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(cm.). Unlike unconditioned reflexes (see), which ensure the body’s adaptation to constant influences of the external environment, conditioned reflexes enable the body to adapt to changing conditions environment. 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 unstable and are acquired in the process of individual development of the organism. Conditioned reflexes are divided into natural and artificial. The first ones arise in response to natural stimuli in natural conditions of existence: a 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 eliminate. 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 education functional connection between foci of excitation from conditioned and unconditioned stimuli. An important role was assigned to the cortex cerebral hemispheres, where the 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 an integral conditioned reflex activity.

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 protoplasm nerve cell 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.

Continuation. See No. 34, 35, 36/2004

Congenital and acquired forms of behavior

Lessons on the topic: “Physiology of higher nervous activity”

Table. Comparison of unconditioned and conditioned reflexes

Signs of comparison	Unconditioned reflexes	Conditioned reflexes
Inheritance	Congenital, passed on from parents to offspring	Acquired by the body during life, they are not inherited
Species specificity		Individual
Stimulus	Carried out in response to an unconditioned stimulus	Carried out in response to any irritation perceived by the body;
are formed on the basis of unconditioned reflexes	Meaning in life	Life without them is usually impossible
Promote the survival of the organism in constantly changing environmental conditions	Duration of existence of a reflex arc	Have ready and permanent reflex arcs
They do not have ready-made and permanent reflex arcs; their arcs are temporary and form under certain conditions	Reflex centers Carried out at the level spinal cord	They are carried out due to the activity of the cerebral cortex, i.e.

reflex arcs pass through the cerebral cortex
Lesson 5.

Generalization of knowledge on the topic “Acquired forms of behavior. Conditioned reflex" Equipment:

tables, diagrams and drawings illustrating acquired forms of behavior, mechanisms for the development of conditioned reflexes.

DURING THE CLASSES

I. Test of knowledge

Working with cards

1. The advantage of behavior formed as a result of learning is that it:
a) is carried out quickly;
b) is carried out the same way every time;
c) provides answers in changing environmental conditions;
d) done correctly the first time;

e) does not occupy a place in the genetic program of the organism. 2. For experiments on studying conditioned reflexes, two dogs were taken. One of them was given a drink a large number of

water. Then the research began. At first, conditioned reflexes were carried out normally in both dogs. But after some time, the conditioned reflexes disappeared in the dog that drank water. There were no random external influences. What is the reason for the inhibition of conditioned reflexes?

3. As is known, a conditioned reflex can be developed to the action of almost any indifferent stimulus. One dog in the laboratory of I.P. Pavlov never managed to develop a conditioned reflex to the gurgling of water.

Try to explain the lack of results in this case.

4. It is known that the strength (biological significance) of the conditioned stimulus should not exceed the strength of the unconditioned stimulus. Otherwise, the conditioned reflex cannot be developed. Therefore, it is very difficult to develop, for example, a conditioned food reflex to painful stimulation (electric current). However, in the laboratory of I.P. In Pavlov’s famous experiments, Erofeeva managed to develop such a conditioned reflex. When exposed to a current (conditioned stimulus), the dog salivated, it licked its lips and wagged its tail. How did you achieve this?

5. During one of the concerts, a listener suddenly began to experience pain in the heart area. Moreover, the onset of pain coincided with the performance of one of Chopin’s nocturnes. Since then, every time the man heard this music, his heart ached. Explain this pattern.
Oral knowledge test on questions
1. Learning and its methods (habituation, trial and error).
2. Imprinting and its characteristics.
3. Methods for developing conditioned reflexes.
6. Rational activity of animals.
7. Dynamic stereotype and its meaning.

Checking the completion of the table “Comparison of unconditioned and conditioned reflexes”

The children had to fill out the table as homework after the previous lesson.

Biological dictation

The teacher reads out the characteristics of reflexes under numbers, and students, working on the options, write down the numbers of the correct answers: option I – unconditioned reflexes, option II – conditioned reflexes.

1. Passed on by inheritance.
2. Not inherited.
3. Reflex centers are located in the subcortical nuclei, brain stem and spinal cord.
4. Reflex centers are located in the cerebral cortex.
5. There is no species specificity; each individual of the species develops its own reflexes.
6. Species specificity - these reflexes are characteristic of all individuals of a certain species.
7. Stable throughout life.
8. Change (new reflexes arise, and old ones fade away).
9. The reasons for the formation of reflexes are events that are vital for the whole species.
10. The causes of reflexes are signals that arise from personal past experience and warn of an important event.

Answers: Option I – 1, 3, 6, 7, 9;

Option II – 2, 4, 5, 8, 10.
Laboratory work No. 2.

Generalization of knowledge on the topic “Acquired forms of behavior. Conditioned reflex"“Development of conditioned reflexes in humans on the basis of unconditioned reflexes”

rubber bulb for pumping air, metronome.

PROGRESS

1. Turn on the metronome at a rhythm of 120 beats per minute and on its second or third beat, press the bulb, directing a stream of air into the subject’s eye.

2. Repeat the steps described in step 1 until the blinking steadily (at least 2-3 times in a row) precedes the pressing of the bulb.

3. After the blink reflex has been developed, turn on the metronome without directing the air stream to the eye. What do you observe?

Draw a conclusion.

What reflex was developed in the subject during the actions you performed?

What performs the role of unconditioned and conditioned stimuli in the developed reflex? What is the difference between the arcs of the unconditioned blink and conditioned blink reflexes?
Homework

Repeat the material about the mechanisms of development of conditioned reflexes in animals and humans. Lesson 6–7.

tables, diagrams and drawings illustrating acquired forms of behavior, mechanisms for the development of conditioned reflexes.

DURING THE CLASSES

I. Test of knowledge

1. Thanks to what innate nervous mechanisms can an animal distinguish good-quality food from spoiled food? What role do neurons and their synapses play in these processes?

2. What facts can be used to prove that instinct is a chain of interconnected unconditioned reflexes? How do instincts interact with acquired conditioned reflexes?

3. Infant when he sees a bottle of kefir, he smacks his lips; a person salivates when he sees a lemon being cut;

Wanting to know what time it is, a man looks at his hand, where he usually wears his watch, although he forgot it at home.

Explain the described phenomena.

Knowledge test
Choose the correct answers to the given statements.
1. This is an unconditioned stimulus.
2. It is an indifferent stimulus.
3. This is an unconditioned reflex.
4. This is a conditioned reflex.
5. This is a combination of an indifferent stimulus with an unconditioned one.
6. Without these stimuli, the conditioned salivary reflex is not formed.
7. Stimulus that excites the visual cortex.

8. An irritant that excites the gustatory cortex.

9. Under this condition, a temporary connection is formed between the visual and gustatory zones of the cortex.
Answer options
A. Turning on the light bulb before experiments without feeding.
B. Food in the mouth.
B. Turning on the light during feeding.

Answers: D. Salivation of food in the mouth.

D. Secretion of saliva to the light of a light bulb.

1 – B, 2 – A, 3 – D, 4 – D, 5 – B, 6 – C, 7 – A, 8 – B, 9 – C.

II. Learning new material

1. Excitation and inhibition are the main processes of nervous activity

As you already know, the regulatory function of the central nervous system is carried out through two processes - excitation and inhibition.

Conversation with students on issues

What is arousal?

What is braking? Why is the process of excitation called the active state of nervous tissue??

What does excitement lead to?

motor centers

Thanks to what process can we mentally imagine them without performing any actions? What processes enable complex coordinated actions such as walking? Thus, excitation– this is an active state of nervous tissue in response to the action of various stimuli of sufficient strength. When excited, neurons generate electrical impulses.

2. Braking- This is an active nervous process leading to inhibition of excitation.

general characteristics

Excitation is involved in the formation of conditioned reflexes and their implementation. The role of inhibition is more complex and varied. It is the process of inhibition that makes conditioned reflexes a mechanism of subtle, precise and perfect adaptation to the environment.

According to I.P. Pavlov, the cortex is characterized by two forms of inhibition: unconditional and conditional.

Unconditional inhibition does not require development; it is inherent in the body from birth (reflexive holding of breath when there is a strong smell of ammonia, inhibition in the triceps brachii muscle during the action of the biceps brachii, etc.). Conditioned inhibition is developed in the process of individual experience. The following types of braking are distinguished. Unconditional braking: beyond (protective); external; innate reflexes.

Conditional braking:

extinct; differentiation; delayed. 3. Types of unconditional (congenital) inhibition and their characteristics

In the process of life, the body is constantly exposed to one or another irritation from the outside or from the inside. Each of these irritations is capable of causing a corresponding reflex. If all these reflexes could be realized, then the body’s activity would be chaotic. However, this does not happen. On the contrary, reflex activity is characterized by consistency and orderliness: with the help of unconditional inhibition, the most important in

this moment For the body, the reflex delays all other, secondary, reflexes for the duration of its implementation. Depending on the reasons underlying the inhibition processes, the following types of unconditional inhibition are distinguished. Transcendental, or protective, braking

occurs in response to very strong stimuli that require the body to act beyond its capabilities. The strength of irritation is determined by the frequency of nerve impulses. The more excited a neuron is, the higher the frequency of nerve impulses it generates. But if this flow exceeds known limits, processes arise that prevent the passage of excitation along the chain of neurons. The flow of nerve impulses following is outside the structures of the inhibitory reflex, it comes from another reflex. This type of inhibition occurs whenever a new activity is started.

The new excitation, being stronger, causes inhibition of the old one. As a result, the previous activity is automatically terminated.

For example, a dog has developed a strong conditioned reflex to light, and the lecturer wants to demonstrate it to the audience. The experiment fails - there is no reflex. An unfamiliar environment, the noise of a crowded audience are new signals that completely turn off conditioned reflex activity, and new excitation arises in the cortex. If the dog is brought into the audience several times, then new signals, which turn out to be biologically indifferent, fade away, and conditioned reflexes are carried out unhindered.

To be continued

Each person, as well as all living organisms, has a number of vital needs: food, water, comfortable conditions. Everyone has instincts of self-preservation and continuation of their kind. All mechanisms aimed at satisfying these needs are laid down at the genetic level and appear simultaneously with the birth of the organism. These are innate reflexes that help to survive.

The concept of an unconditioned reflex

The word reflex itself is not something new and unfamiliar for each of us. Everyone has heard it in their life, and quite many times. This term was introduced into biology by I.P. Pavlov, who devoted a lot of time to studying the nervous system. According to the scientist, unconditioned reflexes arise under the influence of irritating factors on the receptors (for example, withdrawing a hand from a hot object). They contribute to the body’s adaptation to those conditions that remain practically unchanged. This is the so-called product

historical experience

previous generations, which is why it is also called the species reflex.

We live in a changing environment; it requires constant adaptations, which cannot in any way be provided for by genetic experience. Unconditioned reflexes of a person are constantly either inhibited, then modified or arise again, under the influence of those stimuli that surround us everywhere.

Thus, already familiar stimuli acquire the qualities of biologically significant signals, and the formation of conditioned reflexes occurs, which form the basis of our individual experience. This is what Pavlov called higher nervous activity.

1. Congenital reflexes are inherited.
2. They appear equally in all individuals of a given species.
3. For a response to occur, the influence of a certain factor is necessary, for example, for the sucking reflex it is irritation of the lips of a newborn.
4. The area of ​​perception of the stimulus always remains constant.
5. Unconditioned reflexes have a constant reflex arc.
6. They persist throughout life, with some exceptions in newborns.

The meaning of reflexes

All our interaction with the environment is built at the level of reflex responses. Unconditioned and conditioned reflexes play an important role in the existence of the organism.

In the process of evolution, a division occurred between those aimed at the survival of the species and those responsible for adaptability to constantly changing conditions.

Congenital reflexes begin to appear in utero, and their role boils down to the following:

• Maintaining internal environment indicators at a constant level.
• Preserving the integrity of the body.
• Preservation of a species through reproduction.

The role of innate reactions immediately after birth is great; they ensure the survival of the baby in completely new conditions.

The body lives surrounded external factors, which are constantly changing and need to be adapted to. This is where higher nervous activity in the form of conditioned reflexes comes to the fore.

For the body they have the following meaning:

• We will improve the mechanisms of its interaction with the environment.
• The processes of contact between the body and the external environment are clarified and complicated.
• Conditioned reflexes are an indispensable basis for the processes of learning, education and behavior.

Thus, unconditioned and conditioned reflexes are aimed at maintaining the integrity of a living organism and the constancy of the internal environment, as well as effective interaction with the outside world. Between themselves they can be combined into complex reflex acts that have a certain biological orientation.

Classification of unconditioned reflexes

Hereditary reactions of the body, despite their innateness, can differ greatly from each other. It is not at all surprising that the classification can be different, depending on the approach.

Pavlov also divided all unconditioned reflexes into:

• Simple (the scientist included the sucking reflex among them).
• Complex (sweating).
• The most complex unconditioned reflexes. A variety of examples can be given: food reactions, defensive reactions, sexual reactions.

Currently, many adhere to a classification based on the meaning of reflexes. Depending on this, they are divided into several groups:

The first group of reactions has two characteristics:

1. If they are not satisfied, this will lead to the death of the body.
2. Satisfaction does not require the presence of another individual of the same species.

The third group also has its own characteristic features:

1. Self-development reflexes have nothing to do with the body’s adaptation to a given situation. They are aimed at the future.
2. They are completely independent and do not arise from other needs.

We can also divide them according to their level of complexity, then the following groups will appear before us:

1. Simple reflexes. These are the body's normal responses to external stimuli. For example, withdrawing your hand from a hot object or blinking when a speck gets into your eye.
2. Reflex acts.
3. Behavioral reactions.
4. Instincts.
5. Imprinting.

Each group has its own characteristics and differences.

Reflex acts

Almost all reflex acts are aimed at ensuring the vital functions of the body, so they are always reliable in their manifestation and cannot be corrected.

These include:

• Breath.
• Swallowing.
• Vomiting.

In order to stop a reflex act, you simply need to remove the stimulus that causes it. This can be practiced when training animals. If you want natural needs not to distract from training, then you need to walk the dog before this, this will eliminate the irritant that can provoke a reflex act.

Behavioral reactions

This type of unconditioned reflex can be well demonstrated in animals. Behavioral reactions include:

• The dog's desire to carry and pick up objects. Retrieval reaction.
• Showing aggression at the sight of a stranger. Active defensive reaction.
• Finding objects by smell. Olfactory-search reaction.

It is worth noting that a behavioral reaction does not mean that the animal will certainly behave this way. What is meant? For example, a dog that has a strong active-defensive reaction from birth, but is physically weak, most likely will not show such aggression.

These reflexes can determine the animal's actions, but they can be controlled. They should also be taken into account when training: if an animal completely lacks an olfactory-search reaction, then it is unlikely that it will be possible to train it as a search dog.

Instincts

There are also more complex forms in which unconditioned reflexes appear. Instincts come into play here. This is a whole chain of reflex acts that follow each other and are inextricably interconnected.

All instincts are associated with changing internal needs.

When a child is just born, his lungs practically do not function. The connection between him and his mother is interrupted by cutting the umbilical cord, and carbon dioxide accumulates in the blood. He starts his humoral effect on the respiratory center, and an instinctive inhalation occurs. The child begins to breathe on his own, and the first cry of the baby is a sign of this.

Instincts are a powerful stimulant in human life. They may well motivate success in a certain field of activity. When we stop controlling ourselves, instincts begin to guide us. As you yourself understand, there are several of them.

Most scientists are of the opinion that there are three basic instincts:

1. Self-preservation and survival.
2. Continuation of the family.
3. Leadership instinct.

All of them can generate new needs:

• In safety.
• In material prosperity.
• Looking for a sexual partner.
• In caring for children.
• In influencing others.

We could go on and on about the types of human instincts, but, unlike animals, we can control them. For this purpose, nature has endowed us with reason. Animals survive only due to instincts, but for this we are also given knowledge.

Don't let your instincts get the better of you, learn to manage them and become the master of your life.

Imprint

This form of unconditioned reflex is also called imprinting. There are periods in the life of every individual when the entire surrounding environment is imprinted on the brain. For each species, this time period may be different: for some it lasts several hours, and for others it lasts several years.

Remember how easily young children master foreign speech skills. While schoolchildren put a lot of effort into this.

It is thanks to imprinting that all babies recognize their parents and distinguish individuals of their species. For example, after the birth of a baby, a zebra spends several hours alone with it in a secluded place. This is exactly the time that is necessary for the cub to learn to recognize its mother and not confuse her with other females in the herd.

This phenomenon was discovered by Konrad Lorenz. He conducted an experiment with newborn ducklings. Immediately after the hatching of the latter, he presented them with various objects, which they followed like a mother. They even perceived him as a mother, and followed him around.

Everyone knows the example of hatchery chickens. Compared to their relatives, they are practically tame and are not afraid of humans, because from birth they see him in front of them.

Congenital reflexes of an infant

After birth, the baby goes through a complex developmental path that consists of several stages. The degree and speed of mastery of various skills will directly depend on the state of the nervous system. The main indicator of its maturity are the unconditioned reflexes of the newborn.

The presence of them in the baby is checked immediately after birth, and the doctor makes a conclusion about the degree of development of the nervous system.

From the huge number of hereditary reactions, the following can be distinguished:

1. Kussmaul search reflex. When the area around the mouth is irritated, the child turns his head towards the irritant. The reflex usually fades by 3 months.
2. Sucking. If you place your finger in the baby's mouth, he begins to perform sucking movements. Immediately after feeding, this reflex fades away and becomes more active after some time.
3. Palmo-oral. If you press on the child's palm, he opens his mouth slightly.
4. Grasping reflex. If you put your finger in the baby’s palm and lightly press it, a reflexive squeezing and holding occurs.
5. The inferior grasp reflex is caused by light pressure on the front of the sole. The toes flex.
6. Crawling reflex. When lying on the stomach, pressure on the soles of the feet causes a crawling movement forward.
7. Protective. If you lay a newborn on his stomach, he tries to raise his head and turns it to the side.
8. Support reflex. If you take a baby under the armpits and place him on something, he will reflexively straighten his legs and rest on his entire foot.

The unconditioned reflexes of a newborn can go on for a long time. Each of them symbolizes the degree of development of certain parts of the nervous system. After an examination by a neurologist in the maternity hospital, a preliminary diagnosis of some diseases can be made.

From the point of view of their significance for the baby, the mentioned reflexes can be divided into two groups:

1. Segmental motor automatisms. They are provided by segments of the brain stem and spinal cord.
2. Posotonic automatisms. Provide regulation of muscle tone. The centers are located in the midbrain and medulla oblongata.

Oral segmental reflexes

This type of reflexes includes:

• Sucking. Appears during the first year of life.
• Search. Extinction occurs at 3-4 months.
• Proboscis reflex. If you hit a baby on the lips with your finger, he pulls them out into his proboscis. After 3 months, extinction occurs.
• The hand-mouth reflex is a good indicator of the development of the nervous system. If it does not appear or is very weak, then we can talk about damage to the central nervous system.

Spinal motor automatisms

Many unconditioned reflexes belong to this group. Examples include the following:

• Moro reflex. When a reaction is caused, for example, by hitting the table near the baby's head, the latter's arms are spread to the sides. Appears up to 4-5 months.
• Automatic gait reflex. When supported and slightly tilted forward, the baby makes stepping movements. After 1.5 months it begins to fade.
• Galant reflex. If you run your finger along the paravertebral line from the shoulder to the buttocks, the body bends towards the stimulus.

Unconditioned reflexes are assessed on a scale: satisfactory, increased, decreased, absent.

Differences between conditioned and unconditioned reflexes

Sechenov also argued that in the conditions in which the body lives, innate reactions are completely insufficient for survival; the development of new reflexes is required. They will help the body adapt to changing conditions.

How do unconditioned reflexes differ from conditioned reflexes? The table demonstrates this well.

Despite the obvious difference between conditioned reflexes and unconditioned ones, together these reactions ensure the survival and preservation of the species in nature.

Differences between conditioned reflexes and unconditioned ones. Unconditioned reflexes are innate reactions of the body; they were formed and consolidated in the process of evolution and are inherited. Conditioned reflexes arise, become consolidated, and fade away throughout life and are individual. Unconditioned reflexes are specific, i.e. they are found in all individuals of a given species. Conditioned reflexes may be developed in some individuals of a given species, but absent in others; they are individual. Unconditioned reflexes do not require special conditions For their occurrence, they necessarily arise if adequate stimuli act on certain receptors. Conditioned reflexes require special conditions for their formation; they can be formed in response to any stimuli (of optimal strength and duration) from any receptive field. Unconditioned reflexes are relatively constant, persistent, unchanging and persist throughout life. Conditioned reflexes are changeable and more mobile.

Unconditioned reflexes can occur at the level of the spinal cord and brain stem. Conditioned reflexes can be formed in response to any signals perceived by the body and are primarily a function of the cerebral cortex, realized with the participation of subcortical structures.

Unconditioned reflexes can ensure the existence of an organism only at the very early stage of life. The body's adaptation to constantly changing environmental conditions is ensured by conditioned reflexes developed throughout life. Conditioned reflexes are changeable. In the process of life, some conditioned reflexes, losing their meaning, fade away, others are developed.

Biological significance of conditioned reflexes. The body is born with a certain fund of unconditioned reflexes. They provide him with the maintenance of vital functions in relatively constant conditions of existence. These include unconditioned reflexes: food (chewing, sucking, swallowing, secretion of saliva, gastric juice, etc.), defensive (pulling a hand away from a hot object, coughing, sneezing, blinking when a stream of air enters the eye, etc.), sexual reflexes (reflexes associated with sexual intercourse, feeding and caring for offspring), thermoregulatory, respiratory, cardiac, vascular reflexes that maintain the constancy of the internal environment of the body (homeostasis), etc.

Conditioned reflexes provide a more perfect adaptation of the body to changing living conditions. They help to find food by smell, timely escape from danger, and orientation in time and space. Conditioned reflex separation of saliva, gastric, pancreatic juices in appearance, smell, meal time creates Better conditions to digest food before it enters the body. Enhancing gas exchange and increasing pulmonary ventilation before starting work, only when seeing the environment in which the work is being done, contributes to greater endurance and better performance of the body during muscular activity.

When a conditioned signal is applied, the cerebral cortex provides the body with preliminary preparation for responding to those environmental stimuli that will subsequently have an impact. Therefore, the activity of the cerebral cortex is signaling.

Conditions for the formation of a conditioned reflex. Conditioned reflexes are developed on the basis of unconditioned ones. The conditioned reflex was so named by I.P. Pavlov because certain conditions are needed for its formation. First of all, you need a conditioned stimulus, or signal. A conditioned stimulus can be any stimulus from the external environment or a certain change in the internal state of the body. In the laboratory of I.P. Pavlov, the flashing of an electric light bulb, the bell, the gurgling of water, skin irritation, taste, olfactory stimuli, the clinking of dishes, the sight of a burning candle, etc. were used as conditioned stimuli. Conditioned reflexes are temporarily developed in a person by observing a work regime, eating at the same time, consistent with bedtime.

A conditioned reflex can be developed by combining an indifferent stimulus with a previously developed conditioned reflex. In this way, conditioned reflexes of the second order are formed, then the indifferent stimulus must be reinforced with a conditioned stimulus of the first order. It was possible to form conditioned reflexes of the third and fourth orders in the experiment. These reflexes are usually unstable. Children managed to develop sixth-order reflexes.

The possibility of developing conditioned reflexes is hampered or completely eliminated by strong extraneous stimuli, illness, etc.

In order to develop a conditioned reflex, the conditioned stimulus must be reinforced with an unconditioned stimulus, that is, one that evokes an unconditioned reflex. The clinking of knives in the dining room will cause salivation in a person only if this clinking is supported by food one or more times. The ringing of knives and forks in our case is a conditioned stimulus, and the unconditioned stimulus that causes the salivary unconditioned reflex is food. The sight of a burning candle can become a signal for a child to withdraw his hand only if at least once the sight of a candle coincides with pain from a burn. When a conditioned reflex is formed, the conditioned stimulus must precede the action of the unconditioned stimulus (usually by 1-5 s).

The mechanism of formation of a conditioned reflex. According to the ideas of I.P. Pavlov, the formation of a conditioned reflex is associated with the establishment of a temporary connection between two groups of cortical cells: between those who perceive conditioned and those who perceive unconditional stimulation. This connection becomes stronger the more often both areas of the cortex are simultaneously excited. After several combinations, the connection turns out to be so strong that under the influence of only one conditioned stimulus, excitation also occurs in the second focus (Fig. 15).

Initially, an indifferent stimulus, if it is new and unexpected, causes a general generalized reaction of the body - an orienting reflex, which I. P. Pavlov called the exploratory or “what is it?” reflex. Any stimulus, if used for the first time, causes a motor reaction (general shudder, turning the eyes and ears towards the stimulus), increased breathing, heartbeat, generalized changes in the electrical activity of the brain - the alpha rhythm is replaced by rapid oscillations (beta rhythm). These reactions reflect generalized generalized arousal. When a stimulus is repeated, if it does not become a signal for a specific activity, the orienting reflex fades away. For example, if a dog hears a bell for the first time, it will give a general indicative reaction to it, but will not produce saliva. Now let's back up the sounding bell with food. In this case, two foci of excitation will appear in the cerebral cortex - one in the auditory zone, and the other in the food center (these are areas of the cortex that are excited under the influence of the smell and taste of food). After several reinforcements of the bell with food, a temporary connection will arise (close) in the cerebral cortex between the two foci of excitation.

In the course of further research, facts were obtained indicating that the closure of the temporary connection occurs not only along horizontal fibers (bark - bark). Cuts in the gray matter separated different areas of the cortex in dogs, but this did not prevent the formation of temporary connections between the cells of these areas. This gave reason to believe that the cortex-subcortex-cortex pathways also play an important role in establishing temporary connections. In this case, centripetal impulses from the conditioned stimulus through the thalamus and nonspecific system (hippocampus, reticular formation) enter the corresponding zone of the cortex. Here they are processed and along descending pathways reach the subcortical formations, from where the impulses come again to the cortex, but already in the zone of representation of the unconditioned reflex.

What happens in the neurons involved in the formation of a temporary connection? On this occasion there is various points vision. One of them assigns the main role to morphological changes in the endings of nerve processes.

Another point of view about the mechanism of the conditioned reflex is based on the principle of dominance by A. A. Ukhtomsky. In the nervous system at each moment of time there are dominant foci of excitation - dominant foci. The dominant focus has the property of attracting to itself the excitation entering other nerve centers, and thereby intensifying. For example, during hunger, a persistent focus with increased excitability appears in the corresponding parts of the central nervous system - a food dominant. If you let a hungry puppy lap milk and at the same time begin to irritate the paw with an electric current, then the puppy does not withdraw its paw, but begins to lap with even greater intensity. In a well-fed puppy, irritation of the paw with an electric current causes a reaction of its withdrawal.

It is believed that during the formation of a conditioned reflex, the focus of persistent excitation that arose in the center of the unconditioned reflex “attracts” to itself the excitation that arose in the center of the conditioned stimulus. As these two excitations combine, a temporary connection is formed.

Many researchers believe that the leading role in fixing the temporary connection belongs to changes in protein synthesis; Specific protein substances associated with imprinting a temporary connection have been described. The formation of a temporary connection is associated with the mechanisms of storing traces of excitation. However, memory mechanisms cannot be reduced to “belt connection” mechanisms.

There is evidence of the possibility of storing traces at the level of single neurons. Cases of imprinting from a single action of an external stimulus are well known. This gives grounds to believe that the closure of a temporary connection is one of the mechanisms of memory.

Inhibition of conditioned reflexes. Conditioned reflexes are plastic. They can persist for a long time, or they can be inhibited. Two types of inhibition of conditioned reflexes have been described - internal and external.

Unconditional, or external, inhibition. This type of inhibition occurs in cases where in the cerebral cortex, during the implementation of a conditioned reflex, a new, sufficiently strong focus of excitation appears, not associated with this conditioned reflex. If a dog has developed a conditioned salivary reflex to the sound of a bell, then turning on a bright light at the sound of a bell in this dog inhibits the previously developed salivation reflex. This inhibition is based on the phenomenon of negative induction: a new strong focus of excitation in the cortex from extraneous stimulation causes a decrease in excitability in the areas of the cerebral cortex associated with the implementation of the conditioned reflex, and, as a consequence of this phenomenon, inhibition of the conditioned reflex occurs. Sometimes this inhibition of conditioned reflexes is called inductive inhibition.

Inductive inhibition does not require development (that is why it is classified as unconditioned inhibition) and develops immediately as soon as an external stimulus, foreign to the given conditioned reflex, acts.

External braking also includes transcendental braking. It manifests itself when the strength or time of action of the conditioned stimulus increases excessively. In this case, the conditioned reflex weakens or completely disappears. This inhibition has a protective value, as it protects nerve cells from stimuli of too great strength or duration that could disrupt their activity.

Conditioned, or internal, inhibition. Internal inhibition, in contrast to external inhibition, develops within the arc of the conditioned reflex, i.e., in those nervous structures that are involved in the implementation of this reflex.

If external inhibition occurs immediately as soon as the inhibitory agent has acted, then internal inhibition must be developed; it occurs under certain conditions, and this sometimes takes a long time.

One type of internal inhibition is extinction. It develops if the conditioned reflex is not reinforced by an unconditioned stimulus many times.

Some time after extinction, the conditioned reflex can be restored. This will happen if we again reinforce the action of the conditioned stimulus with the unconditioned one.

Fragile conditioned reflexes are restored with difficulty. Extinction can explain the temporary loss of labor skills and the ability to play musical instruments.

In children, decline occurs much more slowly than in adults. This is why it is difficult to wean children from bad habits. Extinction is the basis of forgetting.

The extinction of conditioned reflexes has important biological significance. Thanks to it, the body stops responding to signals that have lost their meaning. How many unnecessary, superfluous movements would a person make during writing, labor operations, and sports exercises without extinctive inhibition!

The delay of conditioned reflexes also refers to internal inhibition. It develops if the reinforcement of a conditioned stimulus by an unconditioned stimulus is delayed. Usually, when developing a conditioned reflex, a conditioned stimulus-signal (for example, a bell) is turned on, and after 1-5 s food is given (unconditioned reinforcement). When the reflex is developed, immediately after the bell is turned on, without giving food, saliva begins to flow. Now let’s do this: turn on the bell, and gradually delay the food reinforcement until 2-3 minutes after the bell starts sounding. After several (sometimes very multiple) combinations of a sounding bell with delayed reinforcement with food, a delay develops: the bell turns on, and saliva will no longer flow immediately, but 2-3 minutes after the bell is turned on. Due to the non-reinforcement of the conditioned stimulus (bell) for 2-3 minutes by the unconditioned stimulus (food), the conditioned stimulus acquires an inhibitory value during the period of non-reinforcement.

The delay creates conditions for better orientation of the animal in the surrounding world. The wolf does not immediately rush at the hare when it sees it at a considerable distance. He waits for the hare to approach. From the moment the wolf saw the hare until the time the hare approached the wolf, a process of internal inhibition took place in the wolf’s cerebral cortex: motor and food conditioned reflexes were inhibited. If this did not happen, the wolf would often be left without prey, breaking into pursuit as soon as he sees the hare. The resulting delay provides the wolf with prey.

Delay in children is developed with great difficulty under the influence of upbringing and training. Remember how a first-grader impatiently reaches out his hand, waving it, getting up from his desk so that the teacher notices him. And only by high school age (and even then not always) do we notice endurance, the ability to restrain our desires, and willpower.

Similar sound, olfactory and other stimuli can signal completely different events. Only an accurate analysis of these similar stimuli ensures biologically appropriate reactions of the animal. Analysis of stimuli consists of distinguishing, separating different signals, differentiating similar interactions on the body. In the laboratory of I.P. Pavlov, for example, it was possible to develop the following differentiation: 100 metronome beats per minute were reinforced with food, and 96 beats were not reinforced. After several repetitions, the dog distinguished 100 metronome beats from 96: at 100 beats she salivated, at 96 beats the saliva did not separate. Discrimination, or differentiation, of similar conditioned stimuli is developed by reinforcing some and non-reinforcing other stimuli. The inhibition that develops suppresses the reflex reaction to non-reinforced stimuli. Differentiation is one of the types of conditioned (internal) inhibition.

Thanks to differential inhibition, it is possible to identify signal-significant signs of a stimulus from many sounds, objects, faces, etc. around us. Differentiation is developed in children from the first months of life.

Dynamic stereotype. The external world acts on the body not through single stimuli, but usually through a system of simultaneous and sequential stimuli. If this system is often repeated in this order, then this leads to the formation of a dynamic stereotype.

A dynamic stereotype is a sequential chain of conditioned reflex acts, carried out in a strictly defined, time-fixed order and resulting from a complex systemic reaction of the body to a complex of conditioned stimuli. Thanks to the formation of chain conditioned reflexes, each previous activity of the body becomes a conditioned stimulus - a signal for the next one. Thus, by previous activity the body is prepared for the subsequent one. A manifestation of a dynamic stereotype is a conditioned reflex for time, which contributes to the optimal functioning of the body with the correct daily routine. For example, eating at certain hours ensures good appetite and normal digestion; Consistency in keeping a bedtime helps children and adolescents fall asleep quickly and thus sleep longer; Carrying out educational work and work activities always at the same hours leads to faster processing of the body and better assimilation of knowledge, skills, and abilities.

A stereotype is difficult to develop, but if it is developed, then maintaining it does not require significant strain on cortical activity, and many actions become automatic. ;d A dynamic stereotype is the basis for the formation of habits in a person, the formation of a certain sequence in labor operations, and the acquisition of skills.

Walking, running, jumping, skiing, playing the piano, using a spoon, fork, knife when eating, writing - all these are skills that are based on the formation of dynamic stereotypes in the cerebral cortex.

The formation of a dynamic stereotype underlies the daily routine of every person. Stereotypes persist long years and form the basis of human behavior. Stereotypes that arise in early childhood are very difficult to change. Let us remember how difficult it is to “retrain” a child if he has learned to hold a pen incorrectly when writing, sit incorrectly at the table, etc. The difficulty of remaking stereotypes forces Special attention on the correct methods of raising and teaching children from the first years of life.

A dynamic stereotype is one of the manifestations of the systemic organization of higher cortical functions aimed at ensuring stable reactions of the body.

UNCONDITIONED REFLEX (specific, innate reflex) - a constant and innate reaction of the body to certain influences of the external world, carried out with the help of the nervous system and does not require special conditions for its occurrence. The term was introduced by I.P. Pavlov while studying the physiology of higher nervous activity. Unconditioned reflex occurs certainly if adequate stimulation is applied to a certain receptor surface. In contrast to this unconditionally occurring reflex, I.P. Pavlov discovered a category of reflexes, for the formation of which a number of conditions must be met - a conditioned reflex (see).

A physiological feature of the unconditioned reflex is its relative constancy. An unconditioned reflex always occurs with corresponding external or internal stimulation, manifesting itself on the basis of innate nerve connections. Since the constancy of the corresponding unconditioned reflex is the result of the phylogenetic development of a given animal species, this reflex received the additional name “species reflex”.

The biological and physiological role of the unconditioned reflex is that, thanks to this innate reaction, animals of a given species adapt (in the form of expedient acts of behavior) to the constant factors of existence.

The division of reflexes into two categories - unconditioned and conditioned - corresponds to two forms of nervous activity in animals and humans, which were clearly distinguished by I. P. Pavlov. The totality of the unconditioned reflex constitutes lower nervous activity, while the totality of acquired, or conditioned, reflexes constitutes higher nervous activity (see).

From this definition it follows that the unconditioned reflex, in its physiological significance, along with the implementation of constant adaptive reactions animal in relation to the action of environmental factors also determines those interactions nervous processes, which in total direct inner life body. This last property of the unconditioned reflex was especially emphasized by I. P. Pavlov. great importance. Thanks to innate nerve connections that ensure the interaction of organs and processes within the body, animals and humans acquire an accurate and stable flow of basic vital functions. important functions. The principle on the basis of which these interactions and integration of activities within the body are organized is self-regulation of physiological functions (see).

The classification of unconditioned reflexes can be built on the basis of the specific properties of the current stimulus and the biological meaning of the responses. It was on this principle that the classification was built in the laboratory of I. P. Pavlov. In accordance with this, there are several types of unconditioned reflex:

1. Food, the causative agent of which is the action nutrients on the receptors of the tongue and on the basis of the study of which all the basic laws of higher nervous activity are formulated. Due to the spread of excitation from the receptors of the tongue towards the central nervous system, excitation of branched innate nervous structures occurs, which generally constitute the food center; As a result of such a fixed relationship between the central nervous system and the working peripheral apparatuses, responses of the whole organism are formed in the form of an unconditioned food reflex.

2. Defensive, or, as it is sometimes called, protective reflex. This unconditioned reflex has a number of forms depending on which organ or part of the body is in danger. For example, applying painful stimulation to a limb causes the limb to be withdrawn, which protects it from further destructive effects.

In a laboratory setting, electric current from appropriate devices (Dubois-Reymond induction coil, city current with a corresponding voltage drop, etc.) is usually used as a stimulus that evokes a defensive unconditioned reflex. If air movement directed at the cornea of ​​the eye is used as a stimulus, then the defensive reflex is manifested by closing the eyelids - the so-called blink reflex. If the irritants are strong gaseous substances that are passed through the upper Airways, then the protective reflex will be a delay in respiratory excursions chest. The most common type of protective reflex in the laboratory of I.P. Pavlov is the acid protective reflex. It is expressed by a strong rejection reaction (vomiting) in response to the infusion of a solution of hydrochloric acid into the animal's oral cavity.

3. Sexual, which certainly occurs in the form of sexual behavior in response to an adequate sexual stimulus in the form of an individual of the opposite sex.

4. Orienting-exploratory, which is manifested by a rapid movement of the head towards the external stimulus that is acting at the moment. The biological meaning of this reflex consists in a detailed examination of the stimulus that acted and, in general, the external environment in which this stimulus arose. Thanks to the presence in the central nervous system Through the innate pathways of this reflex, the animal is able to respond expediently to sudden changes in the external world (see Orienting-exploratory reaction).

5. Reflexes with internal organs, reflexes when muscles and tendons are irritated (see Visceral reflexes, Tendon reflexes).

A common property of all unconditioned reflexes is that they can serve as the basis for the formation of acquired, or conditioned, reflexes. Some of the unconditioned reflexes, for example, defensive, lead to the formation of conditioned reactions very quickly, often after just one combination of any external stimulus with painful reinforcement. The ability of other unconditioned reflexes, for example, blinking or knee reflexes, to form temporary connections with an indifferent external stimulus is less pronounced.

It should also be taken into account that the speed of development of conditioned reflexes is directly dependent on the strength of the unconditioned stimulus.

The specificity of unconditioned reflexes lies in the exact correspondence of the body's response to the nature of the stimulus acting on the receptor apparatus. So, for example, when the taste buds of the tongue are irritated by a certain food, the reaction salivary glands the quality of the separated secretion is in exact accordance with the physical and chemical properties food taken. If the food is dry, then watery saliva is released, but if the food is sufficiently moistened, but consists of pieces (for example, bread), the unconditioned salivary reflex will manifest itself in accordance with this quality of food: saliva will contain a large amount of mucous glucoprotein - mucin, which prevents food injury ways.

Fine receptor assessment is associated with a lack of a particular substance in the blood, for example, the so-called calcium starvation in children during the period of bone formation. Since calcium selectively passes through the capillaries of developing bones, eventually its amount becomes below a constant level. This factor is a selective irritant of some specific cells of the hypothalamus, which in turn keeps increased excitability tongue receptors. This is how children develop a desire to eat plaster, whitewash and other minerals containing calcium.

Such an appropriate correspondence of the unconditioned reflex to the quality and strength of the stimulus that acts depends on the extremely differentiated effect of nutrients and their combinations on the receptors of the tongue. By receiving these combinations of afferent excitations from the periphery, central office The unconditioned reflex sends efferent excitations to the peripheral apparatus (glands, muscles), leading to the formation of a certain composition of saliva or the occurrence of movements. In fact, the composition of saliva can be easily changed through a relative change in the production of its main ingredients: water, proteins, salts. It follows from this that the central salivary apparatus can vary the quantity and quality of excited elements depending on the quality of excitation coming from the periphery. The correspondence of an unconditioned response to the specificity of the applied stimulation can go very far. I.P. Pavlov developed the idea of ​​the so-called digestive warehouse of certain unconditioned reactions. For example, if you feed an animal a certain type of food for a long time, the digestive juices of its glands (stomach, pancreas, etc.) eventually acquire a certain composition in terms of the amount of water, inorganic salts, and especially the activity of enzymes. Such a “digestive warehouse” cannot but be recognized as an expedient adaptation of innate reflexes to the established constancy of food reinforcement.

At the same time, these examples indicate that the stability, or immutability, of the unconditioned reflex is only relative. There is reason to think that already in the first days after birth, the specific “mood” of the tongue receptors is prepared by the embryonic development of animals, which ensures the successful selection of nutrients and the planned course of unconditioned reactions. So, if in mother’s milk, which a newborn baby feeds, increase the percentage of sodium chloride, then the child’s sucking movements are immediately inhibited, and in some cases the child actively throws out the mixture that has already been taken. This example convinces us that the innate properties of food receptors, as well as the properties of intranervous relationships, accurately reflect the needs of the newborn.

Methodology for using unconditioned reflexes

Since in the practice of work on higher nervous activity, the unconditioned reflex is a reinforcing factor and the basis for the development of acquired, or conditioned, reflexes, the question of methodological techniques for using the unconditioned reflex becomes especially important. In experiments on conditioned reflexes, the use of an unconditioned food reflex is based on feeding the animal with certain nutrients from an automatically fed feeder. With this method of using an unconditioned stimulus, the direct effect of food on the receptors of the animal’s tongue is inevitably preceded by a number of side irritations of the receptors related to various analyzers (see).

No matter how technically perfect the feeding of the feeder is, it certainly produces some kind of noise or knocking and, therefore, this sound stimulus is the inevitable precursor of the truest unconditioned stimulus, that is, the stimulus of the taste buds of the tongue. To eliminate these defects, a technique was developed for the direct introduction of nutrients into the oral cavity, while irrigation of the taste buds of the tongue, for example, with a sugar solution, is a direct unconditioned stimulus, not complicated by any side agent.

It should be noted, however, that under natural conditions animals and humans never receive food in oral cavity without preliminary sensations (sight, smell of food, etc.). Therefore, the method of directly introducing food into the mouth has some abnormal conditions and the animal’s reaction to the unusual nature of such a procedure.

In addition to this use of an unconditioned stimulus, there are a number of techniques in which the animal itself receives food with the help of special movements. These include a wide variety of devices with the help of which an animal (rat, dog, monkey) receives food by pressing the corresponding lever or button - the so-called instrumental reflexes.

The methodological features of reinforcement with an unconditioned stimulus have an undoubted influence on the experimental results obtained, and, therefore, the assessment of the results should be made taking into account the type of unconditioned reflex. This especially applies to the comparative assessment of the food and defensive unconditioned reflex.

While reinforcement with a food unconditioned stimulus is a positive factor for the animal biological significance(I.P. Pavlov), on the contrary, reinforcement with a painful stimulus is a stimulus for a biologically negative unconditioned reaction. It follows that “non-reinforcement” of a well-established conditioned reflex with an unconditioned stimulus in both cases will have the opposite biological sign. While non-reinforcement of a conditioned stimulus with food leads to a negative and often aggressive reaction in the experimental animal, on the contrary, non-reinforcement of a conditioned signal with electric current leads to a completely distinct biological positive reaction. These features of the animal’s attitude to the non-reinforcement of a conditioned reflex by one or another unconditioned stimulus can be clearly identified by such a vegetative component as breathing.

Composition and localization of unconditioned reflexes

The development of experimental technology has made it possible to study the physiological composition and localization of the unconditioned food reflex in the central nervous system. For this purpose, the very effect of an unconditioned food stimulus on the receptors of the tongue was studied. Unconditioned stimulus regardless of its nutritional properties and consistency primarily irritates the tactile receptors of the tongue. This is the most quick view excitation that is part of unconditioned stimulation. Tactile receptors produce the fastest and highest-amplitude type of nerve impulses, which first spread along the lingual nerve to the medulla oblongata and only after a few fractions of a second (0.3 seconds) they arrive there nerve impulses from temperature and chemical irritation of tongue receptors. This feature of the unconditioned stimulus, manifested in the sequential excitation of various receptors of the tongue, has a huge physiological significance: conditions are created in the central nervous system for signaling with each previous stream of impulses about subsequent irritations. Thanks to such relationships and characteristics of tactile excitation, depending on the mechanical qualities of a given food, in response only to these excitations, salivation can occur before the chemical qualities of the food act.

Special experiments carried out on dogs and studies of the behavior of newborn children have shown that such relationships between individual parameters of the unconditioned stimulus are used in the adaptive behavior of the newborn.

For example, in the first days after birth, the decisive stimulus for a child’s food intake is its chemical qualities. However, after a few weeks, the leading role passes to the mechanical properties of food.

In the lives of adults, information about the tactile parameters of food is faster than information about chemical parameters in the brain. Thanks to this pattern, the sensation of “porridge”, “sugar”, etc. is born before the chemical signal arrives in the brain. According to the teachings of I.P. Pavlov on the cortical representation of the unconditioned reflex, each unconditioned irritation, along with the inclusion of the subcortical apparatuses, has its own representation in the cerebral cortex. Based on the above data, as well as oscillographic and electroencephalographic analysis of the spread of unconditioned excitation, it was established that it does not have a single point or focus in the cerebral cortex. Each of the fragments of unconditional excitation (tactile, temperature, chemical) is addressed to different points of the cerebral cortex, and only the almost simultaneous stimulation of these points of the cerebral cortex establishes a systemic connection between them. These new data correspond to I. P. Pavlov’s ideas about the structure nerve center, however, require changes in existing ideas about the “cortical point” of the unconditioned stimulus.

Studies of cortical processes using electrical devices have shown that an unconditioned stimulus comes to the cerebral cortex in the form of a very generalized flow of ascending excitations, and, obviously, to every cell of the cortex. This means that not a single excitation of the sensory organs that preceded the unconditioned stimulus can “escape” its convergence with the unconditioned excitation. These properties of the unconditioned stimulus strengthen the idea of ​​“convergent closure” of the conditioned reflex.

Cortical representations of unconditioned reactions are cellular complexes that take an active part in the formation of a conditioned reflex, that is, in the closing functions of the cerebral cortex. By its nature, the cortical representation of the unconditioned reflex must be afferent in nature. As is known, I.P. Pavlov considered the cerebral cortex “an isolated afferent section of the central nervous system.”

Complex unconditioned reflexes. I.P. Pavlov identified a special category of unconditioned reflex, into which he included innate activities that are cyclical and behavioral in nature - emotions, instincts and other manifestations of complex acts of innate activity of animals and humans.

According to the initial opinion of I.P. Pavlov, complex unconditioned reflexes are a function of the “proximal subcortex”. This general expression refers to the thalamus, hypothalamus and other parts of the interstitial and midbrain. However, later, with the development of ideas about the cortical representations of the unconditioned reflex, this point of view was transferred to the concept of complex unconditioned reflexes. Thus, a complex unconditioned reflex, for example, an emotional discharge, has a specific subcortical part, but at the same time the very course of this complex unconditioned reflex at each individual stage is represented in the cerebral cortex. This point of view of I.P. Pavlov was confirmed by research recent years using the neurography method. It has been shown that a number of cortical areas, for example, the orbital cortex, the limbic area, are directly related to the emotional manifestations of animals and humans.

According to I.P. Pavlov, complex unconditioned reflexes (emotions) represent a “blind force” or “the main source of strength” for cortical cells. The provisions expressed by I. P. Pavlov about complex unconditioned reflexes and their role in the formation of conditioned reflexes at that time were only at the stage of the most general development, and only in connection with the discovery physiological characteristics hypothalamus, reticular formation of the brain stem, it became possible to study this problem in more depth.

From the point of view of I.P. Pavlov, the instinctive activity of animals, which includes several different stages of animal behavior, is also a complex unconditioned reflex. The peculiarities of this type of unconditioned reflex are that the individual stages of performing any instinctive action are connected with each other according to the principle of a chain reflex; however, it was later shown that each such stage of behavior must necessarily have a reverse afferentation) from the results of the action itself, that is, carry out the process of comparing the actually obtained result with the previously predicted one. Only after this can the next stage of behavior be formed.

In the process of studying the unconditioned pain reflex, it was revealed that pain excitation undergoes significant transformations at the level of the brain stem and hypothalamus. From these structures, unconditioned excitation generally covers all areas of the cerebral cortex simultaneously. Thus, along with the mobilization in the cerebral cortex of systemic connections that are characteristic of a given unconditional excitation and form the basis of the cortical representation of the unconditioned reflex, unconditioned stimulation also produces a generalized effect on the entire cerebral cortex. In electroencephalographic analysis of cortical activity, this generalized effect of an unconditioned stimulus on the cerebral cortex manifests itself in the form of desynchronization of the cortical waveform electrical activity. The conduction of unconditioned painful excitation to the cerebral cortex can be blocked at the level of the brain stem using a special substance - aminazine. After the introduction of this substance into the blood, even strong damaging (nociceptive) unconditioned excitation (burn hot water) does not reach the cerebral cortex and does not change its electrical activity.

Development of unconditioned reflexes in the embryonic period

The innate nature of the unconditioned reflex is especially clearly revealed in studies of the embryonic development of animals and humans. At different stages of embryogenesis, each stage of the structural and functional formation of the unconditioned reflex can be traced. The vital functional systems of a newborn are completely consolidated at the time of birth. Individual links of a sometimes complex unconditioned reflex, such as the sucking reflex, involve different parts of the body, often at a considerable distance from each other. Nevertheless, they are selectively united by various connections and gradually form a functional whole. The study of the maturation of the unconditioned reflex in embryogenesis makes it possible to understand the constant and relatively unchangeable adaptive effect of the unconditioned reflex upon application of the corresponding stimulus. This property of an unconditioned reflex is associated with the formation of interneuronal relationships based on morphogenetic and genetic patterns.

The maturation of the unconditioned reflex in the embryonic period is not the same for all animals. Because maturation functional systems embryo has the most important biological meaning in preserving the life of a newborn of a given species of animal, then, depending on the characteristics of the conditions of existence of each species of animal, the nature of structural maturation and the final formation of the unconditioned reflex will exactly correspond to the characteristics of the given species.

So, for example, the structural design of spinal coordination reflexes turns out to be different in birds, which, after hatching from an egg, immediately become completely independent (chicken), and in birds, which, after hatching from an egg, are for a long time helpless and in the care of their parents (rook). While a chick stands on its feet immediately after hatching and uses them completely freely every other day, in a rook, on the contrary, the forelimbs, that is, the wings, come into action first.

This selective growth of the nervous structures of the unconditioned reflex occurs even more clearly in the development of the human fetus. The very first and clearly visible motor reaction of the human fetus is the grasping reflex; it is detected already in the 4th month of intrauterine life and is caused by the application of any hard object to the palm of the fetus. Morphological analysis of all links of this reflex convinces us that, before it is revealed, a number of nerve structures differentiate into mature neurons and unite with each other. Myelination of the nerve trunks related to the finger flexors begins and ends earlier than this process unfolds in the nerve trunks of other muscles.

Phylogenetic development of unconditioned reflexes

According to the well-known position of I.P. Pavlov, unconditioned reflexes are a consequence of the consolidation by natural selection and heredity of those reactions acquired over thousands of years that correspond to repeated environmental factors and are useful for a given species.

There is reason to assert that the most rapid and successful adaptations of the organism may depend on favorable mutations, which are subsequently selected by natural selection and are already inherited.

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