Ivan Petrovich Pavlov. Conditioned reflex There is no need to prove that IP Pavlov was an outstanding scientist. During his long life (1849-1936) he achieved great success thanks to great diligence, purposeful work, sharp eyes, theoretical clarity,

Conditional abbreviations aa-t-RNA - aminoacyl (complex) with transport RNATP - adenosine triphosphoric acidDNA - deoxyribonucleic acid-RNA (i-RNA) - matrix (information) RNNAD - nicotinamide adenine dinucleotideNADP -

Conditional abbreviations AG - Golgi apparatus ACTH - adrenocorticotropic hormoneAMP - adenosine monophosphate ATP - adenosine triphosphate GNI - higher nervous activity GABA - ?-aminobutyric acidGMP - guanosine monophosphate GTP - guanine triphosphoric acid

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

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

UNCONDITIONAL AND CONDITIONAL REFLEXES

Higher nervous activity is reflex in nature. Unconditioned and conditioned reflexes are inherent in higher animals and man. Their specifics are as follows.

unconditioned reflexes, ensuring the maintenance of life in relatively constant environmental conditions, inherent in man from birth. These include food (sucking, swallowing, salivation, etc.), defensive (coughing, blinking, hand withdrawal, etc.), reproduction (feeding and caring for offspring), respiratory, etc.

Conditioned reflexes are produced on the basis of unconditioned when exposed to a conditioned stimulus. They provide a more perfect adaptation of the body to changing environmental conditions. They help to find food by smell, get away from danger, navigate, etc.

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

The consciousness of people is connected with the activity of the cerebral cortex. This has been convincingly proven by numerous experiments by IP Pavlov, as well as by the study of diseases and disorders of the brain.

The teachings of IP Pavlov on the higher nervous activity of a person convincingly proved the inconsistency and anti-science of religious ideas about the "soul".

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

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

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

Hygiene of physical and mental labor. The activity of the body depends on the state of the central nervous system. Its overwork leads to a breakdown of the vital functions of the body, reduces perception, attention, memory and performance.

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

To avoid overwork, it is useful to carry out industrial gymnastics during breaks, in which other muscles participate. This, in turn, leads to the excitation of new areas of the cerebral cortex, inhibition of previously working areas, their rest and restoration of working capacity.

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

Of great importance in the formation of conditioned reflexes is the regime of the day. If it is observed, a person develops many important conditioned reflexes that stimulate the better functioning of various organ systems and prevent their overwork.

The alternation of physical and mental labor, rationalization of labor, observance of the daily routine, active rest are of paramount importance for protecting the central nervous system from overwork.

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

The famous Russian physiologist I.P. Pavlov (1849–1936, “Conditioned reflexes: a study of the physiological activity of the cerebral cortex”, 1925), one of the creators of the reflex theory, proposed that the concepts of reflex and instinct be considered identical.

I.P. Pavlov suggested and proved that new forms of behavior can arise as a result of establishing a connection between innate forms of behavior (unconditioned reflexes) and a new stimulus (conditioned stimulus). If a conditioned (new) and an unconditioned (serving as a stimulus for an unconditioned reaction) stimulus coincide in time and space, the new stimulus begins to cause an unconditioned reaction, and this leads to completely new features of behavior. The conditioned reflex formed in this way can later serve as the basis for the formation of conditioned reflexes of the second and higher orders. Thus, according to Pavlov, all human behavior can be understood, studied and predicted on the basis of knowledge of the chain of conditioned reflexes, the mechanisms of their formation and attenuation. Pavlov conducted his experiments on animals, mainly on dogs. The classic conditioned reflex, carefully studied by Pavlov et al., involved the association of salivation at the sight of a dog's food and any other conditioned stimulus (such as the sound of a bell). According to Pavlov, the conditioned reflex is formed as follows: Step 1. The basis of the conditioned reflex is the unconditioned reflex: an unconditioned stimulus (= stimulus) causes an unconditioned reaction. The sight of food unconditionally causes salivation in a dog is an innate, unconditioned form of behavior. Step 2. In some situation, the conditioned reflex coincides in time and space with some other event (conditioned stimulus). Together with the presentation of food to the dog, the bell rings. Step 3. If the conditioned and unconditioned stimulus appear together several times, then a new reflex is formed. The conditioned stimulus gradually replaces the unconditioned stimulus in the reaction scheme. The rate of association of a conditioned stimulus and an unconditioned reaction depends on the characteristics of the organism. Step 4. A conditioned reflex arises: a conditioned stimulus that previously did not cause any behavior begins to cause an unconditioned response. Now just the sound of the bell is enough to make the dog salivate. This process is called classical conditioning. The result of conditioning is called a conditioned reflex. If for some time the conditioned reflex does not receive reinforcement, that is, the conditioned stimulus is not accompanied by the unconditioned for a sufficiently long time, then the conditioned reflex fades - the conditioned stimulus ceases to cause an unconditioned response.

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

The doctrine of conditioned reflexes is the doctrine of higher nervous activity. From the first steps in the study of higher nervous activity, Pavlov emphasized with all his might that he was conducting it in order to understand the work of the human brain, in order to extend accurate scientific research to phenomena designated as mental. The substantiation of the doctrine of conditioned reflexes was a turning point in the history of all natural science. For the first time, human thought, from a subject of speculative discussion by philosophers and psychologists, has become the subject of empirical physiological research. The formation of conditioned reflexes is the main physiological mechanism that determines the development of new relations of the organism to the world around it that develop over the course of life. To develop a conditioned reflex, you must:

1) 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. .);

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

3) the conditioned stimulus must precede the action of the unconditioned one;

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

5) the unconditioned stimulus must be strong enough, otherwise the temporary connection will not be formed;

6) excitation from an unconditioned stimulus must be stronger than from a conditioned one;

7) it is necessary to eliminate extraneous stimuli, since they can cause inhibition of the conditioned reflex;

8) the animal in which the conditioned reflex is developed must be healthy;

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

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.). All other conditioned reflexes are artificial, i.e. are produced in response to agents that are not normally associated with the action of an unconditioned stimulus, for example, a food salivary reflex to a bell.

Reflex arc (nervous arc) - the path traversed by nerve impulses during the implementation of the reflex. The reflex arc consists of:

§ receptor - a nerve link that perceives irritation;

§ afferent link - centripetal nerve fiber processes of receptor neurons that transmit impulses from sensory nerve endings to the central nervous system;

§ central link - nerve center (optional element, for example, for an axon reflex);

§ efferent link - carry out transmission from the nerve center to the effector.

§ effector - an executive body whose activity changes as a result of a reflex.

There are: - monosynaptic, two-neuron reflex arcs; - polysynaptic reflex arcs (include three or more neurons).

The concept was introduced by M. Hall in 1850. At present, the concept of a reflex arc does not fully reflect the mechanism for the implementation of a reflex, and in connection with this, Bernstein N.A. proposed a new term - Reflex ring, which includes the missing link in the control exercised by the nervous the center for the progress of the work of the executive body - the so-called. reverse afferentation.

The simplest reflex arc in humans is formed by two neurons - sensory and motor (motor neuron). An example of a simple reflex is the knee jerk. In other cases, three (or more) neurons are included in the reflex arc - sensory, intercalary and motor. In a simplified form, this is the reflex that occurs when a finger is pricked with a pin. This is a spinal reflex, its arc passes not through the brain, but through the spinal cord. The processes of sensory neurons enter the spinal cord as part of the posterior root, and the processes of motor neurons exit the spinal cord as part of the anterior root. The bodies of sensory neurons are located in the spinal node of the posterior root (in the dorsal ganglion), and the intercalary and motor neurons are located in the gray matter of the spinal cord. The simple reflex arc described above allows a person to automatically (involuntarily) adapt to environmental changes, for example, withdraw his hand from a painful stimulus, change the size of the pupil depending on the lighting conditions. It also helps to regulate the processes occurring inside the body. All this contributes to maintaining the constancy of the internal environment, that is, maintaining homeostasis. In many cases, a sensory neuron relays information (usually through several interneurons) to the brain. The brain processes incoming sensory information and stores it for later use. Along with this, the brain can send motor nerve impulses along the descending path directly to the spinal motor neurons; spinal motor neurons initiate the effector response.

Most of what is now known about the reactions of dogs, modern science owes to the great Russian scientist I.P. Pavlov. The discovery of the conditioned reflex by the great scientist led to the creation of a whole science - the physiology of higher nervous (mental) activity. In his research, I.P. Pavlov was primarily interested not in the mechanisms of the brain, but in the processes of digestion. He noted many of the features associated with drooling in dogs, primarily related to the type of food ingested. Saliva is secreted in different quantities and different consistency. If the food is dry, a lot of saliva is released, if it is liquid, very little. When swallowed, a thick sticky saliva is secreted, and when spitting out - watery. These simple reflexes do not require any mental activity: they arise in response to signals that come from sensitive areas located on the tongue and mouth. Due to the memory of past sensations, the dog's mouth will fill with viscous saliva if it is simply offered meat, and liquid if something inedible is offered (liquid saliva indicates disgust).

Pavlov began his research using food and a metronome. In a room where the dogs were undisturbed, he set up a metronome. It was possible to launch it, as well as to put forward a bowl of food, from the outside, but there was also an observer outside, who could see what was happening in the room through the hole. The dog, not familiar with the metronome, paid attention to it when the device began to tick. After that, a bowl of appetizing food immediately appeared, and the dog ate, at first not connecting these events with each other. Gradually, the natural unconditioned reflex (saliva when the food is in the dog's mouth, or when the bowl just stands in front of it) turned into a conditional one. This was expressed in the fact that the ticking of the metronome began to cause salivation even before the bowl of food appeared.

Then Pavlov did a small operation on the dog - he passed the salivary gland duct under the cheek to the outside. Thus, the scientist was able to observe how saliva flows down and is collected in a test tube.

Then he went even further - he sutured part of the stomach, brought out a tube from the formed blind ventricle, with the help of which he could make observations. So Pavlov discovered that when a metronome is beaten, not only saliva is released, but also gastric juice. The works of Pavlov were supplemented by the research of the American scientist D.B. Watson, who introduced the concepts of conditioned and unconditioned reflex.

In the life of a dog there are many conditioned reflexes that are superimposed on innate, unconditioned ones. Unconditioned reflexes are associated with the lower parts of the nervous system, conditioned - with the higher. If the animal's hemispheres are removed, simple innate reflexes will remain, and the conditioned ones associated with them will disappear.

Conditioned reflexes are responses of the body to a stimulus, developed under certain conditions. This is the way in which a person can control the dog's behavior. The development of certain conditioned reflexes in a dog is the psychophysiological essence of training. If the conditions that caused the conditioned reflexes change, they fade away, since they are temporary reactions. They are carried out by the higher parts of the brain. The cerebral cortex can have both an activating and inhibitory effect on the underlying parts of the brain, and thus either enhance or inhibit response actions.

For the formation of conditioned reflexes, that is, training, the intensity of the stimulus, as well as the general condition of the dog, is of great importance. If the health of the animal is in poor condition, internal stimuli will divert its attention from the trainer.

Any stimulus perceptible to the dog (visual, gustatory, tactile, olfactory, etc.) can be converted into a conditioned stimulus. The conditioned reflex can be formed, for example, as follows. The dog hears the sound of a whistle for the first time, it expresses alertness with its whole posture. If the dog is fed every time the whistle sounds, the whistle turns into a conditioned stimulus. When a dog begins to salivate before it receives food, it can be said that it has formed a conditioned reflex.

There is also another principle of the formation of a conditioned reflex, which is that the reflex action is most effectively fixed when the conditioned stimulus is given no more than a second before the unconditioned one. The secondary conditioned reflex is formed on top of the already established conditioned reflex as a result of the replacement of a new conditioned stimulus. In practice, it may look, for example, like this: the dog gets used to reacting to the whistle by salivating, receiving food for it. Now you can replace the whistle with a verbal command like "Eat!", repeating again the whole process of forming a reflex. In order for the reaction to the whistle to die out, in the course of the formation of a new reflex, you need to periodically whistle the whistle, but do not give the dog food. To maintain a response to both the primary and secondary stimulus, blow the whistle occasionally after the secondary stimulus has elicited the conditioned reflex, and then offer a reward in the form of a treat. The dog can also be trained to the third conditioned stimulus, but not to the fourth. Therefore, it is important, when dealing with a dog, to achieve some specific reaction from it, using the same verbal stimulus or no more than two words for one reaction.

In the process of a dog's life, a constant change of acquired reflexes is carried out. Some of them are fixed, others disappear due to the process of inhibition.

I.P. Pavlov established the existence of two types of inhibition - unconditional (external) and conditional (internal). Unconditional inhibition is an innate property of the nervous system. It appears under the action of extraneous strong stimuli and inhibits the manifestation of conditioned reflexes. Therefore, the development of initial skills in a dog should be carried out in a calm, familiar environment for the dog.

Conditioned reflexes (R.R.) are individually acquired reactions of the body to irritation in the course of life. The creator of the doctrine of conditioned reflexes I.P. Pavlov called them a temporary connection of the stimulus with the response that is formed in the body under certain conditions.

Properties of conditioned reflexes:

1. Formed throughout life as a result of the interaction of the individual with the external environment.

2. They are not persistent and can disappear without reinforcements

3. Do not have a permanent receptive field

4. Do not have a constant reflex arc

5. For the occurrence of a conditioned reflex reaction, the action of a specific stimulus is not required.

An example of a conditioned reflex is the production of salivation from a dog to a call.

Conditioned reflexes are formed only with a certain combination of the properties of the stimulus and external conditions. To develop a conditioned reflex, a combination of an indifferent or conditioned stimulus and a reinforcing unconditioned stimulus is used. An indifferent stimulus is such a stimulus that under natural conditions cannot cause a given reflex reaction, and an unconditioned one is a specific stimulus that always causes the occurrence of this reflex.

The following conditions are necessary for the development of conditioned reflexes:

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

2. A multiple combination of conditioned and unconditioned stimuli is necessary.

3. Indifferent and unconditioned stimuli must have a suprathreshold strength.

4. At the time of the development of the conditioned reflex, there should be no extraneous external stimuli.

5.C.N.S. must be in good working order.

All conditioned reflexes, depending on the emerging behavior, are divided into classical and instrumental..

1. Classical are those that are produced in accordance with the above conditions. An example is salivation generated by a bell.

2. Instrumental - these are reflexes that contribute to the achievement or avoidance of the stimulus. For example, when the bell is turned on, preceding an unconditioned reflex pain stimulus, the dog performs a set of movements to get rid of the electrodes. When calling, preceding food, wags its tail, licks its lips, reaches for a cup, etc.

According to the afferent link of the conditioned reflex arc, i.e. receptors emit exteroceptive and interoreceptive conditioned reflexes. Exteroceptive arise in response to irritation of external receptors and serve to connect the body with the external environment. Interoreceptive - on irritation of the receptors of the internal environment. They are necessary to maintain the constancy of the internal environment.

According to the efferent link of the conditioned reflex arc, motor and vegetative conditioned reflexes are distinguished. An example of a motor activity is the dog's paw withdrawal to the sound of a metronome, if the latter precedes a painful stimulation of the paw. An example of a vegetative one is salivation in response to a bell in a dog.

Higher-order conditioned reflexes are singled out separately. These are conditioned reflexes that are developed not by reinforcing a conditioned stimulus with an unconditioned one, but by reinforcing one conditioned stimulus with another. In particular, a conditioned salivary reflex of the 1st order is developed to the combination of lighting a lamp with giving food. If after that the bell is reinforced by lighting the lamp, then a conditioned reflex salivation to the bell will develop. This will be a second order reflex. In a dog, it is possible to develop conditioned reflexes only of the IVth order, and in a person up to the XXth order. Conditioned reflexes of higher orders are unstable and quickly fade away.

In mammals and humans, the main role in the formation of conditioned reflexes belongs to the cortex. When they are produced from peripheral receptors that perceive conditioned and unconditioned stimuli, nerve impulses travel along ascending pathways to the subcortical centers, and then to those areas of the cortex where the representation of these receptors is located. In the neurons of these 2 sections of the cortex, biopotentials arise, They coincide in time, frequency and phase. Circulation occurs along intercortical pathways, i.e. reverberation of nerve impulses. As a result of synaptic potentiation, synaptic connections located between the neurons of one and the other zone of the cortex are activated. Improvement in conduction is fixed, a temporary or conditioned reflex connection appears (scheme of the arc of a conditioned salivary reflex).

Conditioned reflexes are subdivided as follows.

Biologically:

food;

sexual;

defensive;

motor;

indicative - a reaction to a new stimulus.

The orienting reflex is carried out in 2 phases:

1) the stage of nonspecific anxiety - the 1st reaction to a new stimulus: motor reactions, vegetative reactions change, the rhythm of the electroencephalogram changes. The duration of this stage depends on the strength and significance of the stimulus;

2) stage of exploratory behavior: motor activity, vegetative reactions, electroencephalogram rhythm are restored. Excitation covers a large section of the cerebral cortex and the formation of the limbic system. The result is cognitive activity.

Differences of the orienting reflex from other conditioned reflexes:

innate reaction of the body;

It can fade with repetition of the action of the stimulus.

That is, the orienting reflex occupies an intermediate place between the unconditioned and conditioned reflex.

By the nature of the conditional signal:

natural - conditioned reflexes caused by stimuli acting in natural conditions: sight, smell, talking about food;

artificial - caused by stimuli not associated with this reaction under normal conditions.

According to the complexity of the conditional signal:

simple - the conditioned signal consists of 1 stimulus (light causes saliva);

complex - the conditioned signal consists of a complex of stimuli:

Conditioned reflexes arising on a complex of simultaneously acting stimuli;

Conditioned reflexes arising on a complex of successively acting stimuli, each of them "layers" on the previous one;

· a conditioned reflex to a chain of stimuli also acting one after another, but not "overlapping" on top of each other.

The first two are easy to develop, the last is difficult.

Type of irritant:

exteroceptive - occur most easily;

· interoceptive;

proprioceptive.

The child first appears proprioceptive reflexes (sucking reflex to posture).

By changing a particular function:

positive - accompanied by an increase in function;

Negative - accompanied by a weakening of the function.

By the nature of the response:

somatic;

vegetative (vascular-motor)

According to the combination of the conditioned signal and the unconditioned stimulus in time:

cash - the unconditioned stimulus acts in the presence of a conditioned signal, the action of these stimuli ends at the same time.

Distinguish:

Coinciding cash conditioned reflexes - the unconditioned stimulus acts 1-2 seconds after the conditioned signal;

Delayed - the unconditioned stimulus acts 3-30 seconds after the conditioned signal;

belated - the unconditioned stimulus acts 1-2 minutes after the conditioned signal.

The first two arise easily, the last one is difficult.

trace - the unconditioned stimulus acts after the cessation of the conditioned signal. In this case, a conditioned reflex occurs to trace changes in the brain section of the analyzer. The optimal interval is 1-2 minutes.

In various orders:

Conditioned reflex of the 1st order - is developed on the basis of an unconditioned reflex;

Conditioned reflex of the 2nd order - is developed on the basis of a conditioned reflex of the 1st order, etc.

In dogs, it is possible to develop conditioned reflexes up to the 3rd order, in monkeys - up to the 4th order, in children - up to the 6th order, in adults - up to the 9th order.

9. Formation of a conditioned reflex.

For this you need:

Presence of 2 stimuli: unconditioned stimulus and indifferent(neutral) stimulus, which then becomes the conditioned signal;

Certain strength of stimuli. The unconditioned stimulus must be strong enough to cause dominant excitation in the central nervous system. An indifferent stimulus must be familiar so as not to cause a pronounced orienting reflex.

Repeated combination of stimuli over time, and the indifferent stimulus should act first, then the unconditioned stimulus. In the future, the action of 2 stimuli continues and ends simultaneously. A conditioned reflex will occur if the indifferent stimulus becomes a conditioned stimulus, that is, it signals the action of an unconditioned stimulus.

Environmental constancy- the development of a conditioned reflex requires the constancy of the properties of the conditioned signal.

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

Mechanism Conditioned reflexes In the process of conditioned reflex activity, the analysis and synthesis of stimuli of the external and internal environment is constantly performed. Analysis of irritation consists in distinguishing, separating signals, differentiating effects on the body. The synthesis of stimuli is manifested in the binding, generalization, and unification of excitations that arise in various parts of the cerebral cortex as a result of the interaction that is established between neurons and their groups. The processes of analysis and synthesis are interconnected and run in parallel, constituting the main function of the brain. An example of the analytical and synthetic activity of the cerebral cortex is the formation of a dynamic stereotype, in which several temporary connections are combined into a functional system. The cortex fixes a certain order of stimuli and their corresponding reactions, which facilitates its work when performing a stereotypically repetitive system of reflexes. The mechanism of formation of conditioned reflexes is based on the process of closing the nervous connection between two simultaneously excited points in the brain. A detailed analysis of the nervous mechanism of conditioned reflex communication using subtle modern methods of electroencephalography, evoked potentials, and the study of neural activity confirmed Pavlov's conclusion about the cortical mechanism of closure. Conditioned reflexes According to the hypothesis of P.K. excitations on the same neurons. As a result of interaction at the cellular level of cash and trace processes of excitation, temporary connections arise and are fixed. Each conditioned reflex is based on a special functional organization of groups of neurons capable of reproducing traces of previous stimuli in response to a conditioned signal. It was assumed that excitation from one group of cortical cells that perceive a conditioned signal is transmitted to another only along horizontal nerve fibers passing through the cortex. However, further studies of owls. scientists E. A. Asratyan, I. S. Beritashvili, A. B. Kogan, M. M. Khananashvili, N. Yu. Belenkov showed that a new functional connection can be carried out along a different path: cortex - subcortex - cortex. In addition to the cortex, many subcortical structures, such as the reticular formation, hippocampus, basal ganglia, and hypothalamus, are involved in the formation of conditioned reflexes.

Conditioned reflexes formed by combining a conditioned signal with an unconditioned stimulus are called conditioned reflexes. reflexes of the first order . Those conditioned reflexes that are formed on the basis of a combination of an external agent with a conditioned signal that causes a previously developed strong permanent conditioned first-order reflex are called second-order conditioned reflexes.

By combining an indifferent stimulus with a second-order conditioned stimulus, a third-order conditioned reflex can be developed in a dog. The latter was observed in experiments with defensive motor reflexes, which were evoked by electrical stimulation of the paw. It is not possible to develop conditioned reflexes of the fourth order in a dog. In children, reflexes of the sixth order are described.

If you develop a strong conditioned food reflex, for example, to light, then such a reflex is a first-order conditioned reflex. On its basis, a second-order conditioned reflex can be developed; for this, a new, previous signal is additionally used, for example, a sound, reinforcing it with a first-order conditioned stimulus (light).

As a result of several combinations of sound and light, the sound stimulus also begins to cause salivation. Thus, a new, more complex mediated temporal connection arises. It should be emphasized that the reinforcement for the second-order conditioned reflex is precisely the first-order conditioned stimulus, and not the unconditioned stimulus (food), since if both light and sound are reinforced with food, then two separate first-order conditioned reflexes will arise. With a sufficiently strong second-order conditioned reflex, a third-order conditioned reflex can be developed.

For this, a new stimulus is used, for example, touching the skin. In this case, the touch is reinforced only by a second-order conditioned stimulus (sound), the sound excites the visual center, and the latter excites the food center. An even more complex temporal connection emerges. Reflexes of a higher order (4, 5, 6, etc.) are produced only in primates and humans.

Dominant- "temporarily dominant reflex", which directs the work of the nerve centers at the moment, a functional association of nerve centers, consisting of a relatively mobile cortical component and subcortical, vegetative and humoral components.

The activity of the nerve centers is not constant, and the predominance of the activity of some of them over the activity of others causes noticeable changes in the processes of coordination of reflex reactions.

Exploring the features of intercentral relations, A. A. Ukhtomsky discovered that if a complex reflex reaction occurs in the animal body, for example, repeated acts of swallowing, then electrical stimulation of the motor centers of the cortex not only ceases to cause limb movements at that moment, but also intensifies and accelerates the flow of the begun chain reaction of swallowing, which turned out to be dominant. A similar phenomenon was observed in case of phenol poisoning of the anterior sections of the frog spinal cord. An increase in the excitability of motor neurons led to the fact that the poisoned paw responded with a rubbing (shaking off) reflex not only to direct irritation of its skin with acid, but also to a wide variety of extraneous stimuli: lifting the animal from the table into the air, hitting the table where it sits, touching the front paw of the animal, etc.

In 1923, A. A. Ukhtomsky formulated the principle of dominance as a working principle of the activity of nerve centers.

The term dominant was used to designate the dominant focus of excitation in the central nervous system, which determines the current activity of the organism.

The main features, the dominants are as follows: 1) increased excitability of the nerve centers, 2) persistence of excitation over time, 3) the ability to sum up extraneous irritations, and 4) the inertia of the dominant. The dominant (dominant) focus can arise only with a certain functional state of the nerve centers. One of the conditions for its formation is an increased level of excitability of nerve cells, which is caused by various humoral and nervous influences (long-term afferent impulses, hormonal changes in the body, exposure to pharmacological substances, conscious control of nervous activity in humans, etc.).

The established dominant can be a long-term state that determines the behavior of the organism for a particular period. The ability to steadfastly maintain excitement over time is a characteristic feature of the dominant. However, not every focus of excitation becomes dominant. An increase in the excitability of nerve cells and their functional significance is determined by the ability to summarize excitation when any random impulse arrives.