What conditions are necessary for the development of a conditional. Conditions (rules) for the development of conditioned reflexes

Acquired reflexes are called conditioned, since they are developed only if a number of conditions:"the presence as a basis of an unconditional or previously developed conditional

reflex; "a combination of two stimuli: the future conditional, initially indifferent (indifferent), and reinforcing - unconditional;

■ the sequence of action of stimuli: a conditioned stimulus should always somewhat precede the unconditioned reinforcement, i.e. serve for an animal or a person signal biologically significant stimulus;

■ less force of impact (lower significance) of the conditioned stimulus compared to the unconditioned one; it is the reinforcing stimulus that must be associated with the satisfaction of the dominant need;

■ repeated repetition of a combination of these stimuli;

■ the absence of extraneous irritants;."

■ the normal functional state of the nervous system, primarily the cerebral cortex: the optimal level of excitability of its cells and the balance of the processes of excitation and inhibition.

Mechanisms of Education conditioned reflexes

The mechanisms of formation of conditioned reflexes are largely unclear. Both the structural basis of the temporal connection and its physiological nature have not been sufficiently studied. Classical ideas about the mechanism of development of conditioned reflexes were formed by IP Pavlov. It has been proven that during the formation of a conditioned reflex in the cerebral cortex, temporary connection- structural and functional association of two or more cortical nerve centers in a state of excitation. So, if the body was affected by an unimportant biological significance irritant, in the corresponding perceiving zone of the cerebral hemispheres (visual, auditory, etc.), a rather weak focus of excitation is formed. When this (future conditioned, signal) stimulus is reinforced with an unconditioned one, an unconditioned reflex is realized, and a second, stronger (dominant) focus of excitation appears in the corresponding zone of the cerebral hemispheres. Due to the “attraction” of excitation from the focus of lesser strength to the focus greater strength there is a summation of excitation and the breaking of the nerve path. A temporary nervous connection is formed between both foci: additional synapses are formed, the production of mediators is enhanced, their passage through the synaptic cleft is facilitated, and the excitation of postsynaptic membranes is accelerated. At the same time, the interaction nerve cells is established in the direction from the first focus of excitation to the second, dominant. This connection becomes stronger, the more often both parts of the cortex are simultaneously excited. After several combinations, the connection is so strong that under the action of only the first, signal stimulus, excitation from the

Responsible receptors are transmitted through a temporary connection to the second focus, and from it to the working organs that carry out the response. During this period, we can assume that the conditioned reflex has been developed, and the indifferent stimulus has become conditioned.

The closure of the temporary connection goes not only horizontally (bark - bark). An important role belongs to vertical contacts: cortex - subcortex - cortex. At the same time, centripetal impulses from a conditioned stimulus through the thalamus and a nonspecific activating system (hippocampus, reticular formation) enter the corresponding zone of the cortex, where they are processed and reach the subcortical formations along descending paths, from where the impulses come back to the cortex, but already in the zone of representation unconditioned reflex.

There are two stages in the formation of a conditioned reflex: generalization and specialization.

On the stages of generalization a conditioned reflex action evokes not only a reinforced conditioned stimulus, but also a wide range of stimuli similar to it. Primary sensory generalization occurs, which is a generalization of the signs of conditioned signals. The degree of generalization depends on the characteristics of both conditioned and unconditioned stimuli.

The generalization stage largely determines the plasticity of acquired behavior and allows the body to adapt immediately to a wide range similar signals. For example, if a dog receives food reinforcement after a sound signal with a frequency of 400 Hz, then at the stage of generalization, sounds with a frequency of 200-600 Hz will also cause salivation. IP Pavlov associated this stage of the formation of a conditioned reflex with the wide spread of the excitatory process within the center that receives the signal.

On the early stages the development of a conditioned reflex, generalization of excitation processes in the cortex and subcortical structures of the brain is observed. Excitation of the reticular formation leads to activation of overlying structures, including the cerebral cortex, and activation of the thalamus and hypothalamus provides the vegetative component of the conditioned reflex (changes in the functioning of internal organs).

Then, in the subcortical formations and in different parts of the cortex, the impulse activity of neurons is synchronized (distant synchronization). The rhythm of this synchronous activity corresponds to the frequency of the conditioned stimulus, which indicates the unification of functionally unrelated neurons into a single system. For the emergence of a temporary connection, distant synchronization of the center of the conditioned stimulus (for example, the center of the visual analyzer) and the center of the unconditioned reaction (for example, the motor cortex) is necessary.

On the stages of specialization there is a specialization of the conditioned reflex response, which begins to manifest itself only after the action of a reinforced conditioned signal. All other stimuli of similar quality do not cause a response. The degree of specialization and the speed of its onset also depend on the characteristics of the conditioned and unconditioned stimuli.

The significance of this stage lies in the fact that when a reflex is triggered, from a large "set" of possible stimuli, only a few a large number of significant signals that can cause the development of a reaction.

IP Pavlov believed that this stage is associated with the process of concentration of excitation in the center of the conditioned signal.

The components of the orienting reaction, observed at the stage of generalization, are inhibited, and a connection remains between the cortical centers of the conditioned and unconditioned stimuli. Distant synchronization of neurons in these areas of the cortex becomes more distinct with specialization of the reflex, while in subcortical formations it is inhibited. If before the development of a conditioned motor reflex to light in the Cbra motor area only 2.5% of neurons respond to light stimuli, then after development - already 40%.

Thus, the specialization of the conditioned reflex is associated with the process of
kovy inhibition, on the severity of which the accuracy and stability depend
conditioned reflex response. I,

Classification of conditioned reflexes"

Depending on the criterion adopted as the basis for the division of reflexes, there are several classifications.

By the nature of the conditioned signal reflexes are divided into natural and artificial. natural (natural) reflexes are reflexes that are formed on the basis of natural signs of unconditioned irritation (for example, the smell of food). So, having once tasted an orange, we forever acquire a reflex to its smell. Other conditioned signals, which are not an indispensable property of food, but coincide in time with the moment of its consumption, refer to artificial conditioned signals. The reflexes produced on the basis of these signals are called artificial. Thus, salivation at the sight of dishes is an artificial conditioned reflex. These conditioned reflexes are developed more slowly and are more easily destroyed.

By the nature of the conditional signal allocate exteroceptive, interoceptive and proprioceptive conditioned reflexes.

exteroceptive reflex- a reflex that occurs when environmental stimuli act on exteroreceptors. Exteroceptive reflexes are: visual, auditory, olfactory, gustatory, tactile, temperature. The school bell is perceived by children as a signal for the end of the lesson, the red light of a traffic light is perceived as a danger signal. In addition, exteroceptive conditioned reflexes are divided into distant(visual, auditory) and contact(tactile, gustatory).

Interoceptive reflex- this is a reflex that occurs when the factors of the internal environment of the body are exposed to interoreceptors.

Interoceptive conditioned reflexes according to the type of irritated receptors are divided into mechanical, chemical, temperature, osmotic, etc. If the classification of these reflexes is based on the internal organ, with receptors co-

When this or that interoceptive signal is formed, then gastric, intestinal, cardiac, pulmonary, uterine and other reflexes are isolated. For example: with hiccups, a person hurries to drink a glass of water; feeling hungry, the child runs to the kitchen to find food there; with pain in the region of the heart, the patient takes medicine.

proprioceptive reflex is a reflex that occurs when the state of muscles and tendons changes. So, if you bend a dog's paw with your hand and reinforce this bending with food, then a proprioceptive conditioned salivary reflex is developed. Every time the dog passively flexes the paw, the dog will salivate.

By the nature of the response conditioned reflexes are motor and vegetative.

Vegetative reflexes- reflexes, in which the work of any internal organ or organ systems (heart, gastrointestinal tract, excretory system etc.). For example, the salivary conditioned reflex is vegetative, and the increase in heart rate in an athlete standing at the start is of the same nature.

motor reflexes -. reflexes, in the implementation of which the effectors are skeletal muscles. So, if a conditioned signal (the sound of a metronome) is reinforced by irritation of the dog's paw with a weak electric current, then after several combinations of these stimuli, the dog develops a conditioned motor defensive reflex - turning on the metronome will cause the paw to withdraw.

The division into motor and autonomic conditioned reflexes is rather arbitrary. For example, motor conditioned reflexes associated with food consumption are determined, as a rule, by the type of the corresponding movement (chewing, gnawing, sucking, etc.). However, when they are formed, significant vegetative changes occur (vascular lumen, heart rate, respiratory rhythm, etc.).

By reinforcement features distinguish conditioned reflexes of the first, second and subsequent orders.

Conditioned reflexes of the first order are formed on the basis of unconditioned reflexes, i.e., with unconditioned reflex reinforcement. These reflexes are developed first in the process of ontogenesis. For example, if a child aged 3-4 months is fed only from a red bottle, then he will unmistakably choose it among others: the conditioned stimulus is the bottle, the reinforcer is food.

Conditioned reflexes of the second order are formed on the basis of a previously developed conditioned reflex. So, if before giving food in a red bottle to a 6-8 month old baby, he is put on a special chair, then this stimulus will cause the same reaction as the type of bottle.

There are also conditioned reflexes of the third and subsequent orders, which are formed in children later and form the basis for the development of mental activity and motor stereotypes (see section 4.5 "Dynamic stereotype").

Depending on the presence or absence of reinforcement, conditioned reflexes are divided into positive(reinforced) and negative(braking, or unreinforced). Positive reflexes cause the corresponding reaction of the body, and negative ones do not (see section 4.4.2 "Conditioned reflex inhibition").

By relation in time conditioned and unconditioned stimuli, conditioned reflexes are divided into cash and trace. If immediately or shortly after the beginning of the action of the conditioned signal, an unconditioned stimulus is attached to it, then cash conditioned reflexes - coinciding or delayed. trace conditioned reflexes are formed when there is a pause between the conditioned and unconditioned stimuli.

A special kind of conditioned reflexes are time reflexes. Such reflexes are developed with the systematic presentation of an unconditioned stimulus at regular intervals. Conditioned reflexes play for a while big role in the formation of internal rhythms. For example, students and teachers form conditioned reflexes for the duration of the lesson - 45 minutes.

Conditioned reflexes can be formed on the relative characteristics of objects, such as “more-less”, “more-less”, “quieter-louder” and others. of the proposed number of squares will also choose the largest. Reflexes on the relationship have great importance in human life, their development largely determines the ability to abstract-logical thinking. The formation of these reflexes in a child is one of the signs that he is ready to study at school.

Pavlov studied conditioned reflex activity on dogs. The animal was placed in special straps, the fistula was hung on the salivary gland. The experimenter sat separately. The condition is absolute silence. The experiment was carried out on intact animals, that is, they should not have been exposed to any extraneous stimuli. The unconditioned stimulus acted as a conditioned stimulus. Two irritants:

The unconditioned stimulus is food.
Conditioned stimulus (at first an indifferent stimulus, then it became a conditioned stimulus) - light, sound, pain stimulus, tactile stimulus, etc.

The main mechanism for the formation of the conditional is the establishment of a temporary connection between the conditional and the unconditional. This is the connection between the centers of the brain responsible for the unconditioned and the centers associated with the conditioned stimulus. A conditioned reflex connection is the establishment of the impulse activity of neurons, which is formed between these centers.

- this is an acquired response of the body to irritation with the direct participation of the higher department, i.e. cerebral cortex.

For the formation of a conditioned reflex, the following conditions are necessary:

Normal (active) nervous system and, above all, its leading department - the brain; i.e., the active state of the GM cortex is necessary.
The presence of a conditioned stimulus and unconditioned reinforcement.
The conditioned stimulus must always somewhat precede the unconditioned reinforcement (practically simultaneously), i.e. serve as a biologically significant signal for a person or animal;
The supply of the unconditioned stimulus should be carried out at the end of the action of the conditioned stimulus, that is, we give light, and in the last seconds of the light signal, food is served. If the light is given against the background of food, the animal will not react to the light.
The conditioned stimulus (the one that used to be indifferent) should be physiologically weaker, if it is too strong, it will cause inhibition, in addition, it should not attract attention. Under the action of conditioned and unconditioned stimuli, the excitation from the unconditioned stimulus must be stronger than from the conditioned one.
Multiple combinations of conditioned and unconditioned stimuli.
There should be no action of extraneous irritants. All extraneous stimuli distract the animal (human) from performing one or another reflex.
Conditioned reflexes are able to fade over time if the action of the conditioned stimulus is not reinforced by the unconditioned one. There is a possibility of spontaneous reproduction of extinguished conditioned reflexes (that is, they can be restored by themselves).
A conditioned reflex must always be reinforced by the action of an unconditioned stimulus (reinforcement). If this does not happen, then the temporal connection is broken, and the conditioned reflex fades away.

Indifferent stimulus - light causes excitation in the visual center of the cortex. However, the salivary center is dominant (because the dog is hungry) and it attracts excitation from the visual center. A connection is established between them. After repeated combination, the salivary center is stimulated in response to light. If the unconditioned stimulus precedes the indifferent stimulus, UR is not formed. If the indifferent stimulus is too strong, it will cause inhibition in all centers and SD will not form.

The physiological basis for the emergence of conditioned reflexes is the formation of temporary connections in the most reactive formations of the central nervous system - in its higher departments. Temporal connection is a set of neurophysiological, biochemical and ultrastructural changes in the brain that occur during the combined action of conditioned and unconditioned stimuli. Initially, Pavlov suggested that during a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - cortical representations of conditioned and subcortical unconditioned reflexes. Then the idea was put forward that conditional closure occurs in the cortex between the cortical end of the signal analyzer and the cortical link of the complex unconditioned center. The hypothesis about the cortical mechanism of the closure of the temporary connection received further development in the analysis of the mechanisms of convergence of excitations on individual neurons of the cerebral cortex (P.K. Anokhin).

Modern ideas about the ways of closing temporary connections:

The first way to form a temporary connection between the cortical representations of the conditioned and unconditioned reflexes is intracortical in type bark-bark(the center of the conditioned is the center of the unconditioned reflexes).
With the destruction of the cortical representation of the conditioned reflex, the developed conditioned reflex is preserved. Apparently, the formation of a temporary connection occurs between the subcortical centers of the conditioned reflex and the cortical centers (according to the type subcortex-cortex).
With the destruction of the cortical representation of the unconditioned reflex, the conditioned reflex is also preserved. Consequently, the development of a temporary connection can go between the cortical center of the conditioned reflex and the subcortical center of the unconditioned reflex (according to the type cortex-subcortex).
The separation of the cortical centers of the conditioned and unconditioned reflexes by crossing the cerebral cortex does not prevent the formation of a conditioned reflex. This indicates that a temporary connection can be formed between the cortical center of the conditioned reflex, the subcortical center of the unconditioned reflex and the cortical center of the unconditioned reflex (but of the type bark-subcortex-bark ).
Further studies showed that conditioned reflexes are preserved when the cortex is removed in animals, i.e., the temporal connection is preserved at the level of subcortical centers of conditioned and unconditioned reflexes (according to the type subcortex-subcortex ).

1. To develop a conditioned reflex, the presence of two stimuli is necessary. One of them is an unconditioned stimulus that causes an unconditioned reflex reaction (food, pain stimulus, etc.), this stimulus is reinforcement of the conditioned reflex reactions. The second stimulus - conditioned (signal) will signal unconditional irritation (light, sound, type of food, etc.).

2. A multiple combination of a conditioned and unconditioned stimulus is necessary (although the formation of a conditioned reflex is possible with a single combination of a conditioned and unconditioned stimulus).

3. The conditioned stimulus must precede the action of the unconditioned one. The time during which the conditioned stimulus acts independently is called the time of isolated action of the conditioned stimulus. The time when the conditioned and unconditioned stimuli act together is called the time of joint action of the conditioned and unconditioned stimulus. Depending on the duration of the isolated action of the conditioned stimulus, there are: coincidental conditioned reflex (the time of the isolated action of the conditioned stimulus is 1-2 s); if the time of the isolated action of the conditioned stimulus is more than 2 s, then such a reflex is called retired, he can be:

Short delayed (isolated action time up to 10 s);

Medium delayed (isolated action time up to 20 s);

Long delayed (time of isolated action 20-30 s);

If the unconditioned stimulus acts 30 seconds or more after the onset of the conditioned stimulus, then such a conditioned reflex is called late;

trace conditioned reflex - the unconditioned stimulus begins to act after the cessation of the action of the conditioned stimulus; such reflexes do not have time for the combined action of the conditioned and unconditioned stimuli.

4. Any stimulus of the external or internal environment can be used as a conditioned stimulus, but it must have the following properties:

Should be as indifferent as possible, not in itself cause a defensive reaction;

There should not be excessive force;

Must attract the attention of the animal;

It should be ecologically close to the animal (for example, a conditioned reflex to a bell can be developed in fish, but this requires a large number of combinations of conditioned and unconditioned stimuli, and a conditioned reflex is developed after 2-3 combinations to a combination of splashing water with food supply).

In this regard, conditioned reflexes are divided into natural and artificial . natural conditioned reflexes are developed to agents that, in vivo act together with an irritant that causes an unconditioned reflex (for example, the type of food, its smell, etc.). All other conditioned reflexes artificial, i.e., they are produced for agents that are not normally associated with the action of an unconditioned stimulus, for example, a food salivary reflex to a bell.

5. Under the action of conditioned and unconditioned stimuli, the excitation from the unconditioned stimulus must be stronger than from the conditioned one.

6. Unconditional reinforcement must match its qualities, for example, food must be edible.

7. When developing conditioned reflexes, it is necessary to eliminate extraneous stimuli, since they can cause inhibition of the conditioned reflex.

8. An animal that develops a conditioned reflex must be healthy and maintain normal behavior.

9. During the development of a conditioned reflex, the animal must have a pronounced motivational excitation, for example, during the development of a food salivary reflex, the animal must be hungry, in a satiated animal this reflex is not developed.

IP Pavlov suggested that during the development of a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - cortical representations of conditioned and unconditioned reflexes. There are several possibilities for closing such a temporary connection. First, excitation from the center of the conditioned reflex can be transmitted to the center of the unconditioned reflex from cell to cell, from neuron to neuron - this is an interneuronal pathway. Secondly, excitation can be transmitted along the associative fibers of the cortex. Consequently, the first way to form a temporary connection between the cortical representations of the conditioned and unconditioned reflexes is intracortical, according to the cortex-core type (the center of the conditioned is the center of the unconditioned reflexes).

1. When the cortical representation of the conditioned reflex is destroyed, the developed conditioned reflex is preserved. Apparently, the formation of a temporary connection takes place between the subcortical centers of the conditioned reflex and the cortical centers of the unconditioned reflex (similar to the subcortex-cortex).

2. When the cortical representation of the unconditioned reflex is destroyed, the conditioned reflex is also preserved. Consequently, the development of a temporary connection can go between the cortical center of the conditioned reflex and the subcortical center of the unconditioned reflex (according to the cortex-subcortex type).

3. Separation of the cortical centers of conditioned and unconditioned reflexes by crossing the cerebral cortex does not prevent the formation of a conditioned reflex. This indicates that a temporary connection can be formed between the cortical center of the conditioned reflex, the subcortical center of the unconditioned reflex and the cortical center of the unconditioned reflex (but of the cortex-subcortex-cortex type).

4. Further studies have shown that conditioned reflexes are preserved when the cortex is removed in animals, i.e., the temporal connection is preserved at the level of the subcortical centers of the conditioned and unconditioned reflexes (subcortex-subcortex type).

What is the mechanism for the formation of a temporary connection? A number of researchers have shown that the formation of a temporary connection occurs according to the principle dominants. The focus of excitation from an unconditioned stimulus is always stronger than from a conditioned one, since the unconditioned stimulus is always biologically more significant for the animal. This focus of excitation is dominant. A stronger focus of excitation from the unconditioned stimulus attracts excitation from the focus of the conditioned stimulus. The degree of his arousal will increase. The dominant focus has the property of a long, stable existence. Therefore, conditioned and unconditioned excitations long time will interact with each other. If the excitation has passed through any nerve centers, then the next time it passes through these the paths will pass much easier. This is based, firstly, on the phenomenon of summation of excitations, and secondly, on the phenomenon of “blazing the path”, accompanied by:

A prolonged increase in the excitability of synaptic formations;

Changes in protein chains, accumulation of RNA, changes in the amount of mediator in synapses, activation of the formation of new synapses.

Consequently, structural prerequisites are created for the movement of excitation along certain paths. Now the excitation from the zone of the cortical representation of the conditioned reflex will follow the beaten path and cause the manifestation of a conditioned reflex reaction.

There is another idea about the mechanism of formation of a temporary connection. This idea is based on the ability of neurons to respond to stimuli of different modalities, i.e., the phenomenon of polysensory convergence. The existence of neurons on which excitations from different analyzers converge suggests that the process of establishing temporary connections occurs not due to the unification of various parts of the cortex, but due to the integration of excitations at the level of one neuron - cortical neurons can integrate conditioned and unconditioned excitations. Conditioned and unconditioned excitations, reaching the neurons, are fixed in them in the form of strong chemical compounds, the formation of which is the mechanism of closing the conditioned reflex connection. Such a theory of the mechanism for closing a temporary connection was called convergent theory.

Conditioned reflexes are formed on the basis of unconditioned reflexes under certain conditions. To develop a conditioned reflex, you must:

The presence of two stimuli, one of which is unconditioned (food, pain stimulus, etc.), causing an unconditioned reflex reaction, and the other is conditioned (signal), signaling an upcoming unconditioned stimulus (light, sound, type of food, etc. );

Multiple combination of conditioned and unconditioned stimuli (although the formation of a conditioned reflex is possible with their single combination);

The conditioned stimulus must precede the action of the unconditioned one.

Any stimulus of the external or internal environment can be used as a conditioned stimulus, which should be as indifferent as possible, not cause a defensive reaction, not have excessive force and be able to attract attention;

The unconditioned stimulus must be strong enough, otherwise a temporary connection will not form;

Excitation from an unconditioned stimulus should be stronger than from a conditioned one;

It is necessary to eliminate extraneous stimuli, as they can cause inhibition of the conditioned reflex;

An animal in which a conditioned reflex is developed must be healthy;

When developing a conditioned reflex, motivation must be expressed, for example, when developing a food salivary reflex, the animal must be hungry, in a full one, this reflex is not developed.

The formation of a conditioned reflex begins with the extinction of the orienting reaction to the stimulus, which should later be a conditioned signal. So, if you light a light bulb in front of the dog, then at first it will have indicative a reflex to this stimulus (turning the head, torso, moving the eyes to light). However, when the light bulb is re-ignited, the orienting response decreases and then fades away. The dog ceases to react to the lighting of the light bulb, turning on the light bulb has become an indifferent (indifferent) stimulus. Subsequently, a conditioned signal acts on the animal's organism in isolation for 5-10 seconds, and then an unconditioned stimulus joins it.

So, for the formation of a conditioned salivary reflex to a light stimulus, a light bulb is turned on, for several seconds (5 - 10) it burns in isolation, then the animal is given food (an unconditioned stimulus), and the lamp burns while the dog eats. This combination of the conditioned signal and the unconditioned stimulus is repeated several times (8-10 combinations in one experiment). After several combinations, the lighting of the light bulb will cause the separation of saliva without food reinforcement, which indicates the development of a salivary conditioned reflex to light. Light has become a conditional signal for the separation of saliva.

The mechanism of formation of conditioned reflexes.

The physiological basis for the emergence of conditioned reflexes is the formation of functional temporary connections in the higher parts of the central nervous system. Temporary connection- this is a set of neurophysiological, biochemical and ultrastructural changes in the brain that occur in the process of the combined action of conditioned and unconditioned stimuli.

I.P. Pavlov suggested that during the development of a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - cortical representations of conditioned and unconditioned reflexes (Fig. 1).

The conditioned signal causes excitation in the brain section of the corresponding analyzer. Under the influence of an unconditioned stimulus, the reflex center is excited and at the same time impulses enter the cerebral cortex in the so-called cortical representation of the center of the unconditioned reflex. Thus, during the development of a conditioned reflex, two centers of excitation appear in the cerebral cortex. A temporal connection is gradually established between them.

I. P. Pavlov called this establishment of a connection, or “blazing” a path, a closure.

In our example of the formation of a conditioned salivary reflex to light, the inclusion of a light bulb causes excitation of the photoreceptors of the eye. The resulting nerve impulses travel along the optic nerve to the brain and reach the brain end of the visual analyzer through the intercalary neurons. Irritation of the receptors of the oral cavity with food causes their excitation. Impulses along the corresponding afferent nerves enter the reflex center of salivation (a component of the food center), located in the medulla oblongata. From the salivary center, excitation along the efferent nerves spreads to the salivary glands and causes secretion. At the same time, impulses from the reflex center of salivation enter the cerebral cortex into the cortical representation of the food center. Usually there is no anatomical connection between the brain end of the visual analyzer and the cortical representation of the food center. In the process of developing a conditioned reflex, a temporary nervous connection is formed between them.

Thus, during the formation of a conditioned reflex, complex functional changes occur primarily in the brain end of the analyzer (nerve impulses are received from receptors when a conditioned signal is applied to the animal organism) and in the cortical representation of the unconditioned reflex.

There are different opinions on the issue of the mechanisms for the formation of a temporary connection.

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

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

The process of formation of conditioned reflexes is accompanied by the phenomena of their generalization and concentration.

The phenomenon of generalization(generalization) is observed during the formation of conditioned reflexes. Its essence lies in the fact that conditioned stimuli are generalized and the conditioned reflex formed to a certain stimulus is also reproduced under the action of other stimuli similar to it. The process of excitation arising from the action of any one stimulus, as a result of irradiation, also passes to the cortical centers of other, similar in nature, stimuli. In motor conditioned reflexes, for example, in the formation of motor skills, the phenomenon of generalization is manifested in the participation in a motor act of a significant number of muscles, the contraction of which is not necessary.

Phenomena of concentration observed during the strengthening of conditioned reflexes. The established conditioned reflexes are generalized to a lesser extent than the newly formed ones. This is explained by the fact that the process of excitation, with repeated repetition of conditioned stimuli, is concentrated and irradiates less to other centers. Therefore, the more the conditioned reflex becomes stronger, the less the manifestation of phenomena and generalization becomes.

The meaning of conditioned reflexes. Conditioned reflexes have a signal (adaptive) value for the organism. They warn a person or animal of danger, let them know about the proximity of food, etc. In the struggle for existence, the animal survives in which conditioned reflexes are formed faster and easier. Conditioned reflexes, depending on the conditions, may appear and fade or disappear. As a result, due to conditioned reflexes, the body can more perfectly adapt to environment to the changing conditions of existence.

I. P. Pavlov, characterizing the significance of conditioned reflexes, emphasized that conditioned reflexes clarify, refine and complicate the relationship of the organism with external environment. Chains of the most complex conditioned reflexes underlie discipline, upbringing, and training.

Questions at the beginning of the paragraph.

Question 1. What was the discovery of I. M. Sechenov?

The merit of I. M. Sechenov is that he proved that the brain can both enhance the reflexes of the spinal cord and inhibit them. It was the discovery of central inhibition that brought I. M. Sechenov fame and worldwide recognition. He showed that the higher parts of the nervous system are able to regulate the work of the lower parts. This proved the multilevel organization of the brain. The higher the brain region is located, the more complex functions he performs.

Question 2. What patterns in the work of the brain were discovered by IP Pavlov?

I.P. Pavlov continued his research and found that all reflexes can be divided into two large groups. These are innate reflexes, which he called unconditioned, and reflexes developed after birth, in the process of life, which he called conditional. IP Pavlov associated the formation of conditioned reflexes with the work of the cerebral cortex. They arise under the obligatory condition of combining some irritation, even a minor one, with vital irritations (for example, food, pain, danger) and become their signals.

Question 4. What does the dominant phenomenon discovered by A. A. Ukhtomsky have to do with this?

With an increase in need, a temporarily dominant in the central nervous system a focus of excitation aimed at satisfying precisely this need. The Russian physiologist Aleksey Alekseevich Ukhtomsky (1875-1942) called such a mechanism of temporary domination of excitation a dominant.

Questions at the end of the paragraph.

Question 1. What conditions are necessary for the development of a conditioned reflex?

Conditioned reflexes are reactions acquired during the life of each person, with the help of which his body adapts to changing environmental influences. A conditioned reflex is formed in the case of a combination of any irritation, even a slight one, with an unconditioned reflex.

Question 2. As a result of which the conditioned reflex fades away?

The conditioned reflex fades away, if for some time it is not reinforced by the unconditioned one, it ceases to be of vital importance for the organism.

Question 3. What is a dominant?

Dominant is the predominant this moment a need that governs all the current behavior of the organism.

Question 4. What is the meaning of the dominant in life?

The dominant need, the behavior associated with its satisfaction, and the simultaneous suppression of interfering and distracting reflexes mobilizes all the energy of the body to achieve the goal.

Question 5. The dominant focus of excitation usually inhibits neighboring areas of the cortex. Explain with what law, discovered by IP Pavlov, this is connected.

At the core this fact lies the law of mutual induction of excitation-inhibition, which was discovered by the great Russian physiologist IP Pavlov.

Question 6. What is the relationship of the dominant with the needs?

The significance for us of any event is determined by our inner need. The prevailing need at the moment governs all the current behavior of the organism. A. A. Ukhtomsky discovered the principle of behavior control, called the principle of dominance. According to this principle, the behavior that is associated with the satisfaction of a need activates all the energy of the body to achieve the goal.