What do conditioned reflexes give us? Conditioned and unconditioned reflexes - classification and types

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

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

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Human Anatomy: Conditioned Reflexes

Conditioned reflexes

Higher nervous activity

Subtitles

Formation of a conditioned reflex

To do this you need:

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

The mechanism of formation of conditioned reflexes

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

Types of conditioned reflexes

There are many classifications of conditioned reflexes:

• If we base the classification on without conditioned reflexes, then they distinguish between food, protective, indicative, etc.
• If the classification is based on the receptors on which the stimuli act, exteroceptive, interoceptive and proprioceptive conditioned reflexes are distinguished.
• Depending on the structure of the used conditioned stimulus, simple and complex (complex) conditioned reflexes are distinguished.
  In real conditions of the functioning of the body, as a rule, the conditioned signals are not individual, single stimuli, but their temporal and spatial complexes. And then the conditioned stimulus is a complex of environmental signals.
• There are conditioned reflexes of the first, second, third, etc. order. When a conditioned stimulus is reinforced by an unconditioned one, a first-order conditioned reflex is formed. A second-order conditioned reflex is formed if a conditioned stimulus is reinforced by a conditioned stimulus to which a conditioned reflex was previously developed.
• Natural reflexes are formed in response to stimuli that are natural, accompanying properties of the unconditional stimulus on the basis of which they are developed. Natural conditioned reflexes, compared to artificial ones, are easier to form and more durable.

Notes

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

Human behavior is associated with conditioned-unconditioned reflex activity and represents higher nervous activity, the result of which is a change in the relationship of the organism with the external environment.

Unlike the highest nervous activity lower nervous activity consists of a set of reactions aimed at unifying and integrating functions within the body.

Higher nervous activity manifests itself in the form of complex reflex reactions carried out when mandatory participation the cerebral cortex and the subcortical formations closest to it.

For the first time, the idea of ​​the reflex nature of brain activity was widely and in detail developed by the founder of Russian physiology I.M. Sechenov in his book “Reflexes of the Brain.” The ideological setting of this classic work is expressed in the original title, changed under the influence of censorship: “An attempt to introduce physiological basis into mental processes." Before I.M. Sechenov, physiologists and neurologists did not even dare to raise the question of the possibility of an objective, purely physiological analysis mental processes. The latter remained completely at the mercy of subjective psychology.

The ideas of I.M. Sechenov received brilliant development in the remarkable works of I.P. Pavlov, who opened the way for objective experimental research of the functions of the cerebral cortex and created a harmonious doctrine of higher nervous activity.

I.P. Pavlov showed that while in the underlying sections of the central nervous system- subcortical nuclei, brain stem, spinal cord - reflex reactions are carried out along innate, hereditarily fixed nerve pathways; in the cerebral cortex, nerve connections are developed and created in the process individual life animals and humans, as a result of a combination of countless irritations affecting the body.

The discovery of this fact made it possible to divide the entire set of reflex reactions occurring in the body into two main groups: unconditioned and conditioned reflexes.

Conditioned reflexes

• These are reactions acquired by the body in the process individual development based on "life experience"
• are individual: some representatives of the same species may have them, while others may not
• are unstable and, depending on certain conditions, they can develop, gain a foothold or disappear; this is their property and is reflected in their very name
• can be formed in response to a wide variety of stimuli applied to various receptive fields
• are closed at the level of the cortex. After removing the cerebral cortex, the developed conditioned reflexes disappear and only unconditioned ones remain.
• carried out through functional temporary connections

Conditioned reflexes are developed on the basis of unconditioned reflexes. For the formation of a conditioned reflex, a combination of times of any change is necessary external environment and the internal state of the body, perceived by the cerebral cortex, with the implementation of one or another unconditioned reflex. Only under this condition does a change in the external environment or internal state the body becomes a stimulus for a conditioned reflex - a conditioned stimulus, or signal. The irritation that causes an unconditioned reflex - unconditioned irritation - must, during the formation of a conditioned reflex, accompany the conditioned irritation and reinforce it.

For the formation of conditioned reflexes, it is necessary to create a temporary connection, a closure between the cortical cells that perceive conditioned stimulation and the cortical neurons that are part of the unconditioned reflex arc.

When conditioned and unconditioned stimulation coincide and combine, a connection is established between different neurons in the cerebral cortex and a process of closure occurs between them.

Unconditioned reflexes

• These are innate, hereditary reactions of the body
• are specific, i.e. characteristic of all representatives of a given species
• relatively constant, as a rule, persist throughout life
• carried out in response to adequate stimulation applied to one specific receptive field
• closes at the level of the spinal cord and brainstem
• are carried out through a phylogenetically fixed, anatomically expressed reflex arc.

It should be noted, however, that in humans and monkeys, who have a high degree of corticalization of functions, many complex unconditioned reflexes are carried out with the obligatory participation of the cerebral cortex. This is proven by the fact that its lesions in primates lead to pathological disorders unconditioned reflexes and the disappearance of some of them.

It should also be emphasized that not all unconditioned reflexes appear immediately at the time of birth. Many unconditioned reflexes, for example, those associated with locomotion and sexual intercourse, arise in humans and animals through long term after birth, but they certainly appear provided normal development nervous system.

The entire set of unconditioned and conditioned reflexes formed on their basis is accepted according to their functional significance divided into a number of groups.

1. By receptor
   1. Exteroceptive reflexes
      • visual
      • olfactory
      • flavoring, etc.
   2. Interoreceptive reflexes- reflexes in which the conditioned stimulus is irritation of receptors internal organs change chemical composition, temperature of internal organs, pressure in hollow organs and vessels
2. By effector trait, i.e. by those effectors that respond to stimulation
   1. autonomic reflexes
      • food
      • cardiovascular
      • respiratory, etc.
   2. somato-motor reflexes- manifested in movements of the whole organism or its individual parts in response to a stimulus
      • defensive
3. According to biological significance
   1. Food
      • reflex act of swallowing
      • reflexive act of chewing
      • reflex act of sucking
      • reflex act of salivation
      • reflex act of secretion of gastric and pancreatic juice, etc.
   2. Defensive- reactions to eliminate damaging and painful stimuli
   3. Genital- reflexes associated with sexual intercourse; This group also includes the so-called parental reflexes associated with feeding and nursing the offspring.
   4. Stato-kinetic and locomotor- reflex reactions of maintaining a certain position and movement of the body in space.
   5. Reflexes for maintaining homeostasis
      • thermoregulation reflex
      • breathing reflex
      • cardiac reflex
      • vascular reflexes that help maintain constancy blood pressure and etc.
   6. Orienting reflex- reflex to novelty. It occurs in response to any fairly quickly occurring fluctuation in the environment and is expressed externally in alertness, listening to a new sound, sniffing, turning the eyes and head, and sometimes the whole body towards the emerging light stimulus, etc. The implementation of this reflex provides better perception of the acting agent and has important adaptive significance.

      I. P. Pavlov figuratively called indicative reaction reflex "what is it?" This reaction is innate and does not disappear when complete removal cerebral cortex in animals; it is also observed in children with underdeveloped cerebral hemispheres - anencephals.

The difference between the orienting reflex and other unconditioned reflex reactions is that it fades away relatively quickly with repeated applications of the same stimulus. This feature of the orientation reflex depends on the influence of the cerebral cortex on it.

The above classification of reflex reactions is very close to the classification of various instincts, which are also divided into food, sexual, parental, and defensive. This is understandable due to the fact that, according to I.P. Pavlov, instincts are complex unconditioned reflexes. Their distinctive features is the chain nature of the reactions (the end of one reflex serves as the trigger for the next) and their dependence on hormonal and metabolic factors. Thus, the emergence of sexual and parental instincts is associated with cyclical changes in the functioning of the gonads, and the food instinct depends on those metabolic changes that develop in the absence of food. One of the features of instinctive reactions is also that they are characterized by many properties of the dominant.

The reflex component is a reaction to irritation (movement, secretion, change in breathing, etc.).

Most unconditioned reflexes are complex reactions that include several components. So, for example, with an unconditioned defensive reflex, caused in a dog by strong electrocutaneous irritation of the limb, along with defensive movements, breathing also increases and increases, cardiac activity accelerates, vocal reactions appear (squealing, barking), the blood system changes (leukocytosis, platelets and etc.). The food reflex also distinguishes between its motor (grasping food, chewing, swallowing), secretory, respiratory, cardiovascular and other components.

Conditioned reflexes, as a rule, reproduce the structure of the unconditioned reflex, since the conditioned stimulus excites the same nerve centers as the unconditioned one. Therefore, the composition of the components of the conditioned reflex is similar to the composition of the components of the unconditioned reaction.

Among the components of a conditioned reflex, there are main, specific for a given type of reflex, and secondary components. In the defensive reflex the main component is the motor component, in the food reflex the main component is the motor and secretory ones.

Changes in breathing, cardiac activity, vascular tone, accompanying the main components, are also important for the animal’s holistic reaction to the stimulus, but they play, as I. P. Pavlov said, “a purely service role.” Thus, increased and increased respiration, increased heart rate, increased vascular tone, caused by a conditioned defensive stimulus, contribute to increased metabolic processes in skeletal muscles and thereby create optimal conditions for the implementation of protective motor reactions.

When studying conditioned reflexes, the experimenter often chooses one of its main components as an indicator. That is why they talk about conditioned and unconditioned motor or secretory or vasomotor reflexes. It is necessary, however, to take into account that they represent only individual components of the body’s holistic reaction.

The biological significance of conditioned reflexes is that they make it possible to adapt much better and more accurately to the conditions of existence and to survive in these conditions.

As a result of the formation of conditioned reflexes, the body reacts not only directly to unconditioned stimuli, but also to the possibility of their action on it; reactions appear some time before unconditional irritation. In this way, the body is prepared in advance for the actions that it has to carry out in a given situation. Conditioned reflexes contribute to finding food, avoiding danger in advance, eliminating harmful effects and so on.

The adaptive significance of conditioned reflexes is also manifested in the fact that the precedence of conditioned stimulation by an unconditioned one strengthens the unconditioned reflex and accelerates its development.

Animal behavior is different shapes external, mainly motor activity aimed at establishing vital connections between the body and the environment. Animal behavior consists of conditioned, unconditioned reflexes and instincts. Instincts include complex unconditioned reactions, which, being innate, appear only during certain periods of life (for example, the instinct of nesting or feeding offspring). Instincts play a leading role in the behavior of lower animals. However, the higher an animal is at the evolutionary level, the more complex and varied its behavior, the more perfect and subtle it adapts to the environment, and the greater the role conditioned reflexes play in its behavior.

The environment in which animals exist is very variable. Adaptation to the conditions of this environment through conditioned reflexes will be subtle and accurate only if these reflexes are also changeable, that is, conditioned reflexes unnecessary in the new environmental conditions will disappear, and new ones will form in their place. The disappearance of conditioned reflexes occurs due to inhibition processes.

A distinction is made between external (unconditioned) inhibition of conditioned reflexes and internal (conditioned) inhibition.

External inhibition of conditioned reflexes occurs under the influence of extraneous stimuli that cause a new reflex reaction. This inhibition is called external because it develops as a result of processes occurring in areas of the cortex that are not involved in the implementation of this conditioned reflex.

Extremely strong or long-acting extraneous stimuli can cause extreme inhibition of reflexes.

Internal inhibition of conditioned reflexes occurs in the absence of reinforcement by an unconditioned stimulus of the received signal.

Internal inhibition does not occur immediately. As a rule, repeated use of a non-reinforced signal is required.

The fact that this is inhibition of the conditioned reflex, and not its destruction, is evidenced by the restoration of the reflex the next day, when the inhibition has passed. Various diseases, overwork, and overstrain cause a weakening of internal inhibition.

If a conditioned reflex is extinguished (not reinforced with food) for several days in a row, it may disappear completely.

There are several types of internal inhibition. The form of inhibition discussed above is called extinction inhibition. This inhibition underlies the disappearance of unnecessary conditioned reflexes.

Another type is differentiated (discriminating) inhibition.

A non-reinforced conditioned stimulus causes inhibition in the cortex and is called an inhibitory stimulus. Using the described technique, it was possible to determine the discriminative ability different organs feelings in animals.

The phenomenon of disinhibition. It is known that extraneous stimuli cause inhibition of conditioned reflexes. If an extraneous stimulus occurs during the action of an inhibitory stimulus, for example, during the action of a metronome at a frequency of 100 times per minute, as in the previous case, then this will cause the opposite reaction - saliva will flow. I.P. Pavlov called this phenomenon disinhibition and explained it by the fact that an extraneous stimulus, causing an orienting reflex, inhibits any other process that occurs in this moment in the centers of the conditioned reflex. If the inhibition process is inhibited, then all this leads to excitation and implementation of the conditioned reflex.

The phenomenon of disinhibition also indicates the inhibitory nature of the processes of discrimination and extinction of conditioned reflexes.

The meaning of conditional inhibition very large. Thanks to inhibition, a significantly better matching of the body's reaction is achieved external conditions, more perfectly adapting it to the environment. The combination of two forms of a single nervous process- excitation and inhibition - and their interaction enable the body to navigate in various difficult situations, are the conditions for the analysis and synthesis of stimuli.

Our nervous system is a complex mechanism of interaction between neurons that send impulses to the brain, and it, in turn, controls all organs and ensures their functioning. This process of interaction is possible due to the presence in humans of basic, inseparable acquired and innate forms of adaptation - conditioned and unconditioned reactions. A reflex is a conscious response of the body to certain conditions or stimuli. Such coordinated work of nerve endings helps us interact with the world around us. A person is born with a set of simple skills - this is called an example of such behavior: the ability of a baby to suckle at the mother's breast, swallow food, blink.

and animal

As soon as a living creature is born, it needs certain skills that will help ensure its life. The body actively adapts to the surrounding world, that is, it develops a whole complex of targeted motor skills. It is this mechanism that is called species behavior. Each living organism has its own set of reactions and innate reflexes, which is inherited and does not change throughout life. But behavior itself is distinguished by the method of its implementation and application in life: congenital and acquired forms.

Unconditioned reflexes

Scientists say that the innate form of behavior is an unconditioned reflex. An example of such manifestations is observed from the moment a person is born: sneezing, coughing, swallowing saliva, blinking. The transfer of such information is carried out by inheriting the parent program by the centers that are responsible for reactions to stimuli. These centers are located in the brain stem or spinal cord. Unconditioned reflexes help a person to quickly and accurately respond to changes in the external environment and homeostasis. Such reactions have a clear demarcation depending on biological needs.

• Food.
• Approximate.
• Protective.
• Sexual

Depending on the species, living beings have different reactions to the world, but all mammals, including humans, have a sucking habit. If you put a baby or young animal on the mother's nipple, a reaction will immediately occur in the brain and the feeding process will begin. This is an unconditioned reflex. Examples eating behavior are inherited by all creatures that receive nutrients with mother's milk.

Defensive reactions

These types of reactions to external stimuli are inherited and are called natural instincts. Evolution has given us the need to protect ourselves and take care of our safety in order to survive. Therefore, we have learned to instinctively react to danger; this is an unconditioned reflex. Example: Have you ever noticed how your head tilts when someone raises a fist over it? When you touch a hot surface, your hand jerks back. This behavior is also called unlikely that a person in his right mind would try to jump from a height or eat unfamiliar berries in the forest. The brain immediately starts the process of processing information that will make it clear whether it is worth risking your life. And even if it seems to you that you are not thinking about it, instinct immediately kicks in.

Try to bring your finger to the baby’s palm, and he will immediately try to grab it. Such reflexes have been developed over centuries, however, now a child does not really need such a skill. Even among primitive people, the baby clung to the mother, and that’s how she carried him. There are also unconscious innate reactions, which are explained by the connection of several groups of neurons. For example, if you hit your knee with a hammer, it will jerk - an example of a two-neuron reflex. In this case, two neurons come into contact and send a signal to the brain, forcing it to respond to an external stimulus.

Delayed reactions

However, not all unconditioned reflexes appear immediately after birth. Some arise as needed. For example, a newborn baby practically does not know how to navigate in space, but after about a couple of weeks he begins to respond to external stimuli - this is an unconditioned reflex. Example: the child begins to distinguish the mother’s voice, loud sounds, bright colors. All these factors attract his attention - an orientation skill begins to form. Involuntary attention is the starting point in the formation of an assessment of stimuli: the baby begins to understand that when the mother speaks to him and approaches him, most likely she will pick him up or feed him. That is, a person forms a complex form of behavior. His crying will attract attention to him, and he consciously uses this reaction.

Sexual reflex

But this reflex is unconscious and unconditional, it is aimed at procreation. It occurs during puberty, that is, only when the body is ready for procreation. Scientists say that this reflex is one of the strongest, it determines the complex behavior of a living organism and subsequently triggers the instinct to protect its offspring. Despite the fact that all these reactions are initially characteristic of humans, they are triggered in a certain order.

Conditioned reflexes

In addition to the instinctive reactions that we have at birth, a person needs many other skills to better adapt to the world around him. Acquired behavior is formed in both animals and people throughout life; this phenomenon is called “conditioned reflexes”. Examples: when you see food, salivation occurs; when you follow a diet, you feel hungry at a certain time of the day. This phenomenon is formed by a temporary connection between the center or vision) and the center of the unconditioned reflex. An external stimulus becomes a signal for a specific action. Visual images, sounds, smells can form lasting connections and give rise to new reflexes. When someone sees a lemon, salivation may begin, and when a strong smell or contemplation of an unpleasant picture occurs, nausea may occur - these are examples of conditioned reflexes in humans. Note that these reactions can be individual for each living organism; temporary connections are formed in the cerebral cortex and send a signal when an external stimulus occurs.

Throughout life, conditioned reactions can arise and also disappear. It all depends on For example, in childhood a child reacts to the sight of a bottle of milk, realizing that it is food. But when the baby grows up, this object will not form an image of food for him; he will react to a spoon and a plate.

Heredity

As we have already found out, unconditioned reflexes are inherited in every species of living beings. But conditioned reactions only affect complex human behavior, but are not passed on to descendants. Each organism “adapts” to a particular situation and the reality surrounding it. Examples of innate reflexes that do not disappear throughout life: eating, swallowing, reaction to the taste of a product. Conditioned stimuli change constantly depending on our preferences and age: in childhood, when a child sees a toy, he experiences joyful emotions; in the process of growing up, a reaction is caused by, for example, visual images films.

Animal reactions

Animals, like humans, have both unconditioned innate reactions and acquired reflexes throughout life. In addition to the instinct of self-preservation and food production, living beings also adapt to environment. They develop a reaction to the nickname (pets), and with repeated repetition, an attention reflex appears.

Numerous experiments have shown that it is possible to instill in a pet many reactions to external stimuli. For example, if you call your dog with a bell or a certain signal at each feeding, he will have a strong perception of the situation and he will immediately react. During the training process, rewarding a pet for following a command with a favorite treat forms a conditioned reaction; walking the dog and the sight of a leash signals an imminent walk, where he must relieve himself - examples of reflexes in animals.

Summary

The nervous system constantly sends many signals to our brain, and they shape the behavior of humans and animals. The constant activity of neurons allows us to perform habitual actions and respond to external stimuli, helping us better adapt to the world around us.

The term “reflex” was introduced by the French scientist R. Descartes in the 17th century. But for the sake of explanation mental activity it was applied by the founder of Russian materialistic physiology I.M. Sechenov. Developing the teachings of I.M. Sechenov. I. P. Pavlov experimentally studied the peculiarities of the functioning of reflexes and used the conditioned reflex as a method for studying higher nervous activity.

He divided all reflexes into two groups:

• unconditional;
• conditional.

Unconditioned reflexes

Unconditioned reflexes- innate reactions of the body to vital stimuli (food, danger, etc.).

They do not require any conditions for their production (for example, the release of saliva at the sight of food). Unconditioned reflexes are a natural reserve of ready-made, stereotypical reactions of the body. They arose as a result of the long evolutionary development of this animal species. Unconditioned reflexes are the same in all individuals of the same species. They are carried out using the spinal and lower parts of the brain. Complex complexes of unconditioned reflexes manifest themselves in the form of instincts.

Rice. 14. Location of some functional zones in the human cerebral cortex: 1 - zone of speech production (Broca's center), 2 - area of ​​the motor analyzer, 3 - zone of analysis of oral verbal signals (Wernicke's center), 4 - area auditory analyzer, 5 - analysis of written verbal signals, 6 - area visual analyzer

Conditioned reflexes

But the behavior of higher animals is characterized not only by innate, i.e., unconditioned reactions, but also by such reactions that are acquired by a given organism in the process of individual life activity, i.e. conditioned reflexes. The biological meaning of the conditioned reflex is that numerous external stimuli surrounding the animal in natural conditions and in themselves having no vital important, preceding food or danger in the animal’s experience, the satisfaction of other biological needs, begin to act as signals, by which the animal orients its behavior (Fig. 15).

So, the mechanism of hereditary adaptation is an unconditioned reflex, and the mechanism of individual variable adaptation is conditioned a reflex produced when vital phenomena are combined with accompanying signals.

Rice. 15. Scheme of formation of a conditioned reflex

• a - salivation is caused by an unconditioned stimulus - food;
• b - excitation from a food stimulus is associated with a previous indifferent stimulus (light bulb);
• c - the light of the light bulb became a signal possible appearance food: a conditioned reflex has developed to it

A conditioned reflex is developed on the basis of any of the unconditioned reactions. Reflexes on unusual signals, not found in a natural setting, are called artificial conditional. In laboratory conditions, it is possible to develop many conditioned reflexes to any artificial stimulus.

I. P. Pavlov associated with the concept of a conditioned reflex principle of signaling of higher nervous activity, principle of synthesis external influences and internal states.

Pavlov's discovery of the basic mechanism of higher nervous activity - the conditioned reflex - became one of the revolutionary achievements of natural science, a historical turning point in the understanding of the connection between the physiological and the mental.

The discovery began with the knowledge of the dynamics of formation and changes in conditioned reflexes complex mechanisms activities human brain, identification of patterns of higher nervous activity.

Unconditioned reflexes- These are innate, hereditarily transmitted reactions of the body. Conditioned reflexes- these are reactions acquired by the body in the process of individual development on the basis of “life experience”.

Unconditioned reflexes are specific, that is, characteristic of all representatives of a given species. Conditioned reflexes are individual: some representatives of the same species may have them, while others may not.

Unconditioned reflexes are relatively constant; conditioned reflexes are not constant and, depending on certain conditions, they can be developed, consolidated or disappear; This is their property and is reflected in their very name.

Unconditioned reflexes are carried out in response to adequate stimulation applied to one specific receptive field. Conditioned reflexes can be formed to a wide variety of stimuli applied to various receptive fields.

In animals with a developed cerebral cortex, conditioned reflexes are a function of the cerebral cortex. After removing the cerebral cortex, the developed conditioned reflexes disappear and only unconditioned ones remain. This indicates that in the implementation of unconditioned reflexes, in contrast to conditioned ones, the leading role belongs to the lower parts of the central nervous system - the subcortical nuclei, brain stem and spinal cord. It should be noted, however, that in humans and monkeys, who have a high degree of corticalization of functions, many complex unconditioned reflexes are carried out with the obligatory participation of the cerebral cortex. This is proven by the fact that its lesions in primates lead to pathological disorders of unconditioned reflexes and the disappearance of some of them.

It should also be emphasized that not all unconditioned reflexes appear immediately at the time of birth. Many unconditioned reflexes, for example, those associated with locomotion and sexual intercourse, arise in humans and animals a long time after birth, but they necessarily appear under the condition of normal development of the nervous system. Unconditioned reflexes are part of the fund of reflex reactions strengthened in the process of phylogenesis and hereditarily transmitted.

Conditioned reflexes are developed on the basis of unconditioned reflexes. For the formation of a conditioned reflex, it is necessary to combine in time some kind of change in the external environment or the internal state of the body, perceived by the cerebral cortex, with the implementation of one or another unconditioned reflex. Only under this condition does a change in the external environment or internal state of the body become a stimulus to a conditioned reflex - a conditioned stimulus, or signal. The irritation that causes an unconditioned reflex - unconditioned irritation - must, during the formation of a conditioned reflex, accompany the conditioned irritation and reinforce it.

In order for the clinking of knives and forks in the dining room or the knocking of a cup from which a dog is fed to cause salivation in the first case in a person, in the second case in a dog, it is necessary to re-coincidence of these sounds with food - reinforcement of stimuli that are initially indifferent to salivary secretion by feeding , i.e., unconditional irritation of the salivary glands. Likewise, the flashing of an electric light bulb in front of a dog’s eyes or the sound of a bell will only cause conditioned reflex flexion of the paw if they are repeatedly accompanied by electrical irritation of the skin of the leg, causing an unconditioned flexion reflex whenever it is used.

Similarly, a child’s crying and his hands pulling away from a burning candle will be observed only if the sight of the candle first coincided at least once with the feeling of a burn. In all the above examples, external agents that are initially relatively indifferent - the clinking of dishes, the sight of a burning candle, the flashing of an electric light bulb, the sound of a bell - become conditioned stimuli if they are reinforced by unconditioned stimuli. Only under this condition do the initially indifferent signals of the external world become stimuli for a certain type of activity.

For the formation of conditioned reflexes, it is necessary to create a temporary connection, a closure between the cortical cells that perceive conditioned stimulation and the cortical neurons that are part of the unconditioned reflex arc.