1. To develop a conditioned reflex, the presence of two stimuli is necessary. One of them is an unconditioned stimulus that causes an unconditioned reflex reaction (food, pain stimulus, etc.), this stimulus is reinforcement of the conditioned reflex reactions. The second stimulus - conditioned (signal) will signal unconditional irritation (light, sound, type of food, etc.).

2. A multiple combination of a conditioned and unconditioned stimulus is necessary (although the formation of a conditioned reflex is possible with a single combination of a conditioned and unconditioned stimulus).

3. The conditioned stimulus must precede the action of the unconditioned one. The time during which the conditioned stimulus acts independently is called the time of isolated action of the conditioned stimulus. The time when the conditioned and unconditioned stimuli act together is called the time of joint action of the conditioned and unconditioned stimulus. Depending on the duration of the isolated action of the conditioned stimulus, there are: coincidental conditioned reflex (the time of the isolated action of the conditioned stimulus is 1-2 s); if the time of the isolated action of the conditioned stimulus is more than 2 s, then such a reflex is called retired, he can be:

Short delayed (isolated action time up to 10 s);

Medium delayed (isolated action time up to 20 s);

Long delayed (time of isolated action 20-30 s);

If the unconditioned stimulus acts 30 seconds or more after the onset of the conditioned stimulus, then such a conditioned reflex is called late;

trace conditioned reflex - the unconditioned stimulus begins to act after the cessation of the action of the conditioned stimulus; such reflexes do not have time for the combined action of the conditioned and unconditioned stimuli.

4. Any external or external stimulus can be used as a conditioned stimulus. internal environment, but it must have the following properties:

Should be as indifferent as possible, not in itself cause a defensive reaction;

There should not be excessive force;

Must attract the attention of the animal;

It must be ecologically close to the animal (for example, fish can develop a conditioned reflex to a call, but this requires a large number of combinations of conditioned and unconditioned stimuli, and to the combination of a splash of water with the supply of food, a conditioned reflex is developed after 2-3 combinations).

In this regard, conditioned reflexes are divided into natural and artificial . natural conditioned reflexes are developed to agents that, under natural conditions, act together with an irritant that causes an unconditioned reflex (for example, the type of food, its smell, etc.). All other conditioned reflexes artificial, i.e., they are produced for agents that are not normally associated with the action of an unconditioned stimulus, for example, a food salivary reflex to a bell.

5. Under the action of conditioned and unconditioned stimuli, the excitation from the unconditioned stimulus must be stronger than from the conditioned one.

6. Unconditional reinforcement must match its qualities, for example, food must be edible.

7. When working out conditioned reflexes it is necessary to eliminate extraneous stimuli, since they can cause inhibition of the conditioned reflex.

8. An animal that develops a conditioned reflex must be healthy and maintain normal behavior.

9. During the development of a conditioned reflex, the animal must have a pronounced motivational excitation, for example, during the development of a food salivary reflex, the animal must be hungry, in a satiated animal this reflex is not developed.

The physiological basis for the emergence of conditioned reflexes is the formation of temporary connections in the most reactive formations of the central nervous system - in its higher departments. Temporary connection - it is a set of neurophysiological, biochemical and ultrastructural changes in the brain that occur during the combined action of conditioned and unconditioned stimuli.

IP Pavlov suggested that during the development of a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - cortical representations of conditioned and unconditioned reflexes. There are several possibilities for closing such a temporary connection. First, excitation from the center of the conditioned reflex can be transmitted to the center of the unconditioned reflex from cell to cell, from neuron to neuron - this is an interneuronal pathway. Secondly, excitation can be transmitted along the associative fibers of the cortex. Consequently, the first way to form a temporary connection between the cortical representations of the conditioned and unconditioned reflexes is intracortical, according to the cortex-core type (the center of the conditioned is the center of the unconditioned reflexes).

1. When the cortical representation of the conditioned reflex is destroyed, the developed conditioned reflex is preserved. Apparently, the formation of a temporary connection takes place between the subcortical centers of the conditioned reflex and the cortical centers of the unconditioned reflex (similar to the subcortex-cortex).

2. When the cortical representation of the unconditioned reflex is destroyed, the conditioned reflex is also preserved. Consequently, the development of a temporary connection can go between the cortical center of the conditioned reflex and the subcortical center of the unconditioned reflex (according to the cortex-subcortex type).

3. Separation of the cortical centers of conditioned and unconditioned reflexes by crossing the cerebral cortex does not prevent the formation of a conditioned reflex. This indicates that a temporary connection can be formed between the cortical center of the conditioned reflex, the subcortical center of the unconditioned reflex and the cortical center of the unconditioned reflex (but of the cortex-subcortex-cortex type).

4. Further studies have shown that conditioned reflexes are preserved when the cortex is removed in animals, i.e., the temporal connection is preserved at the level of the subcortical centers of the conditioned and unconditioned reflexes (subcortex-subcortex type).

What is the mechanism for the formation of a temporary connection? A number of researchers have shown that the formation of a temporary connection occurs according to the principle dominants. The focus of excitation from an unconditioned stimulus is always stronger than from a conditioned one, since the unconditioned stimulus is always biologically more significant for the animal. This focus of excitation is dominant. A stronger focus of excitation from the unconditioned stimulus attracts excitation from the focus of the conditioned stimulus. The degree of his arousal will increase. The dominant focus has the property of a long, stable existence. Consequently, conditioned and unconditioned excitations will interact with each other for a long time. If the excitation has passed through some nerve centers, then the next time it will pass through these paths much easier. This is based, firstly, on the phenomenon of summation of excitations, and secondly, on the phenomenon of “blazing the path”, accompanied by:

A prolonged increase in the excitability of synaptic formations;

Changes in protein chains, accumulation of RNA, changes in the amount of mediator in synapses, activation of the formation of new synapses.

Consequently, structural prerequisites are created for the movement of excitation along certain paths. Now the excitation from the zone of the cortical representation of the conditioned reflex will follow the beaten path and cause the manifestation of a conditioned reflex reaction.

There is another idea about the mechanism of formation of a temporary connection. This idea is based on the ability of neurons to respond to stimuli of different modalities, i.e., the phenomenon of polysensory convergence. The existence of neurons on which excitations from different analyzers converge suggests that the process of establishing temporary connections occurs not due to the unification of various parts of the cortex, but due to the integration of excitations at the level of one neuron - cortical neurons can integrate conditioned and unconditioned excitations. Conditioned and unconditioned excitations, reaching the neurons, are fixed in them in the form of strong chemical compounds, the formation of which is the mechanism of closing the conditioned reflex connection. Such a theory of the mechanism for closing a temporary connection was called convergent theory.

Conditioned reflexes are called so because for their development it is necessary to comply with certain conditions, namely:

1. Presence of a basic reflex . A conditioned reflex can be developed only on the basis of an already existing reflex - unconditioned or previously developed conditioned.

2. Leading action of the conditioned stimulus . Future conditional (originally indifferent, indifferent) the stimulus must have alarm value, i.e. precede the action of the unconditional ( reinforcing) stimulus.

3. Less biological significance of the conditioned stimulus . The significance of the reinforcing stimulus should be greater than that of the future conditioned stimulus. Exactly the reinforcing stimulus must be associated with the satisfaction of the dominant need .

4. Optimal stimulus strength . Both signal and reinforcing stimuli must be of a certain strength, since too weak and too strong stimuli do not allow the development of a stable conditioned reflex.

5. Repeated repetition of both stimuli . This condition is important for the development of a stable conditioned reflex, since only the most probable combinations of the conditioned stimulus and the unconditioned reaction are recorded in the individual memory. Random connections are slowed down.

6. Absence of extraneous stimuli . It is necessary that at the time of the development of the conditioned reflex, other stimuli do not act on the body.

7. Optimum performance of the cerebral cortex . For the formation of a conditioned connection, a sufficiently high level of excitability of the cells of the cortex and a balance in the processes of excitation and inhibition are necessary.

4.6.2. Mechanisms for the formation of conditioned reflexes

The mechanisms of formation of conditioned reflexes are largely unclear. Both the structural basis of the temporal connection and its physiological nature have not been sufficiently studied. To address these issues, numerous studies are being carried out on the systemic and cellular levels, while studying electrophysiological and biochemical indicators of the functional state of nerve cells and their complexes.

I. P. Pavlov considered that the closure of the conditioned connection occurs in the cerebral cortex between the cortical center, the excitation in which occurs under the action of a conditioned stimulus, and the cortical center of the unconditioned reflex. For example, when food (an unconditioned stimulus) acts on taste buds, the salivary center of the medulla oblongata is excited and a salivary reaction occurs. Under the action of a light stimulus (future conditioned stimulus), excitation covers the visual cortex. If the action of the future conditioned and unconditioned stimuli coincides in time, a functional connection is established between the visual and food centers of the cortex. With the conditioned reflex developed, the excitation that has arisen in the visual center spreads to the food center, and from there along the efferent pathways to the center of salivation. As a result, a reaction occurs that is characteristic of the action of an unconditioned stimulus (Fig. 4.2).

Rice. 4.2. The mechanism of the formation of a conditioned reflex (according to I.P. Pavlov): I. The action of a food stimulus leads to an unconditional reflex secretion of saliva: 1 - excitation in the center of salivation of the medulla oblongata; 2 - excitation in the food center of the cortex; II. The action of an indifferent light stimulus causes a weak orienting reaction: 3 - excitation in the visual center of the cortex; III. The combination of the action of light and food stimuli: there is a functional connection between the visual and food centers of the cortex; IV. Developed conditioned reflex: the action of a light stimulus leads to the excitation of the visual and food centers of the cortex; conditioned reflex salivation occurs

Pavlov believed that the cortex plays a leading role in the formation of conditioned reflexes . However, he spoke about the need to study roles of cortical-subcortical interactions in providing GNI.

Indeed, numerous studies using various methods have convincingly shown closure of temporary connections through the cerebral cortex. In addition, there are data about the role of subcortical formations in this process.

In the formation of a conditioned reflex, two stages can be distinguished: generalization and specialization.

Generalization stage .At this stageconditioned reflexaction causes not only a reinforced conditioned stimulus, but also a wide range ofktr cxsame irritants with him. At this time it happens primary sensory generalization , generalization of signs of conditional signals. The degree of generalization depends on the characteristics of both conditioned and unconditioned stimuli.

Significance of the stage of generalization large, since it largely determines the plasticity of acquired behavior and allows the body to adapt immediately to a wide range of similar signals. So, if a dog receives food reinforcement after a sound signal with a frequency of 400 Hz, then at the stage of generalization, sounds with a frequency of 200–600 Hz will also cause salivation. I. P. Pavlov associated this stage of the formation of a conditioned reflex with a wide irradiation of the excitatory process within the center receiving the signal.

Electrophysiological studies have shown that in the early stages of the development of a conditioned reflex, wide generalization of excitation processes in the cortex and subcortical structures . Excitation of the reticular formation leads to activation of overlying structures, including the cortex, and activation of the thalamus and hypothalamus provides the vegetative component of the conditioned reflex (changes in the functioning of internal organs).

Then, in the subcortical formations and in different parts of the cortex, the impulse activity of neurons is synchronized. (distant synchronization ) . The rhythm of this synchronous activity corresponds to the frequency of the conditioned stimulus, which indicates uniting previously unconnected functionally neurons into a single system . It is shown that for the emergence of a temporal connection, distant synchronization of the center of the conditioned stimulus (for example, the center of the visual analyzer) and the center of the unconditioned reaction (for example, the motor cortex) is necessary.

Specialization stage . To this stage specialization takes place conditioned reflex answer: it is observed only after the action of the conditioned signal . All other, similar in quality stimuli, do not cause a response. The degree of specialization and the speed of its onset depend on the characteristics of the conditioned and unconditioned stimuli.

The meaning of this stage consists in the fact that when a reflex is triggered from a large "set" of possible stimuli only a small number of significant signals are released that can cause the development of a reaction .

I. P. Pavlov believed that this stage is connected with the process of concentration excitation in the conditional signal analyzer.

The components of the orienting reaction observed at the stage of generalization fade away, and the connection between the cortical centers of the conditioned and unconditioned stimuli remains.

Distant synchronization of neurons in these areas of the cortex becomes more distinct with specialization of the reflex, while in subcortical formations it is inhibited. If before the development of a conditioned motor reflex to light in the motor area of ​​the cortex, only 2.5% of neurons respond to light stimuli, then after development - already 40%.

It can be concluded that the specialization of the conditioned reflex is associated with the processes of cortical inhibition, and the accuracy and stability of the conditioned reflex reaction will depend on the severity of this process.

Question 1. What conditions are necessary for the development of a conditioned reflex?
For the successful development of a conditioned reflex, three conditions must be met. First, the conditioned stimulus (in our example, a call) must precede the unconditioned reinforcement (in our example, food). Second, the biological significance of the conditioned stimulus must be less than that of the unconditioned reinforcer. For example, for a female, the cry of her cub is obviously a stronger stimulus than food reinforcement. Thirdly, the strength of the conditioned and unconditioned stimuli must have a certain value (the law of force), since very weak and very strong irritants do not lead to the development of a stable conditioned reflex.

Question 2. As a result of which the conditioned reflex fades away?
Developed conditioned reflexes may lose their significance when the conditions of existence change. The extinction of conditioned reflexes is called inhibition. There are external and internal inhibition of conditioned reflexes. If, under the influence of a new strong external stimulus, a focus of strong excitation arises in the brain, then the previously developed conditioned reflex connection does not work. For example, a food conditioned reflex is inhibited by strong noise, a frightened dog, the action of a painful stimulus on it, etc. This type of braking is called external. If the salivation reflex developed to the call is not reinforced by feeding, then gradually the sound ceases to play the role of a conditioned stimulus, and the reflex begins to fade and slow down. The temporary connection between the two centers of excitation in the cortex will be destroyed. This type of inhibition of conditioned reflexes is called internal.

Question 3. What is a dominant?
Dominant- this is the need that prevails at the moment, which controls all the current behavior of the organism.

Question 4. What is the meaning of the dominant in life?
The dominant need, the behavior associated with its satisfaction, and the simultaneous suppression of interfering and distracting reflexes mobilize all the energy of the body to achieve the goal.

Question 5. The dominant focus of excitation usually inhibits neighboring plots bark. Explain with what law, discovered by IP Pavlov, this is connected.
This fact is based on the law of mutual induction of excitation-inhibition, which was discovered by the great Russian physiologist IP Pavlov.

Question 6. What is the relationship of the dominant with the needs?
The significance for us of any event is determined by our inner need. The prevailing need at the moment governs all the current behavior of the organism. A. A. Ukhtomsky discovered the principle of behavior control, called the principle of dominance. According to this principle, the behavior that is associated with the satisfaction of a need activates all the energy of the body to achieve the goal.

Conditioned reflexes are formed on the basis of unconditioned reflexes under certain conditions. To develop a conditioned reflex, you must:

The presence of two stimuli, one of which is unconditioned (food, pain stimulus, etc.), causing an unconditioned reflex reaction, and the other is conditioned (signal), signaling an upcoming unconditioned stimulus (light, sound, type of food, etc. );

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

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

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

The unconditioned stimulus must be strong enough, otherwise a temporary connection will not form;

Excitation from an unconditioned stimulus should be stronger than from a conditioned one;

It is necessary to eliminate extraneous stimuli, as they can cause inhibition of the conditioned reflex;

An animal in which a conditioned reflex is developed must be healthy;

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

The formation of a conditioned reflex begins with the extinction of the orienting reaction to the stimulus, which should later be a conditioned signal. So, if you light a light bulb in front of the dog, then at first it will have indicative a reflex to this stimulus (turning the head, torso, moving the eyes to light). However, when the light bulb is re-ignited, the orienting response decreases and then fades away. The dog ceases to react to the lighting of the light bulb, turning on the light bulb has become an indifferent (indifferent) stimulus. Subsequently, a conditioned signal acts on the animal's organism in isolation for 5-10 seconds, and then an unconditioned stimulus joins it.

So, for the formation of a conditioned salivary reflex to a light stimulus, a light bulb is turned on, for several seconds (5 - 10) it burns in isolation, then the animal is given food (an unconditioned stimulus), and the lamp burns while the dog eats. This combination of the conditioned signal and the unconditioned stimulus is repeated several times (8-10 combinations in one experiment). After several combinations, the lighting of the light bulb will cause the separation of saliva without food reinforcement, which indicates the development of a salivary conditioned reflex to light. Light has become a conditional signal for the separation of saliva.

The mechanism of formation of conditioned reflexes.

The physiological basis for the emergence of conditioned reflexes is the formation of functional temporary connections in the higher parts of the central nervous system. Temporary connection- this is a set of neurophysiological, biochemical and ultrastructural changes in the brain that occur in the process of the combined action of conditioned and unconditioned stimuli.

I.P. Pavlov suggested that during the development of a conditioned reflex, a temporary nervous connection is formed between two groups of cortical cells - cortical representations of conditioned and unconditioned reflexes (Fig. 1).

The conditioned signal causes excitation in the brain section of the corresponding analyzer. Under the influence of an unconditioned stimulus, excitation occurs reflex center and at the same time, impulses enter the cerebral cortex in the so-called cortical representation of the center of the unconditioned reflex. Thus, during the development of a conditioned reflex, two centers of excitation appear in the cerebral cortex. A temporal connection is gradually established between them.

I. P. Pavlov called this establishment of a connection, or “blazing” a path, a closure.

In our example of the formation of a conditioned salivary reflex to light, the inclusion of a light bulb causes excitation of the photoreceptors of the eye. The resulting nerve impulses travel along the optic nerve to the brain and reach the brain end of the visual analyzer through the intercalary neurons. Irritation of the receptors of the oral cavity with food causes their excitation. Impulses along the corresponding afferent nerves enter the reflex center of salivation (a component of the food center), located in the medulla oblongata. From the salivary center, excitation along the efferent nerves spreads to the salivary glands and causes secretion. At the same time, impulses from the reflex center of salivation enter the cerebral cortex into the cortical representation of the food center. Usually there is no anatomical connection between the brain end of the visual analyzer and the cortical representation of the food center. In the process of developing a conditioned reflex, a temporary nervous connection is formed between them.

Thus, during the formation of a conditioned reflex, complex functional changes occur primarily in the brain end of the analyzer (nerve impulses are received from receptors when a conditioned signal is applied to the animal organism) and in the cortical representation of the unconditioned reflex.

There are different opinions on the issue of the mechanisms for the formation of a temporary connection.

Perhaps the formation of a temporary connection occurs according to the principle of dominance. The focus of excitation from an unconditioned stimulus is always stronger than from a conditioned one, since the unconditioned stimulus is always biologically more significant for the animal. This focus of excitation is dominant, therefore it attracts excitation from the focus of conditioned irritation. If the excitation has passed along some nerve circuits, then the next time it will pass along these paths much easier (the phenomenon of "breaking the path"). This is based on: the summation of excitations, a prolonged increase in the excitability of synaptic formations, an increase in the amount of a mediator in synapses, and an increase in the formation of new synapses. All this creates structural prerequisites for facilitating the movement of excitation along certain neural circuits.

Another idea of ​​the mechanism of the formation of a temporary connection is the convergent theory. It is based on the ability of neurons to respond to stimuli of different modalities. According to P.K. Anokhin, conditioned and unconditioned stimuli cause widespread activation of cortical neurons due to the inclusion of the reticular formation. As a result, the ascending signals (conditioned and unconditioned stimuli) overlap, i.e. there is a meeting of these excitations on the same cortical neurons. As a result of the convergence of excitations, temporary connections arise and stabilize between the cortical representations of the conditioned and unconditioned stimuli.

The process of formation of conditioned reflexes is accompanied by the phenomena of their generalization and concentration.

The phenomenon of generalization(generalization) is observed during the formation of conditioned reflexes. Its essence lies in the fact that conditioned stimuli are generalized and the conditioned reflex formed to a certain stimulus is also reproduced under the action of other stimuli similar to it. The process of excitation arising from the action of any one stimulus, as a result of irradiation, also passes to the cortical centers of other, similar in nature, stimuli. In motor conditioned reflexes, for example, in the formation of motor skills, the phenomenon of generalization is manifested in the participation in a motor act of a significant number of muscles, the contraction of which is not necessary.

Phenomena of concentration observed during the strengthening of conditioned reflexes. The established conditioned reflexes are generalized to a lesser extent than the newly formed ones. This is explained by the fact that the process of excitation, with repeated repetition of conditioned stimuli, is concentrated and irradiates less to other centers. In this case, the more the conditioned reflex becomes stronger, the less the manifestation of phenomena and generalization becomes.

The meaning of conditioned reflexes. Conditioned reflexes have a signal (adaptive) value for the organism. They warn a person or animal of danger, let them know about the proximity of food, etc. In the struggle for existence, the animal survives in which conditioned reflexes are formed faster and easier. Conditioned reflexes, depending on the conditions, may appear and fade or disappear. As a result, due to conditioned reflexes, the body can more perfectly adapt to environment to the changing conditions of existence.

IP Pavlov, characterizing the significance of conditioned reflexes, emphasized that conditioned reflexes clarify, refine and complicate the relationship of the organism with the external environment. Chains of the most complex conditioned reflexes underlie discipline, upbringing, and training.