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 released in response to the bell, even if the meat is not presented. This phenomenon was discovered independently by Edwin Twitmeier at approximately the same time as in the laboratory of I. P. Pavlov. Conditioned reflexes are the basis acquired behavior. These are the simplest programs. The world 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 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 the brain section of the 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 unconditioned 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 the physiological activity of the brain in children” (L., 1939) and “Higher nervous activity of the child” (L., 1958), Professor Mayorov, who was the official chronicler of the Pavlovian school, melancholy noted: “ Some of our employees expanded the range of experimental objects and began studying conditioned reflexes in other animal species; 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 “Conditioned Reflexes of a Child” (1928 All this is confirmed by protocols, photographs and documentary film“Mechanics of the Brain” (another title is “Animal and Human Behavior”; directed by V. Pudovkin, camera by A. Golovnya, produced by the Mezhrabprom-Rus film factory, 1926)
Higher nervous activity (HNA)
Higher nervous activity (HNA) is a complex and interconnected set of nervous processes that underlie human behavior. GND ensures maximum human adaptability to environmental conditions.
GND is based on complex electrical and chemical processes occurring in the cells of the cortex cerebral hemispheres brain. By receiving information through the senses, the brain ensures the interaction of the body with the environment and maintains the constancy of the internal environment in the body.
At the heart of the doctrine of higher nervous activity are the works of I.M. Sechenov - “Reflexes of the brain”, I.P. Pavlova (theory of conditioned and unconditioned reflexes), P.K. Anokhin (theory functional systems) and numerous other works.
Features of human higher nervous activity:
- developed mental activity;
- speech;
- ability for abstract logical thinking.
The creation of the doctrine of higher nervous activity began with the works of the great Russian scientists I.M. Sechenov and I.P. Pavlova.
Ivan Mikhailovich Sechenov in his book “Reflexes of the Brain” proved that a reflex is a universal form of interaction between the body and the environment, that is, not only involuntary, but also voluntary, conscious movements have a reflex character. They begin with irritation of any sensory organs and continue in the brain in the form of certain nervous phenomena that lead to the launch of behavioral reactions.
A reflex is the body's response to irritation, which occurs with the participation of nervous system.
THEM. Sechenov argued that brain reflexes include three parts:
- The first, initial link is stimulation in the senses caused by external influences.
- The second, central link is the processes of excitation and inhibition occurring in the brain. On their basis, mental phenomena arise (sensations, ideas, feelings, etc.).
- The third, final link is the movements and actions of a person, i.e. his behavior. All these links are interconnected and condition each other.
Sechenov concluded that the brain is an area of continuous change of excitation and inhibition. These two processes constantly interact with each other, which leads to both strengthening and weakening (delay) of reflexes. He also drew attention to the existence of innate reflexes, which people inherit from their ancestors, and acquired ones, which arise throughout life as a result of learning. I.M. Sechenov’s assumptions and conclusions were ahead of their time.
The successor of the ideas of I.M. Sechenov became I.P. Pavlov.
Ivan Petrovich Pavlov divided all reflexes that arise in the body into unconditional and conditional.
Unconditioned reflexes
Unconditioned reflexes are inherited by offspring from their parents, persist throughout the life of the organism and are reproduced from generation to generation ( permanent). They are characteristic of all individuals of a certain species, i.e. group.
In unconditioned reflexes constant reflex arcs, which pass through the brain stem or through the spinal cord (for their implementation participation of the cortex is not necessarycerebral hemispheres).
There are food, defensive, sexual and indicative unconditioned reflexes.
- Food: separation of digestive juices in response to irritation of oral receptors, swallowing, sucking movements in a newborn.
- Defensive: withdrawal of a hand that has touched a hot object or when experiencing painful irritation, coughing, sneezing, blinking, etc.
- Genital: The process of reproduction is associated with sexual reflexes.
- Approximate(I.P. Pavlov called it the “what is this?” reflex) ensures the perception of an unfamiliar stimulus. An indicative reflex appears in response to a new stimulus: a person becomes alert, listens, turns his head, squints his eyes, and thinks.
Thanks to unconditioned reflexes, the integrity of the body is preserved, the constancy of its internal environment is maintained, and reproduction occurs.
A complex chain of unconditioned reflexes is called instinct.
Example:
A mother feeds and protects her child, birds build nests - these are examples of instincts.
Conditioned reflexes
Along with hereditary (unconditioned) reflexes, there are reflexes that are acquired by every person throughout life. Such reflexes individual, and certain conditions are necessary for their formation, which is why they were called conditional.
Conditioned reflexes are complex adaptive reactions of the body, carried out by the higher parts of the central nervous system by forming a temporary connection between a signal stimulus and an unconditioned reflex act that reinforces this stimulus. Based on an analysis of the patterns of formation of conditioned reflexes, the school created the doctrine of higher nervous activity (see). In contrast to unconditioned reflexes (see), which ensure the body’s adaptation to constant influences external environment, conditioned reflexes enable the body to adapt to changing environmental conditions. Conditioned reflexes are formed on the basis of unconditioned reflexes, which requires the coincidence in time of some stimulus from the external environment (conditioned stimulus) with the implementation of one or another unconditioned reflex. The conditioned stimulus becomes a signal of a dangerous or favorable situation, allowing the body to respond with an adaptive reaction.
Conditioned reflexes are not permanent and are acquired in the process individual development body. Conditioned reflexes are divided into natural and artificial. The first arise in response to natural stimuli in natural conditions existence: the puppy, having received meat for the first time, sniffs it for a long time and timidly eats it, and this act of eating is accompanied by. In the future, only the sight and smell of meat causes the puppy to lick and excrete. Artificial conditioned reflexes are developed in an experimental setting, when the conditioned stimulus for an animal is an influence that is not related to unconditioned reactions in the animals’ natural habitat (for example, flickering light, the sound of a metronome, sound clicks).
Conditioned reflexes are divided into food, defensive, sexual, orienting, depending on the unconditional reaction that reinforces the conditioned stimulus. Conditioned reflexes can be named depending on the registered response of the body: motor, secretory, vegetative, excretory, and can also be designated by the type of conditioned stimulus - light, sound, etc.
To develop conditioned reflexes in an experiment, a number of conditions are necessary: 1) the conditioned stimulus must always precede the unconditioned stimulus in time; 2) the conditioned stimulus should not be strong so as not to cause the body’s own reaction; 3) a conditioned stimulus is taken that is usually found in the environmental conditions of the given animal or person; 4) the animal or person must be healthy, cheerful and have sufficient motivation (see).
There are also conditioned reflexes of various orders. When a conditioned stimulus is reinforced by an unconditioned stimulus, a first-order conditioned reflex is developed. If some stimulus is reinforced by a conditioned stimulus to which a conditioned reflex has already been developed, then a second-order conditioned reflex is developed to the first stimulus. Conditioned reflexes of higher orders are developed with difficulty, which depends on the level of organization of the living organism.
A dog can develop conditioned reflexes of up to 5-6 orders, in a monkey - up to 10-12 orders, in humans - up to 50-100 orders.
The work of I.P. Pavlov and his students established that in the mechanism of the emergence of conditioned reflexes, the leading role belongs to the formation of a functional connection between the foci of excitation from conditioned and unconditioned stimuli. An important role was assigned to the cerebral cortex, where conditioned and unconditioned stimuli, creating foci of excitation, began to interact with each other, creating temporary connections. Subsequently, using electrophysiological research methods, it was established that the interaction between conditioned and unconditioned excitations can first occur at the level of subcortical structures of the brain, and at the level of the cerebral cortex, the formation of integral conditioned reflex activity takes place.
However, the cerebral cortex always controls the activity of subcortical formations.
By studying the activity of single neurons of the central nervous system using the microelectrode method, it was established that both conditioned and unconditioned excitations come to one neuron (sensory-biological convergence). It is especially clearly expressed in the neurons of the cerebral cortex. These data forced us to abandon the idea of the presence of foci of conditioned and unconditioned excitation in the cerebral cortex and create the theory of convergent closure of the conditioned reflex. According to this theory, a temporary connection between conditioned and unconditioned excitation arises in the form of a chain of biochemical reactions in the protoplasm of the nerve cell of the cerebral cortex.
Modern ideas about conditioned reflexes have expanded and deepened significantly thanks to the study of the higher nervous activity of animals in conditions of their free natural behavior. It has been established that the environment, along with the time factor, plays an important role in the behavior of the animal. Any stimulus from the external environment can become conditioned, allowing the body to adapt to environmental conditions. As a result of the formation of conditioned reflexes, the body reacts some time before the impact of unconditioned stimulation. Consequently, conditioned reflexes contribute to the successful finding of food by animals, help to avoid danger in advance and most perfectly navigate the changing conditions of existence.
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, attention are freed from performing those operations that have become automated and become skills Everyday life. Most successful path mastering skills means systematic exercises, correcting errors noticed in time, 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.
The main form of activity of the nervous system is reflex. All reflexes are usually divided into unconditioned and conditioned.
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Unconditioned reflexes |
Conditioned reflexes |
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1. Congenital, genetically programmed reactions of the body, characteristic of all animals and humans. 2. Reflex arcs of these reflexes are formed in the process prenatal development, sometimes in postnatal period. Ex: sexual innate reflexes are finally formed in a person only at the time of puberty in adolescence. They have little changing reflex arcs passing through the subcortical parts of the central nervous system. The participation of the cortex in the course of many unconditioned reflexes is optional. 3. Are species-specific, i.e. formed in the process of evolution and are characteristic of all representatives of this species. 4. Regarding permanent and persist throughout the life of the organism. 5. Occur on specific(adequate) stimulus for each reflex. 6. Reflex centers are at the level spinal cord and in brain stem |
1. Purchased reactions of higher animals and humans, developed as a result of learning (experience). 2. Reflex arcs are formed during the process postnatal development. They are characterized by high mobility and the ability to change under the influence of environmental factors. Reflex arcs of conditioned reflexes pass through the highest part of the brain - the cerebral cortex. 3. Are individual, i.e. arise on the basis of life experience. 4. Fickle and, depending on certain conditions, they can be developed, consolidated or fade away. 5. Can form on any stimulus perceived by the body 6. Reflex centers are located in cerebral cortex |
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Example: food, sexual, defensive, indicative. |
Example: salivation to the smell of food, precise movements when writing, playing musical instruments. |
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Meaning: help survival, this is “putting the experience of ancestors into practice” |
Meaning: help adapt to changing environmental conditions. |
Classification of unconditioned reflexes.
The question of the classification of unconditioned reflexes still remains open, although the main types of these reactions are well known.
1. Food reflexes. For example, salivation when food enters the oral cavity or the sucking reflex in a newborn baby.
2. Defensive reflexes. Protect the body from various adverse effects. For example, the reflex of withdrawing a hand when a finger is painfully irritated.
3. Approximate reflexes, or “What is it?” reflexes, as I. P. Pavlov called them. A new and unexpected stimulus attracts attention, for example, turning the head towards an unexpected sound. A similar reaction to novelty, which has important adaptive significance, is observed in various animals. It is expressed in alertness and listening, sniffing and examining new objects.
4.Gaming reflexes. For example, children's games of family, hospital, etc., during which children create models of possible life situations and carry out a kind of “preparation” for various life surprises. The unconditional reflex play activity of a child quickly acquires a rich “spectrum” of conditioned reflexes, and therefore play is the most important mechanism for the formation of the child’s psyche.
5.Sexual reflexes.
6. Parental reflexes are associated with the birth and feeding of offspring.
7. Reflexes that ensure movement and balance of the body in space.
8. Reflexes that support constancy of the internal environment of the body.
Complex unconditioned reflexes I.P. Pavlov called instincts, the biological nature of which remains unclear in its details. In a simplified form, instincts can be represented as a complex interconnected series of simple innate reflexes.
Physiological mechanisms of formation of conditioned reflexes
To understand the neural mechanisms of conditioned reflexes, consider such a simple conditioned reflex reaction as increased salivation in a person when he sees a lemon. This natural conditioned reflex. In a person who has never tasted lemon, this object does not cause any reactions other than curiosity (indicative reflex). What physiological connection exists between such functionally distant organs as the eyes and salivary glands? This issue was resolved by I.P. Pavlov.
The connection between the nerve centers that regulate the processes of salivation and analyze visual stimulation arises as follows:
The excitation that occurs in the visual receptors at the sight of a lemon travels along centripetal fibers to the visual cortex of the cerebral hemispheres (occipital region) and causes excitation cortical neurons- arises source of excitation.
2. If after this a person gets the opportunity to taste the lemon, then a source of excitement arises in the subcortical nerve center salivation and in its cortical representation, located in the frontal lobes of the cerebral hemispheres (cortical food center).
3. Due to the fact that the unconditioned stimulus (the taste of lemon) is stronger than the conditioned stimulus (external signs of lemon), the food source of excitation has a dominant (main) meaning and “attracts” excitation from the visual center.
4. Between two previously unconnected nerve centers, a neural temporal connection, i.e. a kind of temporary “pontoon bridge” connecting two “shores”.
5. Now the excitation arising in the visual center quickly “travels” along the “bridge” of temporary communication to the food center, and from there along the efferent nerve fibers to the salivary glands, causing salivation.
Thus, for the formation of a conditioned reflex, the following are necessary: conditions:
1. The presence of a conditioned stimulus and unconditional reinforcement.
2. The conditioned stimulus must always somewhat precede the unconditional reinforcement.
3. The conditioned stimulus, in terms of the strength of its impact, must be weaker than the unconditioned stimulus (reinforcement).
4. Repetition.
5. A normal (active) functional state of the nervous system is necessary, first of all its leading part - the brain, i.e. the cerebral cortex should be in a state of normal excitability and performance.
Conditioned reflexes formed by combining a conditioned signal with unconditioned reinforcement are called first order reflexes. If the reflex is developed, then it can also become the basis of a new conditioned reflex. It is called second order reflex. Reflexes developed on them - third order reflexes etc. In humans, they are formed on verbal signals, reinforced by the results of joint activities of people.
A conditioned stimulus can be any change in the environmental and internal environment of the body; bell, electric light, tactile skin irritation, etc. Food reinforcement and pain stimulation are used as unconditioned stimuli (reinforcers).
The development of conditioned reflexes with such unconditional reinforcement occurs most quickly. In other words, powerful factors contributing to the formation of conditioned reflex activity are reward and punishment.
Classifications of conditioned reflexes
Due to their large number, it is difficult.
According to the location of the receptor:
1. exteroceptive- conditioned reflexes formed when exteroceptors are stimulated;
2. interoceptive - reflexes formed by irritation of receptors located in internal organs;
3. proprioceptive, arising from irritation of muscle receptors.
By the nature of the receptor:
1. natural- conditioned reflexes formed by the action of natural unconditioned stimuli on receptors;
2. artificial- under the influence of indifferent stimuli. For example, the release of saliva in a child at the sight of his favorite sweets is a natural conditioned reflex (secretion of saliva when irritated oral cavity any food is an unconditioned reflex), and the secretion of saliva that occurs in a hungry child at the sight of dinnerware is an artificial reflex.
By action sign:
1. If the manifestation of a conditioned reflex is associated with motor or secretory reactions, then such reflexes are called positive.
2. Conditioned reflexes without external motor and secretory effects are called negative or braking.
By the nature of the response:
1. motor;
2. vegetative are formed with internal organs– heart, lungs, etc. Impulses from them, penetrating the cerebral cortex, are immediately inhibited, not reaching our consciousness, due to this we do not feel their location in a state of health. And in case of illness, we know exactly where the diseased organ is located.
Reflexes occupy a special place for a while, the formation of which is associated with regularly repeated stimuli at the same time, for example, food intake. That is why, by the time of eating, the functional activity of the digestive organs increases, which has a biological meaning. Temporary reflexes belong to the group of so-called trace conditioned reflexes. These reflexes are developed if unconditional reinforcement is given 10 - 20 seconds after the final action of the conditioned stimulus. In some cases, it is possible to develop trace reflexes even after a 1-2 minute pause.
Reflexes are important imitation, which, according to L.A. Orbels are also a type of conditioned reflex. To develop them, it is enough to be a “spectator” of the experiment. For example, if you develop some kind of conditioned reflex in one person in full view of another, then the “viewer” also forms corresponding temporary connections. In children, imitative reflexes play an important role in the formation of motor skills, speech and social behavior, and in adults in the acquisition of labor skills.
There are also extrapolation reflexes - the ability of humans and animals to foresee situations that are favorable or unfavorable for life.