cortex pathways also play an important role in establishing temporary connections. In this case, centripetal impulses from the conditioned stimulus through the thalamus and nonspecific system (hippocampus, reticular formation) enter the corresponding zone of the cortex. Here they are processed and along descending pathways reach the subcortical formations, from where the impulses come again to the cortex, but already in the zone of representation of the unconditioned reflex.

What happens in the neurons involved in the formation of a temporary connection? There are different points of view on this matter. One of them assigns the main role to morphological changes in the endings of nerve processes.

Another point of view about the mechanism of the conditioned reflex is based on the principle of dominance by A. A. Ukhtomsky. In the nervous system at each moment of time there are dominant foci of excitation - dominant foci. The dominant focus has the property of attracting to itself the excitation entering other nerve centers, and thereby intensifying. For example, during hunger, a persistent focus with increased excitability appears in the corresponding parts of the central nervous system - a food dominant. If you let a hungry puppy lap milk and at the same time begin to irritate the paw with an electric current, then the puppy does not withdraw its paw, but begins to lap with even greater intensity. In a well-fed puppy, irritation of the paw with an electric current causes a reaction of its withdrawal.

It is believed that during the formation of a conditioned reflex, the focus of persistent excitation that arose in the center of the unconditioned reflex “attracts” to itself the excitation that arose in the center of the conditioned stimulus. As these two excitations combine, a temporary connection is formed.

Many researchers believe that the leading role in fixing the temporary connection belongs to changes in protein synthesis; Specific protein substances associated with imprinting a temporary connection have been described. The formation of a temporary connection is associated with the mechanisms of storing traces of excitation. However, memory mechanisms cannot be reduced to “belt connection” mechanisms.

There is evidence of the possibility of storing traces at the level of single neurons. Cases of imprinting from a single action of an external stimulus are well known. This gives grounds to believe that the closure of a temporary connection is one of the mechanisms of memory.

Inhibition of conditioned reflexes. Conditioned reflexes are plastic. They can persist for a long time, or they can be inhibited. Two types of inhibition of conditioned reflexes have been described - internal and external.

Unconditional, or external, inhibition. This type of inhibition occurs in cases where in the cerebral cortex, during the implementation of a conditioned reflex, a new, sufficiently strong focus of excitation appears, not associated with this conditioned reflex. If a dog has developed a conditioned salivary reflex to the sound of a bell, then turning on a bright light at the sound of a bell in this dog inhibits the previously developed salivation reflex. This inhibition is based on the phenomenon of negative induction: a new strong focus of excitation in the cortex from extraneous stimulation causes a decrease in excitability in the areas of the cerebral cortex associated with the implementation of the conditioned reflex, and, as a consequence of this phenomenon, inhibition of the conditioned reflex occurs. Sometimes this inhibition of conditioned reflexes is called inductive inhibition.

Inductive inhibition does not require development (that is why it is classified as unconditioned inhibition) and develops immediately as soon as an external stimulus, foreign to the given conditioned reflex, acts.

External braking also includes transcendental braking. It manifests itself when the strength or time of action of the conditioned stimulus increases excessively. In this case, the conditioned reflex weakens or completely disappears. This inhibition has a protective value, as it protects nerve cells from stimuli of too great strength or duration that could disrupt their activity.

Conditioned, or internal, inhibition. Internal inhibition, in contrast to external inhibition, develops within the arc of the conditioned reflex, i.e., in those nervous structures that are involved in the implementation of this reflex.

If external inhibition occurs immediately as soon as the inhibitory agent has acted, then internal inhibition must be developed; it occurs under certain conditions, and this sometimes takes a long time.

One type of internal inhibition is extinction. It develops if the conditioned reflex is not reinforced by an unconditioned stimulus many times.

Some time after extinction, the conditioned reflex can be restored. This will happen if we again reinforce the action of the conditioned stimulus with the unconditioned one.

Fragile conditioned reflexes are restored with difficulty. Extinction can explain the temporary loss of labor skills and the ability to play musical instruments.

In children, decline occurs much more slowly than in adults. This is why it is difficult to wean children from bad habits. Extinction is the basis of forgetting.

The extinction of conditioned reflexes has important biological significance. Thanks to it, the body stops responding to signals that have lost their meaning. How many unnecessary, superfluous movements would a person make during writing, labor operations, and sports exercises without extinctive inhibition!

The delay of conditioned reflexes also refers to internal inhibition. It develops if the reinforcement of a conditioned stimulus by an unconditioned stimulus is delayed. Usually, when developing a conditioned reflex, a conditioned stimulus-signal (for example, a bell) is turned on, and after 1-5 s food is given (unconditioned reinforcement). When the reflex is developed, immediately after the bell is turned on, without giving food, saliva begins to flow. Now let’s do this: turn on the bell, and gradually delay the food reinforcement until 2-3 minutes after the bell starts sounding. After several (sometimes very multiple) combinations of a sounding bell with delayed reinforcement with food, a delay develops: the bell turns on, and saliva will no longer flow immediately, but 2-3 minutes after the bell is turned on. Due to the non-reinforcement of the conditioned stimulus (bell) for 2-3 minutes by the unconditioned stimulus (food), the conditioned stimulus acquires an inhibitory value during the period of non-reinforcement.

The delay creates conditions for better orientation of the animal in the surrounding world. The wolf does not immediately rush at the hare when it sees it at a considerable distance. He waits for the hare to approach. From the moment the wolf saw the hare until the time the hare approached the wolf, a process of internal inhibition took place in the wolf’s cerebral cortex: motor and food conditioned reflexes were inhibited. If this did not happen, the wolf would often be left without prey, breaking into pursuit as soon as he sees the hare. The resulting delay provides the wolf with prey.

Delay in children is developed with great difficulty under the influence of upbringing and training. Remember how a first-grader impatiently reaches out his hand, waving it, getting up from his desk so that the teacher notices him. And only by high school age (and even then not always) do we notice endurance, the ability to restrain our desires, and willpower.

Similar sound, olfactory and other stimuli can signal completely different events. Only an accurate analysis of these similar stimuli ensures biologically appropriate reactions of the animal. Analysis of stimuli consists of distinguishing, separating different signals, differentiating similar interactions on the body. In the laboratory of I.P. Pavlov, for example, it was possible to develop the following differentiation: 100 metronome beats per minute were reinforced with food, and 96 beats were not reinforced. After several repetitions, the dog distinguished 100 metronome beats from 96: at 100 beats she salivated, at 96 beats the saliva did not separate. Discrimination, or differentiation, of similar conditioned stimuli is developed by reinforcing some and non-reinforcing other stimuli. The inhibition that develops suppresses the reflex reaction to non-reinforced stimuli. Differentiation is one of the types of conditioned (internal) inhibition.

Thanks to differential inhibition, it is possible to identify signal-significant signs of a stimulus from many sounds, objects, faces, etc. around us. Differentiation is developed in children from the first months of life.

Dynamic stereotype. The external world acts on the body not through single stimuli, but usually through a system of simultaneous and sequential stimuli. If this system is often repeated in this order, then this leads to the formation of a dynamic stereotype.

A dynamic stereotype is a sequential chain of conditioned reflex acts, carried out in a strictly defined, time-fixed order and resulting from a complex systemic reaction of the body to a complex of conditioned stimuli. Thanks to the formation of chain conditioned reflexes, each previous activity of the body becomes a conditioned stimulus - a signal for the next one. Thus, by previous activity the body is prepared for the subsequent one. A manifestation of a dynamic stereotype is a conditioned reflex for time, which contributes to the optimal functioning of the body with the correct daily routine. For example, eating at certain hours ensures good appetite and normal digestion; Consistency in keeping a bedtime helps children and adolescents fall asleep quickly and thus sleep longer; Carrying out educational work and work activities always at the same hours leads to faster processing of the body and better assimilation of knowledge, skills, and abilities.

A stereotype is difficult to develop, but if it is developed, then maintaining it does not require significant strain on cortical activity, and many actions become automatic. ;d A dynamic stereotype is the basis for the formation of habits in a person, the formation of a certain sequence in labor operations, and the acquisition of skills.

Walking, running, jumping, skiing, playing the piano, using a spoon, fork, knife when eating, writing - all these are skills that are based on the formation of dynamic stereotypes in the cerebral cortex.

The formation of a dynamic stereotype underlies the daily routine of every person. Stereotypes persist for many years and form the basis of human behavior. Stereotypes that arise in early childhood are very difficult to change. Let us remember how difficult it is to “retrain” a child if he has learned to hold a pen incorrectly when writing, sit incorrectly at the table, etc. The difficulty of remaking stereotypes forces us to pay special attention to the correct methods of raising and teaching children from the first years of life.

A dynamic stereotype is one of the manifestations of the systemic organization of higher cortical functions aimed at ensuring stable reactions of the body.

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 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 terms, the principle of the reflex 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 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 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 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 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 by varying degrees of intensity. I.P. Pavlov attached great importance to 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 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 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 labor 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 of nervous pathology, first noted 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 has long been 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, 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 studies have shown 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. 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 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, 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 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, 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 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 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 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 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 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. 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 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 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 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 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.”

Conditioned reflex- this is an acquired reflex characteristic of an individual (individual). They arise during the life of an individual and are not fixed genetically (not inherited). They appear under certain conditions and disappear in their absence. They are formed on the basis of unconditioned reflexes with the participation of higher parts of the brain. Conditioned reflex reactions depend on past experience, on the specific conditions in which the conditioned reflex is formed.

The study of conditioned reflexes is associated primarily with the name of I. P. Pavlov and the students of his school. They showed that a new conditioned stimulus can trigger a reflex response if it is presented for some time together with an unconditioned stimulus. For example, if a dog is allowed to sniff meat, then gastric juice is released (this is an unconditioned reflex). If, simultaneously with the appearance of meat, a bell rings, then the dog’s nervous system associates this sound with food, and gastric juice will be released in response to the bell, even if the meat is not presented. This phenomenon was discovered independently by Edwin Twitmyer at approximately the same time as in the laboratory of I. P. Pavlov. Conditioned reflexes are the basis acquired behavior. These are the simplest programs. The world around us is constantly changing, so only those who quickly and expediently respond to these changes can live successfully in it. As we gain life experience, a system of conditioned reflex connections develops in the cerebral cortex. Such a system is called dynamic stereotype. It underlies many habits and skills. For example, having learned to skate or bicycle, we subsequently no longer think about how we should move so as not to fall.

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Human Anatomy: Conditioned Reflexes

Conditioned reflexes

Higher nervous activity

Subtitles

Formation of a conditioned reflex

To do this you need:

• The presence of 2 stimuli: an unconditioned stimulus and an indifferent (neutral) stimulus, which then becomes a conditioned signal;
• Certain strength of stimuli. The unconditioned stimulus must be so strong as to cause dominant excitation in the central nervous system. The indifferent stimulus must be familiar so as not to cause a pronounced orienting reflex.
• A repeated combination of stimuli over time, with the indifferent stimulus acting first, then the unconditioned stimulus. Subsequently, the action of the two stimuli continues and ends simultaneously. A conditioned reflex will occur if an indifferent stimulus becomes a conditioned stimulus, that is, it signals the action of an unconditioned stimulus.
• Constancy of the environment - the development of a conditioned reflex requires constancy of the properties of the conditioned signal.

The mechanism of formation of conditioned reflexes

At action of an indifferent stimulus excitation occurs in the corresponding receptors, and impulses from them enter the brain section of the analyzer. When exposed to an unconditioned stimulus, specific excitation of the corresponding receptors occurs, and impulses through the subcortical centers go to the cerebral cortex (cortical representation of the center of the unconditioned reflex, which is the dominant focus). Thus, two foci of excitation simultaneously arise in the cerebral cortex: In the cerebral cortex, a temporary reflex connection is formed between two foci of excitation according to the dominant principle. When a temporary connection occurs, the isolated action of a conditioned stimulus causes an unconditioned reaction. In accordance with Pavlov's theory, the consolidation of temporary reflex communication occurs at the level of the cerebral cortex, and it is based on the principle of dominance.

Types of conditioned reflexes

There are many classifications of conditioned reflexes:

• If the classification is based on unconditioned reflexes, then we distinguish between food, protective, orientation, etc.
• If the classification is based on the receptors on which the stimuli act, exteroceptive, interoceptive and proprioceptive conditioned reflexes are distinguished.
• Depending on the structure of the used conditioned stimulus, simple and complex (complex) conditioned reflexes are distinguished.
  In real conditions of the functioning of the body, as a rule, the conditioned signals are not individual, single stimuli, but their temporal and spatial complexes. And then the conditioned stimulus is a complex of environmental signals.
• There are conditioned reflexes of the first, second, third, etc. order. When a conditioned stimulus is reinforced by an unconditioned one, a first-order conditioned reflex is formed. A second-order conditioned reflex is formed if a conditioned stimulus is reinforced by a conditioned stimulus to which a conditioned reflex was previously developed.
• Natural reflexes are formed in response to stimuli that are natural, accompanying properties of the unconditional stimulus on the basis of which they are developed. Natural conditioned reflexes, compared to artificial ones, are easier to form and more durable.

Notes

Ivan Petrovich Pavlov's school conducted vivisector experiments not only on dogs, but also on people. Street children aged 6–15 years were used as laboratory material. These were tough experiments, but they were the ones that made it possible to understand the nature of human thinking. These experiments were carried out in the children's clinic of the 1st LMI, in the Filatov hospital, in the hospital named after. Rauchfus, in the Department of Experimental Pediatrics of the IEM, as well as in several orphanages. are essential information. In two works by N. I. Krasnogorsky, “Development of the doctrine of the physiological activity of the brain in children” (L., 1939) and “Higher nervous activity of the child” (L., 1958), Professor Mayorov, who was the official chronicler of the Pavlovian school, melancholy noted: “ Some of our employees expanded the range of experimental objects and began studying conditioned reflexes in other animal species; in fish, ascidians, birds, lower apes, as well as children" (F. P. Mayorov, "History of the doctrine of conditioned reflexes." M., 1954). "laboratory material" of a group of Pavlov's students (Prof. N. I. Krasnogorsky , A.G. Ivanov-Smolensky, I. Balakirev, M.M. Koltsova, I. Kanaev) became homeless children. Full understanding at all levels was ensured by the Cheka.A. A. Yushchenko in his work “Conditional Reflexes of a Child” (1928 All this is confirmed by protocols, photographs and the documentary “Mechanics of the Brain” (another title is “Behavior of Animals and Humans”; directed by V. Pudovkin, camera by A. Golovnya, production film factory "Mezhrabprom-Rus", 1926)