8.2. Synthetic theory of evolution The population genetic approach laid the foundations of the modern, so-called synthetic theory of evolution (STE), based on the synthesis of genetics and Darwinism. The relationship between the degree of genetic variation in a population and the rate

Hormones of the adrenal cortex (corticosteroids) More than 40 different steroids are synthesized in the adrenal cortex, differing in structure and biological activity. Biologically active corticosteroids are grouped into 3 main classes: 1. glucocorticoids, which have

6.4. Analytical and synthetic activity of the cerebral cortex

Many stimuli from the external world and the internal environment of the body are perceived by receptors and become sources of impulses that enter the cerebral cortex. Here they are analyzed, differentiated and synthesized, combined, generalized. The ability of the cortex to separate, isolate and distinguish individual irritations, differentiate them is a manifestation analytical activity of the cerebral cortex.

First, stimulation is analyzed in receptors that specialize in light, sound stimuli, etc. Higher forms of analysis are carried out in the cerebral cortex. The analytical activity of the cerebral cortex is inextricably linked with its synthetic activity, expressed in the unification, generalization of excitation that arises in its various parts under the influence of numerous stimuli. An example of the synthetic activity of the cerebral cortex is the formation of a temporary connection, which underlies the development of a conditioned reflex. Complex synthetic activity is manifested in the formation of reflexes of the second, third and higher orders. The basis of generalization is the process of irradiation of excitation.

Analysis and synthesis are interconnected, and complex analytical-synthetic activity occurs in the cortex.

Dynamic stereotype. The external world acts on the body not with single stimuli, but usually with a system of simultaneous and sequential stimuli. If a system of successive stimuli is often repeated, this leads to the formation of systematicity, or a dynamic stereotype in the activity of the cerebral cortex. Thus, 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 system of positive (reinforced) and negative (non-reinforced, or inhibitory) conditioned stimuli.

The development of a stereotype is an example of the complex synthesizing activity of the cerebral cortex. A stereotype is difficult to develop, but if it is formed, then maintaining it does not require much effort in cortical activity, and many actions become automatic. 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. Examples of a dynamic stereotype include walking, running, jumping, skiing, playing musical instruments, using a spoon, fork, knife when eating, writing, etc.

Stereotypes persist for many years and form the basis of human behavior, but they are very difficult to reprogram.

Analysis and synthesis of stimuli in the cerebral cortex.

During the course of its life, the body experiences a huge amount of irritants, many of which are important for maintaining vital processes, and many of which are dangerous and the body must avoid their effects. To evaluate stimuli and respond appropriately, the cerebral cortex performs complex analytical-synthetic activities.

Analysis- this is discrimination, this is the decomposition of the stimulus into its component features, such as: the nature of the stimulus, its strength, place of action, duration of action, etc. Analysis consists of differentiating the stimulus and it begins initially in receptors, and then in those specialized for the perception of certain signs of the stimulus structures of the central nervous system. Depending on the complexity of the stimulus, different parts of the central nervous system are involved in the analysis. Higher analysis takes place in the cerebral cortex on the basis of processes of divergence (irradiation) of excitation in its neural networks, which are capable of identifying individual signs of the stimulus. A special role belongs to the left hemisphere, which is capable of processing information step by step and analytically.

Synthesis- this is a generalization, binding, association of many signs of a stimulus, which are manifested by excitation in various structures of the central nervous system. Synthesis in the cortex is carried out using convergent processes (concentration) on neurons that evaluate complex features. And they are explained by the ability of the right hemisphere to act synthetically, to process information simultaneously under the influence of several stimuli. An example of the synthetic activity of the cortex is the process of forming a temporary connection of a conditioned reflex.

Complex forms of synthetic activity of the cerebral cortex can be observed in the example dynamic stereotype.

Dynamic stereotype- this is a form of response recorded in memory if, for example, in an experiment an animal is presented with the same sequence of various conditioned stimuli day after day, some of which are reinforced by unconditioned stimuli, and some are not reinforced. If the life of animals proceeds day after day in the same type of conditions, then a stereotypical reaction is developed: presenting the animal with only one stimulus instead of all the stimuli from the complex triggers responses of different strengths, as if the animal were presented with the entire complex of stimuli. An example of such behavior is the developed daily routine.

The cerebral cortex in this case reacts according to a pattern. It evaluates only one of the stimulus complex. Conditioned reflex activity is carried out more easily; there is no need to analyze each stimulus in the system. This is associated with facilitation in the processes of learning and adaptation.

A person's dynamic stereotype underlies his habits and skills. The longer a stereotype is maintained, the more difficult it is to change it or abandon it. Therefore, older people are objectively conservative, it is difficult for them to give up their usual way of life and it is difficult for them to adapt to new conditions.

The interaction of excitation and inhibition processes in the cerebral cortex based on the irradiation and concentration of these processes. As already noted, in the process of forming a conditioned reflex, the generalization stage develops at the beginning. Pavlov explained the reason for the development of this stage by the irradiation of excitation to many nerve cells and their inclusion in a temporary connection. For example, if a conditioned reflex to the sound of a bell is developed, then at the beginning the sound of any bell causes the manifestation of this reflex, but as differential inhibition to non-reinforced bell sounds is formed, irradiation is limited and the conditioned reflex manifests itself only to the reinforced sound of the bell.

Later it was found that irradiation of excitation is possible due to numerous horizontal and vertical divergent connections between neurons of different centers.

As the conditioned reflex strengthens, the stage of specialization begins, as a result of the concentration of excitation. According to Pavlov, this becomes possible because Only the centers of the reinforced conditioned signal are involved in the implementation of the conditioned reflex. Concentration of excitation is possible on the basis of convergent connections between centers.

The processes of learning and education become more complex as the student matures. Instead of a summary perception of the explained, associated with the irradiation of excitation, there appears the ability to highlight individual aspects of objects and phenomena in the perception with a subsequent assessment of its holistic state. Thanks to this, the student’s mental activity moves from the particular to the general. The physiological mechanism of such changes is determined by the analytical and synthetic activity of the cerebral cortex.

Analysis(analytical activity) is the body’s ability to decompose, dissect stimuli acting on the body (images of the external world) into the simplest constituent elements, properties and characteristics.

Synthesis(synthetic activity) is a process opposite to analysis, which consists in isolating, among the simplest elements, properties and characteristics decomposed during analysis, the most important, essential at a given moment and combining them into complex complexes and systems.

The unity of the analytical-synthetic activity of the brain lies in the fact that the body, with the help of sensory systems, distinguishes (analyzes) all existing external and internal stimuli and, based on this analysis, forms an idea about them.

VND is the analytical and synthetic activity of the cortex and the nearest subcortical formations of the brain, which manifests itself in the ability to isolate its individual elements from the environment and combine them into combinations that exactly correspond to the biological significance of the phenomena of the surrounding world.

Physiological basis of synthesis consist of concentration of excitation, negative induction and dominance. In turn, synthetic activity is the physiological basis of the first stage of the formation of conditioned reflexes (the stage of generalization of conditioned reflexes, their generalization). The generalization stage can be observed in an experiment if a conditioned reflex is formed to several similar conditioned signals. It is enough to strengthen the reaction to one such signal in order to be convinced of the appearance of a similar reaction to another, similar to it, although a reflex to it has not yet been formed. This is explained by the fact that each new conditioned reflex always has a generalized character and allows a person to form only an approximate idea of ​​the phenomenon caused by it. Consequently, the generalization stage is a state of formation of reflexes in which they manifest themselves not only under the action of reinforced, but also under the action of similar non-reinforced conditioned signals. In humans, an example of generalization can be the initial stage of the formation of new concepts. The first information about the subject or phenomenon being studied is always generalized and very superficial. Only gradually does a relatively accurate and complete knowledge of the subject emerge from it. The physiological mechanism of generalization of the conditioned reflex consists in the formation of temporary connections of the reinforcing reflex with conditioned signals close to the main one. Generalization has important biological significance, because leads to a generalization of actions created by similar conditioned signals. Such a generalization is useful because it makes it possible to assess the general meaning of the newly formed conditioned reflex, without taking into account its particulars, the essence of which can be understood later.

Physiological basis of analysis consists of irradiation of excitation and differential inhibition. In turn, analytical activity is the physiological basis of the second stage of the formation of conditioned reflexes (the stage of specialization of conditioned reflexes).

If we continue the formation of conditioned reflexes to the same similar stimuli with the help of which the generalization stage arose, we will notice that after some time conditioned reflexes arise only to the reinforced signal and do not appear to any of the signals similar to it. This means that the conditioned reflex has become specialized. The stage of specialization is characterized by the emergence of a conditioned reflex to only one main signal with the loss of the signal value of all other similar conditioned signals. The physiological mechanism of specialization consists in the extinction of all side conditioned connections. The phenomenon of specialization underlies the pedagogical process. The first impressions that a teacher creates about an object or phenomenon are always general and only gradually are they clarified and detailed. Only that which corresponds to reality and turns out to be necessary is strengthened. Specialization, therefore, aims at significantly clarifying knowledge about the subject or phenomenon being studied.

Analysis and synthesis are inextricably linked. Analytical-synthetic (integrative) activity of the nervous system is the physiological basis of perception and thinking.

The connection of the organism with the environment is the more perfect, the more developed the ability of the nervous system to analyze, isolate signals from the external environment that act on the organism, and synthesize and combine those of them that coincide with any of its activities. Abundant information coming from the internal environment of the body is also subject to analysis and synthesis.

Using the example of a person’s sensation and perception of parts of an object and the entire object as a whole, I.M. Sechenov proved the unity of the mechanisms of analytical and synthetic activity. A child, for example, sees in a picture an image of a person, his entire figure, and at the same time notices that the person consists of a head, neck, arms, etc. This is achieved thanks to his ability “...to sense each point of a visible object separately from others and at the same time all at once.”

Each analyzer system carries out three levels of analysis and synthesis of stimuli:

1) in receptors - the simplest form of isolating signals from the external and internal environment of the body, encoding them into nerve impulses and sending them to overlying sections;

2) in subcortical structures - a more complex form of isolating and combining stimuli of various kinds of unconditioned reflexes and signals of conditioned reflexes, realized in the mechanisms of interaction between the higher and lower parts of the central nervous system, i.e. analysis and synthesis, which began in the receptors of the sensory organs, continue in the thalamus, hypothalamus, reticular formation and other subcortical structures. Thus, at the level of the midbrain, the novelty of these stimuli will be assessed (analysis) and a number of adaptive reactions will arise: turning the head towards the sound, listening, etc. (synthesis - sensory excitations will be combined with motor ones);

3) in the cerebral cortex - the highest form of analysis and synthesis of signals coming from all analyzers, as a result of which systems of temporary connections are created that form the basis of VNI, images, concepts, semantic differentiation of words, etc. are formed.

Analysis and synthesis are carried out according to a specific program, fixed by both innate and acquired nervous mechanisms.

To understand the mechanisms of analytical and synthetic activity of the brain, I.P. Pavlov’s ideas about the cerebral cortex as a mosaic of inhibitory and excitatory points and at the same time as a dynamic system (stereotype) of these points, as well as about cortical systematicity in the form of a process of combining “points” of excitation and inhibition into a system. The systematic functioning of the brain expresses its ability to achieve higher synthesis. The physiological mechanism of this ability is provided by the following three properties of GNI:

a) the interaction of complex reflexes according to the laws of irradiation and induction;

b) preservation of traces of signals that create continuity between the individual components of the system;

c) consolidation of emerging connections in the form of new conditioned reflexes to complexes. Systematicity creates integrity of perception.

Finally, the well-known general mechanisms of analytical-synthetic activity include the “switching” of conditioned reflexes, first described by E.A. Asratyan.

Conditioned reflex switching is a form of variability of conditioned reflex activity, in which the same stimulus changes its signal value due to a change in the situation. This means that under the influence of the situation there is a change from one conditioned reflex activity to another. Switching is a more complex type of analytical-synthetic activity of the cerebral cortex compared to a dynamic stereotype, chain conditioned reflex and tuning.

The physiological mechanism of conditioned reflex switching has not yet been established. It is possible that it is based on complex processes of synthesis of various conditioned reflexes. It is also possible that a temporary connection is initially formed between the cortical point of the conditioned signal and the cortical representation of unconditional reinforcement, and then between it and the switching agent, and finally between the cortical points of the conditioned and reinforcing signals.

In human activity, the switching process is very important. In teaching activities, teachers working with primary schoolchildren especially often encounter it. Students in these classes often find it difficult to move both from one operation to another within the framework of one activity, and from one lesson to another (for example, from reading to writing, from writing to arithmetic). Teachers often classify students' insufficient switching ability as a manifestation of inattention, absent-mindedness, and distractibility. However, this is not always the case. Violation of switching is very undesirable, because it causes the student to lag behind the teacher’s presentation of the content of the lesson, which subsequently causes a weakening of attention. Therefore, switchability as a manifestation of flexibility and lability of thinking should be nurtured and developed in students.

In a child, the analytical and synthetic activity of the brain is usually underdeveloped. Young children learn to speak relatively quickly, but they are completely unable to isolate parts of words, for example, to break syllables into sounds (weakness of analysis). With even greater difficulty they manage to compose individual words or at least syllables from letters (weakness of synthesis). It is important to take these circumstances into account when teaching children to write. Usually, attention is paid to the development of synthetic activity of the brain. Children are given cubes with letters on them and forced to form syllables and words from them. However, learning progresses slowly because the analytical activity of children's brains is not taken into account. For an adult, it costs nothing to decide what sounds the syllables “da”, “ra”, “mu” are made of, but for a child this is a lot of work. He cannot separate a vowel from a consonant. Therefore, at the beginning of training, it is recommended to break words into individual syllables, and then syllables into sounds.

Thus, the principle of analysis and synthesis covers the entire GNI and, consequently, all mental phenomena. Analysis and synthesis are difficult for a person due to his verbal thinking. The main component of human analysis and synthesis is speech motor analysis and synthesis. Any type of analysis of stimuli occurs with the active participation of the orienting reflex.

Analysis and synthesis occurring in the cerebral cortex are divided into lower and higher. Lower analysis and synthesis are inherent in the first signal system. Higher analysis and synthesis is analysis and synthesis carried out by the joint activity of the first and second signal systems with the obligatory awareness by a person of the objective relations of reality.

Any process of analysis and synthesis necessarily includes as a component its final phase - the results of the action. Mental phenomena are generated by brain analysis and synthesis.

Dynamic stereotype is a system of conditioned and unconditioned reflexes, which is a single functional complex. In other words, a dynamic stereotype is a relatively stable and long-lasting system of temporary connections formed in the cerebral cortex in response to the implementation of the same types of activities at the same time, in the same sequence from day to day, i.e. . it is a series of automatic actions or a series of conditioned reflexes brought to an automatic state. DS can exist for a long time without any reinforcement.

The physiological basis for the formation of the initial stage of a dynamic stereotype is conditioned reflexes for time. But the mechanisms of the dynamic stereotype have not yet been deeply studied.

DS plays an important role in the education and upbringing of children . If a child goes to bed and wakes up at the same time every day, has breakfast and lunch, does morning exercises, carries out hardening procedures, etc., then the child develops a time reflex. Consistent repetition of these actions forms in the child a dynamic stereotype of nervous processes in the cerebral cortex.

It can be assumed that the reason for what is called student overload is of a functional nature and is caused not only by the dosage and difficulty of educational tasks, but also by the negative attitude of teachers towards the dynamic stereotype, as the most important physiological basis of learning. Teachers do not always succeed in constructing a lesson so that it represents a system of dynamic stereotypes. If the content of each new lesson were organically linked with the previous and subsequent ones into a single mobile system, which made it possible, if necessary, to make changes to it, as in a dynamic stereotype, and not as a simple addition, then the work of students would be so facilitated that it would no longer would cause overload.

The strengthening of a dynamic stereotype is the physiological basis of a person’s inclinations, which in psychology are designated as habits. Habits are acquired by a person in different ways, but, as a rule, without sufficient motivation and often completely spontaneously. However, according to the mechanism of a dynamic stereotype, not only such, but also purposeful habits are formed. These include the daily routine developed by the schoolchild.

Each habit is developed and strengthened through training on the principle of a conditioned reflex. At the same time, external and internal irritations serve as trigger signals for them. For example, we do morning exercises not only because we are used to it, but also because we see sports equipment that in our minds is associated with morning exercises. This habit is reinforced by both the morning exercise itself and the feeling of satisfaction that comes after it.

From a physiological point of view, skills are dynamic stereotypes, in other words, chains of conditioned reflexes. A well-developed skill loses connection with the second signaling system, which is the physiological basis of consciousness only if a mistake is made, i.e. a movement is made that does not achieve the desired result, an indicative reflex appears. The resulting excitations disinhibit the inhibited connections of the automatic skill, and it is again carried out under the control of the second signaling system, or, in psychological terms, consciousness. Now the error is corrected and the desired conditioned reflex movement is carried out.

A person’s dynamic stereotype includes not only a large number of different motor skills and habits, but also a habitual way of thinking, beliefs, and ideas about surrounding events.

Analytical and synthetic activity of the cerebral cortex

Analysis is the distinction, separation of different sensory signals, differentiation of various effects on the body. Although the analysis of sensory signals begins already in the receptor apparatus, and various subcortical centers are involved in this process, the main analytical process takes place in the cerebral cortex (therefore it is called higher analysis). It is here, in the cerebral cortex, that depending on the strength, duration and steepness of the increase in the stimulus, a unique spatio-temporal pattern of excitation arises each time, due to which the discrimination of stimuli with similar properties is achieved. A form of analysis specific to the cerebral cortex consists of distinguishing (differentiating) stimuli according to their signal value, which is achieved by the participation in this process of the mechanism underlying internal inhibition. The degree of analysis performed by cortical cells varies. It can be quite simple and primitive, for example, in conditions when the body is affected by only two separate stimuli. But the analysis can also be very complex, for example, when the body is exposed to a complex of stimuli. With the participation of the mechanism of internal inhibition, the cerebral cortex is able to perceive not only individually each component of this complex, and not only in total, but also in a certain sequence. In addition to analyzing stimuli, the cerebral cortex also carries out synthetic activity, that is, linking, generalization, and combining excitations that arise in different areas of the cortex. Cortical cells are characterized by both simple and complex forms of synthesis. It is believed that the brain’s ability to predict and foresee future events is realized thanks to the complex synthetic activity of the brain. The processes of analysis and synthesis in the cerebral cortex are inextricably linked. Therefore, it is customary to talk about the analytical-synthetic activity of the cerebral cortex as a single process that ensures the formation of various forms of human behavior.

The analytical and synthetic activity of the human cerebral cortex is characterized, in comparison with animals, by an immeasurably higher level of development. The higher level of development of the analytical and synthetic activity of the human cerebral cortex is due to the presence of a second signaling system. It is the participation of the word that gives specific features to the process of formation of systems of temporary connections.

Limbic system of the brain

In 1878, the French neuroanatomist P. Broca described brain structures located on the inner surface of each cerebral hemisphere, which, like an edge, or limbus, border the brain stem. He called them the limbic lobe. Subsequently, in 1937, the American neurophysiologist D. Peipets described a complex of structures (Papetz circle), which, in his opinion, are related to the formation of emotions. These are the anterior nuclei of the thalamus, mammillary bodies, hypothalamic nuclei, amygdala, nuclei of the septum pellucida, hippocampus, cingulate gyrus, Gudden's mesencephalic nucleus and other formations. Thus, Peipetz's circle contained various structures, including the limbic cortex and the olfactory brain. The term “limbic system” or “visceral brain” was proposed in 1952 by the American physiologist P. McLean to refer to the Peipetz circle. Later, other structures were included in this concept, the function of which was associated with the archiopaleocortex. Currently, the term “limbic system” is understood as a morphofunctional association, including a number of phylogenetically old structures of the cerebral cortex, a number of subcortical structures, as well as structures of the diencephalon and midbrain, which are involved in the regulation of various autonomic functions of internal organs, in ensuring homeostasis, and in self-preservation species, in the organization of emotional-motivational behavior and the “wakefulness-sleep” cycle.

Limbic system of the brain: 1, 2, 3 nuclei of the thalamus, 4 hypothalamus

The limbic system includes the prepiriform cortex, periamygdala cortex, diagonal cortex, olfactory brain, septum, fornix, hippocampus, dentate fascia, base of the hippocampus, cingulate gyrus, parahippocampal gyrus. Note that the term “limbic cortex” refers to only two formations - the cingulate gyrus and the parahippocampal gyrus. In addition to the structures of the ancient, old and middle cortex, the limbic system includes subcortical structures - the amygdala (or amygdala complex), located in the medial wall of the temporal lobe, the anterior nuclei of the thalamus, mastoid or mamillary bodies, mastoid-thalamic fascicle, hypothalamus, and also the reticular nuclei of Gudden and Bekhterev, located in the midbrain. All the main formations of the limbic cortex cover the base of the forebrain in a ring-like manner and are a kind of boundary between the neocortex and the brainstem. A feature of the limbic system is the presence of multiple connections both between individual structures of this system and between the limbic system and other brain structures, through which information, moreover, can circulate for a long time. Thanks to these features, conditions are created for effective control of brain structures by the limbic system (“imposition” of limbic influence). Currently, such circles as, for example, the Peipets circle (hippocampus - mammillary or mamillary bodies - anterior nuclei of the thalamus - cingulate gyrus - parahippocampal gyrus - hippocampal base - hippocampus), which are related to memory processes and learning processes, are well known. A circle is known that connects such structures as the amygdala, hypothalamus and midbrain structures, regulating aggressive-defensive behavior, as well as eating and sexual behavior. There are circles in which the limbic system is included as one of the important “stations”, due to which important brain functions are realized. For example, a circle connecting the neocortex and limbic system through the thalamus into a single whole is involved in the formation of figurative, or iconic, memory, and a circle connecting the neocortex and limbic system through the caudate nucleus is directly related to the organization of inhibitory processes in the cerebral cortex .

Functions of the limbic system. Due to the abundance of connections within the limbic system, as well as its extensive connections with other brain structures, this system performs a fairly wide range of functions:

1) regulation of the functions of diencephalic and neocortical formations;

2) formation of the emotional state of the body;

3) regulation of vegetative and somatic processes during emotional and motivational activity;

4) regulation of the level of attention, perception, memory, thinking;

5) selection and implementation of adaptive forms of behavior, including such biologically important types of behavior as searching, feeding, sexual, defensive;

6) participation in the organization of the sleep-wake cycle.

The limbic system, as a phylogenetically ancient formation, has a regulatory influence on the cerebral cortex and subcortical structures, establishing the necessary correspondence of their activity levels. There is no doubt that an important role in the implementation of all the listed functions of the limbic system is played by the entry into this brain system of information from olfactory receptors (phylogenetically the most ancient method of receiving information from the external environment) and its processing.

The hippocampus (seahorse, or Ammon's horn) is located deep in the temporal lobes of the brain and is an elongated elevation (up to 3 cm long) on ​​the medial wall of the lower, or temporal, horn of the lateral ventricle. This elevation, or protrusion, is formed as a result of a deep depression from the outside into the cavity of the inferior horn of the hippocampal sulcus. The hippocampus is considered as the main structure of the archiocortex and as an integral part of the olfactory brain. In addition, the hippocampus is the main structure of the limbic system; it is connected with many brain structures, including through commissural connections (commissure of the fornix) with the hippocampus of the opposite side, although in humans a certain independence in the activity of both hippocampuses has been found. Hippocampal neurons are distinguished by pronounced background activity, and most of them are characterized by polysensory properties, i.e., the ability to respond to light, sound and other types of stimulation. Morphologically, the hippocampus is represented by stereotypically repeating neuron modules connected to each other and to other structures. The connection of the modules creates the conditions for the circulation of electrical activity in the hippocampus during learning. At the same time, the amplitude of synaptic potentials increases, the neurosecretion of hippocampal cells and the number of spines on the dendrites of its neurons increase, which indicates the transition of potential synapses to active ones. The modular structure determines the ability of the hippocampus to generate high-amplitude rhythmic activity. Background electrical activity of the hippocampus, as studies have shown in humans, is characterized by two types of rhythms: fast (15–30 oscillations per second) low-voltage rhythms such as the beta rhythm and slow (4–7 oscillations per second) high-voltage rhythms such as the theta rhythm. At the same time, the electrical rhythmicity of the hippocampus is in a reciprocal relationship with the rhythmicity of the neocortex. For example, if during sleep a theta rhythm is recorded in the neocortex, then during the same period a beta rhythm is generated in the hippocampus, and during wakefulness the opposite picture is observed - in the neocortex - an alpha rhythm and a beta rhythm, and in the hippocampus it is predominantly registered theta rhythm. It has been shown that activation of neurons in the reticular formation of the brainstem increases the severity of the theta rhythm in the hippocampus and the beta rhythm in the neocortex. A similar effect (increased theta rhythm in the hippocampus) is observed when a high level of emotional stress is formed (during fear, aggression, hunger, thirst). It is believed that the theta rhythm of the hippocampus reflects its participation in the orienting reflex, in reactions of alertness, increased attention, and in the dynamics of learning. In this regard, the theta rhythm of the hippocampus is considered as an electroencephalographic correlate of the awakening reaction and as a component of the orienting reflex.

The role of the hippocampus in the regulation of autonomic functions and the endocrine system is important. It has been shown that especially hippocampal neurons, when excited, can have a pronounced effect on cardiovascular activity, modulating the activity of the sympathetic and parasympathetic nervous system. The hippocampus, like other structures of the archiopaleocortex, is involved in the regulation of the activity of the endocrine system, including the regulation of the release of glucocorticoids and thyroid hormones, which is realized with the participation of the hypothalamus. The gray matter of the hippocampus belongs to the motor area of ​​the olfactory brain. It is from here that descending impulses arise to the subcortical motor centers, causing movement in response to certain olfactory stimuli.

Involvement of the hippocampus in the formation of motivation and emotions. It has been shown that removal of the hippocampus in animals causes the appearance of hypersexuality, which, however, does not disappear with castration (maternal behavior may be disrupted). This suggests that changes in sexual behavior modulated from the archiopaleocortex are based not only on hormonal origin, but also on changes in the excitability of neurophysiological mechanisms that regulate sexual behavior. It has been shown that irritation of the hippocampus (as well as the forebrain bundle and the cingulate cortex) causes sexual arousal in the male. There is no clear evidence regarding the role of the hippocampus in modulating emotional behavior. However, it is known that damage to the hippocampus leads to a decrease in emotionality, initiative, a slowdown in the speed of basic nervous processes, and an increase in the thresholds for evoking emotional reactions. It has been shown that the hippocampus, as a structure of the archiopaleocortex, can serve as a substrate for the closure of temporary connections, and also, by regulating the excitability of the neocortex, contributes to the formation of conditioned reflexes at the level of the neocortex. In particular, it has been shown that removal of the hippocampus does not affect the rate of formation of simple (food) conditioned reflexes, but inhibits their consolidation and differentiation of new conditioned reflexes. There is information about the participation of the hippocampus in the implementation of higher mental functions. Together with the amygdala, the hippocampus is involved in calculating the probability of events (the hippocampus records the most likely events, and the amygdala records the unlikely ones). At the neural level, this can be ensured by the work of novelty neurons and identity neurons. Clinical observations, including those of W. Penfield and P. Milner, indicate the involvement of the hippocampus in memory mechanisms. Surgical removal of the hippocampus in humans causes memory loss for events in the immediate past while retaining memory for distant events (retroanterograde amnesia). Some mental illnesses that occur with memory impairment are accompanied by degenerative changes in the hippocampus.

Cingulate gyrus. It is known that damage to the cingulate cortex in monkeys makes them less fearful; animals cease to be afraid of humans, and do not show signs of affection, anxiety or hostility. This indicates the presence in the cingulate gyrus of neurons responsible for the formation of negative emotions.

Nuclei of the hypothalamus as a component of the limbic system. Stimulation of the medial nuclei of the hypothalamus in cats causes an immediate rage reaction. A similar reaction is observed in cats when the part of the brain located in front of the hypothalamic nuclei is removed. All this indicates the presence in the medial hypothalamus of neurons that participate, together with the nuclei of the amygdala, in organizing emotions accompanied by rage. At the same time, the lateral nuclei of the hypothalamus are, as a rule, responsible for the appearance of positive emotions (saturation centers, pleasure centers, positive emotion centers).

The amygdala, or cogrus amygdaloideum (synonyms - amygdala, amygdala complex, almond-shaped complex, amygdala), according to some authors, belongs to the subcortical, or basal, nuclei, according to others - to the cerebral cortex. The amygdala is located deep in the temporal lobe of the brain. The neurons of the amygdala are varied in shape, their functions are associated with the provision of defensive behavior, autonomic, motor, emotional reactions, and the motivation of conditioned reflex behavior. The involvement of the amygdala in the regulation of the processes of urine formation, urination and contractile activity of the uterus has also been shown. Damage to the amygdala in animals leads to the disappearance of fear, calmness, and inability to rage and aggression. Animals become gullible. The amygdala regulates eating behavior. Thus, damage to the amygdala in a cat leads to increased appetite and obesity. In addition, the amygdala also regulates sexual behavior. It has been established that damage to the amygdala in animals leads to hypersexuality and the emergence of sexual perversions, which are removed by castration and reappear with the introduction of sex hormones. This indirectly indicates control by the neurons of the amygdala in the production of sex hormones. Together with the hippocampus, which has novelty neurons that reflect the most likely events, the amygdala calculates the probability of events, since it contains neurons that record the most unlikely events.

From an anatomical point of view, the septum pellucidum (septum) is a thin plate consisting of two sheets. The transparent septum passes between the corpus callosum and the fornix, separating the anterior horns of the lateral ventricles. The plates of the transparent septum contain nuclei, i.e., accumulations of gray matter. The septum pellucidum is generally classified as a structure of the olfactory brain; it is an important component of the limbic system.

It has been shown that the septal nuclei are involved in the regulation of endocrine function (in particular, they influence the secretion of corticosteroids by the adrenal glands), as well as the activity of internal organs. The septal nuclei are related to the formation of emotions - they are considered as a structure that reduces aggressiveness and fear.

The limbic system, as is known, includes the structures of the reticular formation of the midbrain, and therefore some authors propose to talk about the limbic-reticular complex (LRC).