Natural conditioned reflexes. The mechanism and process of formation of a conditioned reflex

01.10.2019

Depending on the characteristics of the responses, the nature of the stimuli, the conditions for their application and reinforcement, etc., various types of conditioned reflexes are distinguished. These types are classified based on various criteria, in accordance with the tasks. Some of these classifications are great importance both in theoretical and practical terms, including in sports activities.

Natural (natural) and artificial conditioned reflexes. Conditioned reflexes formed on the action of signals characterizing the constant properties of unconditioned stimuli (For example, smell or type of food) are called natural conditioned reflexes.

An illustration of the patterns of formation of natural conditioned reflexes are the experiments of I. S. Tsitovich. In these experiments, puppies of the same litter were kept on different diets: some were fed only meat, others only milk. In animals that were fed meat, the sight and smell of it already at a distance caused a conditioned food reaction with pronounced motor and secretory components. The puppies, who received only milk, for the first time reacted to meat only with an indicative reaction (i.e., according to the figurative expression of I.P. Pavlov, the reflex “What is it?”) - they sniffed it and turned away. However, even a single combination of the sight and smell of meat with food completely eliminated this "indifference". Puppies have developed a natural food conditioned reflex. The formation of natural (natural) conditioned reflexes to the appearance, smell of food and the properties of other unconditioned stimuli is also characteristic of humans. Natural conditioned reflexes are characterized by rapid development and great durability. They can be held all Life in the absence of subsequent reinforcements. This is explained by the fact that natural conditioned reflexes are of great biological importance, especially in the early stages of the organism's adaptation to the environment. It is the properties of the unconditioned stimulus itself (for example, the type and smell of food) that are the first signals that act on the body after birth.

But conditioned reflexes can also be developed to various indifferent signals (light, sound, smell, temperature changes, etc.) vivo properties of the stimulus that causes the unconditioned reflex. Such reactions, in contrast to natural ones, are called artificial conditioned reflexes. For example, the smell of mint is not inherent in meat. However, if this smell is combined several times with feeding meat, then a conditioned reflex is formed: the smell of mint becomes a conditioned signal of food and begins to cause a salivary reaction without reinforcement. Artificial conditioned reflexes are developed more slowly and fade faster when not reinforced.

An example of the development of conditioned reflexes to artificial stimuli can be the formation in a person of secretory and motor conditioned reflexes to signals in the form of the sound of a bell, metronome beats, strengthening or weakening the illumination of touching the skin, etc.

Conditioned reflexes of the first and higher orders. Reactions formed on the basis of unconditioned reflexes are called conditioned reflexes of the first order, and the reactions developed on the basis of previously acquired conditioned reflexes - conditioned reflexes of higher orders(second, third, etc.). During the development of conditioned reflexes of higher orders, the indifferent signal is reinforced by well-established conditioned stimuli. If, for example, irritation in the form of a call is reinforced with food (an unconditioned reaction), then a first-order conditioned reflex is developed. After strengthening the conditioned reflex of the first order, it is possible to develop on its basis a conditioned reflex of the second order, in particular to light. On the basis of a second-order conditioned reflex, a third-order conditioned reflex can be formed, on the basis of a third-order reflex, a fourth-order reflex, etc.

The formation of conditioned reflexes of higher orders depends on the perfection of the organization nervous system, its functional properties and the biological significance of the unconditioned reflex, on the basis of which the first-order conditioned reflex was developed. For example, in dogs under artificial conditions, against the background of increased food excitability, a salivary conditioned third-order reflex can be developed. In the case of a motor-defensive reaction in the same animals, the formation of fourth-order conditioned reflexes is possible. In monkeys, standing on a higher rung of the phylogenetic ladder, conditioned reflexes of higher orders are formed more easily than in dogs. For a person, the process of formation of conditioned reflexes, of higher orders, turns out to be the most adequate. In the presence of increased excitability of the central nervous system, even in children under the age of one year, conditioned reflexes of the fifth and sixth order are developed (N. I. Krasnogorsky). With the development of the function of speech, the ordinal range of these reactions expands significantly. Thus, the vast majority of motor conditioned reflexes in humans are formed by reinforcement not by any unconditioned stimulus, but by various conditioned signals in the form of verbal instructions, explanations, etc.

The biological significance of conditioned reflexes of higher orders is that they provide a signal about the upcoming activity when reinforced not only by unconditioned, but also by conditioned stimuli. In this regard, the deployment of adaptive reactions of the body occurs more quickly and fully.

Positive and negative conditioned reflexes. Conditioned reflexes, in the dynamics of which the activity of the organism is manifested in the form of motor or secretory reactions, are called positive. Conditional reactions that are not accompanied by external motor and secretory effects due to their inhibition are classified as negative or inhibitory, reflexes. In the process of adapting the organism to changing environmental conditions, both types of reflexes are of great importance. They are closely interrelated, since the manifestation of one type of activity is combined with the oppression of other types. For example, during defensive motor conditioned reflexes, conditioned food reactions are inhibited and vice versa. With a conditioned stimulus in the form of the command "Attention!" the activity of the muscles causing standing in a certain position and inhibition of other conditioned motor reactions that were carried out before this command (for example, walking, running) is called.

Such an important quality as discipline is always associated with a simultaneous combination of positive and negative (inhibitory) conditioned reflexes. For example, when performing certain physical exercises (diving into the water from a tower, gymnastic flips, etc.), inhibition of the strongest negative defensive conditioned reflexes is required to suppress reactions of self-preservation and feelings of fear.

Cash and trace reflexes. Conditioned reflexes, in which the conditioned signal precedes the unconditioned stimulus, acts together with it and ends simultaneously or a few seconds earlier or later than the cessation of the unconditioned stimulus, are called cash (Fig. 63). As already noted, for the formation of a conditioned reflex, it is necessary that the conditioned signal begin to act before the reinforcing Stimulus begins to act. The interval between them, i.e., the degree of separation of the reinforcing stimulus from the conditioned signal, may be different. Depending on the duration of the delay of unconditional reinforcement from the beginning of the action of the conditioned signal, the available conditioned reflexes in animals, for example food, are classified as coinciding (0.5 - 1 sec.), Short-delayed (3 - 5 sec.), Normal (10 - 30 sec.). ) and delayed (1 - 5 minutes or more).

With trace conditioned reflexes, the conditioned stimulus is reinforced after the cessation of its action (see Fig. 63). Trace conditioned reflexes are formed during short (10-20 seconds) and long (late) delays (1-2 minutes or more). The group of trace conditioned reflexes includes, in particular, a reflex to time, which plays the role of the so-called "biological clock".

The present and trace conditioned reflexes with a long delay are complex forms of manifestation of higher nervous activity and are accessible only to animals with a sufficiently developed cerebral cortex. The development of such reflexes in dogs is associated with great difficulties. In humans, trace conditioned reflexes are formed easily.

Trace conditioned responses are of great importance in exercise. For example, in a gymnastic combination consisting of several elements, trace excitation in the cerebral cortex, caused by the action of the first phase of movement, serves as an irritant for programming the chain of all subsequent ones. Inside the chain reaction, each of the elements is a conditional signal for the transition to the next phase of movement.

Exteroceptive, proprioceptive and interoceptive reflexes. Depending on the analyzer on the basis of which the conditioned reflexes are developed, the latter are divided into three types. Reactions developed by stimulation of external analyzers (visual, auditory, etc.) are called exteroceptive, and those developed by stimulation of muscle receptors are called proprioceptive, receptors internal organs- interoceptive.

The main means of communication of the organism with the external environment are extero- and proprioceptive conditioned reflexes. Reactions of greater biological significance are produced faster and are better differentiated. At the same time, they are quite dynamic and can fade away with a change in the signal value of stimuli and their non-reinforcement.

Interoceptive conditioned reflexes are developed and differentiated much more slowly; Afferent impulses from interoreceptors can repeatedly coincide in time with the implementation of response somatic and vegetative reactions that occur when certain environmental signals are exposed to the body. In this case, interoceptive stimuli acquire a signal value for the corresponding reactions. In general, interoceptive stimuli stimulate the coordinating influence of the nerve centers, especially the cortex. hemispheres, on the interaction of factors of the internal and external environment, as a result of which subtle conditioned reflex adaptive reactions develop. With muscular activity, the intensity of manifestation of vegetative functions increases (blood circulation, respiration, etc.). The impulse from the interoreceptors to the central nervous system is noticeably enhanced, and therefore more favorable conditions are created for the formation of interoceptive conditioned reflexes. A certain nature of the change in vegetative functions in the process of performing sports work can be combined according to the mechanism of conditioned reflexes with a specific motor activity and thereby contribute to its more effective implementation.

Conditioned reflexes to complex stimuli. The formation of conditioned reflexes can occur under the action of not only single, but also complex stimuli related to one or different sensory systems. Complex stimuli can act simultaneously and sequentially. With a complex of simultaneously acting stimuli, signals from several stimuli are received. For example, a conditioned food reflex can be triggered by the simultaneous exposure to smell, shape, and color of a stimulus. With a complex of successively acting stimuli, the first of them, for example, light, is replaced by a second, for example, sound (in the form of a high tone), then a third, for example, the sound of a metronome. Reinforcement follows only after the action of this whole complex.

Higher nervous activity- a system that allows the human body and animals 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. An outstanding domestic scientist I.P. Pavlov is the founder of the doctrine of unconditioned and conditioned reflexes. He formed a conditioned reflex theory, which states that the acquisition of a conditioned reflex is possible when a physiologically indifferent stimulus acts 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 stimuli.

Conditioned reflexes

Conditioned reflexes are formed on the basis of unconditional, 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 an impulse to the cortical structures and the formation of a response.

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

The sensitive receptor perceives the stimulus, then the impulse goes to the posterior horns of the spinal cord, where the intercalary neuron 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 catching reflex must be inferior in strength to the biologically significant effect;
the normal functioning of the cerebral cortex and the absence of distractions are mandatory.

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

An example of the development of a conditioned reflex

Classification of conditioned reflexes:

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

Thus, a defensive reflex of the third order was formed in dogs, the fourth could not be developed, and the digestive one 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, dominated by reflex reactions (gustatory, tactile);
intraceptive- are 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 arise under the action of a stimulus that has no connection with an unconditioned stimulus (sound signals, light stimulation).

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

Unconditioned reflexes

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

reflex arcs hereditary reactions are laid down before the birth of a person. 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 with the onset of a certain period they appear (sexual).

Unconditioned reflexes are characterized by the following features:

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

Unconditioned reflexes are needed to fulfill the needs of the body, they are permanent, but as a result of illness or bad habits may disappear. So, with a disease of the iris of the eye, 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 a hot object);
complex(maintaining homeostasis in situations of increased CO 2 concentration in the blood by increasing the frequency of respiratory movements);
the most difficult(instinctive behavior).

Classification of unconditioned reflexes according to Pavlov

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

To food salivation at the sight of food and its entry into the digestive tract, the secretion of hydrochloric acid, gastrointestinal motility, sucking, swallowing, chewing.

Protective are accompanied by contraction of muscle fibers in response to an irritating factor. Everyone knows the situation when the hand reflexively pulls away from a hot iron or sharp knife, sneezing, coughing, lacrimation.

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

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

Statokinetic provide bipedalism, balance, movement of the body.

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, economy of strength), depend only on the individual.

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

The need for self-development(the desire for individual growth, for the discovery of something new).

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

Table comparing conditioned and unconditioned reflexes

Comparison of the characteristics of conditioned (acquired) and unconditioned (innate) reflexes
Unconditional	Conditional
Congenital	Acquired in the course of life
Present in all members of the species	Individual for each organism
Relatively constant	Arise and fade with changes in the external environment
Formed at the level of the spinal cord and medulla oblongata	Carried out by the brain
Are laid in utero	Developed against the background of congenital reflexes
Occurs when an irritant acts on certain receptor zones	Manifested under the influence of any stimulus that is perceived by the individual

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

Braking

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

When several stimuli (light, sound, smell) are simultaneously exposed to the studied organism, the conditioned reflex fades, but over time, the orienting reflex is activated and inhibition disappears. This type of inhibition is called temporary.

Conditional inhibition(acquired) does not arise by itself, it must be worked out. There are 4 types of conditional inhibition:

Fading (disappearance of a persistent conditioned reflex without constant reinforcement by an unconditioned one);
differentiation;
conditional brake;
delayed braking.

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

An example of external inhibition (the reaction of a dog 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. good example is the birth of a child. In the new world for him, many dangers await him. Due to the presence of innate reactions, the cub can survive in these conditions. Immediately after birth, the respiratory system is activated, the sucking reflex provides nutrients, touching sharp and hot objects is accompanied by an instant withdrawal of the hand (manifestation of protective reactions).

For further development and existence have to adapt to the surrounding conditions, this is helped by conditioned reflexes. They provide rapid adaptation of the body and can be formed throughout life.

The presence of conditioned reflexes in animals enables them to quickly respond to the voice of a predator and save their lives. A person at the sight of food carries out conditioned reflex activity, salivation begins, the production of gastric juice for the rapid digestion of food. The sight and smell of some objects, on the contrary, signals danger: the red cap of fly agaric, the smell of spoiled food.

The value of conditioned reflexes in Everyday life human and animal is huge. Reflexes help to navigate the terrain, get food, get away from danger, saving one's life.

Depending on the characteristics of the responses, the nature of the stimuli, the conditions for their application and reinforcement, etc., various types of conditioned reflexes are distinguished. These types are classified based on various criteria, in accordance with the tasks. Some of these classifications are of great importance, both in theoretical and practical terms, including in sports activities.

As well as unconditioned, conditioned reflexes can be divided according to the receptor and effector features and their biological significance.

According to the receptor basis, conditioned reflexes are divided into exteroceptive, interoceptive and proprioceptive. Conditioned reflexes are most easily formed when exteroreceptors are stimulated.

According to the effector basis, conditioned reflexes are divided into vegetative(the effector is the internal organs) and somatomotor(skeletal muscle effector).

According to their biological significance, conditioned reflexes are divided into food, defensive, sexual, statokinetic and locomotor, as well as conditioned reflexes that maintain the constancy of the internal environment of the body(homeostasis).

However, a conditioned reflex can be formed not only to a conditioned signal that is simple in structure, but also to a complex stimulus - a combination of signals related to one or different sensory systems. Complex stimuli can act simultaneously and sequentially.

With a complex of active stimuli, signals come from several stimuli at the same time. For example, a conditioned food reflex can be caused by the simultaneous exposure to the smell, shape and color of the stimulus.

With a complex of successively acting stimuli, the first of them, for example, light, is replaced by a second, for example, sound (in the form of a high tone), then a third, for example, the sound of a metronome. Reinforcement follows only after the action of this whole complex.

The ability to respond to complex stimuli allows us to classify conditioned reflexes according to such an indicator as reflex order . For example, a dog has developed a strong salivary conditioned reflex to the light of a light bulb. Such a reflex is called a reflex of the first order. In the future, a new conditioned signal (the sound of a bell) is used, which is reinforced not by an unconditioned stimulus, but by the already used conditioned one - the light of a light bulb. After several such combinations, it becomes a signal for the separation of saliva. This means that a second-order conditioned reflex has formed.

The most important form of conditioned reflexes are higher order reflexes, which are formed on the basis of established conditioned reflexes. In dogs, it was possible to develop a conditioned reflex up to the third order, in monkeys up to the fourth, in children up to the sixth, in an adult, conditioned reflexes of the ninth order were described.

Sensory and operant conditioned reflexes. Each reflex contains afferent (sensory) and efferent (executive) components (links). In some cases, the formation of new conditioned reflexes can occur with the formation of only new sensory components, in others, with the formation of both components. As a result, conditioned reflexes can be of two types - sensory and operant (effector).

In sensory conditioned reactions (called Yu. Konorsky conditioned reflexes of the 1st kind), response acts are either inherited (food, defensive, orienting, sexual and other unconditioned reflexes), or previously well-fixed conditioned reflexes (conditioned reflexes of higher orders). Consequently, they are characterized by the formation of only the afferent part of the reflex, in which an indifferent stimulus turns into an active one. The response to the conditioned stimulus remains the same as with the unconditioned or previously well-developed conditioned stimulus. For example, during the development of a defensive conditioned reflex to smell in the central nervous system, connections are established between afferent cells that perceive irritation of the olfactory analyzer and the pain center. At the same time, the nature of the response conditional and unconditional reactions coincides. In both cases, salivation begins. Similarly, other sensory conditioned reactions are developed and manifested (in particular, defensive motor conditioned reflexes in the form of hand withdrawal, reinforced by pain stimulation, tendon, pupillary, blinking reflexes).

Conditioned reflexes of this kind cannot always sufficiently change the relationship of the organism with the environment and fully provide adequate adaptation, since new forms of the response reactions themselves are not organized in this case. A more adequate adaptation is ensured by the fact that animals and humans are able to radically change the nature of their effector reactions in their relationship with the environment.

Operant conditioned reflexes(according to the classification of Yu. Konorsky, reflexes of the 2nd kind) are characterized by a new (not inherited from the ancestors or not previously available in the individually acquired fund) form of response. These reflexes are also called "instrumental", since different objects (tools) are used in their implementation. For example, an animal opens a latch on a door with a limb and takes out the food behind it. Since the formation of such reflexes creates a complex set of newly formed movements, these reflexes are also called "manipulative".

In the formation of the corresponding conditioned operant reflexes, the most important role belongs to the impulses coming from the motor apparatus. An elementary model of a conditioned operant reflex was observed at. development of a classical food conditioned reflex to passive paw flexion in a dog (Yu. Konorsky). Two types of conditioned reactions were revealed in the animal - conditioned reflex salivation in response to passive flexion of the paw (sensory conditioned reflex, or reflex of the 1st kind) and multiple active flexion of the limb, which was not only a signal, but also a way of obtaining food (operant conditioned reflex, or reflex of the 2nd kind).

In the formation of operant conditioned reactions, the most important role belongs to the feedback between the cells in the nerve centers of unconditioned or previously well-developed conditioned reflexes and the cells of the centers of the motor analyzer. This is facilitated by a high level of excitability of the motor centers, due to the flow of afferent impulses from the proprioreceptors of the contracting muscles.

Thus, one of the conditions for the development of operant motor conditioned reflexes is the mandatory inclusion in the system of stimuli of an impulsation that arose spontaneously or was caused by active or passive movement. The formation of these reflexes depends on the nature of the reinforcing agent. Operant conditioned reflexes form the basis of motor skills. Contribute to their consolidation feedback, carried out through the proprioceptors of the muscles that perform the movement, and through the receptors of a number of other analyzers. Thanks to this afferentation, the central nervous system signals the results of the movement.

The formation of new movements, i.e., not inherited from ancestors, is observed not only in humans, but also in animals. But for a person, this process is of particular importance, since almost all complex motor acts (in particular, physical exercises in various sports) are formed precisely as a result of training.

Natural (natural) and artificial conditioned reflexes. Conditioned reflexes are easier to develop in response to influences that are ecologically close to a given animal. In this regard, conditioned reflexes are divided into natural and artificial.

Natural conditioned reflexes are developed to agents that, under natural conditions, act together with the stimulus that causes the unconditioned reflex (for example, the type of food, its smell, etc.).

An illustration of the regularities in the formation of natural conditioned reflexes are the experiments of I. S. Tsitovich. In these experiments, puppies of the same litter were kept on different diets: some were fed only meat, others only milk. In animals that were fed meat, the sight and smell of it already at a distance caused a conditioned food reaction with pronounced motor and secretory components. Puppies fed only milk for the first time reacted to meat only with an indicative reaction, sniffed it and turned away. However, even a single combination of the sight and smell of meat with food completely eliminated this "indifference". Puppies have developed a natural food conditioned reflex.

The formation of natural (natural) conditioned reflexes is also characteristic of humans. Natural conditioned reflexes are characterized by rapid development and great durability. They can be held for life in the absence of subsequent reinforcements. This is explained by the fact that natural conditioned reflexes are of great biological importance, especially in the early stages of the organism's adaptation to the environment. It is the properties of the unconditioned stimulus itself (for example, the type and smell of food) that are the first signals that act on the body after birth.

But, since conditioned reflexes can also be developed to various indifferent signals (light, sound, smell, temperature changes, etc.), which in natural conditions do not have the properties of an irritant that causes an unconditioned reflex, then such reactions, in contrast to natural ones, are called artificial conditioned reflexes. For example, the smell of mint is not inherent in meat. However, if this smell is combined several times with feeding meat, then a conditioned reflex is formed: the smell of mint becomes a conditioned signal of food and begins to cause a salivary reaction without reinforcement.

Artificial conditioned reflexes are developed more slowly and fade faster when not reinforced.

Positive and negative conditioned reflexes. Conditioned reflexes, in the dynamics of which the activity of the organism is manifested in the form of motor or secretory reactions, are called positive. Conditional reactions that are not accompanied by external motor and secretory effects due to their inhibition are classified as negative or inhibitory reflexes. In the process of adapting the organism to changing environmental conditions, both types of reflexes are of great importance. They are closely interrelated, since the manifestation of one type of activity is combined with the oppression of other types. For example, during defensive motor conditioned reflexes, conditioned food reactions are inhibited and vice versa. With a conditioned stimulus in the form of the command "Attention!" the activity of the muscles causing standing in a certain position and inhibition of other conditioned motor reactions that were carried out before this command (for example, walking, running) is called.

Cash and trace reflexes. As already noted, I.P. Pavlov determined that for the formation of a conditioned reflex, it is necessary that the conditioned signal begins to act before the unconditioned one. However, the interval between them, i.e., the degree of separation of the unconditioned stimulus from the conditioned signal, may be different.

Conditioned reflexes in which the conditioned signal precedes the unconditioned stimulus, but acts together with it (i.e., the conditioned and unconditioned stimuli act together for some time) are called in cash.(Fig. 2. A, B, C ). Depending on the duration of the delay of unconditional reinforcement from the beginning of the action of the conditioned signal, the available conditioned reflexes in animals are classified as coinciding (0.5 - 1 sec.), Short-delayed (3 - 5 sec.), Normal (10 - 30 sec.) and delayed ( over 1 minute).

At trace conditioned reflexes , the conditioned stimulus is reinforced after the termination of its action (Fig. 2. D, E, F) Between the fading focus of excitation in the cortex from an indifferent agent and the focus of excitation in the cortical representation of the reinforcing unconditioned or previously well-developed reflex, a temporary connection is formed.

Trace conditioned reflexes are formed during short (10-20 seconds) and long (late) delays (1-2 minutes or more). The group of trace conditioned reflexes includes, in particular, a reflex to time, which plays the role of the so-called "biological clock".

◄Fig. 2. Scheme of the combination of conditioned and unconditioned stimuli in time with present and trace stimuli.

Gray rectangles are the duration of the conditioned stimulus:

The black rectangles are the duration of the action of the unconditioned stimulus.

Trace conditioned responses are of great importance in physical exercise. For example, in a gymnastic combination consisting of several elements, trace excitation in the cerebral cortex, caused by the action of the first phase of movement, serves as an irritant for programming the chain of all subsequent ones. Inside the chain reaction, each of the elements is a conditional signal for the transition to the next phase of movement.

The development of the child's higher nervous activity is in close connection with the formation of the structure of the cerebral cortex and the system of analyzers as a whole.

In higher animals and humans postnatal period the main regulatory role in behavior is played by the cerebral cortex big brain, which is an organ of individual adaptation of the organism to the external environment. I.P. Pavlov pointed out that the balancing of the organism with the environment cannot be ensured by unconditioned reflexes alone. “The balancing achieved by these reflexes would be perfect only with the absolute constancy of the external environment. And since external environment despite its extreme diversity, at the same time, it is in constant fluctuation, then unconditional connections, as constant connections, are not enough and it is necessary to supplement them with conditioned reflexes, temporary connections.

A. Neonatal period. The formation of conditioned reflexes begins from the first days or weeks after birth, those. during the period when the most intensive development of cortical structures occurs and separate cortical fields associated with the corresponding receptors are formed.

The earlier formation of conditioned food reflexes in a developing organism compared to defensive reflexes is of great adaptive importance. In the first period of the life of the organism, the main vital functions are reduced to food intake. The appearance during this period of conditioned food reflexes provides him with a more complete implementation of the act of nutrition.

The possibility of earlier development of conditioned food reflexes from phylogenetically older analyzers (olfactory, skin, vestibular) than from phylogenetically newer ones (auditory, visual) indicates that corticolization of phylogenetically old analyzer systems associated with the food center occurs in more early dates than phylogenetically young analyzer systems.

Age features the formation of conditioned reflexes are clearly revealed in the nature of the development of the conditioned reaction itself. The defensive conditioned reflex in various animal species in the process of development, first of all, manifests itself in the form of a general motor reaction and its accompanying vegetative components (changes in respiration and cardiac activity), and then much later its specialized form is formed in the form of a local reflex. Thus, at the early stages of ontogenesis, there is a wide generalization of excitation processes in the effector and afferent parts of the conditioned reflex arc, followed by the appearance at the later stages of cortical inhibition processes, which determines the locality and specialization of the conditioned reaction. Age-related differences in higher nervous activity are revealed mainly in the ability to develop the process of internal inhibition, without which complex forms of conditioned reactions cannot be formed. This ability is found only at a later age, with a certain degree of morphological maturity and activity. biochemical processes cerebral cortex.

The earliest conditioned reflexes in a child are natural food reflexes in the form of sucking movements that occur on the position of the child during feeding. They are formed for the first time at the age of 8-15 days to a complex complex of tactile, proprioceptive and labyrinth stimuli. At the 2-4th week of life, artificial protective and food conditioned reflexes to vestibular stimuli begin to form. From the 3-4th week, conditioned reflexes to proprioceptive stimuli are developed. At the end of the 1st month, conditioned reflexes to odor stimuli are developed, and reflexes are formed somewhat later on odors that act mainly on the olfactory apparatus. In the same period, conditioned food and defensive reflexes to sound signals are formed.

B. Breast age. At the beginning of the 2nd month, conditioned reflexes are formed to light stimuli, conditioned "food and protective reflexes to skin-tactile stimuli, as well as conditioned protective reflexes to taste substances are formed. Thus, there is a certain sequence in the appearance of reflexes from various analyzers: first of all they are formed from the vestibular and auditory receptors, and later - from the visual and skin-tactile.However, during the second half of the 1st month and the first half of the 2nd month, conditioned reflexes

sy in a child are formed from all analyzers. This indicates that it is at this age that the cortex of the cerebral hemispheres of the child gets the opportunity to establish diverse conditioned connections.

Early conditioned reflexes in children are unstable and mild. The receptor from which the reflex is produced is also of decisive importance in the emergence and stability of the conditioned reflex. Ceteris paribus, the vestibular and auditory conditioned reflexes are strengthened before others, then the visual, olfactory and gustatory reflexes, and last of all - skin-tactile and proprioceptive. However, along with the general regularities in the formation of conditioned reflexes, which are characteristic of all children, already at an early age, individual features of the child's cortical functions are revealed, depending on the type of his nervous system. The individual characteristics of the child are most clearly manifested during the period when the cerebral cortex, in addition to the formation of positive conditioned reflex connections, begins to perform another function, closely related to the first, the function of analyzing external stimuli. This last function is based on the development of cortical inhibition.

The ability to analyze external stimuli is revealed by the example of the formation of differentiations. In the 2nd month of a child's life, almost all analyzers differentiate stimuli that differ significantly from each other. At the 3-4th month, the analyzer function of the cerebral cortex is rapidly improving and allows you to develop stronger and more subtle differentiations. The development of mechanisms for closing conditioned reflex connections and differentiating external stimuli quickly complicates and fundamentally changes the entire behavior of the child in the sense of his vigorous activity and cognition of the world around him.

Thus, the essential feature of the conditioned reflex activity of the child in the first six months of life must be considered complex stimuli that are effective for him. For example, the “feeding position”, in which tactile, proprioceptive and vestibular receptors are irritated and naturally excited at the same time. Various types of conditioned (internal) inhibition begin to appear: differential inhibition is formed (3-4th month), a conditioned brake at the 5th month, delayed inhibition at the 6th month, i.e., by the end of the first year of life, all types of internal inhibition (conditioned inhibition of conditioned reflexes - see section 6.8).

C. In the nursery period (from 1 year to 3 years), conditioned reflex activity is characterized not only by the development of individual conditioned reflexes, but also by the formation of dynamic stereotypes, and often in a shorter time than in adults.

D. A 2-year-old child develops a huge number of conditioned reflexes to the ratio of the size, severity, distance, color of objects. These types of conditioned reflexes determine the integrated reflection of the phenomena of the external world; they are considered the basis of concepts formed on the basis of the first signal system. An example of a dynamic stereotype of this age can be changes in the characteristics of the child's GNI according to the daily routine: sleep - wakefulness, nutrition, walks, requiring a sequence of behavioral elements that make up the procedures for washing, feeding, playing.

The systems of conditional connections developed at this time are especially strong, and most of them retain their significance throughout the entire subsequent life of a person. Therefore, one can think that during this period, in a number of cases, imprinting still continues to operate. Raising children in a sensory enriched environment accelerates their mental development. The interaction of the projection and non-projection sections of the cerebral cortex provides a deeper perception of the environment. Of particular importance in this case is the interaction of excitations that provide the emergence of sensations and motor activity, for example, visual perception of an object and grasping it with a hand.

E. At the age of 3-5 years, the improvement of conditioned reflex activity is expressed in an increase in the number of dynamic stereotypes (for more details, see section 6.14).

torii develop a conditioned defensive reflex to the same call in another laboratory. In this case, the call is reinforced by a slight irritation of the limb with an electric current. Soon, the dog reacts to the call not by salivation, but by withdrawing the limb - a defensive conditioned reflex. In this case, the conditioned signal is essentially a set of stimuli - a call and the environment of the laboratory. Such situations often occur in life. For example, a bell before the start of the lesson informs students about the need to start classes, at the end of the lesson - about the beginning of the break.

D. A consistent set of a number of conditioned reflexes is a dynamic stereotype, illustrating the consistency in the activity of the cerebral cortex, analytical and synthetic activity (E.A. Asratyan). In the experiments of E.A. Asratyan, conditioned reflexes were developed in dogs in a certain sequence, for example, a bell, a metronome (60 beats / min), hissing, metronome differentiation (120 beats / min), light, a wheelchair (Fig. 6.5).

conditioned reflexes to each of the stimuli, instead of each conditioned signal, one conditioned signal "light" was used in the experiment. At the same time, various conditioned reflexes were received on one stimulus - light, as with the sequential action of all the listed signals. In the cortex, there was a connection between all the points of the conditioned signals, and it was enough to turn on the “light” stereotype in the first place, as conditions were created for turning on the subsequent ones.

Thus, in the cerebral cortex, with prolonged use of the same sequence of conditioned signals (external stereotype), a certain system of connections (internal stereotype) is created. The reproduction of a stereotype is, as a rule, automatic. A dynamic stereotype prevents the creation of a new one (it is easier to teach a person than to retrain). The elimination of a stereotype and the creation of a new one are often accompanied by significant nervous tension (stress). A stereotype plays a significant role in a person's life: professional skills are associated with the formation of a certain stereotype; a sequence of gymnastic elements, memorizing poetry, playing musical instruments, practicing a certain sequence of movements in ballet, dancing, etc. - all these are examples of dynamic stereotypes, the role of which is obvious.

D. Conditioned reflexes have several components. During the development of a conditioned reflex, for example, a defensive reflex, to a call with stimulation of a limb by an electric current, in addition to a motor reaction, cardiovascular and respiratory system; it is possible to increase the heart rate, increase blood pressure due to the excitation of the sympathoadrenal system and the release of adrenaline into the blood, changes in the frequency and depth of breathing, metabolic changes. Firstly, they are associated with the action of stimuli, and secondly, with the provision of motor responses by vegetative shifts. Subsequently, vegetative shifts, although to a lesser extent, persist under the action of only a conditioned signal, in this case a bell, and accompany the conditioned defensive reflex.

FORMATION OF CONDITIONED REFLEXES

The main elementary act of higher nervous activity is the formation of a conditioned reflex. Here, these properties will be considered, as well as all the general laws of the physiology of higher nervous activity, using the example of the conditioned salivary reflexes of a dog.

The conditioned reflex occupies a high place in the evolution of temporary connections, which are a universal adaptive phenomenon in the animal world. The most primitive mechanism of individual adaptation to changing conditions of life, apparently, is intracellular temporary connections protozoa. The colonial forms develop the beginnings of intercellular temporary connections. The emergence of a primitive nervous system of a reticulated structure gives rise to temporary connections of the diffuse nervous system, found in intestinal. Finally, the centralization of the nervous system into the nodes of invertebrates and the brain of vertebrates leads to rapid progress. temporary connections of the central nervous system and the emergence of conditioned reflexes. So different types temporary connections, obviously, are carried out by physiological mechanisms of various nature.

There are countless conditioned reflexes. Subject to the appropriate rules, any perceived stimulus can be made a stimulus that triggers a conditioned reflex (signal), and any activity of the body can be its basis (reinforcement). According to the type of signals and reinforcements, as well as the relationship between them, different classifications of conditioned reflexes have been created. As for the study of the physiological mechanism of temporary connections, researchers have a lot of work to do here.

General signs and types of conditioned reflexes

On the example of a systematic study of salivation in dogs, general signs of a conditioned reflex, as well as particular signs of different categories of conditioned reflexes, have been outlined. The classification of conditioned reflexes was determined according to the following particular features: 1) the circumstances of formation, 2) the type of signal, 3) the composition of the signal, 4) the type of reinforcement, 5) the relationship in time of the conditioned stimulus and reinforcement.

General signs of conditioned reflexes. What signs are common and obligatory for all conditioned reflexes? Conditioned reflex a) is an individual higher adaptation to changing conditions of life; b) carried out by the higher parts of the central nervous system; c) is acquired through temporary neural connections and is lost if the environmental conditions that caused it have changed; d) is a warning signal reaction.

So, a conditioned reflex is an adaptive activity carried out by the higher parts of the central nervous system through the formation of temporary connections between the signal stimulation and the signaled reaction.

Natural and artificial conditioned reflexes. Depending on the nature of the signal stimulus, conditioned reflexes are divided into natural and artificial.

natural called conditioned reflexes, which are formed in response to the influence of agents that are natural signs of a signaled unconditioned irritation.

An example of a natural conditioned food reflex is the salivation of a dog to the smell of meat. This reflex inevitably develops naturally over the course of a dog's life.

artificial called conditioned reflexes, which are formed in response to the influence of agents that are not natural signs of signaled unconditioned irritation. An example of an artificial conditioned reflex is the salivation of a dog to the sound of a metronome. In life, this sound has nothing to do with food. The experimenter artificially made it a food intake signal.

Nature develops natural conditioned reflexes from generation to generation in all animals according to their way of life. As a result natural conditioned reflexes are more easily formed, more likely to be strengthened and more durable than artificial ones. A puppy that has never tasted meat is indifferent to its appearance. However, it is enough for him to eat meat once or twice, and the natural conditioned reflex is already fixed. At the sight of meat, the puppy begins to salivate. And in order to develop an artificial conditioned reflex of salivation in the form of a flashing light bulb, dozens of combinations are needed. Hence the meaning of the "biological adequacy" of the agents from which the stimuli of conditioned reflexes are made becomes clear.

Selective sensitivity to environmentally adequate signals is manifested in the reactions of brain nerve cells.

Exteroceptive, interoceptive and proprioceptive conditioned reflexes. Conditioned reflexes to external stimuli are called exteroceptive, to irritants from internal organs - interoceptive, on stimuli of the musculoskeletal system - proprioceptive.

Rice. 1. Interoceptive conditioned reflex of urination during "imaginary infusion" of physiological solution (according to K. Bykov):

1 - the initial curve of urination, 2 - urination as a result of infusion into the stomach of 200 ml of saline, 3 - urination as a result of "imaginary infusion" after 25 true

Exteroceptive reflexes are divided into reflexes caused by distant(acting at a distance) and contact(acting by direct contact) irritants. Further, they are divided into groups according to the main types of sensory perception: visual, auditory, etc.

Interoceptive conditioned reflexes (Fig. 1) can also be grouped according to organs and systems that are sources of signaling: gastric, intestinal, cardiac, vascular, pulmonary, renal, uterine, etc. The so-called time reflex. It manifests itself in various vital functions of the body, for example, in the daily periodicity of metabolic functions, in the release of gastric juice at the onset of dinner time, in the ability to wake up at the appointed hour. Apparently, the body "counts time" mainly by interoceptive signals. The subjective experience of interoceptive reflexes does not have the figurative objectivity of exteroceptive ones. It gives only vague "dark feelings" (the term of I.M. Sechenov), from which the general state of health is formed, which is reflected in the mood and performance.

proprioceptive conditioned reflexes underlie all motor skills. They begin to develop from the first flapping of the wings of the chick, from the first steps of the child. Associated with them is the mastery of all types of locomotion. The coherence and accuracy of movement depends on them. The proprioceptive reflexes of the hand and the vocal apparatus in humans are being used in a completely new way in connection with labor and speech. The subjective "experience" of proprioceptive reflexes consists mainly in the "muscular feeling" of the position of the body in space and its members relative to each other. At the same time, for example, signals from the accommodative and oculomotor muscles have a visual nature of perception: they provide information about the distance of the object under consideration and its movements; signals from the muscles of the hand and fingers make it possible to assess the shape of objects. With the help of proprioceptive signaling, a person reproduces the events taking place around him with his movements (Fig. 2).

Rice. 2. The study of the proprioceptive components of the human visual representation:

a- the image previously shown to the subject, b- Light source, in- reflection of a light beam from a mirror mounted on the eyeball, G- the trajectory of eye movement when remembering an image

A special category of conditioned reflexes is made up of model experiments with electrical stimulation of the brain as a reinforcement or signal; using as reinforcement ionizing radiation; the creation of a dominant; development of temporary connections between points of the neuronal-isolated cortex; the study of the summation reflex, as well as the formation of conditioned reactions of the nerve cell to a signal reinforced by a local electrophoretic application of mediators.

Conditioned reflexes to simple and complex stimuli. As has been shown, a conditioned reflex can be developed to any one of the listed extero-, intero-, or proprioceptive stimuli, for example, to turning on a light or to a simple sound. But in real life this rarely happens. More often, a complex of several stimuli becomes a signal, for example, the smell, warmth, soft fur of the mother cat become an irritant of the conditioned sucking reflex for the kitten. Accordingly, conditioned reflexes are divided into simple and complex, or complex, irritants.

Conditioned reflexes to simple stimuli are self-explanatory. Conditioned reflexes to complex stimuli are divided according to the relationship between the members of the complex (Fig. 3).

Rice. 3. The relationship in time between the members of complexes of complex conditioned stimuli. BUT- simultaneous complex; B- total stimulus; AT- sequential complex; G- a chain of stimuli:

single lines show indifferent stimuli, double lines show previously generated signals, dotted lines show reinforcement

Conditioned reflexes developed on the basis of various reinforcements. The basis for the formation of a conditioned reflex is its reinforcements- can be any activity of the body, carried out by the nervous system. Hence the limitless possibilities of conditioned reflex regulation of almost all vital functions organism. On fig. Figure 4 schematically shows various types of reinforcements, on the basis of which conditioned reflexes can be developed.

Rice. 4. Classification of reinforcements to which conditioned reflexes can be formed

Each conditioned reflex, in turn, can become the basis for the formation of a new conditioned reflex. A new conditioned response developed by reinforcing the signal with another conditioned reflex is called second order conditioned reflex. The second-order conditioned reflex, in turn, can be used as the basis for developing conditioned reflex of the third order etc.

Conditioned reflexes of the second, third and further orders are widespread in nature. They constitute the most significant and perfect part of natural conditioned reflexes. For example, when a she-wolf feeds a wolf cub with the meat of torn prey, he develops a natural conditioned first-order reflex. The sight and smell of meat becomes a food signal for him. Then he "learns" to hunt. Now these signals - the sight and smell of the meat of the caught prey - play the role of the basis for developing hunting methods of lying in wait and pursuing live prey. Thus, various hunting signs acquire their secondary signal value: a bush gnawed by a hare, traces of a sheep that has strayed from the herd, etc. They become irritants of second-order conditioned reflexes developed on the basis of natural ones.

Finally, an exceptional variety of conditioned reflexes, reinforced by other conditioned reflexes, is found in the higher nervous activity of man. They will be discussed in more detail in Chap. 17. Here it is only necessary to note that, in contrast to the conditioned reflexes of animals human conditioned reflexes are formed not on the basis of unconditioned food, defensive and other similar reflexes, but on the basis of verbal signals reinforced by the results of people's joint activities. Therefore, the thoughts and actions of a person are guided not by animal instincts, but by the motives of his life in human society.

Conditioned reflexes developed with different correspondence in time of the signal and reinforcement. By the way the signal is located in time relative to the reinforcing reaction, they distinguish cash and trace conditioned reflexes(Fig. 5).

Rice. 5. Options for the timing of the signal and reinforcement. BUT- cash coinciding; B- cash set aside; AT- cash delayed; G- trace conditioned reflex:

the solid line indicates the duration of the signal, the dashed line indicates the time of reinforcement

Cash called conditioned reflexes, in the development of which reinforcement is used during the action of a signal stimulus. Available reflexes are divided depending on the term of reinforcement attachment into coinciding, delayed and delayed. Coinciding reflex is produced when, immediately after the signal is turned on, a reinforcement is attached to it. For example, when working with salivary reflexes, dogs turn on the bell, and after about 1 second they begin to feed the dog. With this method of development, the reflex is formed the fastest and soon strengthens.

retired the reflex is developed in those cases when the reinforcing reaction joins only after a certain time (up to 30 s). This is the most common way to develop conditioned reflexes, although it requires more combinations than the method of matching.

delayed reflex is produced when a reinforcing reaction is added after a long isolated action of the signal. Typically, this isolated action lasts 1-3 minutes. This method of developing a conditioned reflex is even more difficult than both of the previous ones.

trace called conditioned reflexes, in the development of which a reinforcing reaction is presented only some time after the signal is turned off. In this case, the reflex is developed on a trace from the action of a signal stimulus; short intervals (15–20 s) or long intervals (1–5 min) are used. The formation of a conditioned reflex according to the trace method requires the greatest number of combinations. On the other hand, trace conditioned reflexes provide very complex acts of adaptive behavior in animals. An example would be hunting for lurking prey.

Conditions for the development of temporary links

What conditions must be met in order for the activity of the higher parts of the central nervous system to be completed with the development of a conditioned reflex?

Combination of signal stimulus with reinforcement. This condition for the development of temporary connections was revealed from the very first experiments with salivary conditioned reflexes. The footsteps of an attendant carrying food only produced "psychic salivation" when they were combined with food.

This is not contradicted by the formation of trace conditioned reflexes. Reinforcement is combined in this case with a trace of excitation of nerve cells from a previously turned on and already turned off signal. But if the reinforcement begins to get ahead of the indifferent stimulus, then the conditioned reflex can be worked out with great difficulty, only by taking a number of special measures. This is understandable, since if the dog is first fed and then given a food signal, then, strictly speaking, it cannot even be called a signal, since it does not warn of upcoming events, but reflects the past. In this case, the unconditioned reflex suppresses signal excitation and prevents the formation of a conditioned reflex to such a stimulus.

Indifference of the signal stimulus. The agent chosen as the conditioned stimulus of the food reflex must not in itself have anything to do with food. He must be indifferent, i.e. indifferent, for the salivary glands. The signal stimulus should not cause a significant orienting reaction that interferes with the formation of a conditioned reflex. However, each new stimulus causes an orienting reaction. Therefore, in order to lose its novelty, it must be applied repeatedly. Only after the orienting reaction is practically extinguished or reduced to an insignificant value, the formation of a conditioned reflex begins.

The predominance of the strength of excitation caused by reinforcement. The combination of the click of a metronome and feeding the dog leads to a quick and easy formation of a conditioned salivary reflex to this sound. But if you try to combine the deafening sound of a mechanical rattle with food, then such a reflex is extremely difficult to form. For the development of a temporary connection, the ratio of signal strength and reinforcing reaction is of great importance. In order for a temporary connection to form between them, the focus of excitation created by the latter must be stronger than the focus of excitation created by the conditioned stimulus, i.e. there must be a dominant. Only then will the excitation spread from the focus of the indifferent stimulus to the focus of excitation from the reinforcing reflex.

The need for a significant intensity of excitation of just a reinforcing reaction has a deep biological meaning. Indeed, a conditioned reflex is a warning reaction to a signal about upcoming significant events. But if the stimulus that they want to make a signal turns out to be an event even more significant than those that follow it, then this stimulus itself causes the corresponding reaction of the organism.

Absence of extraneous irritants. Each extraneous stimulus, such as an unexpected noise, evokes the already mentioned orienting reaction. The dog becomes alert, turns in the direction of the sound and, most importantly, stops its current activity. The animal is always turned towards the new stimulus. No wonder I.P. Pavlov called the orienting reaction the “What is it?” reflex. In vain at this time the experimenter will give a signal and offer the dog food. The conditioned reflex will be delayed more important in this moment for an animal - an orienting reflex. This delay is created by an additional focus of excitation in the cerebral cortex, which inhibits conditioned excitation and prevents the formation of a temporary connection. In nature, many such accidents affect the course of formation of conditioned reflexes in animals. A distracting environment reduces the productivity and mental work of a person.

Normal functioning of the nervous system. A full-fledged closing function is possible provided that the higher parts of the nervous system are in a normal working condition. Therefore, the method of chronic experiment made it possible to discover and study the processes of higher nervous activity, while maintaining the normal state of the animal. The efficiency of the nerve cells of the brain is sharply reduced with malnutrition, under the action of toxic substances, such as bacterial toxins in diseases, etc. So general state health is an important condition for the normal activity of the higher parts of the brain. Everyone knows how this condition affects the mental work of a person.

The state of the organism has a significant influence on the formation of conditioned reflexes. So, physical and mental work, nutritional conditions, hormone activity, the action of pharmacological substances, breathing at elevated or reduced pressure, mechanical overload and ionizing radiation, depending on the intensity and timing of exposure, can modify, enhance or weaken conditioned reflex activity up to its complete suppression.

The formation of conditioned reflexes and the implementation of acts of higher nervous activity are extremely dependent on the body's need for biologically significant agents used as reinforcements. So, in a well-fed dog it is very difficult to develop a food conditioned reflex, it will turn away from the offered food, and in a hungry animal with high food excitability it is formed quickly. It is well known how the student's interest in the subject of studies contributes to its better assimilation. These examples show the great importance of the factor of the organism's attitude to the manifested stimuli, which is denoted as motivation(K.V. Sudakov, 1971).

Structural bases of the closure of temporary conditional connections

The study of the final, behavioral manifestations of higher nervous activity has significantly outstripped the study of its internal mechanisms. Until now, both the structural foundations of the temporal connection and its physiological nature have not yet been sufficiently studied. Different views are expressed on this issue, but the issue has not yet been resolved. To solve it, numerous studies are being conducted at the systemic and cellular levels; use electrophysiological and biochemical indicators of the dynamics of the functional state of nerve and glial cells, taking into account the results of irritation or shutdown of various brain structures; draw on clinical observational data. However, on modern level research is becoming more and more certain that, along with the structural, it is necessary to take into account the neurochemical organization of the brain.

Change in the localization of the closure of temporary connections in evolution. Whether or not to assume that the conditioned responses coelenterates(diffuse nervous system) arise on the basis of summation phenomena or real temporary connections, the latter do not have a specific localization. At annelids(nodal nervous system) in experiments with the development of a conditioned avoidance reaction, it was found that when a worm is cut in half, the reflex is preserved in each half. Consequently, the temporal connections of this reflex close many times, possibly in all the nerve nodes of the chain and have multiple localization. At higher molluscs(the anatomical consolidation of the central nervous system, which already forms a developed brain in an octopus), is sharply expressed. Experiments with the destruction of parts of the brain showed that the supraesophageal regions carry out many conditioned reflexes. So, after the removal of these departments, the octopus ceases to “recognize” the objects of its hunt, loses the ability to build a shelter from stones. At insects the functions of organizing behavior are concentrated in the head ganglia. Special development in ants and bees is achieved by the so-called mushroom bodies of the protocerebrum, the nerve cells of which form many synaptic contacts with numerous paths to other parts of the brain. It is assumed that it is here that the closure of temporal connections occurs during the learning of insects.

Already at an early stage in the evolution of vertebrates, in the anterior sections of the initially homogeneous brain tube, the cerebrum, which controls adaptive behavior, is isolated. It develops structures that are of the greatest importance for the closure of harmful connections in the process of conditioned reflex activity. Based on experiments with the removal of parts of the brain from fish it was suggested that in them this function is performed by the structures of the midbrain and diencephalon. Perhaps this is determined by the fact that it is here that the paths of all sensory systems, and the forebrain is still developing as an olfactory one.

At birds the striatal bodies, which form the bulk of the cerebral hemispheres, become the leading department in the development of the brain. Numerous facts indicate that temporary connections are closed in them. Dove with hemispheres removed serves visual illustration extreme poverty of behavior, devoid of skills acquired in life. The implementation of particularly complex forms of bird behavior is associated with the development of hyperstriatum structures that form an elevation above the hemispheres, which is called the "vulst". In corvids, for example, its destruction impairs the ability to carry out their complex forms of behavior.

At mammals the brain develops mainly due to the rapid growth of the multilayered cortex of the cerebral hemispheres. The new cortex (neocortex) receives special development, which pushes back the old and ancient cortex, covers the entire brain in the form of a cloak and, not fitting on its surface, gathers in folds, forming numerous convolutions separated by furrows. The question of the structures responsible for the closure of temporal connections and their localization in the cerebral hemispheres is the subject of a large number of studies and is largely debatable.

Removal of parts and the entire cerebral cortex. If the occipital regions of the cortex are removed from an adult dog, then it loses all complex visual conditioned reflexes and cannot restore them. Such a dog does not recognize his master, is indifferent to the sight of the most delicious pieces of food, looks indifferently at a cat running past, which he would have rushed to pursue before. What used to be called "mental blindness" sets in. The dog sees as it avoids obstacles, turns towards the light. But she "does not understand" the meaning of what she saw. Without the participation of the visual cortex, visual signals remain unrelated to anything.

And yet such a dog can form very simple visual conditioned reflexes. For example, the appearance of an illuminated figure of a person can be made a food signal that causes salivation, licking, tail wagging. Consequently, in other areas of the cortex there are cells that perceive visual signals and are able to associate them with certain actions. These facts, confirmed in experiments with damage to the cortical areas of representation of other sensory systems, led to the opinion that the projection zones overlap each other (L. Luciani, 1900). Further studies of the issue of localization of functions in the cortex in the works of I.P. Pavlova (1907–1909) showed a wide overlap of projection zones, depending on the nature of the signals and the temporary connections formed. Summarizing all these studies, I.P. Pavlov (1927) put forward and substantiated the idea of dynamic localization cortical functions. The overlaps are traces of that wide representation of all types of reception in the entire cortex, which took place before their division into projection zones. Each core of the cortical part of the analyzer is surrounded by its scattered elements, which become less and less with distance from the core.

Scattered elements are not able to replace the specialized cells of the nucleus for the formation of thin temporary bonds. The dog, after the removal of the occipital lobes, can develop only the simplest conditioned reflexes, for example, a figure that looks illuminated. It is not possible to force her to distinguish between two such figures, similar in form. However, if the removal of the occipital lobes is carried out at an early age, when the projection zones have not yet been isolated and fixed, then, growing up, these animals show the ability to develop complex forms of conditioned visual reflexes.

The possibility of broad interchangeability of the functions of the cerebral cortex in early ontogenesis corresponds to the properties of the poorly differentiated cerebral cortex of mammals in phylogenesis. From this point of view, the results of experiments on rats are explained, in which the degree of impairment of conditioned reflexes turned out to depend not on a specific area of the removed cortex, but on the total volume of the removed cortical mass (Fig. 6). Based on these experiments, it was concluded that for conditioned reflex activity all parts of the cortex are of the same importance, the cortex "equipotential"(K. Lashley, 1933). However, the results of these experiments can only demonstrate the properties of the poorly differentiated rodent cortex, and the specialized cortex of more highly organized animals does not show "equipotentiality" but a well-defined dynamic specialization of functions.

Rice. 6. Interchangeability of parts of the cerebral cortex after their removal in rats (according to K. Lashley):

remote areas are shaded, the numbers under the brain indicate the amount of removal as a percentage of the entire surface of the cortex, the numbers under the columns - the number of errors during testing in the maze

The first experiments with the removal of the entire cerebral cortex (<…пропуск…>Goltz, 1982) showed that after such an extensive operation, apparently affecting the nearest subcortex, dogs could not learn anything. In experiments on dogs with removal of the cortex without injury to the subcortical structures of the brain, it was possible to develop simple conditioned salivation reflex. However, it took more than 400 combinations to develop it, and it was not possible to extinguish it even after 130 applications of the signal without reinforcement. Systematic studies on cats, which tolerate the operation of decortication more easily than dogs, have shown the difficulty of forming in them simple generalized alimentary and defensive conditioned reflexes and developing some gross differentiations. Experiments with cold shutdown of the cortex demonstrated that full-fledged holistic activity of the brain is impossible without its participation.

The development of the operation of cutting all ascending and descending pathways connecting the cortex with other brain formations made it possible to carry out decortication without direct injury to subcortical structures and to study the role of the cortex in conditioned reflex activity. It turned out that in these cats it was possible with great difficulty to develop only gross conditioned reflexes. general movements, and the defensive conditional flexion of the paw could not be obtained even after 150 combinations. However, already after 20 combinations, a reaction to a change in respiration and some conditioned vegetative reactions appeared on the signal.

Of course, in all surgical operations it is difficult to exclude their traumatic effect on subcortical structures and to be sure that the lost ability for fine conditioned reflex activity was a function of the cortex. Convincing evidence was provided by experiments with a temporary reversible shutdown of cortical functions, which manifests itself in a spreading depression of electrical activity upon application of KCI to its surface. When turning off the cerebral cortex of the rat in this way and testing at this time the reaction of the animal to conditioned and unconditioned stimuli, it can be seen that unconditioned reflexes are completely preserved, while conditioned ones are violated. As can be seen from fig. 7, more complex defensive and especially alimentary conditioned reflexes are completely absent during the first hour of maximum depression, and the simple defensive reaction of avoidance suffers to a lesser extent.

Thus, the results of experiments with partial and complete surgical and functional decortication suggest that higher in animals, the functions of forming precise and subtle conditioned reflexes capable of providing adaptive behavior are mainly performed by the cerebral cortex.

Rice. 7. The effect of temporary shutdown of the cortex by spreading depression on food (1) and defensive (2) conditioned reflexes, unconditioned avoidance reaction (3) and expressiveness of the EEG (4) rats (according to J. Buresh and others)

Cortical-subcortical relations in the processes of higher nervous activity. Modern research confirm the statement of I.P. Pavlov that conditioned reflex activity is carried out by the joint work of the cortex and subcortical structures. From consideration of the evolution of the brain as an organ of higher nervous activity, it follows that the structures of the diencephalon in fish and striatal (striate) bodies in birds, which are phylogenetically the youngest of its departments, showed the ability to form temporary connections that provide adaptive behavior. When the phylogenetically youngest new cortex, which performs the most subtle analysis of signals, arose in mammals over these parts of the brain, the leading role in the formation of temporary connections that organize adaptive behavior passed to it.

The brain structures that turned out to be subcortical retain to some extent their ability to close temporary connections, which provide adaptive behavior characteristic of the level of evolution when these structures were leading. This is evidenced by the behavior of animals described above, which, after turning off the cerebral cortex, could only develop very primitive conditioned reflexes with difficulty. At the same time, it is possible that such primitive temporal connections have not completely lost their significance and form part of the lower level of a complex hierarchical mechanism of higher nervous activity, headed by the cerebral cortex.

The interaction of the cortex and subcortical parts of the brain is also carried out by tonic influences, regulating the functional state of the nerve centers. It is well known how mood and emotional state affect the efficiency of mental activity. I.P. Pavlov said that the subcortex "charges" the cortex. Neurophysiological studies of the mechanisms of subcortical influences on the cortex have shown that reticular formation midbrain is exerting on her upward activating action. Receiving collaterals from all afferent pathways, the reticular formation participates in all behavioral reactions, causing the active state of the cortex. However, its activating influence during the conditioned reflex is organized by signals from the projection zones of the cortex (Fig. 8). Irritation of the reticular formation causes a change in the electroencephalogram in the form of its desynchronization, which is characteristic of the state of active wakefulness.

Rice. 8. Interaction of the reticular formation of the midbrain and the cortex (according to L.G. Voronin):

bold lines indicate specific afferent pathways with collaterals to the reticular formation, intermittent lines indicate ascending pathways to the cortex, thin lines indicate the influence of the cortex on the reticular formation, vertical shading shows the facilitating zone, horizontal shading shows the inhibitory zone, cellular shading shows thalamic nuclei

Another effect on the functional state of the cortex is specific nuclei of the thalamus. Their low-frequency stimulation leads to the development of inhibition processes in the cortex, which can lead to the animal falling asleep, etc. Irritation of these nuclei causes the appearance of peculiar waves in the electroencephalogram - "spindle", that turn into slow delta waves, characteristic of sleep. The rhythm of the spindles can be determined inhibitory postsynaptic potentials(TPSP) in neurons of the hypothalamus. Along with the regulatory influence of nonspecific subcortical structures on the cortex, the reverse process is also observed. Such bilateral cortical-subcortical mutual influences are obligatory in the implementation of the mechanisms for the formation of temporary connections.

The results of some experiments were interpreted as evidence of the inhibitory effect of striatal structures on the behavior of animals. However, further studies, in particular experiments with the destruction and stimulation of the caudate bodies, and other facts led to the conclusion that there are more complex cortical-subcortical relationships.

Some researchers consider the facts about the participation of subcortical structures in the processes of higher nervous activity as a basis for considering them as the site of the closure of temporary connections. Thus arose the idea of "centrencephalic system" as leading in human behavior (W. Penfield, G. Jasper, 1958). As proof of the closure of the temporal connection in the reticular formation, observations were made that during the development of a conditioned reflex, the first changes in the electrical activity of the brain occur precisely in the reticular formation, and then in the cerebral cortex. But this only indicates a quite understandable early activation of the ascending system of cortical activation. Finally, a strong argument in favor of subcortical localization of the closure was considered the possibility of developing a conditioned, for example, visual-motor reflex, despite repeated dissection of the cortex to the full depth, interrupting all cortical pathways between the visual and motor areas. However, this experimental fact cannot serve as proof, since the closure of the temporal connection in the cortex has a multiple character and can occur in any of its sections between afferent and effector elements. On fig. 9, thick lines show the path of the conditioned visual-motor reflex during cortical cuts between the visual and motor areas.

Rice. 9. Multiple closure of temporary connections in the cortex (shown by a dotted line), which are not prevented by its cuts (according to A.B. Kogan):

1, 2, 3 - central mechanisms of defensive, nutritional and orienting reactions, respectively; the path of the conditioned food reflex to a light signal is shown in bold lines

Numerous studies have shown that the participation of subcortical structures in the processes of higher nervous activity is not limited to the regulatory role of the reticular formation of the midbrain and limbic structures. Indeed, already at the subcortical level, the analysis and synthesis of acting stimuli and the assessment of their biological significance take place, which largely determines the nature of the connections formed with the signal. The use of indicators of the formation of the shortest paths along which the signal reaches different subcortical structures of the brain revealed the most pronounced participation in the learning processes of the posterior parts of the thalamus and the CA 3 field of the hippocampus. The role of the hippocampus in memory phenomena is confirmed by many facts. Finally, there is no reason to assume that the ability for primitive closing activity of brain structures, which was acquired in evolution when they were leading, has now completely disappeared when this function has passed to the new cortex.

Thus, cortical-subcortical relationships are defined regulation of the functional state of the cortex by an activating system - reticular formation the midbrain and the inhibitory system of nonspecific nuclei of the thalamus, as well as the possible participation in the formation of primitive temporary connections at the lower level of complex hierarchical mechanisms of higher nervous activity.

interhemispheric relations. How do the hemispheres of the brain, which are a paired organ, participate in the formation of conditioned connections? The answer to this question was obtained in experiments on animals that underwent the operation of "splitting" the brain by transection of the corpus callosum and anterior commissure, as well as longitudinal division of the optic chiasm (Fig. 10). After such an operation, it was possible to develop different conditioned reflexes of the right and left hemispheres, showing different figures to the right or left eye. If a monkey operated in this way develops a conditioned reflex to a light stimulus applied to one eye, and then applies it to the other eye, then no reaction will follow. "Training" of one hemisphere left the other "untaught". However, while maintaining the corpus callosum, the other hemisphere is "trained". The corpus callosum carries out interhemispheric skill transfer.

Rice. 10. Studies of learning processes in monkeys subjected to brain splitting. BUT- a device that directs one image to the right eye, and another to the left; B- special optics for projecting visual images into different eyes (according to R. Sperry)

With the help of the method of functional exclusion of the cerebral cortex in rats, the conditions of the "split" brain were reproduced for some time. In this case, temporary connections could form one remaining active hemisphere. This reflex was also manifested after the cessation of the effect of the spreading depression. It persisted even after the inactivation of the hemisphere, which was active during the development of this reflex. Consequently, the "trained" hemisphere transmitted the acquired skill to the "untrained" through the fibers of the corpus callosum. However, this reflex disappeared if such inactivation was carried out before the activity of the hemisphere switched on during the elaboration of the conditioned reflex was fully restored. Thus, in order to transfer an acquired skill from one hemisphere to another, it is necessary that both of them be active.

Further studies of interhemispheric relations during the formation of temporary connections of conditioned reflexes showed that the processes of inhibition play a specific role in the interaction of the hemispheres. Thus, the hemisphere opposite to the reinforcement side becomes dominant. It first carries out the formation of the acquired skill and its transfer to the other hemisphere, and then, by slowing down the activity of the opposite hemisphere and exerting a selective inhibitory effect on the structure of temporary connections, it improves the conditioned reflex.

Thus, each hemisphere, even being isolated from the other, is capable of forming temporary connections. However, under natural conditions of their paired work, the side of reinforcement determines the dominant hemisphere, which forms a fine excitatory-inhibitory organization of the conditioned reflex mechanism of adaptive behavior.

Assumptions about the location of the closure of temporary connections in the cerebral hemispheres. Having discovered the conditioned reflex, I.P. Pavlov first suggested that the temporal connection is a "vertical connection" between the visual, auditory or other parts of the cerebral cortex and the subcortical centers of unconditioned reflexes, such as food - cortical-subcortical temporal connection(Fig. 11, BUT). However, numerous facts further work and the results of special experiments then led to the conclusion that the temporal connection is a "horizontal connection" between the centers of excitation located within the cortex. For example, during the formation of a conditioned salivary reflex to the sound of a bell, a circuit occurs between the cells of the auditory analyzer and the cells that represent an unconditioned salivary reflex in the cortex (Fig. 11, B). Such cells are called representatives of the unconditioned reflex.

The presence in the cortex of the cerebral hemispheres of the dog of the representation of unconditioned reflexes is proved by the following facts. If sugar is used as a food irritant, then salivation for it is produced only gradually. If any conditioned stimulus is not reinforced, then the “sugar” salivation that follows it decreases. This means that this unconditioned reflex has nerve cells located in the sphere of cortical processes. Further studies have shown that if the bark is removed from the dog, then its unconditioned reflexes (salivary, separation of gastric juice, movements of the limbs) undergo persistent changes. Consequently, unconditioned reflexes, in addition to the subcortical center, also have centers at the cortical level. At the same time, the stimulus that has been made conditioned also has a representation in the cortex. Hence the assumption arose (E.A. Asratyan, 1963) that the temporal connections of the conditioned reflex are closed between these representations (Fig. 11, AT).

Rice. 11. Various assumptions about the structure of the temporal connection of the conditioned reflex (see the text for an explanation):

1 - conditioned stimulus 2 - cortical structures, 3 - unconditioned stimulus 4 - subcortical structures, 5 - reflex reaction; dashed lines show temporary connections

Consideration of the processes of closure of temporary connections as the central links in the formation of a functional system (P.K. Anokhin, 1961) relates the closure to the structures of the cortex, where the content of the signal is compared - afferent synthesis- and the result of a conditioned reflex response - action acceptor(Fig. 11, G).

The study of motor conditioned reflexes showed the complex structure of the temporary connections formed in this case (L.G. Voronin, 1952). Each movement made according to a signal itself becomes a signal for the resulting motor coordinations. Two systems of temporary connections are formed: for a signal and for movement (Fig. 11, D).

Finally, based on the fact that conditioned reflexes are preserved during surgical separation of sensory and motor cortical areas and even after multiple cortical incisions, and also considering that the cortex is abundantly supplied with both incoming and outgoing pathways, it was suggested that the closure of temporary connections can occur in each of its microsections between its afferent and efferent elements, which activate the centers of the corresponding unconditioned reflexes that serve as reinforcements (A.B. Kogan, 1961) (see Fig. 9 and 11, E). This assumption corresponds to the idea of the emergence of a temporary connection within the analyzer of the conditioned stimulus (O.S. Adrianov, 1953), the opinion about the possibility of "local" conditioned reflexes, closing inside the projection zones (E.A. Asratyan, 1965, 1971), and the conclusion that in the closure of a temporary connection, the afferent link always plays a key role (U.G. Gasanov, 1972).

Neural structure of temporal connection in the cerebral cortex. Modern information about the microscopic structure of the cerebral cortex, in combination with the results of electrophysiological studies, makes it possible to judge with a certain degree of probability the possible participation of certain cortical neurons in the formation of temporary connections.

The highly developed cerebral cortex of mammals is known to be divided into six layers of different cellular composition. The nerve fibers coming here end for the most part in two types of cells. One of them is the intercalary neurons located in II, III and partly IV layers. Their axons go to V and VI layers to large pyramidal cells of the associative and centrifugal type. These are the shortest paths, which, perhaps, represent the innate connections of cortical reflexes.

Another type of cells with which the incoming fibers form the greatest number of contacts are bushy branching round and angular short-growth cells, often having a stellate shape. They are located mainly in IV layer. Their number increases with the development of the mammalian brain. This circumstance, along with the fact that stellate cells occupy the position of the terminal station for impulses entering the cortex, suggests that stellate cells are the main receptive cortical cells of analyzers and that an increase in their number in evolution is the morphological basis for achieving a high subtlety and accuracy of reflection of the surrounding environment. peace.

The system of intercalary and stellate neurons can enter into countless contacts with associative and projection large pyramidal neurons located in V and VI layers. Associative neurons, with their axons passing through the white matter, connect different cortical fields, and projection neurons give rise to pathways connecting the cortex with the lower parts of the brain.