The centers of the following functions are located in the limbic system. Structure of the limbic system

limbic (enclosing) system is a group of brain structures connected to each other and responsible for emotions. Sometimes this functional system is also called the "emotional brain".

The structure (composition) of the limbic system

1. Structures old cortex (archicortex, archicortex)

These structures are also called visceral brain, or olfactory brain.

Almost all structures of the archipaleocortex, i.e. old and ancient cortex, have bilateral connections with the limbic area midbrain in the presence of a large number of collaterals to diencephalon thalamus and hypothalamus. This allows the archipaleocortex to change the influence reticular formation of the brain stem on visceromotor and somatomotor functions, and also modulates the influence of the stem reticular formation on the functions of the archipaleocortex itself.

Hippocampus (horn of ammon + dentate gyrus)

Pear share.

Olfactory bulbs.

Olfactory tubercle.

2. Structures ancient cortex (paleocortex, paleocortex)

Belt gyrus.

Subcallosal gyrus.

Parahippocampal gyrus.

Presubiculum.

3. Subcortical structures

Anterior nuclei of the thalamus.

Central gray matter of the midbrain.

Functions of the limbic system

The limbic system provides homeostasis, self-preservation and preservation of the species, it plays an important role in the formation of various affective-emotional and vegetative reactions, has a significant impact on conditioned reflex activity and is involved in the motivation of behavior (R. MacLean).

Excitatory pathways in the limbic system

A circular path of excitation along certain structures was discovered J. Papez and got the title" Peipets emotional circle ".

Circular Excitation Path:hippocampus - fornix - mammillary body - anterior thalamic nucleus - cingulate cortex - presubiculum - hippocampus .

There are also bilateral commissural connections in the limbic system. between hippocampi different hemispheres, providing interhemispheric interaction between them. In humans, a certain independence in the activity of both hippocampus was also found.

The hippocampus responds with evoked potentials to stimulation of many parts of the brain: the entorial, piriform, prepiriform cortex, subiculum, amygdala, hypothalamus, thalamus, midbrain tegmentum, septum, fornix, and others, and stimulation of the hippocampus leads to the appearance of evoked potentials in these structures, which speaks of the neural connections between them.

The hippocampus has projection zones of various sensory systems . At the same time, multimodal projection zones in the hippocampus overlap, which is achieved by convergence of afferent inputs of different modality to the same hippocampal neurons. Most hippocampal neurons are characterized by polysensory responses, although there are also a number of monosensory neurons.

- the widest set, which is a morphofunctional association of systems. They are located in different parts of the brain.

Consider the functions and structure of the limbic system in the diagram below.

System structure

The limbic system includes:

limbic and paralimbic formations
anterior and medial nuclei of the thalamus
medial and basal parts of the striatum
hypothalamus
the oldest subcrustal and mantle parts
cingulate gyrus
dentate gyrus
hippocampus (seahorse)
septum (partition)
amygdala bodies.

There are 4 main structures of the limbic system in the diencephalon:

Then we have the hypothalamus, which is a vital part of the limbic system that is responsible for the production of several chemical messengers called hormones. These hormones control body water levels, sleep cycles, body temperature, and food intake. The hypothalamus is located under the thalamus.

Meanwhile, the flexural gyrus serves as a pathway that relays messages between the inner and outer parts of the limbic system. The amygdala is one of two almond-shaped clusters of nerve cells in the temporal lobe of the brain. Both amygdala are responsible for preparing the body for emergencies, such as being scared, and for storing memories of events for future recognition. The amygdala helps in the development of memories, especially those related to emotional events and emergencies.

habenular nuclei (leash nuclei)
thalamus
hypothalamus
mastoid bodies.

main functions of the limbic system

Connection with emotions

The limbic system is responsible for the following activities:

sensual
motivational
vegetative
endocrine

Instincts can also be added here:

Michelds are also associated with the development of emotions of fear and can be the cause of extreme expressions of fear, as in the case of panic. In addition, the amygdala plays an important role in pleasure and sexual arousal and may vary with a person's sexual activity and maturity.

Components of the limbic system

The hippocampus is another section of the temporal lobe that is responsible for converting short-term memories into long-term memories. The hippocampus is thought to work with the amygdala for memory storage, and damage to the hippocampus can lead to amnesia.

food
sexual
defensive

The limbic system is responsible for regulating the wake-sleep process. It develops biological motivations. They predetermine complex chains of efforts to be made. These efforts lead to the satisfaction of the above vital needs. Physiologists define them as the most complex unconditioned reflexes or instinctive behavior. For clarity, we can recall the behavior of a newborn baby when breastfeeding. It is a system of coordinated processes. With the growth and development of the child, his instincts are increasingly influenced by consciousness, which develops in the course of study and education.

Finally, we have the basal ganglia, which are the collection of nerve cell bodies that are responsible for coordinating muscle movement in posture. In particular, the basal ganglia help block unwanted movements from occurring and communicate directly with the brain for coordination.

Speculation about the development of the limbic system

It is assumed that the limbic system developed from primitive mammals during human evolution. Therefore, many of the functions of the limbic system deal with instincts rather than the study of behavior. Scholars debate whether this system should be considered a single unit biologically, as many of the original ideas that were used to develop the concept are considered obsolete. While they do not dispute the functions of the individual parts, many do not agree on whether the paths associated with these primitive functions are related.

Interaction with the neocortex

The limbic system and neocortex are tightly and inextricably interconnected with each other, and with the autonomic nervous system. On this basis, it connects two of the most important activities of the brain - memory and feelings. As a rule, the limbic system and emotions are tied together.

However, the limbic system is still discussed in many traditional biology and physiology courses as part of the nervous system. The limbic system structures are involved in many of our emotions and motivations, especially those related to survival. Such emotions include fear, anger, and emotions associated with sexual behavior. The limbic system is also connected to feelings of pleasure that are associated with our survival, such as those experienced from food and sex.

Functions of the limbic system

Certain structures of the limbic system are also involved in memory. The two large structures of the limbic system play an important role in memory. The amygdala is responsible for determining what memories are stored and where the memories are stored. This definition is thought to be based on how much of an emotional response an event elicits. The hippocampus sends memories to the appropriate part of the brain hemisphere for long-term storage and retrieves them when needed. Damage to this area of the brain can lead to an inability to form new memories.

Deprivation of a part of the system leads to psychological inertia. The urge leads to psychological hyperactivity. Strengthening the activity of the amygdala triggers ways to provoke anger. These methods are regulated by the hippocampus. The system triggers eating behavior and arouses a sense of danger. These behaviors are regulated by both the limbic system and hormones. Hormones, in turn, are produced by the hypothalamus. This combination significantly influences life activity through the regulation of the functioning of the autonomic nervous system. Its meaning is hugely called the visceral brain. Determines the sensory-hormonal activity of the animal. Such activity is practically not subject to brain regulation either in an animal, or even more so in humans. This shows the relationship between emotions and the limbic system.

The part known as "also" is included in the limbic system. The thalamus is involved in sensory perception and regulation of motor functions. It connects areas that are involved in sensory perception and movement with other parts of the brain that also play a role in sensation and movement. The hypothalamus is a very small but important component of the diencephalon. It plays an important role in regulation, body temperature, and many other vital activities.

Almond-shaped mass of nuclei involved in emotional reactions, hormonal secretions and memory. Myggdala is responsible for the harnessing of fear, or the associative learning process by which we learn to be afraid of something. a fold in the brain associated with sensory input to emotions and the regulation of aggressive behavior. - arches, bands of axons that connect the hippocampus to the hypothalamus. - a tiny noob that acts as a memory indexer - sends memories to the appropriate part of the brain hemisphere for long-term storage and retrieves them when needed. - about the size of pearls, this structure directs many important functions. The hypothalamus is also an important emotional center, controlling the molecules that make you feel excited, angry, or unhappy. - receives sensory information from the olfactory bulb and is involved in the identification of odors. - a large, double-lobed mass of cells that transmit sensory signals in and out. It wakes you up in the morning and gives you an adrenaline rush. . Thus, the limbic system is responsible for controlling various functions in the body.

System functions

The main function of the limbic system is to coordinate actions with memory and its mechanisms. Short-term memory is usually associated with the hippocampus. Long-term memory - with the neocortex. The manifestation of personal skill and knowledge from the neocortex occurs through the limbic system. For this, sensual-hormonal provocation of the brain is used. This provocation brings up all the information from the neocortex.

Some of these functions include interpreting emotional responses, storing memories, and regulating. More recently, Paul McLean, taking the basic foundations of Papez's proposal, created the demonative limbic system and added new structures to the schema: the orbitofrontal and medial-frontal cortex, the paraftopacambic gyrus, and important subcortical groupings such as the amygdala, medial thalamic nucleus, septal region, prosencephalic basal nuclei and several brain stems.

The main areas associated with emotions. It is important to emphasize that all these structures are intensely connected to each other, and none of them is responsible for any particular emotional state. However, some of them contribute more than others to certain emotions. Below we consider, one by one, the most well-known structures of the limbic system.

The limbic system also performs the following significant function - verbal memory of incidents and experience gained, skills, and knowledge. All this looks like a complex of effector structures.

In the works of specialists, the system and functions of the limbic system are depicted as an "anatomical emotional ring". All aggregates are connected to each other and other parts of the brain. Connections with the hypothalamus are especially multifaceted.

Damage or stimulation of the medial dorsal and anterior nuclei of the thalamus is associated with changes in emotional reactivity. However, the importance of these nuclei in regulating emotional behavior is not due to the thalamus itself, but to the connection of these nuclei to other structures in the limbic system. The medial dorsal nucleus connects with the cortical zones of the prefrontal region and with the hypothalamus. The anterior nuclei connect to the mammillary bodies, and through them, through the plunger, to the hippocampus and dentate gyrus, thus participating in the Papez circuit.

It defines:

sensual mood of a person
his motivation to work
behavior
processes of acquiring knowledge and memorization.

Violations and their consequences

In case of violation of the limbic system or a defect in these sets, amnesia progresses in patients. However, it should not be defined as a place where certain information is stored. It combines all the separate parts of memory into generalized skills and incidents that are easy to reproduce. Disturbance of the limbic system does not destroy individual fragments of memories. These damages destroy their conscious repetition. In this case, various pieces of information are preserved and serve as a guarantee for procedural memory. Patients with Korsakov's syndrome can learn some other new knowledge for themselves. However, they will not know how and what exactly they learned.

This structure has extensive connections with other proencephalic areas and mesencephaly. Lesions in the hypothalamic nuclei interfere with several autonomic functions and some of the so-called motivated behaviors such as thermal regulation, sexuality, alertness, hunger, and thirst. The hypothalamus is believed to play a role in emotions. In particular, its lateral parts seem to be associated with pleasure and rage, while the median part seems to be associated with disgust, displeasure, and a tendency to uncontrollable and loud laughter.

Defects in its activities lead to:

brain injury
neuroinfections and intoxications
vascular pathologies
endogenous psychoses and neuroses.

It all depends on how significant the defeat was, as well as the limitations. Quite real:

epileptic convulsive states
automatisms
changes in consciousness and mood
derealization and depersonalization
auditory hallucinations
taste hallucinations
olfactory hallucinations.

It is no coincidence that with the predominant defeat of the hippocampus by alcohol, a person suffers from memory in relation to recent incidents. Patients undergoing treatment for alcoholism in the hospital suffer from the following: they do not remember what they ate for lunch today and dined at all, or not, and when they last took medication. At the same time, they perfectly remember the events that took place in their lives for a long time.

The role of the limbic system in the formation of motivations, emotions, memory organization

However, in general terms, the hypothalamus is more associated with the expression of emotions than with the genesis of affective states. When the physical symptoms of emotions appear, the threat they pose returns through the hypothalamus to the limbic centers and therefore to the anterior frontal nuclei, increasing anxiety. This negative feedback mechanism can be strong enough to create a panic situation. As will be seen later, knowledge of this phenomenon is very important for clinical and therapeutic reasons.

Already scientifically substantiated - the limbic system (more precisely, the amygdala and the transparent septum) is responsible for processing certain information. This information is taken from the olfactory organs. At first, the following was stated - this system is capable of exclusively olfactory function. But over time, it became clear: it is also well developed in animals without smell. Everyone knows the importance of biogenic amines for leading a full life and activity:

Humans show the largest network of connections between the prefrontal area and traditional limbic structures. Perhaps, therefore, among all species, they represent the greatest variety of feelings and emotions. Although some signs of attachment can be perceived in birds, the limbic system only began to develop, in fact, after the first mammals, it is practically non-existent in reptiles, amphibians and all other previous species.

Paul McLean uses to say that "it's very hard to imagine a lonely and more emotionally empty creature than a crocodile." Two behaviors with affective connotations that have appeared in mammals deserve special attention because of their peculiarity.

dopamine
norepinephrine
serotonin.

The limbic system has them in huge quantities. The manifestation of nervous and mental ailments is associated with the destruction of their balance.

The structure and functions of the limbic system are largely unknown. Conducting new research in this area will make it possible to determine its real place among other parts of the brain and will allow our practitioners to treat diseases of the central nervous system with new methods.

The more a mammal develops, the more accentuated these behaviors are. Ablation of important parts of the limbic system of any animal causes it to completely lose both maternal affection and lunar interest. And the evolution of mammals leads us to humanity. Of course, our hominid ancestor could already distinguish between the sensations he experienced on occasion, such as being in his cave, polishing a stone or bone, running after a weak animal, running away from a stronger one, hunting a female of his own kind, etc. P.

Cytoarchitectonics of the limbic system cortex

With the development of language, specific names were given to these sensations, allowing their definition and communication with other members of the group. Because there is an important subjective component that is difficult to convey, even today there is no consensus on the best terminology to be used to refer to many of these sensations in particular.

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A set of nervous structures and their connections located in the mediobasal part, involved in the control of autonomic functions and emotional, instinctive behavior, as well as influencing the change in the phases of sleep and wakefulness.
Non-Emotional Functions of the Limbic System
Therefore, the words "affect", "emotion" and "feeling" are used interchangeably and imprecisely, almost as synonyms. However, we believe that each of these words deserves a precise definition, for the sake of their etymology and because of the physical and mental reactions they evoke.

Curiously, there is a worldwide tendency to regard only positive experiences as affecting. Opposite emotions and feelings can be used to refer to both positive and negative phenomena: “she has good feelings; I had painful emotions." According to Nobre de Melo, denominations influence, in general, events experienced by emotions or feelings. Emotions, as their etymology shows, show reactions to those emotional states that, due to their intensity, turn to some kind of action.

The limbic system is the most ancient part of the cerebral cortex, located on the inside of the cerebral hemispheres. It includes: hippocampus, cingulate gyrus, amygdala nuclei, piriform gyrus. Limbic formations are among the highest integrative centers for the regulation of the autonomic functions of the body. The neurons of the limbic system receive impulses from the cortex, subcortical nuclei, thalamus, hypothalamus, reticular formation and all internal organs. A characteristic property of the limbic system is the presence of well-defined circular neural connections that unite its various structures. Among the structures responsible for memory and learning, the main role is played by the hippocampus and the associated posterior frontal cortex. Their activity is important for the transition of short-term memory to long-term memory. The limbic system is involved in afferent synthesis, in the control of the electrical activity of the brain, regulates metabolic processes and provides a number of vegetative reactions. Irritation of various sections of this system in an animal is accompanied by manifestations of defensive behavior and changes in the activity of internal organs. The limbic system is also involved in the formation of behavioral responses in animals. It contains the cortical section of the olfactory analyzer.

Structural and functional organization of the limbic system

Great Circle of Peipes:

hippocampus;
vault;
mamillary bodies;
mamillary-thalamic bundle Wikd "Azira;
thalamus;
gyrus.

Small circle of Nauta:

amygdala;
end strip;
partition.

Limbic system and its functions

Consists of phylogenetically old parts of the forebrain. In the name (limbus- edge) reflects the peculiarity of its location in the form of a ring between the new cortex and the final part of the brain stem. The limbic system includes a number of functionally integrated structures of the middle, diencephalon, and telencephalon. These are the cingulate, parahippocampal and dentate gyrus, the hippocampus, the olfactory bulb, the olfactory tract, and adjacent areas of the cortex. In addition, the limbic system includes the amygdala, anterior and septal thalamic nuclei, hypothalamus, and mamillary bodies (Fig. 1).

The limbic system has multiple afferent and efferent connections with other brain structures. Its structures interact with each other. The functions of the limbic system are realized on the basis of the integrative processes taking place in it. At the same time, more or less defined functions are inherent in individual structures of the limbic system.

Rice. 1. The most important connections between the structures of the limbic system and the brainstem: a - the circle of Paipez, b - the circle through the amygdala; MT - mammillary bodies

The main functions of the limbic system:

Emotional-motivational behavior (with fear, aggression, hunger, thirst), which may be accompanied by emotionally colored motor reactions
Participation in the organization of complex behaviors, such as instincts (food, sexual, defensive)
Participation in orienting reflexes: reaction of alertness, attention
Participation in the formation of memory and the dynamics of learning (the development of individual behavioral experience)
Regulation of biological rhythms, in particular, changes in the phases of sleep and wakefulness
Participation in maintaining homeostasis by regulating autonomic functions

cingulate gyrus

Neurons cingulate gyrus receive afferent signals from the association areas of the frontal, parietal and temporal cortex. The axons of its efferent neurons follow the neurons of the associative cortex of the frontal lobe, the hipiocampus, the septal nuclei, the amygdala, which are connected with the hypothalamus.

One of the functions of the cingulate gyrus is its participation in the formation of behavioral responses. So, when its anterior part is stimulated, aggressive behavior occurs in animals, and after bilateral removal, the animals become quiet, submissive, asocial - they lose interest in other individuals of the group, not trying to establish contact with them.

The cingulate gyrus can exert regulatory influences on the functions of internal organs and striated muscles. Its electrical stimulation is accompanied by a decrease in the frequency of breathing, heart contractions, a decrease in blood pressure, increased motility and secretion of the gastrointestinal tract, pupil dilation, and a decrease in muscle tone.

It is possible that the effects of the cingulate gyrus on the behavior of animals and the functions of internal organs are indirect and mediated by connections of the cingulate gyrus through the frontal cortex, hippocampus, amygdala and septal nuclei with the hypothalamus and brainstem structures.

It is possible that the cingulate gyrus is related to the formation of pain sensations. People who underwent a cingulate gyrus dissection for medical reasons experienced a reduction in pain.

It has been established that neural networks of the anterior part of the cingulate gyrus are involved in the operation of the brain error detector. Its function is to identify erroneous actions, the progress of which deviates from the program of their execution and actions, at the completion of which the parameters of the final results were not achieved. Error detector signals are used to trigger mechanisms for correcting erroneous actions.

Amygdala

Amygdala located in the temporal lobe of the brain, and its neurons form several subgroups of nuclei, the neurons of which interact with each other and other brain structures. Among these nuclear groups are the corticomesial and basolateral subgroups of the nuclei.

The neurons of the corticomesial nuclei of the amygdala receive afferent signals from the neurons of the olfactory bulb, hypothalamus, nuclei of the thalamus, septal nuclei, gustatory nuclei of the diencephalon, and pain sensitivity pathways of the pons, through which signals from the large receptive fields of the skin and internal organs arrive at the amygdala neurons. Taking into account these connections, it is assumed that the corticomedial group of tonsil nuclei is involved in the control of the implementation of the vegetative functions of the body.

The neurons of the basolateral nuclei of the amygdala receive sensory signals from the neurons of the thalamus, afferent signals about the semantic (conscious) content of signals from the prefrontal cortex of the frontal lobe, the temporal lobe of the brain and the cingulate gyrus.

The neurons of the basolateral nuclei are associated with the thalamus, the prefrontal cortex of the cerebral hemispheres, and the ventral striatum of the basal ganglia, so it is assumed that the nuclei of the basolateral group of the tonsils are involved in the implementation of the functions of the frontal and temporal lobes of the brain.

Amygdala neurons send efferent signals along axons predominantly to the same brain structures from which they received afferent connections. Among them are the hypothalamus, the mediodorsal nucleus of the thalamus, the prefrontal cortex, the visual areas of the temporal cortex, the hippocampus, and the ventral striatum.

The nature of the functions performed by the amygdala is judged by the consequences of its destruction or by the effects of its irritation in higher animals. Thus, the bilateral destruction of the tonsils in monkeys causes a loss of aggressiveness, a decrease in emotions and defensive reactions. Monkeys with removed tonsils are kept alone, do not seek to make contact with other animals. In diseases of the tonsils, there is a disconnect between emotions and emotional reactions. Patients may experience and express great concern for any reason, but at this time the heart rate, blood pressure and other autonomic reactions are not changed. It is assumed that the removal of the tonsils, accompanied by a rupture of its connections with the cortex, leads to a disruption in the processes of normal integration of the semantic and emotional components of efferent signals in the cortex.

Electrical stimulation of the tonsils is accompanied by anxiety, hallucinations, past experiences, and SNS and ANS reactions. The nature of these reactions depends on the localization of irritation. When the nuclei of the cortico-medial group are irritated, reactions from the digestive organs prevail: salivation, chewing movements, bowel movements, urination, and when the nuclei of the basolateral group are irritated, reactions of alertness, raising the head, pupil dilation, search. With strong irritation, animals can develop states of rage or, conversely, fear.

In the formation of emotions, an important role belongs to the presence of closed circles of circulation of nerve impulses between the formations of the limbic system. A special role in this is played by the so-called limbic circle of Paipez (hippocampus - fornix - hypothalamus - mamillary bodies - thalamus - cingulate gyrus - parahippocampal gyrus - hippocampus). The streams of nerve impulses circulating along this circular neural circuit are sometimes called the "stream of emotions."

Another circle (almond - hypothalamus - midbrain - amygdala) is important in the regulation of aggressive-defensive, sexual and nutritional behavioral reactions and emotions.

The tonsils are one of the structures of the CNS, on the neurons of which there is the highest density of sex hormone receptors, which explains one of the changes in the behavior of animals after bilateral destruction of the tonsils - the development of hypersexuality.

Experimental data obtained on animals indicate that one of the important functions of the tonsils is their participation in establishing associative links between the nature of the stimulus and its significance: the expectation of pleasure (reward) or punishment for the actions performed. The neural networks of the tonsils, ventral striatum, thalamus, and prefrontal cortex are involved in the implementation of this function.

Hippocampal structures

hippocampus along with the dentate gyrus subiculun) and the olfactory cortex forms a single functional hippocampal structure of the limbic system, located in the medial part of the temporal lobe of the brain. There are numerous bilateral links between the components of this structure.

The dentate gyrus receives its main afferent signals from the olfactory cortex and sends them to the hippocampus. In turn, the olfactory cortex, as the main gateway for receiving afferent signals, receives them from various associative areas of the cerebral cortex, the hippocampal and cingulate gyrus. The hippocampus receives already processed visual signals from the extrastriate areas of the cortex, auditory signals from the temporal lobe, somatosensory signals from the postcentral gyrus, and information from polysensory associative areas of the cortex.

The hippocampal structures also receive signals from other areas of the brain - the stem nuclei, the raphe nucleus, and the bluish spot. These signals perform a predominantly modulatory function in relation to the activity of hippocampal neurons, adapting it to the degree of attention and motivations that are crucial for the processes of memorization and learning.

The efferent connections of the hippocampus are organized in such a way that they follow mainly those areas of the brain with which the hippocampus is connected by afferent connections. Thus, the efferent signals of the hippocampus go mainly to the association areas of the temporal and frontal lobes of the brain. To perform their functions, the hippocampal structures need a constant exchange of information with the cortex and other brain structures.

One of the consequences of a bilateral disease of the medial part of the temporal lobe is the development of amnesia - memory loss with a subsequent decrease in intelligence. At the same time, the most severe memory impairments are observed when all hippocampal structures are damaged, and less pronounced - when only the hippocampus is damaged. From these observations, it is concluded that the hippocampal structures are part of the structures of the brain, including the medial halamus, cholinergic neuronal groups of the base of the frontal lobes, the amygdala, which play a key role in the mechanisms of memory and learning.

A special role in the implementation of memory mechanisms in the hippocampus is played by the unique property of its neurons to maintain a state of excitation and synaptic signal transmission for a long time after they are activated by any influences (this property is called post-tetanic potentiation). Post-tetanic potentiation, which ensures long-term circulation of information signals in closed neural circuits of the limbic system, is one of the key processes in the mechanisms of long-term memory formation.

Hippocampal structures play an important role in learning new information and storing it in memory. Information about earlier events is stored in memory after damage to this structure. At the same time, hippocampal structures play a role in the mechanisms of declarative or specific memory for events and facts. The mechanisms of non-declarative memory (memory for skills and faces) are more involved in the basal ganglia, the cerebellum, the motor areas of the cortex, and the temporal cortex.

Thus, the structures of the limbic system are involved in the implementation of such complex brain functions as behavior, emotions, learning, memory. The functions of the brain are organized in such a way that the more complex the function, the more extensive the neural networks involved in its organization. From this it is obvious that the limbic system is only a part of the structures of the central nervous system that are important in the mechanisms of complex brain functions, and contributes to their implementation.

So, in the formation of emotions as states that reflect our subjective attitude to current or past events, we can distinguish mental (experience), somatic (gestures, facial expressions) and vegetative (vegetative reactions) components. The degree of manifestation of these components of emotions depends on the greater or lesser involvement in the emotional reactions of the brain structures with the participation of which they are realized. This is largely determined by which group of nuclei and structures of the limbic system is activated to the greatest extent. The limbic system acts in the organization of emotions as a kind of conductor, enhancing or weakening the severity of one or another component of an emotional reaction.

Involvement in the responses of the structures of the limbic system associated with the cerebral cortex enhances the mental component of emotion in them, and the involvement of structures associated with the hypothalamus and the hypothalamus itself as part of the limbic system enhances the autonomic component of the emotional reaction. At the same time, the function of the limbic system in the organization of emotions in humans is under the influence of the cortex of the frontal lobe of the brain, which has a corrective effect on the functions of the limbic system. It inhibits the manifestation of excessive emotional reactions associated with the satisfaction of the simplest biological needs and, apparently, contributes to the emergence of emotions associated with the implementation of social relationships and creativity.

The structures of the limbic system, built between the parts of the brain that are directly involved in the formation of higher mental, somatic and vegetative functions, ensure their coordinated implementation, maintenance of homeostasis and behavioral responses aimed at preserving the life of the individual and species.

LIMBIC SYSTEM AND RETICULAR FORMATION

Structures of the limbic system

Reticular formation of the brain

Question_1

Structures of the limbic system

The limbic system is named after the Latin word limbus –

edge or border.

Definition_1

limbic systemis a collection of subcortical and cortical structuresbrain, which covers the upper part of the brain stem.

The first characterization of this structure was given by the French physiologist Paul Broca (1878). He considered the phylogenetically old areas of the brain located around the brain stem, and called it the "large limbic lobe." Subsequently, this area began to be designated as the "olfactory brain", which does not reflect the leading function of this structure in the organization of complex behavioral acts.

The olfactory brain is phylogenetically the oldest part of the forebrain, which arose in connection with the development of the sense of smell. For example, in fish, the olfactory brain is almost entirely the forebrain. In mammals, this area of the forebrain passes into submission to the cortex of the hemispheres, and is forced out to the lower and medial surface of the forebrain hemispheres. In the olfactory brain, peripheral and central sections are conditionally distinguished.

The peripheral section includes the structures of the ancient crust (paleokertex):

olfactory bulb ( bulbus olfactorius)

olfactory tract ( tractus olfactorius)

olfactory triangle ( trigonum olfactorium)

anterior perforated substance ( substantia perforata anterior)

The central section includes the structures of the old cortex (archiocortex):

vaulted gyrus ( gyrusfornicatus)

dentate gyrus ( gyrus dentatus)

hippocampus ( hippocampus)

amygdala ( corpus amygdaloideum)

mamillary bodies ( corpus mamillare)

The identification of the role of these formations in the regulation of vegetative-visceral functions led to the emergence of the term "visceral brain" (Paul McLean, 1949). Further refinement of the anatomical and functional features and the physiological role of these structures led to the use of the definition - "limbic system".

The vaulted gyrus has an annular shape, goes around the corpus callosum and is located on the medial surface of the cerebral hemispheres. The vaulted gyrus consists of three parts: the cingulate gyrus, the isthmus, and the parahippocampal gyrus. From above, the cingulate gyrus is limited by the cingulate sulcus, and from below by the sulcus of the corpus callosum. Behind, at the level of the parietal-occipital sulcus, the cingulate sulcus passes into the isthmus of the fornix, which passes into the gyrus of the hippocampus. The hippocampal gyrus, or parahippocampal gyrus, in the anterior perforated substance, folds in the form of a hook (the cortical center of the olfactory analyzer).

Figure 1 - The main structures of the limbic system

The hippocampus (Ammon's horn) is a paired formation in the vertebrate brain, which is the main part of the archiocortex - the old cortex and limbic system of mammals. The hippocampus first appeared in lungfish and legless amphibians. The amphibian hippocampus built on top of the hypothalamus, reptiles developed connections between the hippocampus and the hypothalamus, and mammals developed connections with the amygdala complex of the basal ganglia of the brain. As a result of the development of the archiocortex, the limbic system arose.

The dentate gyrus is a twisted part of the temporal cortex that is adjacent to the hippocampal sulcus. The amygdala is a group of nuclei that are located inside the temporal lobe of the brain, and related to both the basal ganglia and the limbic system. Mamillary bodies are a system of thick myelinated fibers and nuclear formations that are part of the hypothalamus of the diencephalon and the limbic system. The mammillary bodies receive fibers from the cerebral cortex and cerebellum and have an inhibitory effect on the structures of the limbic system.

Vault ( fornix) is a structure that connects the hippocampus to the mammillary bodies. It consists of two arcuate strands, has pillars, a body, two legs and a commissure connecting the legs of the vault. Each leg descends and passes into the fringe of the hippocampus.

In addition to these structures, the limbic system currently includes the hypothalamus and the reticular formation of the midbrain.

The limbic system is circular afferent inputs carried out from different areas of the brain, through the hypothalamus, the reticular formation and the fibers of the olfactory nerve, which are considered the main sources of its excitation. Efferent Outputs from the limbic system are carried out through the hypothalamus to the autonomic and somatic centers of the brain stem and spinal cord.

Figure 2 - Scheme of the main internal connections of the limbic system.

A - Peipets circle, B - Naut circle; GT/MT - mammillary bodies of the hypothalamus, SM - midbrain (according to V.M. Smirnov)

A feature of the limbic system is that between its structures there are simple two-way connections and complex paths that form many closed circles. Such an organization creates conditions for the long-term circulation of the same excitation in the system - the reverberation of excitation, and thereby serves to maintain a single state in it and impose this state on other brain systems.

At present, connections between brain structures are well known, organizing circles that have their own functional specifics. These include Peipets circle(hippocampus - mastoid bodies - anterior nuclei of the thalamus - cortex of the cingulate gyrus - parahippocampal gyrus - hippocampus). This circle has to do with memory and learning processes. Another circle nauta circle(almond-shaped body - hypothalamus - mesencephalic structures - amygdala) regulates aggressive-defensive, food and sexual forms of behavior.

Question_2

Reticular formation of the brain

Reticular formation(lat. reticulum- net, formatio- formation) is a section of the brain stem, consisting of a diffuse accumulation of neurons with branched axons and dendrites, representing a single complex. The reticular formation activates the cerebral cortex and controls the reflex activity of the spinal cord. This network of neurons is located in the largest part of the brain stem. It originates from the lower part of the medulla oblongata and extends to the nuclei of the thalamus.

Figure 3 - Reticular formation in the structure of the brain

The term "reticular formation" was introduced by the German anatomist and histologist Otto Deiters. He described a network-like formation located in the central parts of the brain stem (medulla oblongata and midbrain, visual tubercles). In the reticular formation, two morphological parts can be distinguished - the "white" reticular formation (with a predominance of myelinated fibers) and the "gray" reticular formation (consisting of cells and weakly myelinated fibers). RF is formed by groups of small, medium and large multipolar intercalary neurons with different character of branching of dendrites and axons containing various neurotransmitters. Diffusely located elements are replaced by areas of individual nuclear clusters.

Neurons of the reticular formation are characterized by a large number of afferent connections coming from sensory formations. Their processes are sent to the cerebral cortex, to the nuclei of various parts of the brain and cerebellum. Ascending projections provide an activating effect of the reticular formation on the higher centers of the nervous system. The descending projection paths of the reticular formation are considered as a system that inhibits the activity of the underlying centers. An important feature of the reticular formation is the existence in it of a large number of reticular neurons that simultaneously send large axons to the spinal cord and thalamus. The main volume of projections is represented by the fibers of the reticulospinal tract, which inhibits the activity of motor neurons of the spinal cord. The main mediators of the reticular formation: acetylcholine, norepinephrine, dopamine, serotonin.

The discovery of the function of the reticular formation is attributed to Giuseppe Moruzzi and Horace Magoun. These researchers discovered in 1949 that during electrical stimulation of the reticular formation, in experimental animals under anesthesia, the EEG wave activity of sleep is replaced by wave activity of wakefulness.

The reticular formation is attributed to participation in the perception of pain, aggressive and sexual behavior.

- the widest set, which is a morphofunctional association of systems. They are located in different parts of the brain.

Consider the functions and structure of the limbic system in the diagram below.

System structure

The limbic system includes:

limbic and paralimbic formations
anterior and medial nuclei of the thalamus
medial and basal parts of the striatum
hypothalamus
the oldest subcrustal and mantle parts
cingulate gyrus
dentate gyrus
hippocampus (seahorse)
septum (partition)
amygdala bodies.

There are 4 main structures of the limbic system in the diencephalon:

habenular nuclei (leash nuclei)
thalamus
hypothalamus
mastoid bodies.

main functions of the limbic system

Connection with emotions

The limbic system is responsible for the following activities:

sensual
motivational
vegetative
endocrine

Instincts can also be added here:

food
sexual
defensive

Interaction with the neocortex

System functions

The limbic system also performs the following significant function - verbal memory of incidents and experience gained, skills, and knowledge. All this looks like a complex of effector structures.

It defines:

sensual mood of a person
his motivation to work
behavior
processes of acquiring knowledge and memorization.

Violations and their consequences

Defects in its activities lead to:

brain injury
neuroinfections and intoxications
vascular pathologies
endogenous psychoses and neuroses.

It all depends on how significant the defeat was, as well as the limitations. Quite real:

epileptic convulsive states
automatisms
changes in consciousness and mood
derealization and depersonalization
auditory hallucinations
taste hallucinations
olfactory hallucinations.

dopamine
norepinephrine
serotonin.

The limbic system has them in huge quantities. The manifestation of nervous and mental ailments is associated with the destruction of their balance.

LIMBIC SYSTEM(syn.: visceral brain, limbic lobe, limbic complex, thymencephalon) - a complex of structures of the final, intermediate and middle parts of the brain that make up the substrate for the manifestation of the most general states of the body (sleep, wakefulness, emotions, motivations, etc.). The term "limbic system" was introduced by P. McLane in 1952.

There is no consensus on the exact composition of the structures that make up L. s. Most researchers, in particular, consider the hypothalamus (see) as an independent entity, separating it from H. s. However, this allocation is conditional, since it is on the hypothalamus that the convergence of influences emanating from the structures involved in the regulation of various autonomic functions and the formation of emotionally colored behavioral reactions occurs. Communication of functions L. with. with the activity of internal organs gave rise to some authors to designate this entire system of structures as the "visceral brain", but this term only partially reflects the function, meaning of the system. Therefore, most researchers use the term "limbic system", thereby emphasizing that all the structures of this complex are phylogenetically, embryologically and morphologically related to Broca's large limbic lobe.

The main part of L. with. make up structures related to the ancient, old and new cortex, located mainly on the medial surface of the cerebral hemispheres, and numerous subcortical formations closely associated with them.

At the initial stage of development of vertebrate animals, the structures of L. s. provided all the most important reactions of the body (food, orientation, defensive, sexual). These reactions were formed on the basis of the first distant sense - smell. Therefore sense of smell (see) acted as the organizer of a set of complete functions of an organism, having united also morfol, their basis - structure of final, intermediate and average departments of a brain (see).

L. s. - a complex interweaving of ascending and descending paths, forming within this system a set of closed concentric circles of different diameters. Of these, the following circles can be distinguished: amygdaloid region - terminal strip - hypothalamus - amygdaloid region; hippocampus - fornix - septal region - mamillary (mastoid, T.) bodies - mastoid-thalamic bundle (Vic d'Azira) - thalamus - cingulate gyrus - cingulate bundle - hippocampus (Peips circle, Fig. 1).

Ascending paths of L. s. insufficiently studied anatomically. It is known that, along with the classical sensory pathways, they also include diffuse ones that do not go as part of the medial loop. The descending paths of HP, connecting it with the hypothalamus, the reticular formation (see) of the midbrain and other structures of the brain stem, pass mainly as part of the medial bundle of the forebrain, the final (terminal, t.) strip and fornix. The fibers going from a hippocampus (see), terminate hl. arr. in the region of the lateral part of the hypothalamus, in the funnel, preoptic zone and mamillary bodies.

Morphology

Pm. includes olfactory bulbs, olfactory legs, passing into the corresponding tracts, olfactory tubercles, anterior perforated substance, Broca's diagonal bundle, limiting the anterior perforated substance from behind, and two olfactory gyrus - lateral and medial with corresponding stripes. All these structures are united by the common name "olfactory lobe".

On the medial surface of the brain to L. s. include the anterior part of the brain stem and interhemispheric adhesions, surrounded by a large arcuate gyrus, the dorsal half of which is occupied by the cingulate gyrus, and the ventral half by the parahippocampal gyrus. Behind, the cingulate and parahippocampal gyrus form a retrosplenial region, or isthmus (isthmus). Anteriorly, between the anterior-lower ends of these gyri, is the cortex of the posterior orbital surface of the frontal lobe, the anterior part of the insula, and the pole of the temporal lobe. The parahippocampal gyrus should be distinguished from the hippocampal formation formed by the body of the hippocampus, the dentate gyrus, or dentate fascia, the near-callosal remnant of the old cortex and, according to some authors, the subiculum and presubiculum (i.e., the base and pre-basement of the hippocampus).

The parahippocampal gyrus is subdivided into the following three parts: 1. The pear-shaped area (area piriformis), which in macrosmatics forms a pear-shaped lobe (lobus piriformis), which occupies the largest part of the hook (uncus). It is subdivided, in turn, into the periamygdaloid and prepiriform regions: the first covers the nuclear mass of the amygdaloid region and is very poorly separated from it, the second merges in front with the lateral olfactory gyrus. 2. The entorhinal region (area entorhinalis), which occupies the middle part of the gyrus below and behind the hook. 3. Subicular and presubicular regions located between the entorial cortex, hippocampus and retrosplenial region and occupying the medial surface of the gyrus.

The subcallosal (paraterminal, t.) gyrus, together with the rudimentary anterior hippocampus, septal nuclei, and gray precommissural formations, is sometimes called the septal region, as well as the pre- or paracommissural region.

From formations of new bark to L. page. nek-ry researchers carry its temporal and frontal departments and an intermediate (frontal and temporal) zone. This zone lies between the prepiriform and periamygdaloidal cortex, on the one hand, and the orbitofrontal and temporopolar, on the other. It is sometimes referred to as the orbito-insulotemporal cortex.

Phylogenesis

All formations of the brain that make up the L. s. belong to the most phylogenetically ancient areas of it and therefore they can be found in all vertebrates (Fig. 2).

The evolution of limbic structures in a number of vertebrates is closely related to the evolution of the olfactory analyzer and those brain structures that receive impulses from the olfactory bulb. In lower vertebrates (cyclostomes, fish, amphibians, and reptiles), the first acceptors of such olfactory impulses are the septal and amygdaloid regions, the hypothalamus, and also the old, ancient, and interstitial regions of the cortex. Already at the earliest stages of evolution, these structures were closely connected with the nuclei of the lower brain stem and performed the most important integrative functions, which provided the body with adequate adaptation to environmental conditions.

In the process of evolution, due to the extremely intensive growth of the neocortex, neostriatum, and specific nuclei of the thalamus, the relative (but not absolute) development of limbic structures somewhat decreased, but did not stop. They only underwent nek-ry morfol, and topographical changes. So, for example, in lower vertebrates, the archistriatum, or amygdala, occupies an almost median position in the region of the telencephalon, in marsupials it is located at the bottom of the temporal horn of the lateral ventricle, and in most mammals it shifts to the temporal end of the horn of the lateral ventricle, acquiring the shape of an almond, in from which it was called the tonsil. In humans, this structure occupies the region of the pole of the temporal lobe.

The septal region in all animals, except primates, is an extensive part of the telencephalon, which makes up the medial surface of the hemispheres. In humans, the entire nuclear mass of the septal region is displaced in the ventral direction, and therefore the superomedial wall of the lateral ventricle is formed not by the ganglionic elements of the brain, but by a kind of film - a transparent septum (septum pellucidum).

Ancient crustal formations in the process of evolution have undergone such serious changes that they have turned from surface structures such as a cloak into separate discrete formations of the most bizarre shape. So, the old bark acquired the shape of a horn and became known as the ammon horn, the ancient and interstitial areas of the bark turned into an olfactory tubercle, an isthmus, and a cortex of the piriform gyrus.

In the course of evolution, limbic structures came into close contact with younger brain formations, providing highly organized animals with a more subtle adaptation to the increasingly complex and constantly changing conditions of existence.

Cytoarchitectonics of the limbic system cortex

The ancient bark (paleocortex), according to I. N. Filimonov, is characterized by a primitively constructed cortical plate, which is indistinctly separated from the underlying subcortical cell clusters. It consists of the pear-shaped region, the olfactory tubercle, the diagonal region, and the basal part of the septum. On top of the molecular layer of the ancient cortex are afferent fibers, in other cortical areas passing in the white matter under the cortex. Therefore, the cortex is not so clearly separated from the subcortex. Under the fiber layer there is a molecular layer, then a layer of giant polymorphic cells, even deeper - a layer of pyramidal cells with cystic dendrites at the base of the cell (flower cells) and, finally, a deep layer of polymorphic cells.

The old cortex (archicortex) has an arched shape. Surrounding the corpus callosum and fimbria of the hippocampus, it comes into contact in front with its posterior end with the periamygdaloid, and with its anterior end, with the diagonal regions of the ancient cortex. The old cortex includes the hippocampal formation and the subicular region. The old bark differs from the ancient one by the complete separation of the cortical plate from the underlying formations, and from the new one by a simpler structure and the absence of a characteristic division into layers.

The intercortex is the area of the cortex that separates the new cortex from the old (periarchocortical) and ancient (peripaleocortical).

The cortical plate of the periarchicortical zone, which separates the old cortex from the new one throughout, is divided into three main layers: outer, middle and inner. The interstitial cortex of this type includes the presubicular, entorhinal, and peritectal regions. The latter is part of the cingulate gyrus and is in direct contact with the supracallosal rudiment of the hippocampus.

The peripaleocortical, or transitional insular, zone surrounds the ancient cortex, separating it from the new cortex, and merges behind the periarchocortical zone. It consists of a number of fields that make a successive but discontinuous transition from the ancient to the new crust and occupy the outer lower surface of the island's crust.

In literature it is often possible to meet also other classification of cortical structures of L. page - from the cytoarchitectonic point of view. So, Vogt (S. Vogt) and O. Vogt (1919) together call the archi- and paleocortex the allocortex or the heterogenetic cortex. K. Brod May (1909), Rose (M. Rose, 1927) and Rose (J. E. Rose, 1942) the limbic, retrosplenial and some other areas (eg, islets) that form the intermediate cortex between the neocortex and the allocortex is called the mesocortex. IN Filimonov (1947) calls the intermediate cortex paraallocortex (juxtallocortex). Pribram, Kruger (K. N. Pribram, L. Kruger, 1954), Kaada (B. R. Kaada, 1951) consider the mesocortex only as part of the paraallocortex.

Subcortical structures. To subcrustal educations L. of page. the basal ganglia, nonspecific nuclei of the thalamus, the hypothalamus, the leash and, according to some authors, the reticular formation of the midbrain are included.

neurochemistry

Based on the data obtained in recent decades with the help of histochemical, research methods, mainly the method of fluorescent microscopy, it was shown that almost all structures of L. s. accept the terminals of neurons that secrete various biogenic amines (the so-called monoaminergic neurons). The bodies of these neurons lie in the region of the lower brain stem. In accordance with the secreted biogenic amine, three types of monoaminergic neuronal systems are distinguished - dopaminergic (Fig. 4), noradrenergic (Fig. 5) and serotonergic. The first one has three paths.

1. Nigroneo-striatal begins in the substantia nigra and ends on the cells of the caudate nucleus and putamen. Each neuron of this pathway has many terminals (up to 500,000) with a total length of processes up to 65 cm, which makes it possible to instantly act on a large number of neostriatal cells. 2. Mesolimbic begins in the ventral region of the tegmentum of the midbrain and ends on the cells of the olfactory tubercle, septal and amygdaloid regions. 3. Tubero-infundibular originates from the anterior part of the arcuate nucleus of the hypothalamus and ends on the cells of the eminentia mediana. All of these pathways are mononeuronal and do not contain synaptic switches.

The ascending projections of the noradrenergic system are presented in two ways: dorsal and ventral. The dorsal one starts from the blue spot, and the ventral one starts from the lateral reticular nucleus and the red nuclear-spinal tract. They extend anteriorly and terminate on cells of the hypothalamus, preoptic region, septal and amygdaloid regions, olfactory tubercle, olfactory bulb, hippocampus, and neocortex.

The ascending projections of the serotonergic system start from the midbrain raphe nuclei and the tegmental reticular formation. They extend forward along with the fibers of the medial forebrain bundle, giving off many collaterals to the tegmental region at the border of the diencephalon and midbrain.

Shat and Lyois (G. C. D. Shute, P. R. Lewis, 1967) showed that in L. s. there are a large number of substances associated with the metabolism of acetylcholine; they traced clear cholinergic pathways from the reticular and tegmental nuclei of the brainstem to many formations of the forebrain, and above all to the limbic ones, the so-called. dorsal and ventral tegmental pathways, to-rye directly or with one or two synaptic switches reach many thalamo-hypothalamic nuclei, structures of the striatum, amygdaloid and septal regions, olfactory formation, hippocampus and new cortex.

In HP, especially in olfactory structures, it is found a lot of glutamine, aspartic and gamma-aminobutyric to - t that can testify to mediator function of these substances.

L. s. contains a significant amount of biologically active substances belonging to the group of enkephalins and endorphins. Most of them are found in the striatum, amygdala, leash, hippocampus, hypothalamus, thalamus, interpeduncular nucleus and other structures. Only in these structures receptors are found, to-rye perceive the action of substances of this group - the so-called. opiate receptors [Snyder (S. I. Snyder), 1977].

In 1976, Weindl et al. (A. Weindl) it was found that, in addition to the hypothalamus, the septal and amygdaloid regions, and partly the thalamus, contain neurons capable of secreting neuropeptides such as vasopressin, etc.

Physiology

Combining the formation of the final, intermediate and middle parts of the brain, L. s. ensures the formation of the most general functions of the body, realized through a whole range of individual or conjugated private reactions. In the structures of L. s. there is an interaction of exteroceptive (auditory, visual, olfactory, etc.) and interoceptive influences. Even with the most primitive impact on almost all structures of L. s. (mechanical, chemical, electrical) one can detect a number of isolated simple or fragmentary responses, differing in severity and latent period depending on which structure is irritated. Vegetative reactions such as salivation, piloerection, defecation, etc., changes in the functioning of the respiratory, cardiovascular and lymph systems, changes in pupillary reaction, thermoregulation, etc. are often observed. The duration of these reactions is sometimes very significant, which indicates inclusion in the work and individual endocrine apparatus. Often such autonomic responses are observed along with coordinated motor manifestations (eg, chewing, swallowing, and other movements).

Along with the vegetative reactions of L. s. determines vestibulosomatic functions, as well as such somatic reactions as postural and tonic and vocal. Apparently, L. s. should be considered as a center for the integration of vegetative and somatic components of reactions of a hierarchically higher level - emotional and motivational states, sleep, orienting-exploratory activity, etc. These complex reactions manifest themselves in animals or humans when stimulating well-defined structures of HP. It has been shown that irritation or destruction of the amygdala, septum, frontotemporal cortex, hippocampus and other parts of the limbic system can lead to an increase or, conversely, a weakening of food-procuring, defensive and sexual reactions. Especially evident in this regard is the destruction of the temporal, orbital and insular cortex, the amygdala and the part of the cingulate gyrus adjacent to them, causing the emergence of the so-called. Klüver-Bucy syndrome, with Krom, the ability of animals to assess both their internal state and the usefulness or harmfulness of external stimuli is impaired. Animals after such an operation become tame; constantly examining the surrounding objects, they indiscriminately grab everything that comes across, lose their fear even of fire and, even burning themselves, continue to touch it (so-called visual agnosia occurs). Often they become hypersexual expressions, showing sexual reactions even in relation to animals of a different species. Their relationship to food is also changing.

The wealth of relationships within L. s. defines also other party of emotional activity - a possibility of considerable strengthening of emotion, duration of its deduction and quite often its transition to stagnant patol, a state. Peips (J. W. Papez), for example, believes that the emotional state is the result of the circulation of excitations through the structures of HP. from the hippocampus through the mammillary bodies (see) and the anterior nuclei of the thalamus to the cingulate gyrus, and the latter, in his opinion, is the true receptive zone of the experienced emotion. However, an emotional state that manifests itself not only subjectively, but also contributes to one or another purposeful activity, i.e., reflecting one or another motivation of the animal, appears, apparently, only when the excitation from the limbic structures spreads to the new cortex, and above all in its frontal regions (Fig. 6). Without the participation of the new cortex, the emotion is defective; it loses its biol, meaning and appears as false.

Motivational states of animals that arise in response to electrical stimulation of the hypothalamus and closely related limbic formations can be behaviorally manifested in all their natural complexity, i.e., in the form of rage and organized reactions of an attack on another animal or, conversely, in the form of defense reactions and avoiding an unpleasant stimulus or running away from an attacking animal. Particularly noticeable is the participation of L. s. in the organization of food-procuring behavior. Thus, bilateral removal of the amygdala leads either to a prolonged refusal of animals from food, or to hyperphagia. As shown by K. V. Sudakov (1971), Noda (K. Noda) et al. (1976), Paxinos (G. Paxinos, 1978), changes in food-procuring behavior and thirst quenching reactions are also observed in case of irritation or destruction of the transparent septum, piriform cortex and some mesencephalic nuclei.

Removal of the amygdala and piriform cortex leads to the gradual development of pronounced hypersexual behavior, which can be reduced or removed by destruction of the inferomedial nucleus of the hypothalamus or septal region.

Impact on L. s. can lead to higher order motivational changes manifesting themselves at the community level. The emotional and motivational states of animals manifest themselves most demonstratively in the case of their reactions of self-irritation or avoidance of an unfavorable stimulus, when various formations of HP are exposed to the effect.

The formation of a behavioral act based on any motivation (see) begins with an orienting-research reaction (see). The latter, as experimental data show, is also realized with the obligatory participation of L. s. It has been established that the action of indifferent stimuli that cause a behavioral reaction of alertness is accompanied by characteristic electrographic changes in the structures of HP. While in bark of big hemispheres at the same time desynchronization of electric activity is registered, in nek-ry structures of L. of page, napr, in an amygdaloid area, a hippocampus and a piriform cortex, there are other changes in electric activity. Against the background of a sufficiently reduced activity, paroxysmal flashes of high-frequency oscillations are detected; in the hippocampus, a slow regular rhythm is recorded with a frequency of 4-6 per 1 sec. Such a reaction typical of the hippocampus occurs not only with sensory stimuli, but also with direct electrical stimulation of the reticular formation and any limbic structure, leading to a behavioral reaction of alertness or anxiety.

Numerous experiments show that weak stimulation of the limbic structures in the absence of a specific emotional reaction always causes alertness or an orienting-exploratory reaction in the animal. The orienting-exploratory reaction is closely related to the identification by animals in the environment of signals that are significant for a given situation and their memorization. In the implementation of these mechanisms of orientation, learning and memorization, a large role is assigned to the hippocampus and the amygdaloid region. Destruction of a hippocampus sharply breaks short-term memory (see). During stimulation of the hippocampus and for some time after it, animals lose the ability to respond to conditioned stimuli.

Wedge, observations show that bilateral removal of the medial surface of the temporal lobes also causes severe memory disorders. Patients have retrograde amnesia, they completely forget the events that preceded the operation. In addition, the ability to memorize deteriorates. The patient cannot remember the names of the b-tsy, in which he is located. Short-term memory suffers sharply: patients lose the thread of conversation, are unable to keep track of the score of sports games, etc. In animals, after such an operation, previously acquired skills are violated, the ability to develop new ones, especially complex ones, worsens.

According to O. S. Vinogradova (1975), the main function of the hippocampus is the registration of information, and according to M. L. Pigareva (1978), it is to provide reactions to signals with a low probability of reinforcement in cases where there is a shortage of pragmatic information, i.e. e. emotional stress.

L. s. closely related to the mechanisms of sleep (see). Hernandez-Peon (R. Hernandez-Peon) et al. showed that when injections of small doses of acetylcholine or anticholinesterase substances into various departments of H. p. animals develop sleep. The following departments of HP are especially effective in this respect: the medial preoptic region, the medial bundle of the forebrain, the interpeduncular nuclei, Bechterew's nuclei, and the medial part of the pontine tegmentum. These structures make up the so-called. hypnogenic limbic-midbrain circle. Excitation of structures of this circle makes funkts, blockade of the ascending activating influences of a reticular formation of a mesencephalon on bark of big hemispheres, to-rye define a state of wakefulness. At the same time, it has been shown that sleep can occur when acetylcholine and anticholinesterase substances are applied to the overlying formations of HP: prepiriform and periamygdaloidal regions, olfactory tubercle, striatum, and cortical areas of HP, located on the anterior and medial surfaces of the hemispheres brain The same effect can be obtained by stimulating the cerebral cortex, especially its anterior sections.

Characteristically, the destruction of the medial forebrain bundle in the preoptic region prevents the development of sleep caused by chem. irritation of the upstream divisions of H. s. and the cerebral cortex.

Some authors [Winter (P. Winter) et al., 1966; Robinson (W. W. Robinson), 1967; Delius (J. D. Delius), 1971] believe that in L. s. are located so-called communication centers of animals (their vocal manifestations), clearly correlated with their behavior towards their relatives. These centers are formed by the structures of the amygdaloid, septal and preoptic regions, the hypothalamus, the olfactory tubercle, some nuclei of the thalamus and the tegmentum. Robinson (1976) suggested that a person has two speech centers. The first, phylogenetically older, is located in L. s.; it is closely related to motivational-emotional factors and provides low-information signals. This center is controlled by the second - the highest center, located in the new cortex and associated with the dominant hemisphere.

L.'s participation with. in the formation of complex integrative functions of the body is confirmed by the data of the survey of mentally ill patients. So, for example, senile psychoses are accompanied by clear degenerative changes in the septal and amygdaloid regions, the hippocampus, the arch, the medial parts of the thalamus, the entorhinal, temporal and frontal areas of the cortex. In addition, in the structures of L. s. at patients with schizophrenia find a large amount of dopamine, norepinephrine and serotonin, i.e. biogenic amines, disturbance of normal metabolism to-rykh is connected with development of a number of mental diseases, including and schizophrenia.

Particularly noticeable is the participation of L. s. in the development of epilepsy (see) and various epileptoid conditions. Patients suffering from psychomotor epilepsy, as a rule, have organic lesions in areas involving limbic structures. This is primarily the orbital part of the frontal and temporal cortex, the parahippocampal gyrus, especially in the area of the hook, the hippocampus and dentate gyrus, as well as the amygdala nuclear complex.

The wedge described above, the symptoms are usually accompanied by a clear electrographic indicator - electrical convulsive discharges are recorded in the corresponding parts of the brain. This activity is most clearly recorded in the hippocampus, although it also manifests itself in other structures, for example, in the amygdala and septum. The presence in them of diffuse plexuses of nerve processes, multiple feedback circuits creates conditions for multiplication, retention and prolongation of activity. Hence the inherent for the structures of L. s. extremely low threshold for the occurrence of so-called. after discharges, to-rye can continue after the cessation of electrical or chemical. irritation for a long time.

The lowest threshold for electrical post-discharge is found in the hippocampus, amygdala, and piriform cortex. A characteristic feature of these post-discharges is their ability to spread from the site of irritation to other structures of HP.

The wedge, and experimental data show that in the period of convulsive discharges in Hp. memory processes are disrupted. In patients with temporo-diencephalic lesions, complete or partial amnesia is observed, or, conversely, violent outbreaks of paroxysms of sensation already seen, heard, experienced.

Thus, occupying a median position within c. and. With., the limbic system is able to quickly "turn on" in almost all functions of the body, aimed at actively adapting it (in accordance with the available motivation) to environmental conditions. L. s. receives afferent sendings of excitation from the formations of the lower trunk, to-rye in each case can be very specific, from the rostral (olfactory) structures of the brain and from the new cortex. These excitations through a system of mutual connections quickly reach all the necessary areas of L. s. and instantly (through the fibers of the medial bundle of the forebrain or direct neostriatal-tegmental pathways) activate (or inhibit) the executive (motor and autonomic) centers of the lower trunk and spinal cord. This achieves the formation of a func- tion "specialized" for these specific conditions, a system with a clear morfol, and neurochemical, architectonics, which ends with the body achieving the necessary beneficial result (see Functional systems).

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E. M. Bogomolova.