The term “reflex” was introduced by the French scientist R. Descartes in the 17th century. But to explain mental activity it was used 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. The 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 - area of ​​analysis of oral verbal signals (Wernicke's center), 4 - area of ​​the auditory analyzer, 5 - analysis of written verbal signals, 6 - visual analyzer area

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 that surround the animal in natural conditions and in themselves do not have vital significance, preceding in the animal’s experience food or danger, 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 of the possible appearance of food: a conditioned reflex was developed to it

A conditioned reflex is developed on the basis of any of the unconditioned reactions. Reflexes to unusual signals that do not occur in a natural environment are called artificial conditioned. 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, the principle of synthesis of 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.

Understanding the dynamics of formation and changes in conditioned reflexes began the discovery of complex mechanisms of human brain activity and the identification of patterns of higher nervous activity.

Unconditioned reflexes are constant innate reactions of the body to certain influences from the external world, carried out through the nervous system and do not require special conditions for their occurrence.

All unconditioned reflexes, according to the degree of complexity and severity of the body’s reactions, are divided into simple and complex; depending on the type of reaction - to food, sexual, defensive, orientation-exploratory, etc.; depending on the animal’s attitude to the stimulus - into biologically positive and biologically negative. Unconditioned reflexes arise mainly under the influence of contact irritation: food unconditioned reflex - when food enters and is exposed to the tongue; defensive - when pain receptors are irritated. However, the emergence of unconditioned reflexes is also possible under the influence of such stimuli as the sound, sight and smell of an object. Thus, the sexual unconditioned reflex occurs under the influence of a specific sexual stimulus (sight, smell and other stimuli emanating from a female or male). The approximate exploratory unconditioned reflex always occurs in response to a sudden, little-known stimulus and usually manifests itself in turning the head and moving the animal towards the stimulus. Its biological meaning lies in the examination of a given stimulus and the entire external environment.

Complex unconditioned reflexes include those that are cyclical in nature and are accompanied by various emotional reactions (see). Such reflexes are often referred to as (see).

Unconditioned reflexes serve as the basis for the formation of conditioned reflexes. Violation or distortion of unconditioned reflexes is usually associated with organic lesions of the brain; the study of unconditioned reflexes is carried out to diagnose a number of diseases of the central nervous system (see Pathological reflexes).

Unconditioned reflexes (specific, innate reflexes) are innate reactions of the body to certain influences of the external or internal environment, carried out through the central nervous system and not requiring special conditions for their occurrence. The term was introduced by I.P. Pavlov and means that the reflex certainly occurs if adequate stimulation is applied to a certain receptor surface. The biological role of unconditioned reflexes is that they adapt an animal of a given species in the form of appropriate acts of behavior to constant, habitual environmental factors.

The development of the doctrine of unconditioned reflexes is associated with the research of I. M. Sechenov, E. Pfluger, F. Goltz, S. S. Sherrington, V. Magnus, N. E. Vvedensky, A. A. Ukhtomsky, who laid the foundations for the next stage in the development of reflex theory, when it finally became possible to fill with physiological content the concept of a reflex arc, which previously existed as an anatomical and physiological scheme (see Reflexes). The undoubted condition that determined the success of these quests was the full awareness that the nervous system acts as a single whole, and therefore acts as a very complex formation.

The brilliant foresights of I.M. Sechenov about the reflex basis of mental activity of the brain served as a starting point for research, which, developing the doctrine of higher nervous activity, discovered two forms of neuro-reflex activity: unconditioned and conditioned reflexes. Pavlov wrote: “... we must admit the existence of two types of reflex. One reflex is ready-made, with which the animal is born, a purely conductive reflex, and the other reflex is constantly, continuously formed during individual life, with exactly the same pattern, but based on another property of our nervous system - closure. One reflex can be called innate, the other - acquired, and also, accordingly: one - specific, the other - individual. We called the innate, specific, constant, stereotypical unconditional, the other, since it depends on many conditions, constantly fluctuates depending on many conditions, we called conditional...”

The complex dynamics of the interaction of conditioned reflexes (see) and unconditioned reflexes is the basis of the nervous activity of humans and animals. The biological significance of unconditioned reflexes, as well as conditioned reflex activity, lies in the body’s adaptation to various kinds of changes in the external and internal environment. Such important acts as self-regulation of functions are based on the adaptive activity of unconditioned reflexes. The precise adaptation of unconditioned reflexes to the qualitative and quantitative characteristics of the stimulus, especially carefully studied in Pavlov’s laboratories using examples of the work of the digestive glands, made it possible to interpret the problem of the biological expediency of unconditioned reflexes materialistically, bearing in mind the exact correspondence of the function to the nature of the irritation.

The differences between unconditioned and conditioned reflexes are not absolute, but relative. Various experiments, in particular with the destruction of various parts of the brain, allowed Pavlov to create a general idea of ​​​​the anatomical basis of conditioned and unconditioned reflexes: “Higher nervous activity,” wrote Pavlov, “is composed of the activity of the cerebral hemispheres and the nearest subcortical nodes, representing the combined activity of these two most important parts of the central nervous system. These subcortical nodes are... centers of the most important unconditioned reflexes, or instincts: food, defensive, sexual, etc....". Pavlov’s stated views must now be recognized only as a diagram. His doctrine of analyzers (see) allows us to believe that the morphological substrate of unconditioned reflexes actually covers various parts of the brain, including the cerebral hemispheres, meaning the afferent representation of the analyzer from which this unconditioned reflex is evoked. In the mechanism of unconditioned reflexes, an important role belongs to feedback about the results and success of the action performed (P.K. Anokhin).

In the early years of the development of the doctrine of conditioned reflexes, individual students of Pavlov, who were studying salivary unconditioned reflexes, asserted their extreme stability and immutability. Subsequent studies showed the one-sidedness of such views. In Pavlov's own laboratory, a number of experimental conditions were found under which unconditioned reflexes changed even during one experiment. Subsequently, facts were presented indicating that it is more correct to talk about the variability of unconditioned reflexes than about their immutability. Important points in this regard are: the interaction of reflexes with each other (both unconditioned reflexes with each other, and unconditioned reflexes with conditioned ones), hormonal and humoral factors of the body, the tone of the nervous system and its functional state. These questions acquire particular importance in connection with the problem of instincts (see), which a number of representatives of the so-called ethology (the science of behavior) try to present as unchanged, independent of the external environment. Sometimes it is difficult to determine specific factors of variability of unconditioned reflexes, especially if it concerns the internal environment of the body (hormonal, humoral or interoceptive factors), and then some scientists fall into the error of speaking about spontaneous variability of unconditioned reflexes. Such adeterministic constructions and idealistic conclusions lead away from the materialistic understanding of the reflex.

I. P. Pavlov repeatedly emphasized the importance of systematization and classification of unconditioned reflexes, which serve as the foundation for the rest of the nervous activity of the body. The existing stereotyped division of reflexes into food, self-preservation, and sexual ones is too general and inaccurate, he pointed out. A detailed systematization and careful description of all individual reflexes are necessary. Speaking about systematization along with classification, Pavlov meant the need for a broad study of individual reflexes or their groups. The task should be recognized as both very important and very difficult, especially since Pavlov did not distinguish such complex reflexes as instincts from the series of unconditioned reflex phenomena. From this point of view, it is especially important to study already known ones and to find new and complex forms of reflex activity. Here we must pay tribute to this logical direction, which in a number of cases obtains facts of undoubted interest. However, the ideological basis of this trend, which fundamentally denies the reflex nature of instincts, remains completely unacceptable.

An unconditioned reflex “in its pure form” can manifest itself one or several times after the birth of an animal, and then in a fairly short time it is “overgrown” with conditioned and other unconditioned reflexes. All this makes it very difficult to classify unconditioned reflexes. Until now, it has not been possible to find a single principle for their classification. For example, A.D. Slonim based his classification on the principle of balancing the organism with the external environment and maintaining a constant composition of its internal environment. In addition, he identified groups of reflexes that do not ensure the preservation of an individual, but are important for the preservation of the species. The classification of unconditioned reflexes and instincts proposed by N. A. Rozhansky is extensive. It is based on biological and environmental characteristics and the dual (positive and negative) manifestation of the reflex. Unfortunately, Rozhansky’s classification suffers from a subjective assessment of the essence of the reflex, which is reflected in the names of some reflexes.

Systematization and classification of unconditioned reflexes should provide for their ecological specialization. Given the ecological adequacy of the stimuli and the biological training of the effector, a very subtle differentiation of unconditioned reflexes appears. The speed, strength, and the very possibility of forming a conditioned reflex depend not so much on the physical or chemical characteristics of the stimulus, but on the ecological adequacy of the stimulus and the unconditioned reflex.

The problem of the emergence and development of unconditioned reflexes is of great interest. I. P. Pavlov, A. A. Ukhtomsky, K. M. Bykov, P. K. Anokhin and others believed that unconditioned reflexes arise as conditioned, and subsequently become fixed in evolution and become innate.

Pavlov pointed out that new emerging reflexes, while maintaining the same living conditions in a number of successive generations, apparently continuously transform into permanent ones. This is probably one of the operating mechanisms for the development of an animal organism. Without recognizing this position, it is impossible to imagine the evolution of nervous activity. Nature cannot allow such wastefulness, said Pavlov, that each new generation would have to start everything from the very beginning. Transitional forms of reflexes that occupied an intermediate position between conditioned and unconditioned were found with great biological adequacy of the stimuli (V.I. Klimova, V.V. Orlov, A.I. Oparin, etc.). These conditioned reflexes did not fade away. See also Higher nervous activity.

Unconditioned and conditioned reflexes.

An element of higher nervous activity is a conditioned reflex. The path of any reflex forms a kind of arc, consisting of three main parts. The first part of this arc, which includes the receptor, sensory nerve and brain cell, is called the analyzer. This part perceives and distinguishes the entire complex of various external influences entering the body.

The cerebral cortex (according to Pavlov) is a collection of the brain ends of various analyzers. Stimuli from the external world arrive here, as well as impulses from the internal environment of the body, which causes the formation of numerous foci of excitation in the cortex, which, as a result of induction, cause points of inhibition. Thus, a kind of mosaic arises, consisting of alternating points of excitation and inhibition. This is accompanied by the formation of numerous conditioned connections (reflexes), both positive and negative. As a result, a certain functional dynamic system of conditioned reflexes is formed, which is the physiological basis of the psyche.

Two main mechanisms carry out higher nervous activity: conditioned reflexes and analyzers.

Each animal organism can exist only if it is constantly balanced (interacts) with the external environment. This interaction is carried out through certain connections (reflexes). I.P. Pavlov identified constant connections, or unconditioned reflexes. An animal or a person will be born with these connections - these are ready-made, constant, stereotypical reflexes. Unconditioned reflexes, such as the reflex for urination, defecation, sucking reflex in a newborn, salivation, are various forms of simple defensive reactions. Such reactions are constriction of the pupil to light, squinting of the eyelid, withdrawal of the hand during sudden irritation, etc. Complex unconditioned reflexes in humans include instincts: food, sexual, orientation, parental, etc. Both simple and complex unconditioned reflexes are innate mechanisms; they operate even at the lowest levels of development of the animal world. So, for example, the weaving of a web by a spider, the construction of honeycombs by bees, the nesting of birds, sexual desire - all these acts do not arise as a result of individual experience or learning, but are innate mechanisms.

However, the complex interaction of animals and humans with the environment requires the activity of a more complex mechanism.

In the process of adaptation to living conditions, another type of connections with the external environment is formed in the cerebral cortex - temporary connections, or conditioned reflexes. A conditioned reflex, according to Pavlov, is an acquired reflex, developed under certain conditions, and is subject to fluctuations. If not reinforced, it can weaken and lose its direction. Therefore, these conditioned reflexes are called temporary connections.

The main conditions for the formation of a conditioned reflex in its elementary form in animals are, firstly, the combination of a conditioned stimulus with unconditioned reinforcement and, secondly, the conditioned stimulus preceding the action of the unconditioned reflex. Conditioned reflexes are developed on the basis of unconditioned or on the basis of well-developed conditioned reflexes. In this case, they are called conditioned or conditioned reflexes of the second order. The material basis of unconditioned reflexes is the lower levels of the brain, as well as the spinal cord. Conditioned reflexes in higher animals and humans are formed in the cerebral cortex. Of course, in every nervous act it is impossible to clearly distinguish between the actions of unconditioned and conditioned reflexes: undoubtedly, they represent a system, although the nature of their formation is different. The conditioned reflex, being generalized at first, is then refined and differentiated. Conditioned reflexes as neurodynamic formations enter into certain functional relationships with each other, forming various functional systems, and are thus the physiological basis of thinking,

knowledge, skills, labor abilities.

To understand the mechanism of formation of a conditioned reflex in its elementary form in a dog, the well-known experience of I.P. Pavlov and his students (Fig. 56).

The essence of the experience is as follows. It is known that during the act of feeding, animals (in particular dogs) begin to secrete saliva and gastric juice. These are natural manifestations of the unconditioned food reflex. In the same way, when acid is poured into a dog’s mouth, saliva is released abundantly, washing away acid particles that irritate it from the mucous membranes of the mouth. This is also a natural manifestation of the defensive reflex, which in this case occurs through the salivary center in the medulla oblongata. However, under certain conditions, it is possible to force a dog to salivate to an indifferent stimulus, for example, the light of a light bulb, the sound of a horn, a musical tone, etc. To do this, before giving the dog food, light a lamp or ring a bell. If you combine this technique one or several times, and then use only one conditioned stimulus, without accompanying it with food, you can cause the dog to salivate in response to the action of an indifferent stimulus. What explains this? In the dog’s brain, during the period of action of a conditioned and unconditioned stimulus (light and food), certain areas of the brain come into a state of excitation, in particular the visual center and the center of the salivary gland (in the medulla oblongata). The food center, which is in a state of excitation, forms an excitation point in the cortex as a cortical representation of the center of the unconditioned reflex. Repeated combination of indifferent and unconditioned stimuli leads to the formation of an easier, “trodden” path. Between these points of excitation a chain is formed in which a number of irritated points are closed. In the future, it is enough to irritate only one link in a closed chain, in particular the visual center, and the entire developed connection will be activated, which will be accompanied by a secretory effect. Thus, a new connection was established in the dog’s brain - a conditioned reflex. The arc of this reflex closes between the cortical foci of excitation that arise as a result of the action of an indifferent stimulus and the cortical representations of the centers of unconditioned reflexes. However, this connection is temporary. Experiments have shown that for some time the dog will salivate only to the action of a conditioned stimulus (light, sound, etc.), but soon this reaction will stop. This will indicate that the connection has faded; True, it does not disappear without a trace, but only slows down. It can be restored again by combining feeding with the action of a conditioned stimulus; again it is possible to obtain salivation only in response to the action of light. This experience is elementary, but it is of fundamental importance.

The point is that the reflex mechanism is the main physiological mechanism in the brain not only of animals, but also of humans. However, the ways of formation of conditioned reflexes in animals and humans are not the same. The fact is that the formation of conditioned reflexes in humans is regulated by a special, uniquely human, second signaling system, which does not exist in the brain even of higher animals. The real expression of this second signaling system is the word, speech. Hence, the mechanical transfer of all laws obtained in animals to explain all higher nervous activity in humans will not be justified. I.P. Pavlov suggested observing “the greatest caution” in this matter. However, in general terms, the principle of the reflex and a number of basic laws of higher nervous activity in animals retain their significance for humans.

Students of I.P. Pavlova N.I. Krasnogorsky, A.G. Ivanov - Smolensky, N.I. Protopopov and others did a lot of research on conditioned reflexes in people, in particular in children. Therefore, material has now accumulated that allows us to make an assumption about the characteristics of higher nervous activity in various acts of behavior. For example, in the second signaling system, conditioned connections can be formed quickly and more firmly held in the cerebral cortex.

Let’s take for example a process that is close to us, such as teaching children to read and write. Previously, it was assumed that the basis of literacy acquisition (learning to read and write) was the development of special reading and writing centers. Now science denies the existence in the cerebral cortex of any local areas, anatomical centers, as if specialized in the area of ​​these functions. In the brains of people who have not mastered literacy, such centers do not naturally exist. However, how do these skills develop? What are the functional mechanisms of such completely new and real manifestations in the mental activity of a child who has mastered literacy? This is where the most correct idea would be that the physiological mechanism of literacy skills is the neural connections that form specialized systems of conditioned reflexes. These connections are not inherent in nature; they are formed as a result of the interaction of the student’s nervous system with the external environment. In this case, such an environment will be a classroom - a literacy lesson. The teacher, starting to teach literacy, shows the students on the appropriate tables or writes individual letters on the board, and the students copy them in their notebooks. The teacher not only shows letters (visual perception), but also pronounces certain sounds (auditory perception). As is known, writing is carried out by a certain movement of the hand, which is associated with the activity of the motor-kinesthetic analyzer. When reading, there is also a movement of the eyeball, which moves in the direction of the lines of the text being read. Thus, during the period of learning to read and write, the child’s cerebral cortex receives numerous irritations signaling the optical, acoustic and motor appearance of letters. This whole mass of irritation leaves nerve traces in the cortex, which are gradually balanced, reinforced by the teacher’s speech and the student’s own oral speech. As a result, a specialized system of conditional connections is formed, reflecting sound-letters and their combinations in various verbal complexes. This system - a dynamic stereotype - is the physiological basis of school literacy skills. It can be assumed that the formation of various labor skills is a consequence of the formation of neural connections that arise in the process of learning skills - through vision, hearing, tactile and motor receptors. At the same time, one must keep in mind the importance of innate inclinations, on which the nature and results of the development of a particular ability depend. All these connections, arising as a result of nervous stimulation, enter into complex relationships and form functional-dynamic systems, which are also the physiological basis of labor skills.

As is known from elementary laboratory experiments, a conditioned reflex that is not reinforced by food fades away, but does not disappear completely. We see something similar in people's lives. There are known facts when a person who learned to read and write, but then, due to life circumstances, did not have to deal with a book, largely lost the literacy skills he had once acquired. Who does not know such facts when the acquired skill in the field of theoretical knowledge or work skills, not supported by systematic work, is weakened. However, it does not disappear completely, and a person who has studied this or that skill, but then leaves it for a long period of time, only feels very insecure at first if he again has to return to his previous profession. However, it will relatively quickly restore the lost quality. The same can be said about people who once studied a foreign language, but then completely forgot it due to lack of practice; undoubtedly, it is easier for such a person, with appropriate practice, to again master the language than for another who will be learning a new language for the first time.

All this suggests that traces of past irritations remain in the cerebral cortex, but, not reinforced by exercise, they fade away (inhibited).

Analyzers

By analyzers we mean formations that carry out knowledge of the external and internal environment of the body. These are, first of all, taste, skin, and olfactory analyzers. Some of them are called distant (visual, auditory, olfactory) because they can perceive stimuli at a distance. The internal environment of the body also sends constant impulses to the cerebral cortex.

1-7 – receptors (visual, auditory, skin, olfactory, gustatory, motor system, internal organs). I – area of ​​the spinal cord or medulla oblongata where afferent fibers enter (A); impulses from which are transmitted to the neurons located here, forming the ascending pathways; the axons of the latter go to the area of ​​the visual hillocks (II); the axons of the nerve cells of the visual thalamus ascend into the cerebral cortex (III). At the top (III) the location of the nuclear parts of the cortical sections of various analyzers is outlined (for the internal, gustatory and olfactory analyzers, this location has not yet been precisely established); The scattered cells of each analyzer scattered throughout the cortex are also indicated (according to Bykov)

One of these analyzers is the motor analyzer, which receives impulses from skeletal muscles, joints, ligaments and reports to the cortex about the nature and direction of movement. There are other internal analyzers - interoceptors, which signal to the cortex about the state of the internal organs.

Each analyzer consists of three parts (Fig. 57). The peripheral end, i.e. receptor directly facing the external environment. These are the retina of the eye, the cochlear apparatus of the ear, sensitive devices of the skin, etc., which connect through the conducting nerves to the brain end, i.e. specific area of ​​the cerebral cortex. Hence, the occipital cortex is the cerebral end of the visual, the temporal – the auditory, the parietal – the cutaneous and muscular-articular analyzers, etc. In turn, the cerebral end, already in the cerebral cortex, is divided into a nucleus, where the most subtle analysis and synthesis of certain stimuli is carried out, and secondary elements located around the main nucleus and representing the analyzing periphery. The boundaries of these secondary elements between individual analyzers are fuzzy and overlap. In the analyzer periphery, similar analysis and synthesis are carried out only in the most elementary form. The motor area of ​​the cortex is the same analyzer of the skeletal-motor energy of the body, but its peripheral end faces the internal environment of the body. It is characteristic that the analyzing apparatus acts as an integral formation. Thus, the cortex, including numerous analyzers, itself is a grandiose analyzer of the external world and the internal environment of the body. Irritations entering certain cells of the cortex through the peripheral ends of the analyzers produce excitation in the corresponding cellular elements, which is associated with the formation of temporary nerve connections - conditioned reflexes.

Excitation and inhibition of nervous processes

The formation of conditioned reflexes is possible only when the cerebral cortex is in an active state. This activity is determined by the occurrence of basic nervous processes in the cortex - excitation and inhibition.

Excitation is an active process that occurs in the cellular elements of the cortex when it is exposed to certain stimuli from the external and internal environment through analyzers. The process of excitation is accompanied by a special state of nerve cells in one or another area of ​​the cortex, which is associated with the active activity of coupling devices (synapses) and the release of chemicals (transmitters) such as acetylcholine. In the area where foci of excitation occur, increased formation of nerve connections occurs - here a so-called active working field is formed.

Braking(detention) is also not a passive, but an active process. This process seems to forcibly restrain excitement. Braking is characterized by varying degrees of intensity. I.P. Pavlov attached great importance to the inhibitory process, which regulates the activity of excitation, “holds it in its fist.” He identified and studied several types, or forms, of the inhibitory process.

External inhibition is an innate mechanism, which is based on unconditioned reflexes, acts immediately (from the spot) and can suppress conditioned reflex activity. An example illustrating the effect of external inhibition was a fact, not uncommon in the laboratory, when the established conditioned reflex activity in dogs in response to the action of a conditioned stimulus (for example, salivation towards light) suddenly stopped as a result of some extraneous strong sounds, the appearance of a new face, etc. d. The indicative unconditioned reflex to novelty that arose in the dog inhibited the course of the developed conditioned reflex. In people's lives, we can often encounter similar facts, when intense mental activity associated with the performance of a particular work may be disrupted due to the appearance of some extra stimuli, for example, the appearance of new faces, loud conversation, some sudden noises and etc. External inhibition is called fading, because if the action of external stimuli is repeated many times, then the animal already “gets used” to them and they lose their inhibitory effect. These facts are well known in human practice. So, for example, some people get used to working in a difficult environment, where there are many external stimuli (work in noisy workshops, work as cashiers in large stores, etc.), causing the newcomer to feel confused.

Internal inhibition is an acquired mechanism based on the action of conditioned reflexes. It is formed in the process of life, education, work. This type of active inhibition is inherent only in the cerebral cortex. Internal inhibition has a twofold character. During the day, when the cerebral cortex is active, it is directly involved in the regulation of the excitatory process, is fractional in nature and, mixing with foci of excitation, forms the basis of the physiological activity of the brain. At night, this same inhibition radiates through the cerebral cortex and causes sleep. I.P. Pavlov in his work “Sleep and internal inhibition are the same process” emphasized this feature of internal inhibition, which, participating in the active work of the brain during the day, delays the activity of individual cells, and at night, spreading, irradiating throughout the cortex, causes inhibition of the entire cerebral cortex , which determines the development of physiological normal sleep.

Internal inhibition, in turn, is divided into extinction, delayed and differentiation. In well-known experiments on dogs, the mechanism of extinctive inhibition causes a weakening of the effect of a developed conditioned reflex when it is reinforced. However, the reflex does not disappear completely; it can reappear after some time and is especially easy with appropriate reinforcement, for example, food.

In humans, the process of forgetting is caused by a certain physiological mechanism - extinctive inhibition. This type of inhibition is very significant, since the inhibition of currently unnecessary connections contributes to the emergence of new ones. Thus, the desired sequence is created. If all formed connections, both old and new, were at the same optimal level, then rational mental activity would be impossible.

Delayed inhibition is caused by a change in the order of stimuli. Typically, in experience, a conditioned stimulus (light, sound, etc.) somewhat precedes an unconditioned stimulus, such as food. If you leave the conditioned stimulus aside for some time, i.e. lengthen the time of its action before giving the unconditioned stimulus (food), then as a result of such a change in the regime, the conditioned salivary reaction to light will be delayed by approximately the time for which the conditioned stimulus was left.

What causes the delay in the appearance of a conditioned reaction and the development of delay inhibition? The mechanism of delayed inhibition underlies such properties of human behavior as endurance, the ability to restrain one or another type of mental reactions that are inappropriate in the sense of reasonable behavior.

Differential inhibition is extremely important in the functioning of the cerebral cortex. This inhibition can dissect conditional connections down to the smallest details. Thus, dogs developed a salivary conditioned reflex to 1/4 of a musical tone, which was reinforced with food. When they tried to give 1/8 of the musical tone (the difference in acoustic terms is extremely insignificant), the dog did not salivate. Undoubtedly, in the complex and subtle processes of human mental and speech activity, which have chains of conditioned reflexes as their physiological basis, all types of cortical inhibition are of great importance, and among them, differentiation should be especially emphasized. The development of the finest differentiations of the conditioned reflex determines the formation of higher forms of mental activity - logical thinking, articulate speech and complex labor skills.

Protective (extraordinary) inhibition. Internal inhibition has various forms of manifestation. During the day it is fractional in nature and, mixing with foci of excitation, takes an active part in the activity of the cerebral cortex. At night, irradiating, it causes diffuse inhibition - sleep. Sometimes the cortex can be exposed to extremely strong stimuli, when the cells work to the limit and their further intense activity can lead to their complete exhaustion and even death. In such cases, it is advisable to turn off weakened and exhausted cells from work. This role is played by a special biological reaction of the nerve cells of the cortex, expressed in the development of an inhibitory process in those areas of the cortex whose cells have been weakened by super-strong stimuli. This type of active inhibition is called healing-protective or transcendental and is predominantly innate in nature. During the period when certain areas of the cortex are covered by extreme protective inhibition, weakened cells are switched off from active activity, and restoration processes occur in them. As the diseased areas normalize, the inhibition is removed, and those functions that were localized in these areas of the cortex can be restored. The concept of protective inhibition created by I.P. Pavlov, explains the mechanism of a number of complex disorders that occur in various nervous and mental diseases.

“We are talking about inhibition, which protects the cells of the cerebral cortex from the danger of further damage, or even death, and prevents a serious threat that arises when the cells are overexcited, in cases where they are forced to perform impossible tasks, in catastrophic situations, in exhaustion and weakening them under the influence of various factors. In these cases, inhibition occurs not in order to coordinate the activity of the cells of this higher part of the nervous system, but in order to protect and protect them" (E.A. Asratyan, 1951).

In cases observed in the practice of defectologists, such causative factors are toxic processes (neuroinfections) or skull injuries that cause weakening of nerve cells due to their exhaustion. A weakened nervous system is favorable soil for the development of protective inhibition in it. “Such a nervous system,” wrote I.P. Pavlov, “when encountering difficulties... or after unbearable excitement inevitably goes into a state of exhaustion. And exhaustion is one of the most important physiological impulses for the emergence of an inhibitory process as a protective process.”

Disciples and followers of I.P. Pavlova – A.G. Ivanov-Smolensky, E.A. Asratyan, A.O. Dolin, S.N. Davydenko, E.A. Popov and others attached great importance to further scientific developments related to clarifying the role of healing and protective inhibition in various forms of nervous pathology, first noted by I.P. Pavlov in the physiological analysis of schizophrenia and some other neuropsychiatric diseases.

Based on a number of experimental works carried out in his laboratories, E.A. Asratyan formulated three main provisions characterizing the significance of healing-protective inhibition as a protective reaction of nervous tissue under various harmful influences:

1) healing-protective inhibition belongs to the category of universal coordination properties of all nervous elements, to the category of general biological properties of all excitable tissues;

2) the process of protective inhibition plays the role of a healing factor not only in the cerebral cortex, but throughout the entire central nervous system;

3) the process of protective inhibition plays this role not only in functional, but also in organic lesions of the nervous system.

The concept of the role of healing-protective inhibition is particularly fruitful for the clinical and physiological analysis of various forms of nervous pathology. This concept makes it possible to more clearly imagine some complex clinical symptom complexes, the nature of which has long been a mystery.

Undoubtedly, the role of protective-healing inhibition in the complex system of brain compensation is great. It is one of the active physiological components that contribute to the development of compensatory processes.

The duration of the existence of healing-protective inhibition in individual areas of the cortex in the residual stage of the disease, apparently, can have different periods. In some cases it does not last long. This mainly depends on the ability of the affected cortical elements to recover. E.A. Asratyan points out that in such cases a peculiar combination of pathology and physiology occurs. In fact, on the one hand, the protective inhibitory process is healing, since turning off a group of cells from active work gives them the opportunity to “heal their wounds.” At the same time, the loss of a certain mass of nerve cells operating at a reduced level from the general cortical activity leads to a weakening of the performance of the cortex, to a decrease in individual abilities, and to peculiar forms of cerebral asthenia.

Applying this position to our cases, we can assume that some forms of undeveloped individual abilities in students who have suffered from a brain disease, for example, reading, writing, counting, as well as some types of speech deficiencies, weakening of memory, shifts in the emotional sphere are based on the presence stagnant inhibitory process, causing a violation of the mobility of general neurodynamics. Improvement in development, activation of weakened abilities, which is witnessed at school, occurs gradually, as individual areas of the cortical mass are released from inhibition. However, it would be an attempt to simplify to explain the noticeable improvements that occur in the condition of children who have suffered trauma, encephalitis, only by the gradual removal of protective inhibition.

Based on the very nature of this type of healing process, which is a unique form of self-medication of the body, it should be assumed that the removal of protective inhibition from certain areas of the cerebral cortex is associated with the simultaneous development of a whole complex of restorative processes (resorption of foci of hemorrhage, normalization of blood circulation, reduction of hypertension and a number of others ).

It is known that sleep usually does not occur immediately. Between sleep and wakefulness there are transitional periods, the so-called phase states, which cause drowsiness, which is some kind of threshold to sleep. Normally, these phases can be very short-lived, but in pathological conditions they are fixed for a long time.

Laboratory studies have shown that animals (dogs) react differently to external stimuli during this period. In this regard, special forms of phase states were identified. The equalizing phase is characterized by the same reaction to both strong and weak stimuli; during the paradoxical phase, weak stimuli produce a noticeable effect, and strong ones – an insignificant one, and during the ultraparadoxical phase, positive stimuli have no effect at all, and negative ones cause a positive effect. Thus, a dog in an ultraparadoxical phase turns away from food offered to it, but when the food is removed, it reaches for it.

Patients with certain forms of schizophrenia sometimes do not answer the questions of others asked in a normal voice, but they give an answer to a question addressed to them, asked in a whisper. The occurrence of phase states is explained by the gradual spread of the inhibitory process throughout the cerebral cortex, as well as the strength and depth of its effect on the cortical mass.

Natural sleep in the physiological sense is a diffuse inhibition in the cerebral cortex, extending to some of the subcortical formations. However, inhibition may be incomplete, then sleep will be partial. This phenomenon can be observed during hypnosis. Hypnosis is a partial sleep in which certain areas of the cortex remain excited, which determines the special contact between the doctor and the person being hypnotized. Various types of sleep treatments and hypnosis have become part of the therapeutic arsenal, especially in the clinic of nervous and mental diseases.

Irradiation, concentration and mutual induction of nerves

processes

Excitation and inhibition (retention) have special properties that naturally arise during the implementation of these processes. Irradiation is the ability of excitation or inhibition to spread, spread across the cerebral cortex. Concentration is the opposite property, i.e. the ability of nervous processes to gather and concentrate at any one point. The nature of irradiation and concentration depends on the strength of the stimulus. I.P. Pavlov pointed out that with weak irritation, irradiation of both irritating and inhibitory processes occurs, with irritants of medium strength - concentration, and with strong ones - irradiation again.

By mutual induction of nervous processes we mean the closest connection of these processes with each other. They constantly interact, conditioning each other. Emphasizing this connection, Pavlov figuratively said that excitation will give rise to inhibition, and inhibition will give rise to excitation. There are positive and negative induction.

These properties of the basic nervous processes are distinguished by a certain constancy of action, which is why they are called the laws of higher nervous activity. What do these laws established in animals provide for understanding the physiological activity of the human brain? I.P. Pavlov pointed out that it can hardly be disputed that the most general foundations of higher nervous activity, confined to the cerebral hemispheres, are the same in both higher animals and humans, and therefore the elementary phenomena of this activity should be the same in both . Undoubtedly, the application of these laws, adjusted for that special specific superstructure that is characteristic only of humans, namely the second signaling system, will help in the future to better understand the basic physiological patterns that operate in the human cerebral cortex.

The cerebral cortex is integrally involved in certain nervous acts. However, the degree of intensity of this participation in certain parts of the cortex is not the same and depends on which analyzer the person’s active activity is predominantly associated with in a given period of time. So, for example, if this activity for a given period is primarily associated with the visual analyzer in nature, then the leading focus (working field) will be localized in the region of the brain end of the visual analyzer. However, this does not mean that during this period only the visual center will work, and all other areas of the cortex will be turned off from activity. Everyday life observations prove that if a person is engaged in an activity primarily related to the visual process, such as reading, then he simultaneously hears sounds coming to him, the conversation of others, etc. However, this other activity - let's call it secondary - is carried out inactively, as if in the background. The areas of the cortex that are associated with side activities are, as it were, covered with a “haze of inhibition”; the formation of new conditioned reflexes there is limited for some time. When moving to an activity associated with another analyzer (for example, listening to a radio broadcast), the active field, the dominant focus, moves from the visual analyzer to the auditory one in the cerebral cortex, etc. More often, several active foci are simultaneously formed in the cortex, caused by external and internal stimuli of different nature. At the same time, these foci enter into interaction with each other, which may not be established immediately (“struggle of centers”). The active centers that have entered into interaction form a so-called “constellation of centers” or a functional-dynamic system, which for a certain period will be the dominant system (dominant, according to Ukhtomsky). When activity changes, this system is inhibited, and in other areas of the cortex another system is activated, which occupies a dominant position in order to again give way to other functional-dynamic formations that have replaced them, again associated with new activity caused by the entry into the cortex of new stimuli from the external and internal environment. Such an alternation of points of excitation and inhibition, due to the mechanism of mutual induction, is accompanied. the formation of numerous chains of conditioned reflexes and represents the basic mechanisms of brain physiology. The dominant focus, the dominant, is the physiological mechanism of our consciousness. However, this point does not remain in one place, but moves along the cerebral cortex depending on the nature of human activity, mediated by the influence of external and internal stimuli.

Systematicity in the cerebral cortex

(dynamic stereotype)

The various irritations acting on the cortex are diverse in the nature of their influence: some have only an approximate value, others form neural connections, which are initially in a somewhat chaotic state, then are balanced by the inhibitory process, refined and form certain functional-dynamic systems. The stability of these systems depends on certain conditions of their formation. If the complex of acting irritations acquires some periodicity and the irritations arrive in a certain order over a certain time, then the developed system of conditioned reflexes is more stable. I.P. Pavlov called this system a dynamic stereotype.

Thus, a dynamic stereotype is a developed
a balanced system of conditioned reflexes that perform

specialized functions. The development of a stereotype is always associated with a certain nervous labor. However, after the formation of a certain dynamic system, the performance of functions is greatly facilitated.

The significance of the developed functional-dynamic system (stereotype) is well known in the practice of life. All our habits, skills, and sometimes certain forms of behavior are determined by the developed system of nervous connections. Any change or violation of a stereotype is always painful. Everyone knows from life how difficult it is sometimes to perceive a change in lifestyle, habitual forms of behavior (breaking a stereotype), especially for older people.

The use of systematic cortical functions is extremely important in the upbringing and education of children. Reasonable, but steady and systematic presentation of a number of specific requirements to the child determines the strong formation of a number of general cultural, sanitary-hygienic and labor skills.

The question of the strength of knowledge is sometimes a sore point for schools. The teacher’s knowledge of the conditions under which a more stable system of conditioned reflexes is formed also ensures the students’ strong knowledge.

It is often necessary to observe how an inexperienced teacher, not taking into account the possibilities that the higher nervous activity of students, especially in special schools, has, leads the lesson incorrectly. When forming any school skill, it gives too many new irritations, and chaotically, without the necessary sequence, without dosing the material and without making the necessary repetitions.

So, for example, while explaining to children the rules for dividing multi-digit numbers, such a teacher suddenly gets distracted at the moment of explanation and remembers that this or that student did not bring a certificate of illness. Such inappropriate words, by their nature, are a kind of extra-irritant: they interfere with the correct formation of specialized systems of connections, which then turn out to be unstable and are quickly erased by time.

Dynamic localization of functions in the cortex

hemispheres

In constructing his scientific concept of localization of functions in the cerebral cortex, I.P. Pavlov proceeded from the basic principles of reflex theory. He believed that neurodynamic physiological processes occurring in the cortex necessarily have a root cause in the external or internal environment of the body, i.e. they are always deterministic. All nervous processes are distributed among the structures and systems of the brain. The leading mechanism of nervous activity is analysis and synthesis, which provide the highest form of adaptation of the body to environmental conditions.

Without denying the different functional significance of individual areas of the cortex, I.P. Pavlov substantiated a broader interpretation of the concept of “center”. On this occasion, he wrote: “And now it is still possible to remain within the limits of previous ideas about the so-called centers in the central nervous system. To do this, it would only be necessary to add a physiological point of view to the exclusive, as before, anatomical point of view, allowing for unification through a special well-trodden connections and paths of different parts of the central nervous system to perform a certain reflex act.”

The essence of the new additions made by I.P. Pavlov’s teaching on the localization of functions was, first of all, that he considered the main centers not only as local areas of the cortex, on which the performance of various functions, including mental ones, depends. The formation of centers (analyzers, according to Pavlov) is much more complicated. The anatomical region of the cortex, characterized by a unique structure, represents only a special background, the basis on which certain physiological activities develop, caused by the influence of various irritations of the external world and the internal environment of the body. As a result of this influence, nervous connections (conditioned reflexes) arise, which, gradually balancing, form certain specialized systems - visual, auditory, olfactory, gustatory, etc. Thus, the formation of the main centers occurs according to the mechanism of conditioned reflexes formed as a result of the interaction of the organism with the external environment.

The importance of the external environment in the formation of receptors has long been noted by evolutionary scientists. Thus, it was known that some animals living underground, where the sun’s rays do not reach, had underdevelopment of the visual organs, for example, moles, shrews, etc. The mechanical concept of the center as a narrow-local area in the new physiology was replaced by the concept of an analyzer - a complex device, providing cognitive activity. This device combines both anatomical and physiological components, and its formation is due to the indispensable participation of the external environment. As mentioned above, I.P. Pavlov identified a central part at the cortical end of each analyzer - the nucleus, where the accumulation of receptor elements of this analyzer is especially dense and which correlates with a certain area of ​​the cortex.

The core of each analyzer is surrounded by an analyzer periphery, the boundaries of which with neighboring analyzers are unclear and may overlap each other. The analyzers are closely interconnected by numerous connections that determine the closure of conditioned reflexes due to alternating phases of excitation and inhibition. Thus, the entire complex cycle of neurodynamics, proceeding according to certain patterns, represents a tuphysiological “canvas” on which a “pattern” of mental functions arises. In this regard, Pavlov denied the presence in the cortex of so-called mental centers (attention, memory, character, will, etc.), as if connected with certain local areas in the cerebral cortex. The basis of these mental functions are different states of the basic nervous processes, which also determine the different nature of conditioned reflex activity. So, for example, attention is a manifestation of the concentration of the excitatory process, in connection with which the formation of the so-called active or working field occurs. However, this center is dynamic, it moves depending on the nature of human activity, hence visual, auditory attention, etc. Memory, which usually means the ability of our cortex to store past experience, is also determined not by the presence of an anatomical center (memory center), but represents a combination numerous nerve traces (trace reflexes) that arose in the cortex as a result of stimuli received from the external environment. Due to constantly changing phases of excitation and inhibition, these connections can be activated, and then the necessary images appear in consciousness, which are inhibited when unnecessary. The same should be said about the so-called “supreme” functions, which usually included the intellect. This complex function of the brain was previously exclusively correlated with the frontal lobe, which was considered to be the only carrier of mental functions (the center of the mind).

In the 17th century the frontal lobes were seen as a thought factory. In the 19th century the frontal brain was recognized as an organ of abstract thinking, a center of spiritual concentration.

Intelligence, a complex integral function, arises as a result of the analytical and synthetic activity of the cortex as a whole and, of course, cannot depend on individual anatomical centers in the frontal lobe. However, clinical observations are known when damage to the frontal lobe causes sluggishness of mental processes, apathy, and motor initiative suffers (according to Lhermit). The tracts observed in clinical practice led to views on the frontal lobe as the main center for the localization of intellectual functions. However, analysis of these phenomena in the aspect of modern physiology leads to other conclusions. The essence of the pathological changes in the psyche observed in the clinic with damage to the frontal lobes is not due to the presence of special “mental centers” affected as a result of the disease. This is about something else. Mental phenomena have a certain physiological basis. This is a conditioned reflex activity that occurs as a result of alternating phases of excitatory and inhibitory processes. In the frontal lobe there is a motor analyzer, which is presented in the form of a nucleus and scattered periphery. The importance of the motor analyzer is extremely important. It regulates motor movements. Disruption of the motor analyzer due to various reasons (deterioration of blood supply, skull injury, brain tumor, etc.) may be accompanied by the development of a kind of pathological inertia in the formation of motor reflexes, and in severe cases, their complete blocking, which leads to various movement disorders (paralysis, lack of motor coordination ). Disorders of conditioned reflex activity are based on insufficiency of general neurodynamics; in them, the mobility of nervous processes is disrupted, and stagnant inhibition occurs.” All this, in turn, is reflected in the nature of thinking, the physiological basis of which is conditioned reflexes. A kind of rigidity of thinking, lethargy, lack of initiative arises - in a word, the whole complex of mental changes that were observed in the clinic in patients with damage to the frontal lobe and which were previously interpreted as the result of a disease of individual local points that carry “supreme” functions. The same should be said about the essence of speech centers. The lower parts of the frontal region of the dominant hemisphere, which regulate the activity of the speech organs, are separated into the speech motor analyzer. However, this analyzer also cannot be mechanically considered as a narrow local center of motor speech. Here only the highest analysis and synthesis of all speech reflexes coming from all other analyzers is carried out.

It is known that I.P. Pavlov emphasized the unity of the somatic and mental in the whole organism. In the studies of academician K.M. Bykov, the connection between the cortex and internal organs was experimentally confirmed. Currently, the so-called interoreceptor analyzer is located in the cerebral cortex, which receives signals about the state of internal organs. This area of ​​the cortex is conditionally reflexively connected with the entire internal structure of our body. Facts from everyday life confirm this connection. Who does not know such facts when mental experiences are accompanied by various sensations from the internal organs? So, with excitement or fear, a person usually turns pale, often experiences an unpleasant sensation from the heart (“the heart sinks”) or from the gastrointestinal tract, etc. Corticovisceral connections have bilateral information. Hence, the primarily impaired activity of internal organs, in turn, can have a depressing effect on the psyche, causing anxiety, lowering mood, and limiting ability to work. The establishment of corticovisceral connections is one of the important achievements of modern physiology and is of great importance for clinical medicine.

Centers and activities can be considered in the same aspect
which were usually associated with the management of individual skills and labor
skills, such as writing, reading, counting, etc. These centers in the past also
were interpreted as local areas of the cortex with which graphical
and lexical functions. However, this idea from the standpoint of modern
physiology also cannot be accepted. In humans, as mentioned above, from
birth, there are no special cortical centers for writing and reading formed by specialized elements. These acts are specialized systems of conditioned reflexes that are gradually formed during the learning process.

However, how can we understand the facts that at first glance may confirm the presence of local cortical centers for reading and writing in the cortex? We are talking about observations of writing and reading disorders with damage to certain areas of the parietal lobe cortex. For example, dysgraphia (writing disorder) more often occurs when field 40 is affected, and dyslexia (reading disorder) most often occurs when field 39 is affected (see Fig. 32). However, it is wrong to believe that these fields are the direct centers of the described functions. The modern interpretation of this issue is much more complicated. The writing center is not only a group of cellular elements on which the specified function depends. The basis of writing skill is a developed system of neural connections. The formation of this specialized system of conditioned reflexes, which represent the physiological basis of the writing skill, occurs in those areas of the cortex where the corresponding junction of pathways occurs that connect a number of analyzers involved in the formation of this function. For example, to perform the function of writing, the participation of at least three receptor components is necessary - visual, auditory, kinesthetic and motor. Obviously, at certain points in the cortex of the parietal lobe, the closest combination of associative fibers occurs, connecting a number of analyzers involved in the act of writing. It is here that the closure of neural connections occurs, forming a functional system - a dynamic stereotype, which is the physiological basis of this skill. The same applies to field 39, associated with the reading function. As is known, the destruction of this area is often accompanied by alexia.

Thus, the reading and writing centers are not anatomical centers in a narrow local sense, but dynamic (physiological), although they arise in certain cortical structures. Under pathological conditions, during inflammatory, traumatic and other processes, systems of conditioned connections can quickly disintegrate. We are talking about aphasic, lexical and graphic disorders that develop after brain disorders, as well as the breakdown of complex movements.

In cases of optimal excitability of a particular point, the latter becomes dominant for some time and other points that are in a state of less activity are attracted to it. Between them, paths are paved and a unique dynamic system of working centers (dominant) is formed, performing one or another reflex act, as mentioned above.

It is characteristic that the modern doctrine of the localization of functions in the cerebral cortex is based on anatomical and physiological correlations. Now the idea that the entire cerebral cortex is divided into many isolated anatomical centers that are associated with the performance of motor, sensory and even mental functions will seem naive. On the other hand, it is also undeniable that all these elements are combined at any given moment into a system where each of the elements interacts with all the others.

Thus, the principle of functional unification of centers into certain working systems, in contrast to narrow static localization, is a new characteristic addition to the old doctrine of localization, which is why it received the name dynamic localization of functions.

A number of attempts have been made to develop the provisions expressed by I.P. Pavlov, in connection with the question of dynamic localization of functions. The physiological nature of the reticular formation as a tonic apparatus for cortical processes was clarified. Finally, and most importantly, ways were identified to explain the connections that exist between higher mental processes (as a complex product of socio-historical development) and their physiological basis, which was reflected in the works of L.S. Vygotsky, A.N. Leontyeva, A.R. Luria et al. “If higher mental functions are complexly organized functional systems, social in their genesis, then any attempt to localize them in special narrowly limited areas of the cerebral cortex, or centers, is even more unjustified than” an attempt to look for narrowly limited “centers” “for biological functional systems... Therefore, we can assume that the material basis of higher mental processes is the entire brain as a whole, but as a highly differentiated system, the parts of which provide different aspects of the whole.”

Reflex– the body’s response is not an external or internal irritation, carried out and controlled by the central nervous system. The development of ideas about human behavior, which has always been a mystery, was achieved in the works of Russian scientists I. P. Pavlov and I. M. Sechenov.

Reflexes unconditioned and conditioned.

Unconditioned reflexes- These are innate reflexes that are inherited by offspring from their parents and persist throughout a person’s life. The arcs of unconditioned reflexes pass through the spinal cord or brain stem. The cerebral cortex is not involved in their formation. Unconditioned reflexes are provided only to those environmental changes that have often been encountered by many generations of a given species.

These include:

Food (salivation, sucking, swallowing);
Defensive (coughing, sneezing, blinking, withdrawing your hand from a hot object);
Approximate (squinting eyes, turns);
Sexual (reflexes associated with reproduction and care of offspring).
The importance of unconditioned reflexes lies in the fact that thanks to them the integrity of the body is preserved, constancy is maintained and reproduction occurs. Already in a newborn child the simplest unconditioned reflexes are observed.
The most important of these is the sucking reflex. The stimulus of the sucking reflex is the touching of an object to the child’s lips (mother’s breast, pacifier, toy, finger). The sucking reflex is an unconditioned food reflex. In addition, the newborn already has some protective unconditioned reflexes: blinking, which occurs if a foreign body approaches the eye or touches the cornea, constriction of the pupil when exposed to strong light on the eyes.

Particularly pronounced unconditioned reflexes in various animals. Not only individual reflexes can be innate, but also more complex forms of behavior, which are called instincts.

Conditioned reflexes– these are reflexes that are easily acquired by the body throughout life and are formed on the basis of an unconditioned reflex under the action of a conditioned stimulus (light, knock, time, etc.). I.P. Pavlov studied the formation of conditioned reflexes in dogs and developed a method for obtaining them. To develop a conditioned reflex, a stimulus is needed - a signal that triggers the conditioned reflex; repeated repetition of the action of the stimulus allows you to develop a conditioned reflex. During the formation of conditioned reflexes, a temporary connection arises between the centers and the centers of the unconditioned reflex. Now this unconditioned reflex is not carried out under the influence of completely new external signals. These stimuli from the surrounding world, to which we were indifferent, can now acquire vital significance. Throughout life, many conditioned reflexes are developed that form the basis of our life experience. But this vital experience has meaning only for a given individual and is not inherited by its descendants.

In a separate category conditioned reflexes distinguish motor conditioned reflexes developed during our lives, i.e. skills or automated actions. The meaning of these conditioned reflexes is to master new motor skills and develop new forms of movements. During his life, a person masters many special motor skills related to his profession. Skills are the basis of our behavior. Consciousness, thinking, and attention are freed from performing those operations that have become automated and become skills of everyday life. The most successful way to master skills is through systematic exercises, correcting errors noticed in time, and knowing the ultimate goal of each exercise.

If you do not reinforce the conditioned stimulus with the unconditioned stimulus for some time, then inhibition of the conditioned stimulus occurs. But it doesn't disappear completely. When the experience is repeated, the reflex is restored very quickly. Inhibition is also observed when exposed to another stimulus of greater strength.

Conditioned reflexes are reactions of the whole organism or any part of it to external or internal stimuli. They manifest themselves through the disappearance, weakening or strengthening of certain activities.

Conditioned reflexes are the body’s assistants, allowing it to quickly respond to any changes and adapt to them.

Story

The idea of ​​a conditioned reflex was first put forward by the French philosopher and scientist R. Descartes. Somewhat later, the Russian physiologist I. Sechenov created and experimentally proved a new theory regarding the reactions of the body. For the first time in the history of physiology, it was concluded that conditioned reflexes are a mechanism that is activated not only; the entire nervous system is involved in its work. This allows the body to maintain a connection with the environment.

Studied by Pavlov. This outstanding Russian scientist was able to explain the mechanism of action of the cerebral cortex and cerebral hemispheres. At the beginning of the 20th century, he created the theory of conditioned reflexes. This scientific work became a real revolution in physiology. Scientists have proven that conditioned reflexes are reactions of the body that are acquired throughout life, based on unconditioned reflexes.

Instincts

Certain reflexes of the unconditioned type are characteristic of each type of living organism. They are called instincts. Some of them are quite complex. An example of this would be bees making honeycombs or birds making nests. Thanks to the presence of instincts, the body is able to optimally adapt to environmental conditions.

They are congenital. They are inherited. In addition, they are classified as species, since they are characteristic of all representatives of a certain species. Instincts are permanent and persist throughout life. They manifest themselves in response to adequate stimuli that are applied to a specific single receptive field. Physiologically, unconditioned reflexes are closed in the brainstem and at the level of the spinal cord. They manifest themselves through anatomically expressed

As for monkeys and humans, the implementation of most of the complex unconditioned reflexes is impossible without the participation of the cerebral cortex. When its integrity is violated, pathological changes in unconditioned reflexes occur, and some of them simply disappear.

Classification of instincts

Unconditioned reflexes are very strong. Only under certain conditions, when their manifestation becomes unnecessary, can they disappear. For example, the canary, domesticated about three hundred years ago, does not currently have the instinct to build nests. The following types of unconditioned reflexes are distinguished:

Which is the body's reaction to a variety of physical or chemical stimuli. Such reflexes, in turn, can manifest locally (withdrawal of the hand) or be complex (flight from danger).
- Food instinct, which is caused by hunger and appetite. This unconditioned reflex includes a whole chain of sequential actions - from searching for prey to attacking it and further eating it.
- Parental and sexual instincts associated with the maintenance and reproduction of the species.

A comfortable instinct that serves to keep the body clean (bathing, scratching, shaking, etc.).
- Orienting instinct, when the eyes and head are turned towards the stimulus. This reflex is necessary to preserve life.
- The instinct of freedom, which is especially clearly expressed in the behavior of animals in captivity. They constantly want to break free and often die, refusing water and food.

The emergence of conditioned reflexes

During life, acquired reactions of the body are added to the inherited instincts. They are called conditioned reflexes. They are acquired by the body as a result of individual development. The basis for obtaining conditioned reflexes is life experience. Unlike instincts, these reactions are individual. They may be present in some members of the species and absent in others. In addition, a conditioned reflex is a reaction that may not persist throughout life. Under certain conditions, it is produced, consolidated, and disappears. Conditioned reflexes are reactions that can occur to various stimuli applied to different receptor fields. This is their difference from instincts.

The mechanism of the conditioned reflex closes at the level. If it is removed, then only instincts will remain.

The formation of conditioned reflexes occurs on the basis of unconditioned ones. To carry out this process, a certain condition must be met. In this case, any change in the external environment must be combined in time with the internal state of the body and perceived by the cerebral cortex with a simultaneously carried out unconditional reaction of the body. Only in this case does a conditioned stimulus or signal appear that contributes to the emergence of a conditioned reflex.

Examples

For the body’s reaction to occur, such as the release of saliva when knives and forks clink, as well as when an animal’s feeding cup is knocked (in humans and dogs, respectively), an indispensable condition is the repeated coincidence of these sounds with the process of providing food.

In the same way, the sound of a bell or the turning on of a light bulb will cause the dog's paw to flex if these phenomena have repeatedly occurred accompanied by electrical stimulation of the animal's leg, as a result of which an unconditioned type of flexion reflex appears.

The conditioned reflex is the child's hands being pulled away from the fire and subsequent crying. However, these phenomena will only occur if the type of fire, even once, coincides with a burn.

Reaction components

The body's reaction to irritation is a change in breathing, secretion, movement, etc. As a rule, unconditioned reflexes are quite complex reactions. That is why they contain several components at once. For example, the defensive reflex is accompanied not only by defensive movements, but also by increased breathing, accelerated activity of the heart muscle, and changes in blood composition. In this case, vocal reactions may also appear. As for the food reflex, there are also respiratory, secretory and cardiovascular components.

Conditioned reactions usually reproduce the structure of unconditioned ones. This occurs due to the stimulation of the same nerve centers by stimuli.

Classification of conditioned reflexes

The responses acquired by the body to various stimuli are divided into types. Some of the existing classifications are of great importance in solving not only theoretical, but also practical problems. One of the areas of application of this knowledge is sports activities.

Natural and artificial reactions of the body

There are conditioned reflexes that arise under the action of signals characteristic of the constant properties of unconditioned stimuli. An example of this is the sight and smell of food. Such conditioned reflexes are natural. They are characterized by rapid production and great durability. Natural reflexes, even in the absence of subsequent reinforcement, can be maintained throughout life. The importance of the conditioned reflex is especially great in the very first stages of an organism’s life, when it adapts to the environment.
However, reactions can also be developed to a variety of indifferent signals, such as smell, sound, temperature changes, light, etc. Under natural conditions, they are not irritants. It is precisely such reactions that are called artificial. They are developed slowly and, in the absence of reinforcement, quickly disappear. For example, artificial conditioned human reflexes are reactions to the sound of a bell, touching the skin, weakening or increasing lighting, etc.

First and highest order

There are types of conditioned reflexes that are formed on the basis of unconditioned ones. These are first order reactions. There are also higher categories. Thus, reactions that are developed on the basis of already existing conditioned reflexes are classified as higher-order reactions. How do they arise? When developing such conditioned reflexes, the indifferent signal is reinforced with well-learned conditioned stimuli.

For example, irritation in the form of a bell is constantly reinforced by food. In this case, a first-order conditioned reflex is developed. On its basis, a reaction to another stimulus, for example, to light, can be fixed. This will become a conditioned reflex of the second order.

Positive and negative reactions

Conditioned reflexes can influence the activity of the body. Such reactions are considered positive. The manifestation of these conditioned reflexes can be secretory or motor functions. If there is no activity of the body, then the reactions are classified as negative. For the process of adaptation to constantly changing environmental conditions, both one and the second species are of great importance.

At the same time, there is a close relationship between them, since when one type of activity is manifested, the other is certainly suppressed. For example, when the command “Attention!” is heard, the muscles are in a certain position. At the same time, motor reactions (running, walking, etc.) are inhibited.

Education mechanism

Conditioned reflexes occur with the simultaneous action of a conditioned stimulus and an unconditioned reflex. In this case, certain conditions must be met:

The unconditioned reflex is biologically stronger;
- the manifestation of the conditioned stimulus is somewhat ahead of the action of the instinct;
- the conditioned stimulus is necessarily reinforced by the influence of the unconditional;
- the body must be awake and healthy;
- the condition of the absence of extraneous stimuli producing a distracting effect is met.

The centers of conditioned reflexes located in the cerebral cortex establish a temporary connection (closure) with each other. In this case, the irritation is perceived by cortical neurons, which are part of the unconditioned reflex arc.

Inhibition of conditioned reactions

In order to ensure adequate behavior of the organism and for better adaptation to environmental conditions, the development of conditioned reflexes alone will not be enough. An action in the opposite direction will be required. This is the inhibition of conditioned reflexes. This is the process of eliminating those reactions of the body that are not necessary. According to the theory developed by Pavlov, certain types of cortical inhibition are distinguished. The first of these is unconditional. It appears as a response to the action of some extraneous stimulus. There is also internal inhibition. It is called conditional.

External braking

This reaction received this name due to the fact that its development is facilitated by processes taking place in those areas of the cortex that do not participate in reflex activity. For example, an extraneous smell, sound, or change in lighting before the onset of the food reflex can reduce it or contribute to its complete disappearance. A new stimulus acts as an inhibitor for a conditioned response.

Eating reflexes can also be eliminated by painful stimuli. Inhibition of the body's reaction is facilitated by bladder overflow, vomiting, internal inflammatory processes, etc. All of them inhibit food reflexes.

Internal inhibition

It occurs when the received signal is not reinforced by an unconditioned stimulus. Internal inhibition of conditioned reflexes occurs if, for example, an animal is periodically turned on an electric light bulb in front of its eyes during the day without bringing food. It has been experimentally proven that saliva production will decrease each time. As a result, the reaction will fade away completely. However, the reflex will not disappear without a trace. He will simply slow down. This has also been proven experimentally.

Conditioned inhibition of conditioned reflexes can be eliminated the very next day. However, if this is not done, then the body’s reaction to this stimulus will subsequently disappear forever.

Types of internal braking

Several types of elimination of the body's reaction to stimuli are classified. Thus, the basis for the disappearance of conditioned reflexes, which are simply not needed under given specific conditions, is extinctive inhibition. There is another type of this phenomenon. This is discriminative or differentiated inhibition. Thus, an animal can distinguish the number of metronome beats at which food will be brought to it. This happens when this conditioned reflex is previously developed. The animal distinguishes between stimuli. The basis of this reaction is internal inhibition.

The value of eliminating reactions

Conditioned inhibition plays a significant role in the life of the body. Thanks to it, the process of adaptation to the environment occurs much better. The ability to navigate in a variety of complex situations is provided by a combination of excitation and inhibition, which are two forms of a single nervous process.

Conclusion

There are an infinite number of conditioned reflexes. They are the factor that determines the behavior of a living organism. With the help of conditioned reflexes, animals and humans adapt to their environment.

There are many indirect signs of body reactions that have signaling value. For example, an animal, knowing in advance that danger is approaching, organizes its behavior in a certain way.

The process of developing conditioned reflexes, which belong to a higher order, is a synthesis of temporary connections.

The basic principles and patterns manifested in the formation of not only complex but also elementary reactions are the same for all living organisms. From this follows an important conclusion for philosophy and the natural sciences that something cannot but obey the general laws of biology. In this regard, it can be studied objectively. However, it is worth keeping in mind that the activity of the human brain is qualitatively specific and fundamentally different from the activity of the animal brain.