The pathogenic agent, acting on the body of higher animals and humans, primarily causes irritation of the neuroreceptor devices (extero- or interoreceptors), the sensitivity of which is many times higher than the sensitivity threshold of other tissue elements. Receptor formations are initial link reflex arcs, with the help of which the body's response to disease-causing effects emanating from its external or internal environment is carried out.

The pathological process may initially manifest itself as tissue damage at the point of application of the stimulus: mechanical, chemical, thermal, infectious, etc. In this case, metabolic disorders and tissue structure arise. But such direct and limited disturbances due to the simultaneous stimulation of neuro-receptor formations that send signals to the central nervous system, lead to a general reaction of the body, which is based on a reflex mechanism. This can be seen, for example, in the burn-inducing experiment. Exposure to the body surface of a thermal agent is accompanied by tissue damage and, at the same time, a reflex increase in blood pressure, changes in blood formation, metabolism, respiratory distress, etc.

As illustrations, one can also cite the participation of the nervous system in the mechanism of occurrence of those phenomena that often accompany the blockage of a blood vessel (embolism), for example, embolism of the vessels of the pulmonary circulation. They consist in a reflex spasm of the pulmonary and coronary arteries, a drop in total blood pressure and a change in breathing. Interruption of reflex pathways with the help of surgical or pharmacological influences weakens these phenomena, which, to a certain extent, depend on local mechanical disturbances of blood flow. Influences on the nervous system can also weaken and restore functions impaired by embolism.

Pathological processes can occur by mechanism Not only unconditional, but also conditional reflexes. With repeated combination of a pathogenic factor with an indifferent stimulus, the latter can also cause this disease, which in this case occurs by a conditioned reflex pathway. For example, in dogs, by the conditioned reflex mechanism, it is possible to reproduce intoxication with morphine, eserine, atropine, bulbocapnine, camphor by the introduction of a physiological solution of sodium chloride. Pathological conditioned reflexes sometimes underlie the occurrence of attacks of bronchial asthma, hay, fever, eczematous skin lesions and other diseases.

In addition to the reflex, there may also be direct effect of pathogenic irritants on the central nervous system, for example, carbon dioxide accumulated in the blood, microbial toxins or toxic metabolic products.

Depending on the etiological factor, the place of its impact and the properties of the organism, the pathogenesis of a particular disease may be associated with a change in the functions of various parts of the nervous system - from the peripheral endings of the centripetal nerves to the cerebral cortex. So, breathing disorders can arise in one case from the initial irritation of the peripheral endings of the pulmonary branches of the vagus nerves, in another - from damage to the medulla oblongata or some parts of the diencephalon, in the third - from dysfunction of the cerebral cortex (for example, shortness of breath during excitement or breakdown of the higher nervous activity). In the experiment, an increase in blood sugar content can be obtained in several ways: by irritation of the central end of the cut sciatic nerve or by an injection into the medulla oblongata, or by strong emotional arousal. In other words, the emergence of a pathological process can occur in various parts of the body. In this case, the sequence and degree of dysfunction of one or another part of the nervous system have a certain significance in the nature and speed of development of this pathological process. However, as a result of reflex activity, in the end, other parts of the nervous system are inevitably involved in the pathological process, the parts of which are closely interconnected.

To clarify the participation of the higher parts of the nervous system in the pathogenesis of diseases, it is also important to study its basic laws: typological properties, the ratio of the processes of excitation and inhibition, the phenomena of parabiosis, dominant, trace reactions, etc. (see Chapter IV).

In the pathogenesis of diseases, an important place is occupied by disturbances in the relationship between the central nervous system and the internal environment of the body.

Function dependency internal organs from the activity of the higher parts of the central nervous system was often noted by clinical medicine. On the one hand, the influence of various experiences and worries on the activity of the heart, breathing and digestion is known, for example, cases of heart paralysis from severe experiences, a change in the rhythm of breathing from sudden fright, indigestion due to a state of mental depression and chronic lack of appetite. On the other hand, there are well-known examples of overcoming bodily ailments in moments of emotional uplift.

On the basis of many years of in-depth studies of the activity of the cerebral hemispheres, IP Pavlov showed that the function of internal organs, regulated by subcortical formations, also has its own "cortical representation". For example, a long-term violation of the motor and secretory activity of the stomach in dogs was observed as a result of a violation of the functional state of the higher parts of the brain caused by a collision of the processes of excitation and inhibition (collision).

The significance of violations of higher nervous activity in changes in the functions of other internal organs - bile secretion, blood pressure, urine output, and hematopoietic processes - was clarified.

Other studies have shown the possibility of the formation of conditioned reflexes on the activity of internal organs and the importance of interoreception in this process. The possibility of the occurrence of conditioned reflex polyuria (increased urination) and anuria (absence of urination), conditioned reflex bile secretion, spleen contraction, vasoconstriction and dilation, changes in respiration, metabolism, etc. was shown.

These studies served as the basis for the idea of ​​a two-way relationship between the activity of the cerebral cortex and the function of internal organs (cortical-visceral relationships according to K.M.Bykov).

When impulses are received from both extero- and interoreceptors, a complex process of analysis and synthesis takes place in the cerebral cortex, the relationships between the processes of excitation and inhibition are created, which determine the nature of its influence on the function of internal organs.

Violations of the normal relationship between the cortex and the subcortical region often underlie a number of diseases, such as peptic ulcer and hypertension, bronchial asthma, and coronary insufficiency.

This influence of the higher parts of the central nervous system is carried out through the lower parts of the nervous system, through the region of the hypothalamus, where centers are located that regulate the processes taking place in the internal environment of the body with the help of efferent neurons. The hypothalamus and the underlying parts of the nervous system themselves may be the initial beginning of the onset of pathological processes, for example, polyuria, obesity, and growth disorders.

A very important link in the regulation of functions is also humoral mechanisms, especially neuro-endocrine and endocrine regulation. In view of the variety of their functions, the endocrine glands often, in close interaction with the nervous system, determine the reaction of a complex organism to the action of an irritant. So, the disorder of urination in the kidneys can be carried out through the subcortical autonomic centers and their connection with the posterior lobe of the pituitary gland, which secretes an antidiuretic hormone that affects the reabsorption function of the kidneys.

With the evolutionary development of organisms, neurohormonal relationships become increasingly important in pathological reactions. In higher animals and humans, a particularly large role belongs to the diencephalo-pituitary ratios and the pituitary-adrenal function closely related to them. When exposed to pathogenic stimuli, the body reflexively produces hormones by the anterior pituitary gland, which affect the hormonal secretion of the adrenal cortex (see the chapter on reactivity). This entire system takes an active part in the adaptability of the organism, in its nonspecific reactions to the action of any pathogenic stimulus.

In addition to the hormones of the endocrine glands, tissue hormones, physiologically active substances, such as active polypeptides and proteins, histamine, acetylcholine, and serotonin, can also participate in the pathogenesis of diseases. They can also be involved in dysregulation of functions, often found during the development of pathological processes, affecting tissue at the site of their release and formation, or due to their delivery to tissues using the bloodstream.

Thus, the mechanisms of occurrence of pathological processes are defined as properties disease agent and body reaction, its regulatory systems.

LECTURE 2. PHYSIOLOGY OF HIGHER NERVOUS ACTIVITY. INTEGRATED BRAIN ACTIVITY AND SYSTEM ORGANIZATION OF ADAPTIVE BEHAVIORAL REACTIONS. TEACHING I.P. PAVLOVA ON TYPES OF HIGHER NERVOUS ACTIVITY

The highest nervous activity and its age characteristics. Conditioned and unconditioned reflexes.

1. Differences between conditioned and unconditioned reflexes:

Unconditioned reflexes- innate reactions of the organism, they were formed and fixed in the process of evolution and are inherited.

Conditioned reflexes arise, consolidate, fade away during life and are individual.

Unconditioned reflexes necessarily arise if adequate stimuli act on certain receptors.

Conditioned reflexes for their formation require special conditions; they can be formed to any stimuli (of optimal strength and duration) from any receptive field.

Unconditioned reflexes are relatively constant, stable, unchanged and persist throughout life.

Conditioned reflexes are changeable and more mobile.

Unconditioned reflexes can be carried out at the level of the spinal cord and brainstem.

Conditioned reflexes are a function of the cerebral cortex, realized with the participation of subcortical structures.

Unconditioned reflexes can ensure the existence of an organism only at the earliest stage of life.

The adaptation of the organism to constantly changing environmental conditions is ensured by conditioned reflexes developed throughout life.

Conditioned reflexes are variable. In the process of life, some conditioned reflexes, losing their meaning, fade away, others are developed.

1. The biological significance of unconditioned reflexes.

An organism is born with a certain set unconditioned reflexes... They ensure the maintenance of the body's vital activity in relatively constant conditions of existence. These include unconditioned reflexes:

food- chewing, sucking, swallowing, separating saliva, gastric juice, etc.,

defensive- pulling the hand away from a hot object, coughing, sneezing, blinking when a jet of air enters the eye, etc.,

sexual reflexes- the implementation of sexual intercourse, feeding and caring for the offspring,

thermoregulatory,

respiratory,

cardiovascular,

maintaining the constancy of the internal environment of the body(homeostasis), etc.

1. The biological significance of conditioned reflexes.

Conditioned reflexes provide a more perfect adaptation of the body to changing living conditions. They help to find food by smell, timely avoidance of danger, orientation in time and space.

1. Conditions for the formation of a conditioned reflex.

Conditioned reflexes are developed on the basis of unconditioned ones. For the formation of a conditioned reflex, certain conditions are required. First of all, you need a conditioned stimulus, or signal. A conditioned stimulus can be any stimulus from the external environment or the internal environment of the organism.

For example :

in Pavlov's laboratory, the flashing of an electric light bulb, a bell, the gurgling of water, skin irritation, gustatory and olfactory stimuli, the clink of dishes, the sight of a burning candle, etc., were used as conditioned stimuli;

conditioned reflexes are temporarily developed in a person, subject to the work regimen, eating at the same time, and a constant time of going to bed.

To develop a conditioned reflex, a conditioned stimulus must be reinforced with an unconditioned stimulus, that is, one that causes an unconditioned reflex. When a conditioned reflex is formed, the conditioned stimulus must precede the action of the unconditioned stimulus (usually by 1-5 s).

A conditioned reflex can be developed by combining an indifferent stimulus with a previously developed conditioned reflex - these are conditioned reflexes of the second order, then the indifferent stimulus must be reinforced with a conditioned stimulus of the first order.

For example :

The clanging of knives in the dining room will cause a person to salivate only if this clinking has been reinforced with food one or more times. The ringing of knives and forks in our case is a conditioned stimulus, and food is the unconditioned stimulus that causes the unconditioned salivary reflex.

The sight of a burning candle can be a signal to pull away the child's hand only if at least once the sight of the candle coincides with the pain of the burn.

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Since conditioned reflexes are simply special cases of associations in which a stimulus that excites receiving neurons causes an external reaction, it is obvious that in human life this type of phenomena occurs as often as associations of other types. In this chapter, we will briefly review the conditioned reflexes commonly observed in humans and show that they do not differ in their properties from the conditioned reflexes found in animals.
Conditioned reflexes in humans can be divided into two categories: those that are found in each person, since they are an integral part of his life, and those that are formed only in certain circumstances, based on the special experience of one person or group of people. Most of the defensive conditioned reflexes belong precisely to the second category. It seems to us that it is not of interest to dwell on them, since the reader may not have the appropriate reflexes. Therefore, let us dwell on the first category of conditioned reflexes in humans and discuss those of them that seem especially interesting to us. It will focus on conditioned reflexes associated with eating and sleeping.
Food intake. A person usually eats food at regular intervals and at certain times of the day. Both the hours of eating and the environment in which it happens, although different for different nations and social groups, are characterized by striking constancy and even severity within each group. This constancy, which seems natural to us, is directly related to conditioned reflexes. A person who always eats at a certain time of the day and in a certain environment develops a strong conditioned reflex of hunger, which makes him eat at the same hours and in the same place on the following days. This, in turn, further strengthens the conditioned food reflexes and further strengthens the habit to a certain diet. Moreover, the presence of such habits in the whole group leads to such spatio-temporal events as preparing for food at a certain time, serving in certain places, which again sets clear boundaries for food intake, thereby causing further consolidation of the corresponding conditioned reflexes.
It is interesting to analyze the interaction between the two main conditioned reflexes associated with food intake: the conditioned hunger reflex and the conditioned reflex to food in their manifestations in human life.
The conditioned reflex of hunger is mainly determined by the time factor, that is, the period of time elapsed after the previous meal. Evidence that this factor acts to a large extent as a conditioned, and not as an unconditioned stimulus, is the fact that the appearance of hunger is completely dependent on our daily stereotype and is confined to it. We feel hungry for our usual meal times, regardless of how they are distributed throughout the day and what the intervals between them are. If at the usual time we did not eat, then hunger, as a rule, disappears (revealing its conditioned reflex nature) and appears approximately at the time of the next meal.
These conditioned reflexes of hunger are associated not only with the moment of eating, but also with the quantity and quality of food. Although, as indicated in Ch. I, both the amount of food consumed during one meal and its composition (assuming free choice) depends on the intensity of the unconditioned-reflex drive of hunger, and selectivity is dictated by the body's needs, nevertheless, the quantity and quality of food eaten largely depend on conditioned reflexes ... If we are used to getting a light breakfast at some time, then the intensity of the conditioned hunger reflex will correspond to this and it will be unpleasant for us if the light snack is replaced with another type of food. On the contrary, accustomed to the fact that lunch is usually hearty, consisting of a number of dishes, we will not get enough if instead we are given a light snack. Likewise, if we are accustomed to a breakfast of coffee, toast, eggs and jam, and we are offered soup and meat instead, we will have a negative reaction to this change, since the conditioned reflex drive of hunger at this moment is directed to a different type of food. It even seems to us that we were given simply inedible food, although in a few hours we will eat the same dishes with great appetite.
If the conditioned reflexes of hunger are established mainly for a time and to a lesser extent on external stimuli, the conditioned reflex to food, on the contrary, depends exclusively on external stimuli immediately preceding the act of eating, in particular on the external environment of the meal. When we get up from our workplace, put on our coats and go to the dining room, saliva does not come out, although we experience a very strong hunger drive. But when we arrive, sit down, unfold the napkin, read the menu - that's when we start salivating, a sign of a conditioned reflex to food.
It should be noted that the conditioned reflex to food in the form of salivation can also manifest itself in an environment different from that associated with food intake. If, for example, in the company of gourmets, someone skillfully describes various dishes, the audience begins to salivate profusely. This is because vivid images of food, caused by the activation of the corresponding gnostic neurons through the connections from the audio-verbal neurons, can replace the direct perception of food; we kind of get food in our imagination.
The relationship between the conditioned reflex to food and the conditioned hunger reflex in humans is the same as in animals. People who adhere strictly to stereotypes in food (for example, in boarding houses) and usually overeat rarely experience real hunger, and the stimuli that signal the moment of eating for them are of a different nature (for example, social). However, the strong conditioned reflex to food, which begins when they sit down at a well-served table, and especially when they taste the first bites of tasty food, causes a strong hunger drive. To their surprise, they are able to eat all their food with great appetite and pleasure. After all, it is not for nothing that they say: "Appetite comes with eating."
Conversely, if a person experiences a strong, even unbearable, hunger that makes him go to eat, then when he comes and sits down at a well-set table, powerful conditioned stimuli begin to act on him, signaling the upcoming food intake, and the feeling of hunger is weakened.
The state of satiety, like the drive of hunger, can easily become conditioned reflex. It is well known that if a person overeats some food in a certain place, then later both this food and the place associated with it cause hostility, since at the same time conditioned reflex satiation begins to act, which suppresses appetite.
Dream. Unconditional reflex sleep, like food and defensive activity, has a dual nature. It is necessary to clearly distinguish between the drive of sleep - the desire to fall asleep, which we call the unconditioned reflex of sleepiness, and actual sleep - the unconditioned reflex of sleep. The unconditioned reflex of sleepiness is excited by a more or less prolonged lack of sleep, while the unconditioned reflex of sleep develops under the action of such external stimuli as acceptance of a recumbent or semi-recumbent position, muscle relaxation, monotony of the environment, and a comfortable bed.
It is easy to see that, as with food activity, drowsiness and sleep can easily become conditioned reflexes, just like hunger drive and food intake.
The conditioned reflex of drowsiness is developed at the time when, according to the usual daily routine, we go to bed. People who are accustomed to sleeping in the afternoon develop sleepiness by this time too, and they suffer if circumstances do not allow them to go to bed. But if this sleep is prevented, then drowsiness gradually disappears, which indicates its conditioned reflex nature. If afternoon sleep is prevented from day to day, then drowsiness, not supported by sleep, ceases to appear in accordance with the principles of extinction of conditioned reflexes. Most people begin to want to sleep in the evening, because they are used to going to bed at this time, but those who work at night, on the contrary, are fresh and vigorous at this time and become drowsy by the morning.
The conditioned sleep reflex, on the other hand, is developed for those stimuli that usually accompany falling asleep: the type of bedroom, a comfortable bed, night clothes, a certain position in which a person usually falls asleep, reading a book, radio, smoking a cigarette. This is due to the formation of connections between gnostic neurons, in which the corresponding perceptions are presented, and neurons, in which the hypnogenic stimuli listed above are presented. It is well known that if something changes greatly in a normal environment, where we are used to sleeping, then it is impossible to fall asleep, unless, of course, we do not want to sleep very much. Strong unconditioned drowsiness, caused, as a rule, by a prolonged lack of sleep, makes us fall asleep even in an unfamiliar environment; it helps to establish a new conditioned reflex to a new environment and contributes to the establishment of connections between the corresponding gnostic neurons and hypnogenic neurons.
A legitimate question arises: how can conditioned reflexes of drowsiness and sleep be developed if both of these states are fundamentally opposite to the “awakening reaction”?
This question can be answered as follows. As emphasized earlier, the formation of associations does not necessarily have to occur against the background of general activation (which generally seems to us to be a physiological artifact obtained under artificial experimental conditions); for this, partial activation is sufficient, affecting only certain structures and not affecting others. Taking this into account, we can assume that sleepiness is a state no less active than any other drive. On the contrary, when drowsy, the animal actively searches for a place to sleep, just as a hungry animal searches for food; it is, of course, more sensitive to all stimuli related to the goal. Consequently, sleepiness activates the conditioned sleep reflex associations as well as hunger does for conditioned food reflexes.
We have presented above an ethological analysis of two important conditioned reflexes in order to illustrate the role of conservative classical conditioned reflexes in human life. The main conclusion from this analysis comes down to the fact that both preparatory and executive activity are of an unconditioned reflex nature and are regulated primarily by the “needs of the body”, which it “makes known” to the corresponding nerve centers, mainly through chemoreceptors, which are present both on the periphery and and in the central nervous system. However, a more subtle regulation of both activities is carried out through conditioned reflexes, which, perhaps, are not strong enough to cause significant changes in them, but which distribute them in such a way in time and space in order to adapt them to the peculiarities of the life of an individual or collective.
Social behavior a person turns out to be another area of ​​manifestation of conditioned reflexes; let's call them social conditioned reflexes. The social environment surrounds a person from the moment of his birth until his death, largely determining the conditions of his life; most of all external irritations that affect a person's life come from this environment. Without intending to go into all the details of human relationships, we would like, however, to draw attention to only one side of them, closely related to the issues under consideration.
Every person, be it an adult or a child, with constant communication with other people develops highly specific emotional relationships, which are based on conditioned reflexes. The formation of these conditioned reflexes occurs as follows. For a given person, whom we will consider an object (let's call him O), the attitude of other people with whom he is associated with him can be considered as a kind of unconditioned irritation (therefore, we will call them P1, P2, P3-); as a result, various conditioned reflexes arise, both emotional and executive. For example, P1 is usually aggressive towards our O, he insults or harms him; P2 is always kind and gentle with O; Р3 - his partner in sexual activity; P4 saves O from danger (real or imagined), thereby weakening the latter's feeling of anxiety; P5 tried to harm O, but he failed, after which O felt a victory. Accordingly, behavior P1 evokes in O an unconditioned reflex of fear and rage, behavior P2 causes a feeling of attachment, P3 - sexual desire and the corresponding unconditioned executive reflex, P4 - causes a state of relief in O, and P5 - a feeling of satisfaction. Usually, various behavioral acts of a given person cause a number of emotional unconditioned reflexes, either complementing each other (for example, attachment and sexual desire), and sometimes antagonistic to each other (for example, attachment and fear).
As a result, according to the principles of the formation of conditioned reflexes, a given person, that is, his face, voice or image, become typical conditioned stimuli and cause corresponding emotional conditioned reflexes of fear, attachment, sexual drive, and relief. The properties of these social conditioned reflexes are remarkably similar to the properties of the classical conditioned reflexes developed in experimental animals. This will be shown again in the next chapter, where we will discuss the alteration of conditioned reflexes caused by a change in the reinforcing agent associated with this conditioned signal.
Another type of classical conditioned reflexes that play an important role in human life are conditioned reflexes associated with words read or heard. As stated many times before, there are strong associations between words and the stimulus-objects they denote and cause their images or hallucinations. If these stimulus-objects, in turn, are associated with unconditioned stimuli from the sphere of emotional or executive reflexes, then the words cause typical conditioned reflexes of the second order.
Here are some examples. If the company is talking about tasty food, then very soon this conversation begins to evoke in its participants a conditioned reflex of hunger and (or) a conditioned reflex to food. When reading a story that touches on a sexual theme, images that have arisen under the influence of the read can trigger a sexual conditioned reflex. If the story describes some terrible events, then the corresponding images cause a conditioned reflex of fear.

The same principle of verbal conditioned reflexes operates in a related group of phenomena called suggestion. If you tell a person with conviction that the room he just entered is very cold, he will really begin to experience a hallucination of cold and tremble. Likewise, if you persistently convince someone that there was a worm in the food they just eaten, the person may experience nausea and even vomiting. If you instill in a person that he wants to sleep, his eyelids become heavy and he really falls asleep.
The susceptibility to suggestion is different for different people and depends, among other things, on the degree of emotionality in general, on the strength of associations between words and emotions, as well as on the emotional state in which a person is at the moment and which is determined by his own motives. So, it is much easier for a person to convince that a bush in a dark forest is a lurking bandit if he is already frightened than if he is in a cheerful, carefree mood. It is much easier for a hungry person to suggest that the smell he smells is the smell of food than it is for a well-fed person. In the examples cited, the summation of the excitation of neurons corresponding to the unconditioned stimulus is clearly revealed with the simultaneous action of a weak conditioned signal and a weak unconditioned agent. Naturally, the same mechanism operates here as in the summation of the excitation of gnostic neurons through perception and through associations.

CONCLUSION AND CONCLUSIONS

In accordance with the considerations outlined in this chapter, the development of classical conditioned reflexes is nothing more than the formation of associations between an indifferent and biologically significant stimulus, that is, one that causes an external unconditioned response. In this case, the indifferent stimulus acquires the ability to elicit the same response as the unconditioned stimulus; this allows you to study the association in an objective and relatively accurate method. By definition, the classical conditioned reflex includes only those effects that are caused by a reinforcing agent, although it is not clear whether all or only part of the effects of an unconditioned stimulus can become conditioned reflex.
Since the main types of innate activity of the organism consist of preparatory reflexes (drives) and executive ones, the same is true for conditioned reflexes. Thus, conditioned food reflexes can be divided into conditioned hunger reflexes and conditioned reflexes to food, and defensive reflexes into conditioned fear reflexes and conditioned pain reflexes, etc.
The conditioned hunger reflex is based on the connections between the receiving neurons of the representation of the conditioned signal and the neurons of the representation of the drive of hunger, localized at the highest level of the emotive system. The conditioned reflex to food is based on connections between conditioned signal neurons and certain taste neurons. The main indicator of the conditioned reflex of hunger is motor restlessness, which can turn into an instrumental reaction if special training is carried out for this (see Chapter IX). The main indicator of the conditioned reflex to food is the secretion of saliva.
The unconditioned hunger reflex serves as an activating factor that ensures the formation of the conditioned hunger reflex, and for the conditioned reflex to food - the formed conditioned hunger reflex, which causes the simultaneous activation of neurons in the gnostic field of the conditioned signal and in the gnostic gnostic field.

Food, in addition to a specific unconditioned response, also induces the antidrive reflex of hunger, which inhibits the drive of hunger. The same applies to the conditioned reflex to food. As a result, the conditioned food signal and the conditioned hunger signal are usually represented by different stimulus objects. The conditioned signal of hunger is, as a rule, the entire environment associated with feeding and (or) the time of feeding, while the conditioned signal of food is usually a sporadic signal immediately preceding the unconditioned food stimulus. Both conditioned reflexes - the hunger reflex and the food reflex - often turn out to be intertwined, replacing each other in the presence of the same conditioned signal. If an indifferent stimulus is usually reinforced by the presentation of food during a short isolated action of the conditioned signal, then the conditioned reflex to food prevails over the conditioned reflex of hunger to such an extent that the animal, due to the absence of hunger, is reluctant to take food. If this stimulus is sometimes not reinforced with food, or if another similar conditioned agent is introduced, which is used without reinforcement, then the hunger drive increases. In general, it can be said that confidence in the appearance of food or any other attractive unconditioned stimulus in the presence of the conditioned signal tends to weaken the corresponding drive, making the animal relatively indifferent to the achievement of the goal. At the same time, insecurity, on the contrary, increases the drive and makes the goal more desirable. In fact, the entire courtship ritual, so common in both animals and humans, the purpose of which is to postpone sexual intercourse somewhat, leads to an increase in sexual desire and facilitates the subsequent executive sexual reflex. The problem of the relationship between sexual drive and the availability of a sexual goal is analyzed in detail in the monumental work of M. Proust (48).
The situation is somewhat different with respect to conditioned defensive reflexes, since a reinforcing harmful stimulus causes both an unconditioned fear reflex and an executive defensive unconditioned reflex. Therefore, both corresponding conditioned reflexes overlap each other in to a greater extent than with conditioned food reflexes. However, here, too, a long-acting stimulus, for example, an experimental setting, causes mainly (or even exclusively) a conditioned fear reflex, while a short stimulus preceding the harmful unconditioned stimulus also causes an executive conditioned reflex. The stronger the fear component in a given defensive conditioned reflex, the more stable and stronger the executive response, unless, of course, the conditioned fear reflex is strong enough to destroy the corresponding association between conditioned and unconditioned stimuli.
The usual development of conditioned reflexes leads not only to the formation of associations directed from the experimental setting and the sporadic signal to the unconditioned drive agent and the agent of the executive reflex, respectively, but also to the formation of associations of other types: 1) associations between the experimental setting and the conditioned signal; 2) associations between the unconditional drive agent and the conditioned signal (Fig. 51). Due to these associations, the excitability of neurons that perceive the conditioned signal increases during the experiment. That is why the same conditioned signal, given outside the experimental setting, elicits a weaker response or no response at all.

The magnitude of the classical conditioned reflexes depends on the intensity of activation in the gnostic fields involved in the formation of the conditioned reflex, on the strength of the reinforcing stimulus, and on the nature of the conditioned signal.
Numerous experiments have shown that the strength of a conditioned response caused by a given conditioned signal depends on its intensity, lack of monotony, and spatial coincidence with the unconditioned agent. In dogs, auditory conditioned signals are more effective than visual signals. All these facts find their explanation in the general properties of neuronal excitability and the effect of activation on them.

FIG. 51. Basic relationships between conditioned signals (CA), experimental setting (Exp. Obs.) And unconditioned agents of the executive (I) and drive reflex (D).
The best time regime for the formation of a conditioned reflex is a certain advance of the conditioned signal when it partially coincides with reinforcement. It is not clear, however, why the simultaneous presentation of a conditioned signal and unconditioned stimulation does not lead to the formation of a conditioned reflex. If, in the same setting, two stimuli are given in a random order, then mutual weak associations are formed between them. It is possible that overlap is a special case of this phenomenon.
Experiments with the removal of certain areas of the cortex, as well as of the entire neocortex, showed that although such damage impairs the ability to perceive conditioned signals and unconditioned stimuli, the ability to form conditioned reflexes, as such, remains. We propose a hypothesis according to which the gross perception of stimulus-objects is carried out by the basal ganglia; these ganglia are a primitive multi-analyzer system that makes connections primarily with the emotive brain. This explains why the destruction of the cortex can be detrimental to certain conditioned executive reflexes, but does not disturb the conditioned drive reflexes.
Experimental data concerning classical conditioned reflexes in animals shed light on analogous phenomena in humans. V Everyday life In humans, the following classical conditioned reflexes play an important role: 1) the conditioned reflex of hunger and the conditioned reflex to food; 2) conditioned drive reflexes and executive reflexes associated with other types of conservative activity (sexual behavior, sleep, defecation, etc.); 3) social conditioned reflexes, when acts of behavior of other people serve as unconditioned agents for a person, and people themselves become conditioned signals; 4) conditioned reflexes to printed and spoken words, which evoke images of the stimulus-objects described by words, evoking the corresponding conditioned reflexes. Suggestions are also based on this mechanism.

The formation and significance of conditioned reflexes is sufficient interesting question for consideration.

Conditioned Reflex Values

Once the scientist Pavlov divided all reflex reactions into 2 groups - conditioned and unconditioned reflexes.

The formation of conditioned reflexes occurs in the process of combining a conditioned stimulus with an unconditioned reflex. For this to happen, two conditions must be met:

1. The action of the conditioned stimulus must necessarily be somewhat preceded by the action of the unconditioned stimulus.
2. The conditioned stimulus is repeatedly reinforced by the influence of the unconditioned stimulus.

The environment is in constantly changing conditions, therefore, in order to preserve the vital activity of the organism and adaptive behavior, conditioned reflexes are needed, the impact of which is possible due to the participation of the cerebral hemispheres.

It should be noted that conditioned reflexes are not congenital, they are formed throughout life on the basis of unconditioned reflexes under the influence of some factors the environment... Such reflexes are individual, that is, in individuals of the same species, the same reflex may be absent in some, while in others it may be present.

The mechanism for the formation of conditioned reflexes is the process of establishing a temporary connection between 2 sources of excitation in the foci of the brain. They are constantly produced in higher animals, especially in humans. This can be explained by the dynamism of the environment, the constant change of living conditions, to which the nervous system must quickly adapt.

The biological significance of the conditioned reflex huge in the life of animals and humans - they provide adaptive behavior. Thanks to them, it is possible to accurately navigate in time and space, find food, avoid hazards and eliminate harmful effects for the body. The number of conditioned reflexes increases with age. In addition, behavioral experiences are acquired that help adult organisms better adapt to life.