Classical studies of the conditioned reflex activity of the body, which laid the foundation for I. P. Pavlov's theory of higher nervous activity, were carried out using salivation reflexes (the effector link of the reflex arc is the salivary glands). The technique is quite simple and boils down to the following scheme. To develop a positive (or negative) conditioned food reflex, the animal is presented with a stimulus (for example, a light or sound stimulus) that is indifferent to the unconditioned salivation reflex, followed by or simultaneously reinforcing it with an unconditioned stimulus (food). To collect saliva from an animal, an operation is first performed to remove the duct of the salivary gland (parotid, sublingual or submandibular) to the outer surface of the skin. The characteristics of both the unconditioned and the conditioned reflex developed on its basis are studied by analyzing the qualitative or quantitative composition of the secreted saliva.
When developing a defensive conditioned reflex (for example, to painful irritation), electrical stimulation of the skin is used as a reinforcing unconditioned reflex in this scheme.
Subsequently, in the study of the conditioned reflex activity of animals and humans, other methods began to be widely used, for example, motor conditioned reflexes. In this case, the effector link of the reflex arc is formed by muscles that determine and provide certain motor acts.
In the analysis of the neurophysiological mechanism of the formation and implementation of conditioned reflex activity, along with the study of salivary and motor indicators of the reflex reaction, methods for recording electrophysiological, biochemical, morphological (cyto- and histological) indicators of functioning are currently widely used. nervous system; study the vegetative and behavioral components of complex conditioned reflex acts of the animal and human body.
37. Physiology of higher nervous activity(GNI) is a branch of physiology that studies the functions of the higher part of the central nervous system - the cerebral cortex, through which the most complex relationships of a highly developed organism with the external environment are provided.
The physiology of GNI studies the formation of conditioned reflexes, the interaction of the processes of excitation and inhibition occurring in the cerebral cortex of the cerebral hemispheres. The physiology of GNI uses experimental research methods.
The physiology of GNI is the science of the activity of the leading parts of the brain.
38. Electroencephalography (EEG) - a method of recording the total electrical activity (biopotentials) of the cells of the cerebral hemispheres through intact integuments of the head, which makes it possible to judge its physiological maturity, functional state, the presence of focal lesions, cerebral disorders and their nature. The genetic conditionality of human EEG characteristics is confirmed by the fact that the individual characteristics of the electrical activity of the human brain are extremely stable. They are formed by the age of 20-25 and remain stable for a long time. This concerns both the frequency-amplitude characteristics of the EEG and the features of their temporal and spatial organization. Destructive changes in the EEG begin to appear in old age and are associated with the aging process.
One of the latest classifications of EEG types was proposed by E.A. Zhirmunskaya and V.S. Losev (1984). The authors identified 5 types and 17 groups of EEG activity, which do not exhaust all the richness of EEG phenomena, but fix only one of the most important characteristics - the degree and nature of the organization of an integral EEG pattern. The proposed classification is used not only to identify the most stable features of the organization of the bioelectrical activity of the central nervous system, but also to assess possible disturbances in its activity. The identified stable bioelectrical phenomena may be relevant to the determination of the general properties of a person, which determine his psychological, personal characteristics. Identification of signs of gross EEG disorders is a very alarming signal that determines the obligatory consultation with a neuropsychiatrist.
When analyzing an electroencephalogram, the frequency, amplitude, shape and duration of bioelectric oscillations are taken into account. According to these parameters, a number of activity rhythms can be distinguished in the human EEG. In an adult at rest and in the absence of external stimuli (especially when closed eyes in a darkened room) regular waves with a frequency of 8-13 Hz and an amplitude of up to 100 μV predominate. They are called the alpha rhythm, which is the main "rhythm of calm wakefulness" of a person. This rhythm is best expressed in the occipital regions; towards the frontal regions, it is replaced by higher-frequency and low-amplitude activity.
When a person moves from a state of rest to activity (perception of sensory signals, emotional response, mental work, etc.), the alpha rhythm is replaced by a beta rhythm: frequent (14-30 Hz) low-amplitude (up to 25 μV) oscillations. This phenomenon is called the EEG desynchronization response.
If a person goes from rest to sleep, then slow and high-amplitude waves appear in his EEG: theta (4-7 Hz) and delta ranges (0.5-3 Hz). The amplitude of these slow rhythms varies from 100 to 300 μV. Normally, theta and delta rhythms are not typical for the EEG of an awake adult. Theta rhythm accompanies dominant states, including those arising against the background of emotional reactions.
The process of activation of the nervous system, associated with the level of human behavioral activity, his level of wakefulness, is accompanied by a decrease in local synchronization of brain biopotentials - a decrease in amplitude and an increase in the frequency of oscillations. The lower the level of activity, the higher the amplitude and the lower the frequency of oscillations, the local synchronization of brain biopotentials increases.
Characteristics of EEG types
Type 1 organized (in time and space). The main component of the EEG is the alpha rhythm, which is characterized by a high degree of regularity, fairly good modulation in amplitude, or a slightly changed amplitude gradient across regions.
Type 2 is hypersynchronous (moderately disturbed). Excessively regular alpha, beta and theta activity with loss of regional differences.
Type 3 desynchronized (moderately modified). It is characterized by almost complete disappearance or a significant decrease in the amplitude of alpha waves, an increase in the amplitude and severity of beta oscillations or their absence, and the presence of a small number of slow waves. The amplitude of all EEG oscillations is very small.
Type 4 is disorganized (significantly impaired). Expressed, but not sufficiently regular in frequency or disorganized high-amplitude alpha activity, sometimes dominant in all areas. Beta activity is enhanced in amplitude, often represented by low-frequency oscillations. Delta and/or theta waves of sufficiently high amplitude may be present.
Type 5 is disorganized, with a predominance of theta and / or delta activity (grossly impaired). It is characterized by a slight expression of alpha activity. Either separate delta, theta and beta oscillations, or a delta and / or theta rhythm are recorded. The amplitude of EEG fluctuations either does not differ from the norm, or is high.
A conditioned reflex is an acquired reflex individual(individuals). Individuals arise during the life and are not fixed genetically (not inherited). They appear under certain conditions and disappear in their absence. They are formed on the basis of unconditioned reflexes with the participation of higher parts of the brain. Conditioned reflex reactions depend on past experience, on the specific conditions in which the conditioned reflex is formed.
I. P. Pavlov considered the conditioned reflex as a universal adaptive phenomenon to conditions environment. Unlike unconditional, it is not congenital, but is formed during life or is developed during training and is not inherited. Conditioned reflexes can form and disappear, but in the end they accumulate and represent life experience animal. Therefore, conditioned reflexes are not specific, but are individual in nature.
For example, a dog responds to its name and the voice of its handler. Each dog has its own set of conditioned reflexes that determine the individual characteristics of its behavior. That is why the behavior of a trained dog differs markedly from that of an untrained dog, the behavior of an old dog from that of a young one.
Conditioned reflexes are developed to any stimulus perceived by the body. Therefore, they can be formed in unlimited quantities. Unlike unconditioned reflexes, conditioned reflexes do not have ready-made reflex arcs. They are formed in the cerebral cortex by temporarily shorting conditioned signals with unconditioned reactions through neural connections.
Conditioned reflexes form the basis of dog training. During training, one can notice that some conditioned reflexes are formed easily and quickly, others slowly and with great difficulty; some reflexes are active and are resistant to extinction, while others are weak and easily inhibited. The qualitative characteristics of conditioned reflexes are determined by their species affiliation and the degree of physiological necessity for the organism at a given moment.
Methods for developing conditioned reflexes:
1. Classical salivation technique (Pavlovian). IP Pavlov studied the activity of the cerebral cortex according to the conditioned reflex reactions of the salivary gland, the duct of which led outward. As conditioned stimuli, you can use a variety of sound and light signals, smells, touching the skin, etc. It is necessary to observe the conditioned reflex activity of animals in isolated soundproof chambers (Fig. 1).
The salivation technique has played an exceptional role in the study of the basic patterns of higher nervous activity. An important advantage of this technique lies in the fact that the degree of excitation and inhibition processes in the corresponding areas of the cerebral cortex can be traced by the amount of saliva released. A lot of saliva is secreted - which means that a strong process of excitation, the amount of saliva decreases - the excitatory process weakens. Salivation technique has been used and is used mainly on dogs under experimental conditions.
2. The motor-defensive technique was first developed on dogs by V. M. Bekhterev and V. P. Protopopov, and was subsequently applied to study the higher nervous activity of farm animals. It is known that their salivation has a number of specific features that make it difficult to use the salivation technique; therefore, a motor-defensive technique is used to develop conditioned reflexes in horses and ruminants. The unconditioned reflex in this case is the defensive reflex of the forelimb to its stimulation by the induction current. Before applying irritation with current in the area of the fetlock on the forelimb, the hair is cut off. This place is moistened with isotonic sodium chloride solution; electrodes from the secondary induction coil are strengthened on it. Each pain stimulus is accompanied by a defensive reaction in the form of limb flexion. The movement of the limb is recorded on the kymograph tape using a pneumatic transmission. Various auditory, visual, olfactory, and skin stimuli can be used as conditioned stimuli.
The disadvantage of the motor-defensive technique is the obligatory application of painful irritation to the animal. After all, only feeling pain, the animal will withdraw the limb. It also cannot escape from painful irritation by flight, since it is firmly fixed. Therefore, when using this technique, complications often arise, manifested either in general motor restlessness, or, on the contrary, in severe depression of the animal.
3. Motor-food technique. One of its varieties is the method of free movement. It has found wide application for studying GNI in the most various kinds animals - from small (mice, rats) to large farm animals. This technique is most consistent with the natural habitat of animals and is easily applicable both in an experimental setting and in a production environment. The animal is in a room where it can move freely; the unconditioned stimulus is the portion of food in the feeder. A repeated combination of one or another conditioned stimulus (lighting a light bulb, knocking a metronome, etc.) with an unconditioned stimulus leads to the fact that the animal goes to the feeder only to the knock of a metronome or lighting a light bulb. The experimenter monitors his reaction.
Method of formation of conditioned reflexes
In connection with the fact that conditioned reflexes are acquired functions of the body, it is necessary to consider the method of their formation. Academician I.P. Pavlov said about this:
“So, the first and main condition for the formation of a conditioned reflex is the coincidence in time of the action of a previously indifferent (indifferent. - M. Kh.) agent with the action of an unconditioned agent that causes a certain unconditioned reflex.
Second important condition consists of the following. In the formation of a conditioned reflex, the indifferent agent must somewhat precede the action of the unconditioned stimulus. If we do the opposite and first begin to act as an unconditioned stimulus, and then add an indifferent agent, then no conditioned reflex is formed.
* (Pavlov I.P. Full. coll. soch., v. 4. Ed. 2nd, add. M.-L.: Publishing House of the Academy of Sciences of the USSR, 1951, p. 40.)
It follows from the foregoing that if any stimulus that is indifferent to a dog, for example, the sound of a whistle, is produced simultaneously with feeding, then this previously indifferent stimulus (I.P. Pavlov called it an agent) outside world begins to cause a food reaction after a few repetitions. Having heard the whistle, the dog will rush to where it received food at the same time as this signal. This reaction of the dog to the whistle is the conditioned reflex. Interestingly, this conditioned reflex is already developed in three-week-old puppies literally after two or three repetitions.
Starting to feed the puppies (after they "bite" what is in the plate and start to lap), whistle. When you re-feed, whistle again. At the third and subsequent feedings, you will not have to collect the puppies and carry them to the bowls. As soon as you put down bowls of food and whistle, the whole "nest" will jump up, fuss, start looking for food and rush straight to the whistle.
For an untrained dog, the command "Come to me!" is indifferent. A trained dog, having heard this command, will immediately approach you. When developing this conditioned reflex, absolutely the same thing happens as in the first example. You give the command "To me!" (this is a conditioned stimulus), and after a second you pull the dog towards you with a leash (this is an unconditioned stimulus). When the dog is near you, reinforce the irritant with a treat. After several such repetitions (the command "Come to me!" and food reinforcement), the dog, having heard only the command, will approach you, since it has formed a conditioned reflex to this conditioned stimulus.
Thus, in order to develop a conditioned reflex, it is necessary to coincide in time the conditioned and unconditioned stimuli with the obligatory reinforcement of the conditioned stimulus with encouragement, and most often with a treat. Why a treat? Academician I. P. Pavlov wrote on this occasion that "from the facts just cited, it becomes obvious that we use the unconditioned food reflex for experiments, since it is at the top of the hierarchical ladder of reflexes" *.
* (Pavlov I.P. Full. coll. soch., v. 4. Ed. 2nd, add. M.-L.: Publishing House of the Academy of Sciences of the USSR, 1951, p. 45.)
The second part of the methodology for the formation of conditioned reflexes affirms the need for the conditioned stimulus to somewhat precede the unconditioned stimulus. If the stimulus, which should become a conditioned reflex signal, is given after the unconditioned reflex stimulus, then the conditioned reflex is not formed.
So, when teaching a dog to walk alongside, you should always initially give the command "near" and after a second make a jerk with the leash. After a certain number of repetitions, the command "near" (conditioned stimulus) for your student will acquire the value of an unconditioned stimulus (jerking the leash). The dog, having heard only the command, will take place at your left leg - no jerking of the leash is required.
When teaching a dog to lie down when a shot is fired, to which it is already accustomed and executes the “down” command, it is necessary to ensure that the sound of the shot is a conditioned reflex signal for it. One or two seconds before the shot, the dog should be given the command to "lie down" and, as soon as it lies down, shoot.
If you don't have a treat, thank your dog with at least a treat, provided he did everything right. This will be the reinforcement that is necessary for the formation of a conditioned reflex. By continuing this procedure, you will achieve that your dog will lie down at the same time as the shot and when the bird takes off, since it will form a conditioned reflex to the sound of the shot, which will acquire the meaning of the “down” command. If the actions are performed in the reverse order, then a conditioned reflex is not formed. Here is what I. P. Pavlov wrote about this:
“In one dog, 427 combinations of the smell of vanillin with an infusion of acid were made, and the case began with an infusion, and the smell joined after 5-10 seconds. , was a good conditioned stimulus after only 20 combinations.In another dog, a strong electrical bell, which begins to act 5-10 seconds after the start of eating, did not become a conditioned stimulus of the food reaction after 374 combinations, already after five combinations, it turned out to be a conditioned stimulus ... " *
* (Pavlov I.P. Full. coll. soch., v. 4. Ed. 2nd, add. M.-L.: Publishing House of the Academy of Sciences of the USSR, 1951, p. 41.)
The essence of the third principle is that the hemispheres of the dog's brain should be free from other activities while working on the formation of a conditioned reflex. In laboratories, dogs are always imprisoned not only in special machines, but also in soundproof chambers. This is done in order to exclude the possible influence of extraneous stimuli.
It is impossible to do anything like this when training pointing dogs, and it is not necessary, since a hunting dog will never work in such conditions. However, it is necessary to strive to ensure that when working with a dog, distracting stimuli (especially sharp ones) at first would be as small as possible. In the future, as the skill, that is, the formation of a conditioned reflex, the situation must be complicated, so that by the end of practicing this technique, the dog would have to perform it in such conditions in which it will have to work.
The fourth condition is the strength of the conditioned stimulus. The weaker it is, the slower the conditioned reflex is formed. A sluggish and very quiet command will be sluggishly executed. But this does not mean at all that the command must be given in a thunderous voice, and a jerk of the leash, when teaching the dog to walk alongside, should knock it down. Trainers are aware of cases when a dog, having found itself on the lunge while developing the correct search, lies down after one or two strong jerks and cannot be lifted and forced to run by any means.
If the dog is full, and besides, spoiled when feeding, then it is unlikely that with the help of treats you will quickly achieve the development of a conditioned reflex. You will have to come up with a lot of tricks to get your student to take the treat.
A conditioned reflex is formed faster with an excitable unconditioned reflex. This means that when developing a conditioned reflex, the dog must be hungry enough, then every bite that you reward him with will be a treat for him. All dogs perform any command at first willingly, cheerfully, but after a while their actions become slow, as if forced. As soon as you notice this, immediately stop practicing the technique you have begun and switch to another one, as monotonous actions quickly tire the dog's nervous system. In no case do not use violent actions, threatening intonations, whips, lashes and other attributes of punishment. Know that if the dog is stubborn, it means that its nervous system is tired of the same actions.
Development of instrumental conditioned reflexes.
The classic technique for developing a conditioned reflex.
Techniques for the development of conditioned reflexes.
Reflexes developed using this technique are called reflexes of the first kind or classical reflexes.
Methodology.
First, a conditioned signal is given, after a short period of time an unconditioned stimulus (food, pain) is given. For a while they work together. The experiment is repeated several times, until the unconditional reaction begins to manifest itself already under the action of the conditioned signal (saliva is released at the sight of a light bulb). Most higher mammals require 10-15 repetitions.
Pavlov believed that the conditioned stimulus becomes a substitute for the unconditioned, as it begins to cause the same reaction. This is the stimulus substitution theory.
Conditions for the development of a classical conditioned reflex:
The coincidence in time of the conditioned and unconditioned stimuli is necessary;
The conditional signal must precede the unconditional signal;
The conditioned stimulus should not cause a strong reaction by itself;
The normal state of the higher parts of the central nervous system and a high level of motivation.
Absence of extraneous irritants.
Reflexes developed using this technique are called reflexes of the second kind or instrumental reflexes.
Methodology.
The animal is placed in a cage (“problem box”), to get out of the cage, it must press the lever. This technique is also called the "discrete trial" or "trial, error, and random success" method, since the animal initially acts at random until it succeeds by chance. The difference between instrumental conditioned reflexes and classical ones lies in the development methodology. The animal must itself be active, whereas in classical experiments the animal is passive.
Methodology.
The animal is placed in a cage and allowed to do whatever it wants. Some actions are reinforced and the animal begins to repeat them (or, on the contrary, avoid them). Subsequently, a method of successive approximation was developed, when the animal is taught complex actions, gradually complicating the task.
B. Skinner believed that by this method it was possible to develop any set of actions, but later it turned out that this was not the case if the applied stimulus caused instinctive behavior.
5. The concept of unconditioned reflexes and their classification
Animal behavior is based on simple and complex innate reactions - unconditioned reflexes persistently inherited. For the manifestation of unconditioned reflexes, an animal does not need training; it is born with reflex mechanisms ready for their manifestation, including a certain conductor apparatus, i.e. a ready-made nerve pathway - a reflex arc that provides the passage of nerve irritation from the receptor to the corresponding working organ (muscle or gland) when exposed to a certain stimulus. So, if you apply pain irritation to a dog's limb, it will certainly pull it back. This reaction undoubtedly will manifest itself with a strict pattern in any dog, therefore, reactions of this type I.P. Pavlov named unconditioned reflexes .
The very first innate reactions of a newborn cub: breathing, sucking, urination and other physiological acts are all unconditioned reflex reactions that ensure the existence of the organism for the first time. They arise under the influence of irritations coming mainly from the internal organs: a full bladder causes urination, the presence of feces in the rectum causes attempts, leading to defecation, etc. As the animal grows and matures, a number of other, more complex unconditioned reflexes appear. Such, for example, is the sexual reflex. A number of simple unconditional reflex acts are involved in the manifestation of a complex unconditioned reflex reaction. So, for example, the food reaction of a newborn puppy is carried out with the participation of a number of simpler acts - sucking, swallowing movements, reflex activity of the salivary glands and glands of the stomach. At the same time, since the previous unconditioned reflex act is a stimulus for the manifestation of the next one, they speak of chain nature of unconditioned reflexes . In practice, it is possible to observe a single simple unconditioned reflex only in laboratory conditions, by applying a point irritation to one single nerve ending and observing the response of one reflex arc. Under natural conditions, even in the case of a simple prick of the finger with a pin, several sensory neurons are always involved, and a whole bundle of motor neurons innervating the corresponding muscles takes part in the withdrawal of the hand. Therefore, in the process of studying the behavior of animals, it is more correct to use the term "unconditioned reflex reaction" instead of the term "unconditioned reflex".
The innate reflex can manifest itself until the higher centers have yet matured, but "disappears" as soon as the higher centers begin to exert an inhibitory effect. (for example, in a newborn baby). This is because the ontogenetic development of the nervous system occurs in the direction from the posterior caudal lower part of the brain, where the centers of simple congenital reflexes are located, to the anterior, rostral, higher parts. From the moment an organism is born, it has all the properties of an integral system that enters into continuous interaction with the external environment. The product of this interaction is behavior. In the process of individual development, organisms learn which behavioral responses produce the best results and modify their behavior accordingly. Holistic behavior includes two types of adaptive reactions - genotypic, due to the gene program, and phenotypic - due to the interaction of the genotype and environmental conditions, or individually acquired, based on learning.
There are several classifications of unconditioned reflexes.
1. By the nature of the stimulus and the biological meaning of the reaction (food, sexual, defensive, orienting reflex, children's, etc.).
2. According to the degree of complexity (simple ones are reactions to a simple, single stimulus and the spinal cord is responsible for them, they are performed automatically. The medulla oblongata is responsible for the complicated ones, the midbrain is responsible for the complex ones, the subcortical nuclei and partly the cerebral cortex are responsible for the most complex (instincts) ).
3. According to the function performed (classification by the Polish physiologist Yu. Konorsky)
. Conservation reflexes:
Reflexes of substances entering the body (inhalation, swallowing, etc.);
Reflexes of excretion of substances from the body (exhalation, urination, etc.);
Recovery reflexes (sleep);
Reflexes of species conservation (copulation, pregnancy, care for offspring).
B. Protective reflexes:
Withdrawal or withdrawal reflexes;
Reflexes to eliminate the stimulus from the surface of the body;
reflexes of destruction or neutralization of harmful agents (offensive reflexes).