The theme of our lectureFunctions of the cerebral cortex.

The brain is located in the cranial cavity. It has a convex upper-lateral and lower surfaces, as well as a flattened surface - the base of the brain.

The large brain consists of two hemispheres - the right and left, which are connected by a commissure - the corpus callosum. The right and left hemispheres are divided by a longitudinal fissure. Under the commissure there is an arch, which is two curved fibrous strands, which are interconnected in the middle part, and diverge in front and behind, forming pillars and legs of the arch. In front of the pillars of the vault is the anterior commissure. Between the corpus callosum and the arch is a thin vertical plate of brain tissue - a transparent septum.

The hemispheres have superior lateral, medial, and inferior surfaces. The upper lateral is convex, the medial is flat, facing the same surface of the other hemisphere, and the lower is irregular in shape. On three surfaces there are deep and shallow furrows, and between them are convolutions. Furrows are depressions between gyri. Convolutions - elevations of the medulla.

The surfaces of the cerebral hemispheres are separated from each other by edges - the upper, lower lateral and lower vertical. In the space between the two hemispheres, a large sickle-shaped process enters, which is a thin plate of the hard shell, which penetrates into the longitudinal fissure of the large brain, without reaching the corpus callosum, and separates the right and left hemispheres from each other.

The most protruding parts of the hemispheres are called poles: frontal, occipital and temporal. The relief of the surfaces of the cerebral hemispheres is very complex and is due to the presence of more or less deep furrows of the cerebral cortex and ridge-like elevations located between them - convolutions. The depth, length of some furrows and convolutions, their shape and direction are very variable.

Each hemisphere is divided into lobes - frontal, parietal, occipital, temporal, insular. The central sulcus separates the frontal lobe from the parietal, the lateral sulcus separates the temporal lobe from the frontal and parietal, the parietal-occipital sulcus separates the parietal and occipital lobes.

The cerebral cortex consists of horizontal layers located in the direction from the surface to the depth.

I. The molecular layer has very few cells, but a large number of branching pyramidal cell dendrites forming a plexus parallel to the surface. On these dendrites, afferent fibers form synapses, coming from the associative and nonspecific nuclei of the thalamus.

II. The outer granular layer is composed mainly of stellate and partially small pyramidal cells. The fibers of the cells of this layer are located mainly along the surface of the cortex, forming corticocortical connections.

III. The outer pyramidal layer consists mainly of pyramidal cells of medium size. The axons of these cells, like the granular cells of layer II, form corticocortical associative connections.

IV. The inner granular layer is similar to the outer granular layer in terms of the nature of the cells and the arrangement of their fibers. On the neurons of this layer, synaptic endings form afferent fibers coming from the neurons of the specific nuclei of the thalamus and, consequently, from the receptors of sensory systems.

V. The inner pyramidal layer is formed by medium and large pyramidal cells, with Betz's giant pyramidal cells located in the motor cortex. The axons of these cells form efferent corticospinal and corticobulbar motor pathways.

VI. The layer of polymorphic cells is formed mainly by spindle-shaped cells, the axons of which form the corticothalamic pathways.

In the first and fourth layers, the perception and processing of signals entering the cortex occurs. The neurons of the second and third layers carry out corticocortical associative connections. Efferent pathways leaving the cortex are formed mainly in the fifth and sixth layers.

A more detailed division of the cortex into different fields was carried out on the basis of the shape and location of neurons by Brodman, who identified 11 areas, including 52 fields, many of which are characterized by functional and neurochemical features. According to Brodman, the frontal region includes the following fields: 8, 9, 10, 11, 12, 44, 45, 46, 47. The precentral region includes fields 4 and 6, the postcentral region includes fields 1, 2, 3 and 43. The parietal region includes fields 5, 7, 39, 40, and the occipital region 17 18 19. The temporal region consists of a very large number of fields.

In the cortex, sensory, associative and motor zones are distinguished, based on the location of neurons:

The problem of function localization in the cerebral cortex has three concepts:

The principle of narrow localization - all functions are placed in one, separately taken structure.

The concept of equipotential - different cortical structures are functionally equivalent.

The principle of multifunctionality of cortical fields.

The property of multifunctionality allows this structure to be included in the provision of various forms of activity, while realizing the main, genetically inherent function. The degree of multifunctionality of different cortical structures is not the same: for example, in the fields of the associative cortex it is higher than in the primary sensory fields, and in the cortical structures it is higher than in the stem ones. The multifunctionality is based on the multichannel input of afferent excitation into the cerebral cortex, the overlap of afferent excitations, especially at the thalamic and cortical levels, the modulating effect of various structures (nonspecific thalamus, basal ganglia) on cortical functions, the interaction of cortical-subcortical and intercortical pathways for conducting excitation.

One of the largest options for the functional division of the new cerebral cortex is the allocation of sensory, associative and motor areas in it.

Sensory areas of the cortex are areas into which sensory stimuli are projected. The sensory areas of the cortex are otherwise called: the projection cortex or the cortical sections of the analyzers. They are located mainly in the parietal, temporal and occipital lobes. Afferent pathways to the sensory cortex come predominantly from specific sensory nuclei of the thalamus. The sensory cortex has well-defined second and fourth layers and is called granular.

Areas of the sensory cortex, irritation or destruction of which causes clear and permanent changes in the sensitivity of the body, are called primary sensory areas. They consist mainly of monomodal neurons and form sensations of the same quality. In the primary sensory areas, there is usually a clear spatial representation of body parts, their receptor fields. Around the primary sensory areas are less localized secondary sensory areas, the polymodal neurons of which respond to the action of several stimuli.

The most important sensory area is the parietal cortex of the postcentral gyrus and the corresponding part of the paracentral lobule on the medial surface of the hemispheres, which is designated as the primary somatosensory area. Here there is a projection of skin sensitivity of the opposite side of the body from tactile, pain, temperature receptors, interoceptive sensitivity and sensitivity of the musculoskeletal system from muscle, articular and tendon receptors. The projection of parts of the body in this area is characterized by the fact that the projection of the head and upper parts of the body is located in the inferolateral areas of the postcentral gyrus, the projection of the lower half of the trunk and legs is in the upper medial zones of the gyrus, the projection of the lower part of the leg and feet is in the cortex of the paracentral lobule on the medial surface of the hemispheres . At the same time, the projection of the most sensitive areas (tongue, lips, larynx, fingers) has relatively large zones compared to other parts of the body. It is assumed that the projection of taste sensitivity is also located in the zone of tactile sensitivity of the tongue.

The secondary somatosensory area of ​​a smaller size is located on the upper wall of the lateral sulcus, at the border of its intersection with the central sulcus. The functions of the secondary somatosensory area are poorly understood. It is known that the localization of the body surface in it is less clear, the impulse comes here both from the opposite side of the body and from the “own” side, suggesting its participation in the sensory and motor coordination of the two sides of the body.

Another primary sensory area is the auditory cortex, which is located deep in the lateral sulcus. In this zone, in response to irritation of the auditory receptors of the organ of Corti, sound sensations are formed that change in volume, tone, and other qualities. Here it has a clear topical projection: in different parts of the cortex, different parts of the organ of Corti are represented. The projection cortex of the temporal lobe also includes the center of the vestibular analyzer in the superior and middle temporal gyri. The processed sensory information is used to form the "body map" and regulate the functions of the cerebellum (temporocerebellar tract).

Another primary projection area of ​​the neocortex is located in the occipital cortex - the primary visual area. Here it has a topical representation of retinal receptors, and each point of the retina corresponds to its own area of ​​the visual cortex, while the zone of the macula has a large zone of representation. In connection with the incomplete decussation of the visual pathways, the same halves of the retina are projected into the visual region of each hemisphere. The presence in each hemisphere of the projection of the retina of both eyes is the basis of binocular vision.

Irritation of the cortex of the 17th field leads to the appearance of light sensations. Near field 17 is the cortex of the secondary visual area. The neurons of these zones are polymodal and respond not only to light, but also to tactile and auditory stimuli. In this visual area, a synthesis of various types of sensitivity occurs and more complex visual images and their identification arise. Irritation of these fields causes visual hallucinations, obsessive sensations, eye movements.

The main part of the information about the environment and the internal environment of the body, received in the sensory cortex, is transmitted for further processing to the associative cortex.

Associative areas of the cortex include areas of the new cortex located near the sensory and motor areas, but not directly performing sensory and motor functions. The boundaries of these areas are not clearly marked, the uncertainty is mainly associated with the secondary projection zones, the functional properties of which are transitional between the properties of the primary projection and associative zones. In humans, the association cortex makes up 70% of the neocortex.

The main physiological feature of the neurons of the associative cortex is polymodality: they respond to several stimuli with almost the same strength. Polymodality (polysensory) neurons of the associative cortex is created due, firstly, to the presence of corticocortical connections with different projection zones, and secondly, due to the main afferent input from the associative nuclei of the thalamus, in which complex processing of information from various sensory pathways has already taken place. As a result, the associative cortex is a powerful apparatus for the convergence of various sensory excitations, which makes it possible to perform complex processing of information about the external and internal environment of the body and use it to implement higher psychophysiological functions. In the associative cortex, there are three associative systems of the brain: thalamo-temporal, thalamo-frontal, and thalamo-temporal.

The thalamo-temporal system is represented by associative zones of the parietal cortex, which receive the main afferent inputs from the posterior group of the associative nuclei of the thalamus. The parietal association cortex has efferent outputs to the nuclei of the thalamus and hypothalamus, the motor cortex, and the nuclei of the extrapyramidal system.

The main functions of the thalamo-temporal system are gnosis, the formation of a "body schema" and praxis.

Gnosis is understood as the function of various types of recognition: forms, sizes, meanings of objects, understanding of speech, knowledge of processes, patterns. Gnostic functions include the evaluation of spatial relationships. In the parietal cortex, a center of stereognosis is isolated, located behind the middle sections of the postcentral gyrus (fields 7, 40, partially 39) and providing the ability to recognize objects by touch. A variant of the gnostic function is the formation in the mind of a three-dimensional model of the body, the center of which is located in field 7 of the parietal cortex. Under praxis understand purposeful action, its center is located in the supramarginal gyrus (fields 39 and 40 of the dominant hemisphere). This center ensures the storage and implementation of the program of motorized automated acts.

The thalamolobic system is represented by associative zones of the frontal cortex, which have the main afferent input from the associative mediodorsal nucleus of the thalamus. The main function of the frontal associative cortex is the formation of goal-directed behavior programs, especially in a new environment for a person. The implementation of this general function is based on other functions of the thalamo-frontal system: 1) the formation of the dominant motivation that provides the direction of human behavior. This function is based on the close bilateral connections of the pubic cortex with the limbic system and the role of the latter in the regulation of higher human emotions associated with its social activity and creativity; 2) providing probabilistic forecasting, which is expressed by a change in behavior in response to changes in the environment and the dominant motivation; 3) self-control of actions by constantly comparing the result of the action with the original intentions, which is associated with the creation of a foresight apparatus (acceptor of the result of the action).

When the prefrontal cortex, where the connections between the frontal lobe and the thalamus intersect, is damaged, a person becomes rude, tactless, unreliable, he has a tendency to repeat any motor acts, although the situation has already changed and other actions must be performed.

The thalamotemporal system has not been studied enough. But if we talk about the temporal cortex, then it should be noted that some associative centers, such as stereognosis and praxis, also include sections of the temporal cortex. The auditory speech center is located in the temporal cortex, located in the posterior regions of the superior temporal gyrus. This center provides speech gnosis - recognition and storage of oral speech, both one's own and someone else's. In the middle part of the superior temporal gyrus, there is a center for recognizing musical sounds and their combinations. On the border of the temporal, parietal and occipital lobes there is a center for reading written speech, which provides recognition and storage of images of written speech.

The motor cortex is divided into primary and secondary motor areas.

The primary motor cortex contains neurons that innervate the motor neurons of the muscles of the face, trunk, and limbs. It has a clear topographic projection of the muscles of the body. At the same time, the projections of the muscles of the lower extremities and the trunk are located in the upper parts of the precentral gyrus and occupy a relatively small area, and the projection of the muscles of the upper extremities, face and tongue are located in the lower parts of the gyrus and occupy a large area. The main pattern of topographic representation is that the regulation of the activity of muscles that provide the most accurate and diverse movements (speech, writing, facial expressions) requires the participation of large areas of the motor cortex. Motor reactions to stimulation of the primary motor cortex are carried out with a minimum threshold (high excitability), and are represented by elementary contractions of the muscles of the opposite side of the body (for the muscles of the head, the contraction can be bilateral). With the defeat of this area of ​​​​the cortex, the ability to fine coordinated movements of the hands, especially fingers, is lost.

The secondary motor cortex is located on the lateral surface of the hemispheres, in front of the precentral gyrus. It performs higher motor functions associated with the planning and coordination of voluntary movements. The cortex of field 6 receives the main part of the efferent impulses of the basal nuclei and the cerebellum and is involved in recoding information about the program of complex movements. Irritation of the cortex of field 6 causes more complex coordinated movements, for example, turning the head, eyes and torso in the opposite direction, friendly contractions of the flexor muscles or extensor muscles on the opposite side. In the premotor cortex there are motor centers associated with human social functions: the center of written speech in the posterior part of the middle frontal gyrus, the center of Broca's motor leak in the posterior part of the inferior frontal gyrus, which provides speech praxis, as well as the musical motor center, which determines the tonality of speech, the ability to sing .

In the motor cortex, a layer containing Betz's giant pyramidal cells is better expressed than in other areas of the cortex. Motor cortex neurons receive afferent inputs through the thalamus from muscle, joint, and skin receptors, as well as from the basal ganglia and the cerebellum. The main efferent output of the motor cortex to the stem and spinal motor centers is formed by the pyramidal cells of the fifth layer. Pyramidal and associated intercalary neurons are located vertically with respect to the surface of the cortex and form neural motor columns. Pyramidal neurons of the motor column can excite or inhibit the motor neurons of the stem and spinal centers. Neighboring columns functionally overlap, and pyramidal neurons that regulate the activity of one muscle are usually located not in one, but in several columns.

The main efferent connections of the motor cortex are carried out through the pyramidal and extrapyramidal pathways, which start from the Betz giant pyramidal cells and smaller pyramidal cells of the fifth layer of the cortex of the precentral gyrus (60% of fibers), premotor cortex (20% of fibers) and postcentral gyrus (20% of fibers) . Large pyramidal cells have fast-conducting axons and a background impulse activity of about 5 Hz, which increases to 20-30 Hz during movement. These cells innervate large (high-threshold) α-motor neurons in the motor centers of the brainstem and spinal cord that regulate physical movements. Thin slow-conducting myelinated axons depart from small pyramidal cells. These cells have a background activity of about 15 Hz, which increases or decreases during movement. They innervate small (low-threshold) α-motor neurons in the stem and spinal motor centers that regulate muscle tone.

The pyramidal tracts consist of 1 million fibers of the corticospinal tract, which originate from the cortex of the upper and middle third of the precentral gyrus, and 20 million fibers of the corticobulbar tract, which originate from the cortex of the lower third of the precentral gyrus.

The fibers of the pyramidal pathway terminate on the alpha motor neurons of the motor nuclei of the third - seventh and ninth - twelfth cranial nerves (corticobulbar pathway) or on the spinal motor centers (corticospinal pathway).

Arbitrary simple movements and complex purposeful motor programs, for example, professional skills, are carried out through the motor cortex and pyramidal pathways, the formation of which begins in the basal ganglia and cerebellum and ends in the secondary motor cortex.

Most of the fibers of the pyramidal pathways cross, however, a small part of the fibers remains uncrossed, which helps to compensate for impaired movement functions in unilateral lesions. Through the pyramidal pathways, the premotor cortex also performs its functions: motor skills of writing, turning the head, eyes and torso in the opposite direction, as well as speech. In the regulation of writing and especially oral speech, there is a pronounced asymmetry of the cerebral hemispheres: in 95% of right-handers and 70% of left-handers, oral speech is controlled by the left hemisphere.

The cortical extrapyramidal pathways include the corticorubral and corticoreticular pathways, starting approximately from those zones that give rise to the pyramidal pathways. The fibers of the corticorubral pathway terminate on the neurons of the red nuclei of the midbrain, from which the rubrospinal pathways continue.

The fibers of the corticoreticular pathways terminate on the neurons of the medial nuclei of the reticular formation of the pons (the medial reticulospinal pathways originate from them) and on the neurons of the reticular giant cell nuclei of the medulla oblongata, from which the lateral reticulospinal pathways originate.

Through these pathways, the regulation of tone and posture is carried out, which provide precise targeted movements. Cortical extrapyramidal pathways are a component of the extrapyramidal system of the brain, which includes the cerebellum, basal ganglia, and motor centers of the brainstem. The extrapyramidal system regulates tone, balance posture, and the performance of learned motor acts, such as walking, running, speech, and writing. Since the corticopyramidal pathways give their numerous collaterals to the structures of the extrapyramidal system, both systems work in a functional unity.

Assessing in general terms the role of various structures of the brain and spinal cord in the regulation of complex directed movements, it can be noted that the impulse (motivation) to move is created in the limbic system, the idea of ​​movement is created in the associative cortex of the cerebral hemispheres, the programs of movements are created in the basal ganglia, cerebellum and premotor cortex, and the execution of complex movements occurs through the motor cortex, motor centers of the brainstem and spinal cord.

Interhemispheric relationships in humans manifest themselves in two forms - functional asymmetry of the cerebral hemispheres and their joint activity.

Interhemispheric asymmetry, as one of the important features of the functioning of the higher parts of the brain, is mainly determined by two points: 1) asymmetric localization of the nervous apparatus of the second signaling system and 2) the dominance of the right hand as a powerful means of human adaptive behavior. This explains why the first ideas about the functional role of interhemispheric asymmetry arose only when it was possible to establish the localization of the nerve centers of speech (motor - Broca's center and sensory - Wernicke's center in the left hemisphere).

The cross-projection of the types of sensory sensitivity and the descending pyramidal pathways - the regulators of the motor sphere of the body - in combination with the left-sided localization of the center of oral and written speech determines the dominant role of the left hemisphere in the behavior of a person controlled by the cerebral cortex.

The experimental data obtained confirm the idea of ​​the dominant role of the left hemisphere of the brain in the implementation of the functions of the second signaling system, in mental operations, in creative activity with a predominance of forms of abstract thinking. In general, we can assume that people with left hemisphere dominance belong to the mental type, and those with right hemisphere dominance belong to the artistic type.

Functional asymmetry of the hemispheres is the most important psychophysiological property of the human brain. Allocate mental, sensory and motor interhemispheric functional asymmetries of the brain.

In the study of psychophysiological functions, it was shown that in speech the verbal information channel is controlled by the left hemisphere, and the non-verbal channel (voice, intonation) is controlled by the right.

Abstract thinking and consciousness are associated mainly with the left hemisphere. During the development of the conditioned reflex, the right hemisphere dominates in the initial phase, and during the strengthening of the reflex, the left hemisphere dominates.

The right hemisphere processes information simultaneously, synthetically, according to the principle of deduction, the spatial and relative features of an object are better perceived. The left hemisphere processes information sequentially, analytically, according to the principle of induction, perceives the absolute features of the object and temporal relationships better.

In the emotional sphere, the right hemisphere causes predominantly negative emotions, controls the manifestations of strong emotions, in general it is more “emotional”. The left hemisphere causes mainly positive emotions, controls the manifestation of weaker emotions.

In the sensory realm, the role of the right and left hemispheres is best manifested in visual perception. The right hemisphere perceives the visual image holistically, immediately in all details, it is easier to solve the problem of distinguishing objects and identifying visual images of objects, which is difficult to describe in words, creates the prerequisites for concrete-sensory thinking. The left hemisphere evaluates the visual image dissected, analytically, with each feature being analyzed separately. Familiar objects are more easily recognized and tasks of similarity of objects are solved, visual images are devoid of specific details and have a high degree of abstraction; prerequisites for logical thinking are created.

Motor asymmetry is expressed primarily in right-left handedness, which is controlled by the motor cortex of the opposite hemisphere. The asymmetry of other muscle groups is individual, not specific.

Pairing in the activity of the cerebral hemispheres is ensured by the presence of the commissural system (corpus callosum, anterior and posterior, hippocampal and habenular commissures, interthalamic fusion), which anatomically connect the two hemispheres of the brain. In other words, both hemispheres are connected not only by horizontal connections, but also by vertical ones.

The main facts obtained with the help of electrophysiological techniques showed that excitation from the area of ​​irritation of one hemisphere is transmitted through the commissural system not only to the symmetrical area of ​​the other hemisphere, but also to asymmetrical areas of the cortex. The study of the method of conditioned reflexes showed that in the process of developing a reflex, a “transfer” of a temporary connection to the other hemisphere occurs. Elementary forms of interaction between the two hemispheres can be carried out through the quadrigemina and the reticular formation of the trunk.

In humans, as in many animals, most of the organs are paired: two arms, two legs, two eyes, two ears, two kidneys, two hemispheres of the brain. The pairing of organs does not mean their identical functioning. We know which hand we have is leading - it performs the most complex, subtle operations. For most people, this is the right hand. We eat, we sew, we write, we draw with our right hand. Among people - right-handed, using the right hand for precise actions, 90%, while left-handers make up an average of 10%.

Left-handers of all races and cultures, past and present, have been in the minority among the right-handed environment.

When studying the question of the origin of leftism, three main directions emerged: "genetic", "cultural" and "pathological".

Currently, two genetic models are most widely used. According to one, brain asymmetry is determined by the presence of one gene, which she called the "right shift" factor. If this factor is present in an individual, the latter is predisposed to be right-handed. If the factor is absent, the person may be either left-handed or right-handed depending on random circumstances. At the same time, great importance is attached to brain damage in the prenatal and early postnatal period, which can affect the phenotypic implementation of the “right shift” factor.

A more complex model has been proposed by Levy and Nagilaki (1972). These scientists suggest that handedness is a function of two genes. One gene with two alleles determines the hemisphere that will control speech and the dominant hand.

Morgan (1978) points to the possibility of not genetic, but cytoplasmic encoding of asymmetry, putting forward the concept according to which both cerebral lateralization and manual preference are considered in a broad general biological aspect. It is assumed that brain development is influenced by the left-right gradient, and this leads to earlier and faster maturation of the left hemisphere in ontogeny, which at the same time has an inhibitory effect on the right - as a result, the left hemisphere dominates in speech and right-handedness occurs.

The "genetic" direction is directly combined with studies related to the identification of anatomical, physiological and morphological stigmata characteristic of right-handed and left-handed people. It was shown that in right-handers the Sylvian sulcus on the right is located higher than the left, while in 71% of left-handers the right and left sulci are approximately symmetrical.

Right-handers have a larger diameter of the internal carotid artery on the left and higher pressure in it than in the right, while left-handers have the opposite picture.

A similar dissociation is detected in right-handers and left-handers when studying the middle cerebral artery. The hypothesis of Gershwind and Galaburda also suggests an endocrine influence on the formation of differences in the structure of the brain of men and women. Previk's theory is well-known, according to which cerebral lateralization in humans is formed during asymmetric prenatal development of the inner ear system and the labyrinth.

There is also a genetic and cultural hypothesis of functional asymmetry. Leland, an English scientist from Cambridge, and his colleagues believe that left-handedness is equally genetically and culturally conditioned.

Hypotheses of the emergence of interhemispheric asymmetry, based on the recognition of the determining role of cultural conditions in the formation of handiness, seem to be alternative to "genetic". "Cultural-social" concepts consider right-handedness-left-handedness as a consequence of social education, experience, living conditions.

Along with the theories presented above, ideas about the pathological origin of left-handedness are widespread. Backan (1973) adheres to the extreme point of view, who argues that any manifestation of left-handedness is a consequence of birth trauma. According to Chuprikov (1975), a change in motor dominance is one of the objective evidence of congenital encephalopathy. In confirmation, the facts of an increase in left-handedness among twins are given, the features of prenatal development of which suggest the risk of intrauterine cerebral hypoxia. This approach is also supported by the results of Wada's tests, according to which damage to the left hemisphere in the early stages of ontogenesis can lead to a change in the dominant hand and the hemisphere dominant in speech.

The study of the origin of laterality continues. The abundance of facts, sometimes contradicting each other, shows that each of the theories of functional interhemispheric asymmetry of the brain requires further substantiation. At the same time, it is obvious that the fundamental principles of the above approaches form the basis for future systematic research, the need for which follows from the many problems and questions that remain open.

The cerebral cortex is the center of higher nervous (mental) human activity and controls the implementation of a huge number of vital functions and processes. It covers the entire surface of the cerebral hemispheres and occupies about half of their volume.

The cerebral hemispheres occupy about 80% of the volume of the cranium, and are composed of white matter, the basis of which consists of long myelinated axons of neurons. Outside, the hemisphere is covered with gray matter or the cerebral cortex, consisting of neurons, non-myelinated fibers and glial cells, which are also contained in the thickness of the departments of this organ.

The surface of the hemispheres is conditionally divided into several zones, the functionality of which is to control the body at the level of reflexes and instincts. It also contains centers of higher mental activity of a person, which provide consciousness, assimilation of the information received, allowing one to adapt to the environment, and through it, at the subconscious level, the autonomic nervous system (ANS) is controlled by the hypothalamus, which controls the organs of blood circulation, respiration, digestion, excretion , reproduction, and metabolism.

In order to understand what the cerebral cortex is and how its work is carried out, it is required to study the structure at the cellular level.

Functions

The cortex occupies most of the cerebral hemispheres, and its thickness is not uniform over the entire surface. This feature is due to the large number of connecting channels with the central nervous system (CNS), which ensure the functional organization of the cerebral cortex.

This part of the brain begins to form during fetal development and improves throughout life, by receiving and processing signals from the environment. Thus, it is responsible for the following functions of the brain:

• connects the organs and systems of the body with each other and the environment, and also provides an adequate response to changes;
• processes the information received from the motor centers with the help of mental and cognitive processes;
• consciousness, thinking are formed in it, and intellectual work is also realized;
• controls the speech centers and processes that characterize the psycho-emotional state of a person.

At the same time, data is received, processed, and stored due to a significant number of impulses that pass through and are formed in neurons connected by long processes or axons. The level of cell activity can be determined by the physiological and mental state of the body and described using amplitude and frequency indicators, since the nature of these signals is similar to electrical impulses, and their density depends on the area in which the psychological process occurs.

It is still unclear how the frontal part of the cerebral cortex affects the functioning of the body, but it is known that it is not very susceptible to processes occurring in the external environment, therefore, all experiments with the impact of electrical impulses on this part of the brain do not find a clear response in the structures . However, it is noted that people whose frontal part is damaged experience problems in communicating with other individuals, cannot realize themselves in any work activity, and they are indifferent to their appearance and third-party opinions. Sometimes there are other violations in the implementation of the functions of this body:

• lack of concentration on household items;
• manifestation of creative dysfunction;
• violations of the psycho-emotional state of a person.

The surface of the cerebral cortex is divided into 4 zones, outlined by the most clear and significant convolutions. Each of the parts at the same time controls the main functions of the cerebral cortex:

1. parietal zone - responsible for active sensitivity and musical perception;
2. in the back of the head is the primary visual area;
3. the temporal or temporal is responsible for the speech centers and the perception of sounds coming from the external environment, in addition, it is involved in the formation of emotional manifestations, such as joy, anger, pleasure and fear;
4. the frontal zone controls motor and mental activity, and also controls speech motor skills.

Features of the structure of the cerebral cortex

The anatomical structure of the cerebral cortex determines its features and allows it to perform the functions assigned to it. The cerebral cortex has the following number of distinctive features:

• neurons in its thickness are arranged in layers;
• nerve centers are located in a specific place and are responsible for the activity of a certain part of the body;
• the level of activity of the cortex depends on the influence of its subcortical structures;
• it has connections with all underlying structures of the central nervous system;
• the presence of fields of different cellular structure, which is confirmed by histological examination, while each field is responsible for the performance of any higher nervous activity;
• the presence of specialized associative areas makes it possible to establish a causal relationship between external stimuli and the body's response to them;
• the ability to replace damaged areas with nearby structures;
• this part of the brain is able to store traces of excitation of neurons.

The large hemispheres of the brain consist mainly of long axons, and also contains clusters of neurons in its thickness, forming the largest nuclei of the base, which are part of the extrapyramidal system.

As already mentioned, the formation of the cerebral cortex occurs even during intrauterine development, and at first the cortex consists of the lower layer of cells, and already at 6 months of the child all structures and fields are formed in it. The final formation of neurons occurs by the age of 7, and the growth of their bodies is completed at 18 years of age.

An interesting fact is that the thickness of the cortex is not uniform throughout and includes a different number of layers: for example, in the region of the central gyrus, it reaches its maximum size and has all 6 layers, and areas of the old and ancient cortex have 2 and 3 layers. x layer structure, respectively.

The neurons of this part of the brain are programmed to repair the damaged area through synoptic contacts, thus each of the cells actively tries to repair the damaged connections, which ensures the plasticity of neural cortical networks. For example, when the cerebellum is removed or dysfunction, the neurons that connect it with the final section begin to grow into the cerebral cortex. In addition, the plasticity of the cortex also manifests itself under normal conditions, when a process of learning a new skill takes place or as a result of pathology, when the functions performed by the damaged area are transferred to neighboring parts of the brain or even the hemisphere.

The cerebral cortex has the ability to retain traces of neuronal excitation for a long time. This feature allows you to learn, remember and respond with a certain reaction of the body to external stimuli. This is how the formation of a conditioned reflex occurs, the nervous path of which consists of 3 devices connected in series: an analyzer, a closing apparatus of conditioned reflex connections and a working device. Weakness of the closing function of the cortex and trace manifestations can be observed in children with severe mental retardation, when the conditioned connections formed between neurons are fragile and unreliable, which leads to learning difficulties.

The cerebral cortex includes 11 areas, consisting of 53 fields, each of which is assigned a number in neurophysiology.

Areas and zones of the cortex

The cortex is a relatively young part of the CNS, developed from the terminal part of the brain. The evolutionary formation of this organ occurred in stages, so it is usually divided into 4 types:

1. The archicortex or ancient cortex, due to atrophy of the sense of smell, has turned into a hippocampal formation and consists of the hippocampus and its associated structures. It regulates behavior, feelings and memory.
2. The paleocortex, or old cortex, makes up the bulk of the olfactory zone.
3. The neocortex or neocortex is about 3-4 mm thick. It is a functional part and performs higher nervous activity: it processes sensory information, gives motor commands, and it also forms conscious thinking and speech of a person.
4. The mesocortex is an intermediate variant of the first 3 types of cortex.

Physiology of the cerebral cortex

The cerebral cortex has a complex anatomical structure and includes sensory cells, motor neurons and internerons that have the ability to stop the signal and be excited depending on the received data. The organization of this part of the brain is built on a columnar principle, in which the columns are made into micromodules that have a homogeneous structure.

The system of micromodules is based on stellate cells and their axons, while all neurons respond in the same way to an incoming afferent impulse and also send an efferent signal synchronously in response.

The formation of conditioned reflexes that ensure the full functioning of the body occurs due to the connection of the brain with neurons located in various parts of the body, and the cortex ensures the synchronization of mental activity with the motility of organs and the area responsible for the analysis of incoming signals.

Signal transmission in the horizontal direction occurs through transverse fibers located in the thickness of the cortex, and transmit an impulse from one column to another. According to the principle of horizontal orientation, the cerebral cortex can be divided into the following areas:

• associative;
• sensory (sensitive);
• motor.

When studying these zones, various methods of influencing the neurons included in its composition were used: chemical and physical irritation, partial removal of areas, as well as the development of conditioned reflexes and registration of biocurrents.

The associative zone connects the incoming sensory information with previously acquired knowledge. After processing, it generates a signal and transmits it to the motor zone. Thus, it is involved in remembering, thinking and learning new skills. Associative areas of the cerebral cortex are located in proximity to the corresponding sensory area.

The sensitive or sensory zone occupies 20% of the cerebral cortex. It also consists of several components:

• somatosensory, located in the parietal zone is responsible for tactile and autonomic sensitivity;
• visual;
• auditory;
• taste;
• olfactory.

Impulses from the limbs and tactile organs on the left side of the body are sent along afferent pathways to the opposite lobe of the cerebral hemispheres for further processing.

The neurons of the motor zone are excited by impulses received from muscle cells and are located in the central gyrus of the frontal lobe. The input mechanism is similar to that of the sensory area, as the motor pathways form an overlap in the medulla oblongata and follow to the opposite motor area.

Crinkles furrows and fissures

The cerebral cortex is formed by several layers of neurons. A characteristic feature of this part of the brain is a large number of wrinkles or convolutions, due to which its area is many times greater than the surface area of ​​the hemispheres.

Cortical architectonic fields determine the functional structure of sections of the cerebral cortex. All of them are different in morphological features and regulate different functions. Thus, 52 different fields are allocated, located in certain areas. According to Brodman, this division looks like this:

1. The central sulcus separates the frontal lobe from the parietal region, the precentral gyrus lies in front of it, and the posterior central gyrus lies behind it.
2. The lateral furrow separates the parietal zone from the occipital zone. If you spread its lateral edges, then inside you can see a hole, in the center of which there is an island.
3. The parieto-occipital sulcus separates the parietal lobe from the occipital lobe.

The core of the motor analyzer is located in the precentral gyrus, while the upper parts of the anterior central gyrus belong to the muscles of the lower limb, and the lower parts belong to the muscles of the oral cavity, pharynx and larynx.

The right-sided gyrus forms a connection with the motor apparatus of the left half of the body, the left-sided - with the right side.

The retrocentral gyrus of the 1st lobe of the hemisphere contains the core of the analyzer of tactile sensations and is also connected with the opposite part of the body.

Cell layers

The cerebral cortex performs its functions through the neurons located in its thickness. Moreover, the number of layers of these cells may differ depending on the site, the dimensions of which also vary in size and topography. Experts distinguish the following layers of the cerebral cortex:

1. The surface molecular layer is formed mainly from dendrites, with a small interspersed with neurons, the processes of which do not leave the layer boundary.
2. The outer granular consists of pyramidal and stellate neurons, the processes of which connect it with the next layer.
3. The pyramidal neuron is formed by pyramidal neurons, the axons of which are directed downward, where they break off or form associative fibers, and their dendrites connect this layer with the previous one.
4. The inner granular layer is formed by stellate and small pyramidal neurons, the dendrites of which go into the pyramidal layer, and its long fibers go into the upper layers or go down into the white matter of the brain.
5. Ganglionic consists of large pyramidal neurocytes, their axons extend beyond the cortex and connect various structures and departments of the central nervous system with each other.

The multiform layer is formed by all types of neurons, and their dendrites are oriented to the molecular layer, and the axons penetrate the previous layers or go beyond the cortex and form associative fibers that form a connection between gray matter cells and the rest of the functional centers of the brain.

Video: Cerebral cortex

New bark(neocortex) is a layer of gray matter with a total area of ​​​​1500-2200 square centimeters, covering the large hemispheres. The neocortex makes up about 72% of the total area of ​​the cortex and about 40% of the mass of the brain. The new bark contains 14 mln. Neurons, and the number of glial cells is approximately 10 times greater.

The cerebral cortex in phylogenetic terms is the youngest nervous structure. In humans, it carries out the highest regulation of body functions and psychophysiological processes that provide various forms of behavior.

In the direction from the surface of the new cortex in depth, six horizontal layers are distinguished.

molecular layer. It has very few cells, but a large number of branching dendrites of pyramidal cells forming a plexus parallel to the surface. On these dendrites, afferent fibers form synapses, coming from the associative and nonspecific nuclei of the thalamus.

Outer granular layer. Composed mainly of stellate and partially pyramidal cells. The fibers of the cells of this layer are located mainly along the surface of the cortex, forming corticocortical connections.

outer pyramidal layer. Consists mainly of pyramidal cells of medium size. The axons of these cells, like the granular cells of the 2nd layer, form corticocortical associative connections.

Inner granular layer. By the nature of the cells (stellate cells) and the location of their fibers, it is similar to the outer granular layer. In this layer, afferent fibers have synaptic endings coming from neurons of specific nuclei of the thalamus and, consequently, from receptors of sensory systems.

Inner pyramidal layer. Formed by medium and large pyramidal cells. Moreover, Betz's giant pyramidal cells are located in the motor cortex. The axons of these cells form the afferent corticospinal and corticobulbar motor pathways.

Layer of polymorphic cells. It is formed mainly by spindle-shaped cells, the axons of which form the corticothalamic pathways.

Assessing the afferent and efferent connections of the neocortex as a whole, it should be noted that in layers 1 and 4, perception and processing of signals entering the cortex occur. Neurons of the 2nd and 3rd layers carry out corticocortical associative connections. The efferent pathways leaving the cortex are formed mainly in the 5th and 6th layers.

Histological data show that the elementary neural circuits involved in information processing are located perpendicular to the surface of the cortex. At the same time, they are located in such a way that they capture all layers of the cortex. Such associations of neurons were called by scientists. neural columns. Neighboring neural columns can partially overlap and also interact with each other.

The increase in the phylogenesis of the role of the cerebral cortex, the analysis and regulation of body functions and the subordination of the underlying parts of the central nervous system by scientists are defined as function corticalization(an association).

Along with the corticalization of the functions of the neocortex, it is customary to single out the localization of its functions. The most commonly used approach to the functional division of the cerebral cortex is the allocation of sensory, associative and motor areas in it.

Sensory areas of the cortex - zones in which sensory stimuli are projected. They are located mainly in the parietal, temporal and occipital lobes. Afferent pathways enter the sensory cortex predominantly from specific sensory nuclei of the thalamus (central, posterior lateral, and medial). The sensory cortex has well-defined layers 2 and 4 and is called granular.

Areas of the sensory cortex, irritation or destruction of which causes clear and permanent changes in the sensitivity of the body, are called primary sensory areas(nuclear parts of analyzers, as I.P. Pavlov believed). They consist mainly of monomodal neurons and form sensations of the same quality. Primary sensory areas usually have a clear spatial (topographic) representation of body parts, their receptor fields.

Around the primary sensory areas are less localized secondary sensory areas, whose polymodal neurons respond to the action of several stimuli.

The most important sensory area is the parietal cortex of the postcentral gyrus and the corresponding part of the postcentral lobule on the medial surface of the hemispheres (fields 1–3), which is designated as somatosensory area. Here there is a projection of skin sensitivity of the opposite side of the body from tactile, pain, temperature receptors, interoceptive sensitivity and sensitivity of the musculoskeletal system from muscle, articular, tendon receptors. The projection of body parts in this area is characterized by the fact that the projection of the head and upper parts of the body is located in the inferolateral areas of the postcentral gyrus, the projection of the lower half of the trunk and legs is in the upper medial zones of the gyrus, and the projection of the lower part of the lower leg and feet is in the cortex of the postcentral lobule on the medial surface hemispheres (Fig. 12).

At the same time, the projection of the most sensitive areas (tongue, larynx, fingers, etc.) has relatively large zones compared to other parts of the body.

Rice. 12. Projection of parts of the human body on the area of ​​the cortical end of the analyzer of general sensitivity

(section of the brain in the frontal plane)

In the depth of the lateral groove is located auditory cortex(cortex of the transverse temporal gyri of Heschl). In this zone, in response to irritation of the auditory receptors of the organ of Corti, sound sensations are formed that change in volume, tone, and other qualities. There is a clear topical projection here: in different parts of the cortex, different parts of the organ of Corti are represented. The projection cortex of the temporal lobe also includes, as scientists suggest, the center of the vestibular analyzer in the superior and middle temporal gyri. The processed sensory information is used to form the "body map" and regulate the functions of the cerebellum (temporal-bridge-cerebellar pathway).

Another area of ​​the neocortex is located in the occipital cortex. it primary visual area. There is a topical representation of retinal receptors here. In this case, each point of the retina corresponds to its own area of ​​the visual cortex. In connection with the incomplete decussation of the visual pathways, the same halves of the retina are projected into the visual region of each hemisphere. The presence in each hemisphere of the projection of the retina of both eyes is the basis of binocular vision. Irritation of the cerebral cortex in this area leads to the appearance of light sensations. Near the primary visual area secondary visual area. The neurons of this region are polymodal and respond not only to light, but also to tactile and auditory stimuli. It is no coincidence that it is in this visual area that the synthesis of various types of sensitivity occurs and more complex visual images and their identification arise. Irritation of this area of ​​the cortex causes visual hallucinations, obsessive sensations, eye movements.

The main part of the information about the surrounding world and the internal environment of the body, received in the sensory cortex, is transmitted for further processing to the associative cortex.

Association areas of the cortex (intersensory, interanalyzer), includes areas of the new cerebral cortex, which are located next to the sensory and motor areas, but do not directly perform sensory or motor functions. The boundaries of these areas are not clearly marked, which is associated with the secondary projection zones, the functional properties of which are transitional between the properties of the primary projection and associative zones. The associative cortex is phylogenetically the youngest area of ​​the neocortex, which has received the greatest development in primates and humans. In humans, it makes up about 50% of the entire cortex, or 70% of the neocortex.

The main physiological feature of the neurons of the associative cortex, which distinguishes them from the neurons of the primary zones, is polysensory (polymodality). They respond with practically the same threshold not to one, but to several stimuli - visual, auditory, skin, etc. The polysensory nature of the neurons of the associative cortex is created both by its corticocortical connections with different projection zones, and by its main afferent input from the associative nuclei of the thalamus, in which complex processing of information from various sensory pathways has already taken place. As a result, the associative cortex is a powerful apparatus for the convergence of various sensory excitations, which makes it possible to perform complex processing of information about the external and internal environment of the body and use it to implement higher mental functions.

According to thalamocortical projections, two associative systems of the brain are distinguished:

thalamothemenal;

talomotemporal.

thalamotenal system it is represented by associative zones of the parietal cortex, which receive the main afferent inputs from the posterior group of associative nuclei of the thalamus (lateral posterior nucleus and pillow). The parietal association cortex has afferent outputs to the nuclei of the thalamus and hypothalamus, the motor cortex, and the nuclei of the extrapyramidal system. The main functions of the thalamo-temporal system are gnosis, the formation of a "body schema" and praxis.

Gnosis- these are various types of recognition: shapes, sizes, meanings of objects, understanding of speech, etc. Gnostic functions include the assessment of spatial relationships, for example, the relative position of objects. In the parietal cortex, the center of stereognosis is isolated (located behind the middle sections of the postcentral gyrus). It provides the ability to recognize objects by touch. A variant of the gnostic function is also the formation in the mind of a three-dimensional model of the body (“body schema”).

Under praxis understand purposeful action. The praxis center is located in the supramarginal gyrus and ensures the storage and implementation of the program of motorized automated acts (for example, combing, shaking hands, etc.).

Thalamolobic system. It is represented by associative zones of the frontal cortex, which have the main afferent input from the mediodorsal nucleus of the thalamus. The main function of the frontal associative cortex is the formation of goal-directed behavior programs, especially in a new environment for a person. The implementation of this function is based on other functions of the thalomolobic system, such as:

the formation of the dominant motivation that provides the direction of human behavior. This function is based on the close bilateral connections of the frontal cortex and the limbic system and the role of the latter in the regulation of higher human emotions associated with his social activity and creativity;

providing probabilistic forecasting, which is expressed in a change in behavior in response to changes in the environment and the dominant motivation;

self-control of actions by constantly comparing the result of the action with the original intentions, which is associated with the creation of a foresight apparatus (according to the theory of the functional system of P.K. Anokhin, the acceptor of the result of the action).

As a result of medically indicated prefrontal lobotomy, in which the connections between the frontal lobe and the thalamus intersect, there is the development of "emotional dullness", a lack of motivation, firm intentions and plans based on prediction. Such people become rude, tactless, they have a tendency to repeat any motor acts, although the changed situation requires the performance of completely different actions.

Along with the thalamo-temporal and thalamo-temporal systems, some scientists propose to distinguish the thalamo-temporal system. However, the concept of the thalamotemporal system has not yet received confirmation and sufficient scientific study. Scientists note a certain role of the temporal cortex. Thus, some associative centers (for example, stereognosis and praxis) also include sections of the temporal cortex. In the temporal cortex is the auditory center of Wernicke's speech, located in the posterior sections of the superior temporal gyrus. It is this center that provides speech gnosis - the recognition and storage of oral speech, both one's own and someone else's. In the middle part of the superior temporal gyrus, there is a center for recognizing musical sounds and their combinations. On the border of the temporal, parietal and occipital lobes there is a center for reading written speech, which provides recognition and storage of images of written speech.

It should also be noted that the psychophysiological functions performed by the associative cortex initiate behavior, an obligatory component of which is voluntary and purposeful movements, carried out with the obligatory participation of the motor cortex.

Motor areas of the cortex . The concept of the motor cortex of the cerebral hemispheres began to form in the 1980s, when it was shown that electrical stimulation of certain cortical zones in animals causes movement of the limbs of the opposite side. Based on modern research in the motor cortex, it is customary to distinguish two motor areas: primary and secondary.

AT primary motor cortex(precentral gyrus) are neurons that innervate the motor neurons of the muscles of the face, trunk and limbs. It has a clear topography of the projections of the muscles of the body. In this case, the projections of the muscles of the lower extremities and the trunk are located in the upper parts of the precentral gyrus and occupy a relatively small area, and the projection of the muscles of the upper extremities, face and tongue are located in the lower parts of the gyrus and occupy a large area. The main pattern of topographic representation is that the regulation of the activity of muscles that provide the most accurate and diverse movements (speech, writing, facial expressions) requires the participation of large areas of the motor cortex. Motor reactions to stimulation of the primary motor cortex are carried out with a minimum threshold, which indicates its high excitability. They (these motor reactions) are represented by elementary contractions of the opposite side of the body. With the defeat of this cortical region, the ability to fine coordinated movements of the limbs, especially the fingers, is lost.

secondary motor cortex. It is located on the lateral surface of the hemispheres, in front of the precentral gyrus (premotor cortex). It performs higher motor functions associated with the planning and coordination of voluntary movements. The premotor cortex receives the bulk of the efferent impulses from the basal ganglia and the cerebellum and is involved in recoding information about the plan of complex movements. Irritation of this area of ​​the cortex causes complex coordinated movements (for example, turning the head, eyes and torso in opposite directions). The premotor cortex contains motor centers associated with human social functions: in the posterior part of the middle frontal gyrus is the center of written speech, in the posterior part of the inferior frontal gyrus is the center of motor speech (Broca's center), as well as the musical motor center, which determines the tonality of speech and the ability to sing.

The motor cortex is often referred to as the agranular cortex because the granular layers are poorly expressed in it, but the layer containing Betz's giant pyramidal cells is more pronounced. Motor cortex neurons receive afferent inputs through the thalamus from muscle, joint, and skin receptors, as well as from the basal ganglia and cerebellum. The main efferent output of the motor cortex to the stem and spinal motor centers is formed by pyramidal cells. Pyramidal and associated intercalary neurons are located vertically with respect to the surface of the cortex. Such adjacent neuronal complexes that perform similar functions are called functional motor columns. Pyramidal neurons of the motor column can excite or inhibit the motor neurons of the stem and spinal centers. Neighboring columns functionally overlap, and pyramidal neurons that regulate the activity of one muscle are usually located in several columns.

The main efferent connections of the motor cortex are carried out through the pyramidal and extrapyramidal pathways, starting from the giant pyramidal cells of Betz and the smaller pyramidal cells of the cortex of the precentral gyrus, premotor cortex and postcentral gyrus.

pyramid path consists of 1 million fibers of the corticospinal tract, starting from the cortex of the upper and middle third of the precentral gyrus, and 20 million fibers of the corticobulbar tract, starting from the cortex of the lower third of the precentral gyrus. Arbitrary simple and complex goal-directed motor programs are carried out through the motor cortex and pyramidal pathways (for example, professional skills, the formation of which begins in the basal ganglia and ends in the secondary motor cortex). Most of the fibers of the pyramidal pathways are crossed. But a small part of them remain uncrossed, which helps to compensate for impaired movement functions in unilateral lesions. Through the pyramidal pathways, the premotor cortex also performs its functions (motor skills of writing, turning the head and eyes in the opposite direction, etc.).

To cortical extrapyramidal pathways include corticobulbar and corticoreticular pathways, starting approximately in the same area as the pyramidal pathways. The fibers of the corticobulbar pathway terminate on the neurons of the red nuclei of the midbrain, from which the rubrospinal pathways continue. The fibers of the corticoreticular pathways terminate on the neurons of the medial nuclei of the reticular formation of the pons (the medial reticulospinal pathways originate from them) and on the neurons of the reticular giant cell nuclei of the medulla oblongata, from which the lateral reticulospinal pathways originate. Through these pathways, the regulation of tone and posture is carried out, providing accurate targeted movements. Cortical extrapyramidal pathways are a component of the extrapyramidal system of the brain, which includes the cerebellum, basal ganglia, and motor centers of the brainstem. This system regulates tone, posture, coordination and correction of movements.

Assessing in general the role of various structures of the brain and spinal cord in the regulation of complex directional movements, it can be noted that the impulse (motivation) to move is created in the frontal system, the idea of ​​movement is created in the associative cortex of the cerebral hemispheres, the program of movements is created in the basal ganglia, cerebellum and premotor cortex, and the execution of complex movements occurs through the motor cortex, motor centers of the trunk and spinal cord.

Interhemispheric relationships Interhemispheric relationships are manifested in humans in two main forms:

functional asymmetry of the cerebral hemispheres:

joint activity of the cerebral hemispheres.

Functional asymmetry of the hemispheres is the most important psychophysiological property of the human brain. The study of functional asymmetry of the hemispheres began in the middle of the 19th century, when the French physicians M. Dax and P. Broca showed that a person’s speech impairment occurs when the cortex of the inferior frontal gyrus, usually the left hemisphere, is damaged. Some time later, the German psychiatrist K. Wernicke discovered an auditory speech center in the posterior cortex of the superior temporal gyrus of the left hemisphere, the defeat of which leads to impaired understanding of oral speech. These data and the presence of motor asymmetry (right-handedness) contributed to the formation of the concept according to which a person is characterized by left-hemispheric dominance, which was formed evolutionarily as a result of labor activity and is a specific property of his brain. In the 20th century, as a result of the use of various clinical methods (especially in the study of patients with a split brain - the corpus callosum was cut), it was shown that in a number of psychophysiological functions, not the left, but the right hemisphere dominates in a person. Thus, the concept of partial dominance of the hemispheres arose (its author is R. Sperry).

It is customary to allocate mental, sensory and motor interhemispheric asymmetry of the brain. Again, in the study of speech, it was shown that the verbal information channel is controlled by the left hemisphere, and the non-verbal channel (voice, intonation) is controlled by the right. Abstract thinking and consciousness are predominantly associated with the left hemisphere. When developing a conditioned reflex, the right hemisphere dominates in the initial phase, and during exercises, that is, the strengthening of the reflex, the left hemisphere dominates. The right hemisphere processes information simultaneously statically, according to the principle of deduction, the spatial and relative features of objects are better perceived. The left hemisphere processes information sequentially, analytically, according to the principle of induction, it better perceives the absolute features of objects and temporal relationships. In the emotional sphere, the right hemisphere mainly determines the older, negative emotions, controls the manifestation of strong emotions. In general, the right hemisphere is "emotional". The left hemisphere determines mainly positive emotions, controls the manifestation of weaker emotions.

In the sensory realm, the role of the right and left hemispheres is best manifested in visual perception. The right hemisphere perceives the visual image holistically, immediately in all details, it is easier to solve the problem of distinguishing objects and identifying visual images of objects that are difficult to describe in words, creates the prerequisites for concrete-sensory thinking. The left hemisphere evaluates the visual image dissected. Familiar objects are more easily recognized and problems of similarity of objects are solved, visual images are devoid of specific details and have a high degree of abstraction, the prerequisites for logical thinking are created.

Motor asymmetry is due to the fact that the muscles of the hemispheres, providing a new, higher level of regulation of complex brain functions, simultaneously increase the requirements for combining the activity of the two hemispheres.

Joint activity of the cerebral hemispheres is provided by the presence of the commissural system (corpus callosum, anterior and posterior, hippocampal and habenular commissures, interthalamic fusion), which anatomically connect the two hemispheres of the brain.

Clinical studies have shown that in addition to the transverse commissural fibers that provide the interconnection of the cerebral hemispheres, there are also longitudinal, as well as vertical commissural fibers.

Questions for self-control:

General characteristics of the new cortex.

Functions of the new cortex.

The structure of the new cortex.

What are neural columns?

What areas of the cortex are distinguished by scientists?

Characteristics of the sensory cortex.

What are primary sensory areas? Their characteristic.

What are secondary sensory areas? Their functional purpose.

What is the somatosensory cortex and where is it located?

Characteristics of the auditory cortex.

Primary and secondary visual areas. Their general characteristics.

Characteristics of the association area of ​​the cortex.

Characteristics of the associative systems of the brain.

What is the thalamotenoid system. Her functions.

What is the thalamolobal system. Her functions.

General characteristics of the motor cortex.

Primary motor cortex; her characteristic.

secondary motor cortex; her characteristic.

What are functional motor columns.

Characteristics of the cortical pyramidal and extrapyramidal pathways.

Modern scientists know for certain that thanks to the functioning of the brain, such abilities as awareness of signals received from the external environment, mental activity, and memorization of thinking are possible.

The ability of a person to be aware of his own relationships with other people is directly related to the process of excitation of neural networks. And we are talking about those neural networks that are located in the cortex. It is the structural basis of consciousness and intellect.

In this article, we will consider how the cerebral cortex is arranged, the zones of the cerebral cortex will be described in detail.

neocortex

The cortex includes about fourteen billion neurons. It is thanks to them that the functioning of the main zones is carried out. The vast majority of neurons, up to ninety percent, form the neocortex. It is part of the somatic NS and its highest integrative department. The most important functions of the cerebral cortex are the perception, processing, interpretation of information that a person receives with the help of various sense organs.

In addition, the neocortex controls the complex movements of the human body's muscle system. It contains centers that take part in the process of speech, memory storage, abstract thinking. Most of the processes that take place in it form the neurophysical basis of human consciousness.

What parts of the cerebral cortex are made up of? The areas of the cerebral cortex will be discussed below.

paleocortex

It is another large and important section of the cortex. Compared to the neocortex, the paleocortex has a simpler structure. The processes that take place here are rarely reflected in consciousness. In this section of the cortex, the higher vegetative centers are localized.

Communication of the cortical layer with other parts of the brain

It is important to consider the connection that exists between the underlying parts of the brain and the cerebral cortex, for example, with the thalamus, bridge, middle bridge, basal ganglia. This connection is carried out with the help of large bundles of fibers that form the inner capsule. The fiber bundles are represented by wide layers, which are composed of white matter. They contain a huge number of nerve fibers. Some of these fibers provide transmission of nerve signals to the cortex. The rest of the bundles transmits nerve impulses to the nerve centers located below.

How is the cerebral cortex structured? The areas of the cerebral cortex will be presented below.

The structure of the bark

The largest part of the brain is its cortex. Moreover, cortical zones are only one type of parts distinguished in the cortex. In addition, the cortex is divided into two hemispheres - right and left. Between themselves, the hemispheres are connected by bundles of white matter, forming the corpus callosum. Its function is to ensure the coordination of the activities of both hemispheres.

Classification of areas of the cerebral cortex according to their location

Despite the fact that the bark has a huge number of folds, in general, the location of its individual convolutions and furrows is constant. The main ones are a guideline in the selection of areas of the cortex. These zones (lobes) include - occipital, temporal, frontal, parietal. Although they are classified by location, each of them has its own specific functions.

auditory area of ​​the cerebral cortex

For example, the temporal zone is the center in which the cortical section of the hearing analyzer is located. If there is damage to this section of the cortex, deafness may occur. In addition, Wernicke's speech center is located in the auditory zone. If it is damaged, then the person loses the ability to perceive oral speech. The person perceives it as simple noise. Also in the temporal lobe there are neuronal centers that belong to the vestibular apparatus. If they are damaged, the sense of balance is disturbed.

Speech areas of the cerebral cortex

The speech zones are concentrated in the frontal lobe of the cortex. The speech motor center is also located here. If it is damaged in the right hemisphere, then the person loses the ability to change the timbre and intonation of his own speech, which becomes monotonous. If the damage to the speech center occurred in the left hemisphere, then articulation, the ability to articulate speech and singing disappear. What else is the cerebral cortex made of? The areas of the cerebral cortex have different functions.

visual zones

In the occipital lobe is the visual zone, in which there is a center that responds to our vision as such. The perception of the surrounding world occurs precisely with this part of the brain, and not with the eyes. It is the occipital cortex that is responsible for vision, and damage to it can lead to partial or complete loss of vision. The visual area of ​​the cerebral cortex is considered. What's next?

The parietal lobe also has its own specific functions. It is this zone that is responsible for the ability to analyze information that relates to tactile, temperature and pain sensitivity. If there is damage to the parietal region, the reflexes of the brain are disturbed. A person cannot recognize objects by touch.

Motor zone

Let's talk about the motor zone separately. It should be noted that this area of ​​the cortex does not correlate in any way with the lobes discussed above. It is part of the cortex containing direct connections to motor neurons in the spinal cord. This name is given to neurons that directly control the activity of the muscles of the body.

The main motor area of ​​the cerebral cortex is located in the gyrus, which is called the precentral. This gyrus is a mirror image of the sensory area in many ways. Between them there is a contralateral innervation. In other words, the innervation is directed to the muscles that are located on the other side of the body. An exception is the facial area, which is characterized by bilateral muscle control located on the jaw, lower face.

Slightly below the main motor zone is an additional zone. Scientists believe that it has independent functions that are associated with the process of outputting motor impulses. The additional motor zone has also been studied by specialists. Experiments that were performed on animals show that stimulation of this zone provokes the occurrence of motor reactions. A feature is that such reactions occur even if the main motor zone was isolated or completely destroyed. It is also involved in planning movements and motivating speech in the dominant hemisphere. Scientists believe that if the additional motor is damaged, dynamic aphasia can occur. The reflexes of the brain suffer.

Classification according to the structure and functions of the cerebral cortex

Physiological experiments and clinical trials, which were carried out at the end of the nineteenth century, made it possible to establish the boundaries between areas on which different receptor surfaces are projected. Among them, there are sense organs that are directed to the outside world (skin sensitivity, hearing, vision), receptors embedded directly in the organs of movement (motor or kinetic analyzers).

The areas of the cortex, in which various analyzers are located, can be classified according to their structure and functions. So, there are three of them. These include: primary, secondary, tertiary areas of the cerebral cortex. The development of the embryo involves the laying of only primary zones, characterized by simple cytoarchitectonics. Next comes the development of secondary, tertiary develop in the very last turn. Tertiary zones are characterized by the most complex structure. Let's consider each of them in a little more detail.

Center fields

Over the years of clinical research, scientists have managed to accumulate significant experience. Observations made it possible to establish, for example, that damage to various fields, as part of the cortical sections of different analyzers, may not be equally reflected in the overall clinical picture. If we consider all these fields, then among them one can be distinguished, which occupies a central position in the nuclear zone. Such a field is called the central or primary. It is located simultaneously in the visual zone, in the kinesthetic zone, in the auditory zone. Damage to the primary field entails very serious consequences. A person cannot perceive and carry out the most subtle differentiation of stimuli that affect the corresponding analyzers. How else are areas of the cerebral cortex classified?

Primary Zones

In the primary zones, there is a complex of neurons that is most predisposed to providing bilateral connections between the cortical and subcortical zones. It is this complex that connects the cerebral cortex with a variety of sensory organs in the most direct and shortest way. In this regard, these zones have the ability to very detailed identification of stimuli.

An important common feature of the functional and structural organization of the primary areas is that they all have a clear somatic projection. This means that individual peripheral points, for example, skin surfaces, retina, skeletal muscles, cochlea of ​​the inner ear, have their own projection into strictly limited, corresponding points that are located in the primary zones of the cortex of the corresponding analyzers. In this regard, they were given the name of the projection zones of the cerebral cortex.

Secondary zones

In another way, these zones are called peripheral. This name was not given to them by chance. They are located in the peripheral sections of the cortex. Secondary zones differ from the central (primary) zones in their neuronal organization, physiological manifestations, and architectonic features.

Let's try to figure out what effects occur if the secondary zones are affected by an electrical stimulus or if they are damaged. The effects that arise mainly concern the most complex types of processes in the psyche. In the event that secondary zones are damaged, elementary sensations remain relatively intact. Basically, there are violations in the ability to correctly reflect the mutual relationships and entire complexes of elements that make up the various objects that we perceive. For example, if the secondary zones of the visual and auditory cortex were damaged, then one can observe the occurrence of auditory and visual hallucinations that unfold in a certain temporal and spatial sequence.

Secondary areas are of significant importance in the implementation of the mutual connections of stimuli that are distinguished using the primary areas of the cortex. In addition, they play a significant role in the integration of functions that are carried out by the nuclear fields of different analyzers as a result of combining into complex complexes of receptions.

Thus, secondary zones are of particular importance for the implementation of mental processes in more complex forms that require coordination and are associated with a detailed analysis of the relationships between objective stimuli. During this process, specific connections are established, which are called associative. Afferent impulses entering the cortex from the receptors of various external sense organs reach the secondary fields through many additional switches in the associative nucleus of the thalamus, which is also called the thalamic thalamus. Afferent impulses following in the primary zones, in contrast to impulses, follow in the secondary zones, reach them in a way that is shorter. It is implemented by means of a relay-core, in the thalamus.

We figured out what the cerebral cortex is responsible for.

What is the thalamus?

From the thalamic nuclei, fibers approach each lobe of the cerebral hemispheres. The thalamus is a visual mound located in the central part of the anterior part of the brain, consists of a large number of nuclei, each of which transmits an impulse to certain areas of the cortex.

All signals that enter the cortex (the only exception is olfactory ones) pass through the relay and integrative nuclei of the thalamus opticus. From the nuclei of the thalamus, the fibers are sent to the sensory areas. Taste and somatosensory zones are located in the parietal lobe, auditory sensory zone - in the temporal lobe, visual - in the occipital lobe.

Impulses come to them, respectively, from the ventrobasal complexes, medial and lateral nuclei. Motor zones are associated with the ventral and ventrolateral nuclei of the thalamus.

EEG desynchronization

What happens if a very strong stimulus acts on a person who is in a state of complete rest? Naturally, a person will completely concentrate on this stimulus. The transition of mental activity, which is carried out from a state of rest to a state of activity, is reflected on the EEG by a beta rhythm, which replaces the alpha rhythm. The fluctuations become more frequent. This transition is called EEG desynchronization; it appears as a result of sensory excitation entering the cortex from nonspecific nuclei located in the thalamus.

activating reticular system

Diffuse nervous system is made up of non-specific nuclei. This system is located in the medial parts of the thalamus. It is the anterior part of the activating reticular system that regulates the excitability of the cortex. A variety of sensory signals can activate this system. Sensory signals can be both visual and olfactory, somatosensory, vestibular, auditory. The reticular activating system is a channel that transmits signal data to the surface layer of the cortex through non-specific nuclei located in the thalamus. The arousal of ARS is necessary for a person to be able to maintain a state of wakefulness. If disturbances occur in this system, then coma-like sleep-like states can be observed.

Tertiary zones

There are functional relationships between the analyzers of the cerebral cortex, which have an even more complex structure than the one described above. In the process of growth, the fields of the analyzers overlap. Such overlap zones, which are formed at the ends of the analyzers, are called tertiary zones. They are the most complex types of combining the activities of the auditory, visual, skin-kinesthetic analyzers. The tertiary zones are located outside the boundaries of the analyzers' own zones. In this regard, damage to them does not have a pronounced effect.

Tertiary zones are special cortical areas in which scattered elements of different analyzers are collected. They occupy a very vast territory, which is divided into regions.

The upper parietal region integrates the movements of the whole body with the visual analyzer, and forms a scheme of bodies. The lower parietal region combines generalized forms of signaling, which are associated with differentiated subject and speech actions.

No less important is the temporo-parieto-occipital region. She is responsible for the complicated integration of auditory and visual analyzers with oral and written speech.

It should be noted that in comparison with the first two zones, the tertiary ones are characterized by the most complex chains of interaction.

Based on all the above material, we can conclude that the primary, secondary, tertiary zones of the human cortex are highly specialized. Separately, it is worth emphasizing the fact that all three cortical zones that we considered, in a normally functioning brain, together with the systems of connections and formations of the subcortical location, function as a single differentiated whole.

We examined in detail the zones and sections of the cerebral cortex.

Spinal Cord Functions

In the white matter of the spinal cord, adjacent to the gray matter between the anterior and posterior horns, is located reticular formation. This formation is formed by clusters of nerve cells that have numerous connections with each other. R eticular formation ensures the activity of other neurons of the spinal cord due to the property of automation (see below).

Vegetative reflexes(vasomotor, sweating, genitourinary, defecation) are due to the presence of centers of the autonomic nervous system in the spinal cord (see below).

Conductor functions

They are carried out according to the Bell-Magendie law: afferent information enters the spinal cord through the posterior roots, efferent impulses are transmitted through the anterior roots.

Ascending (sensitive) pathways spinal cord are located in back pillars white substances and carry information from the outside world and the internal environment of the body:

1) from skin receptors (pain, temperature, touch, pressure, vibration);

2) from proprioceptors (muscle spindles, Golgi tendon receptors, periosteum and joint membranes);

3) from receptors of internal organs - visceroreceptors (mechano- and chemoreceptors).

Descending (motor) pathways located in front pillars and transmit impulses to the skeletal muscles about voluntary (conscious) movements, tonic influences on the muscles, impulses that ensure the maintenance of posture and balance. Vegetative influences (on internal organs) are also transmitted along descending paths.

The conduction functions are similar in other stem structures (medulla oblongata, midbrain and pons): afferent pathways pass along the posterior group of white fibers, and efferent pathways along the anterior group.

Functions of the medulla oblongata

Main the function of the pyramids is to conduct signals about voluntary movements.

The functions of the olive nuclei are associated with maintaining balance.

In the medulla oblongata are nuclei of the VIII-XII cranial nerves, therefore, the medulla oblongata carries out protective reflexes (coughing, sneezing, vomiting, tearing, eyelid closure, pupil constriction) (see).

The medulla oblongata performs sensory functions: reception of skin sensitivity of the face, primary analysis of taste. The medulla oblongata receives signals from chemoreceptors and baroreceptors of vessels, interoreceptors of internal organs and vestibuloreceptors. The influence of these structures determines the functioning at the level of the medulla oblongata respiratory, cardiac and vascular centers. The structures of the reticular formation also perform the functions of regulation skeletal muscle tone.

Conductor functions - see spinal cord.

Structures of the hindbrain

The hindbrain includes the pons and cerebellum.

Bridge facial(VII pair) and vestibulocochlear (VIII pair) nerves.

Responsible for the physiological reaction of tension and anxiety, is involved in the mechanisms of sleep. Many of its neurons noradrenergic.

Bridge functions:

conductive (predominate);

Ensures the maintenance of the posture and maintaining the balance of the body in space when changing the speed of movement;

Provides tone to the neck muscles;

It contains vegetative centers for the regulation of respiration (pneumotoxic center), heart rate, and activity of the gastrointestinal tract.

Regulates chewing and swallowing (see. Complex reflexes of the brain stem);

plays an important role in the activation of the cerebral cortex (including in a state of anxiety);

Limits sensory inflows of nerve impulses to the cerebral hemispheres during sleep.

Cerebellum

The functions of the cerebellum are mainly related to organization of motor acts and regulation of autonomic functions. From the motor cortex and basal nuclei, information about the planned movement, as well as afferentation from the somatosensory system, enters the cerebellum. The cerebellum provides mutual coordination of movements, as well as movement correction(required, because during the implementation of a motor act, the moving parts of the body are influenced by inertial forces, which violates the smoothness and accuracy of the movement).

Cerebellar functions:

maintaining body posture and balance;

coordination of purposeful movements;

construction of fast ballistic movements;

regulation of muscle tone;

regulation of vegetative functions (heartbeat, vascular tone, intestinal motility, etc.);

conductor.

midbrain functions

In the midbrain, a dorsally located roof and ventrally going legs of the brain.

reticular formation, kernels oculomotor and bloc cranial nerves (III-IV pair).

The roof of the midbrain consists of four elevations ( quadrigemina) - mounds that look like hemispheres.

Legs of the brainrepresented by two thick, longitudinally striated rollers going to the right and left hemispheres of the brain. In the thickness of the legs of the brain are paired substantia nigra nuclei. They lie in the tire nuclei of the extrapyramidal motor system (red nuclei, black substance and etc.).

Nuclei of cranial nerves (III-V) and reticular formation participate in the implementation complex brain stem reflexes.

black substance one of the areas of the brain that produces dopamine. Besides, black substance performs a number of important functions: regulation of muscle tone, especially during sleep, ensuring homeostasis, are included in the anti-pain and sleep-forming systems of the body.

Tonic reactions together with the postural reflexes of the spinal cord, they provide a redistribution of the tone of various muscle groups when the position of the body or its individual parts (for example, the head) in space changes. They are divided into two groups: static and statokinetic. Static reactions arise when a change in the position of the body is not associated with its movement in space (i.e. postural reflexes). Statokinetic reactions are manifested in the redistribution of skeletal muscle tone, which ensures the balance of the human body during angular and linear accelerations of its active or passive movement in space

diencephalon

diencephalonis the uppermost section of the brainstem, the cavity of which is III ventricle. The diencephalon is located under corpus callosum and vault brain, most of it is surrounded by the hemispheres of the telencephalon. The diencephalon includes the optic tubercles (thalamus), hypothalamus (hypothalamus), suprathalamic part (epithalamus) and zathalamic region (metathalamus). The diencephalon also includes two endocrine glands - pituitary and epiphysis(pineal body).

thalamus

Thalamus (optical tubercles)are an accumulation of gray matter, have an ovoid shape, connected interthalamic adhesion. Its nerve cells are grouped into a large number of nuclei (up to 120). Functionally, the nuclei of the thalamus are divided into specific, non-specific, associative and motor.

Specific nuclei associated with certain sensitive areas of the cortex - auditory, visual, etc. (all except olfactory). Here there is a convergence of afferent signals with the suppression of biologically insignificant ones. Non-specific nuclei thalamus are connected with many areas of the cortex and, together with the structures of the reticular formation, take part in the formation of ascending activating influences. Associative nuclei are formed by multipolar ones, the axons of which go to the layers of the associative and partially projection areas. Associative nuclei are involved in higher integrative processes (multisensory convergence, etc.), but their functions have not yet been studied enough. To motor nuclei The thalamus includes the ventral nucleus, which has input from the cerebellum and basal ganglia, and at the same time gives projections to the motor cortex of the cerebral hemispheres. This core is included in the movement regulation system.

Hypothalamus

Hypothalamusforms the walls and bottom of the 3rd ventricle, hangs from it on a thin stalkpituitary . Secreted in the hypothalamus three areas of accumulation of nuclei: anterior, middle (medial) and posterior. In the front area hypothalamus is located supraoptic and paraventricular nuclei. In the neurosecretory cells of these nuclei, hormones are produced that enter the posterior pituitary gland. (neurohypophysis). In the middle (medial) region neurons where neurohormones are produced liberals and statins, respectively activating or inhibiting the activity of the anterior pituitary gland ( adenohypophysis). To the cores posterior region include scattered large cells, as well as nuclei mastoid body.

The hypothalamus is a structure of the central nervous system that performs a complex integration of the functions of various internal organs to the overall functioning of the organism. It changes the activity of the cardiovascular, respiratory and other visceral systems with changes in the external or internal environment (changes in weather conditions, physical activity, infections, and other factors that threaten homeostasis). Depending on the performed autonomic functions There are two zones in the hypothalamus. The first zone is dynamogenic, occupying the middle and back parts of the hypothalamus. When it is excited, “motor reactions” are observed: pupil dilation, increased heart rate, increased blood pressure, activation of respiration, increased motor excitability, i.e. manifestations of sympathetic influences autonomic nervous system. The second zone is trophogenic, its excitation is manifested in the narrowing of the pupil, lowering blood pressure, slowing down breathing, vomiting, defecation, urination, salivation, i.e. symptoms characteristic of influences of the parasympathetic nervous system.

Located in the hypothalamus motivational centers: hunger, satiety, thirst, as well as sexual and aggressive-defensive centers. Receiving afferent streams of excitations from interoreceptors (osmoreceptors, chemoreceptors, thermoreceptors, etc.) and integrating them with humoral influences on the nerve cells of the hypothalamus, these centers form the corresponding motivational states of the body.

limbic system

limbic system(synonym: limbic complex, visceral brain) - a complex of structures of the middle, intermediate and final brain involved in the organization of visceral, motivational and emotional reactions of the body. The limbic system is formed by: the olfactory bulb; olfactory tract; olfactory triangle; anterior perforated substance; cingulate gyrus; parahippocampal gyrus; hippocampus; amygdala; hypothalamus; mastoid body; reticular formation midbrain.

The limbic system provides modulating effect on the cerebral cortex and subcortical structures, establishing, together with the reticular formation, the necessary their activity level(ascending: coma → deep sleep → light sleep (drowse) → quiet wakefulness → active wakefulness → agitated state → affect). The limbic system controls emotions, the sleep-wake cycle, sexual behavior, and learning and memory. Receiving information about the external and internal environments of the body, the limbic system triggers vegetative and somatic emotional reactions (increased heart rate and respiration, increased blood pressure and sweating, muscle tension). Limbic formations are classified as higher integrative centers regulation of vegetative functions of the body. From them, excitatory impulses are sent to the autonomic centers of the hypothalamus and through it to the pituitary gland and the stem and spinal nuclei of the autonomic nervous system. Through their connections to the basal ganglia, anterior thalamus, and the reticular formation, the limbic structures can influence skeletal muscle tone.

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 ( Peipes circle). Such an organization creates conditions for the long-term circulation of the same excitation in the system and, thereby, for the preservation of a single state in it and the imposition of this state on other brain systems ( excitation reverb). This determines not only the tonic activation of the cerebral cortex, but also the strength and severity of the emotional states of the body; is related to memory and the processes of learning and short-term memory, regulates aggressive-defensive, food and sexual forms of behavior.

Basal nuclei

In the white matter of the cerebral hemispheres, closer to its base, there is gray matter forming the subcortical or basal nuclei: striatum, consisting of caudate lentiform nuclei (includes shell, lateral and medial globus pallidus), fences, amygdala.

The basal ganglia occupy a central place among the structures voluntary movement systems. (motor nuclei). With the participation of the basal nuclei, synergy of all elements of such complex motor acts as walking, running, climbing is carried out; the smoothness of movements and the setting of the initial posture for their implementation are achieved. The basal nuclei coordinate the tone and phase motor activity of the muscles. Their activity is associated with the performance of slow movements, such as slow walking, stepping over an obstacle, threading a needle.

The basal nuclei are involved not only in the regulation of motor activity, but also in the analysis of afferent flows, in the regulation of a number of vegetative functions, in the implementation of complex forms of innate behavior, in the mechanisms of short-term memory, and also in the regulation of the sleep-wake cycle.

Functions of the cerebral cortex

The highest division of the CNS is cerebral cortex. Different areas of the cerebral cortex have different fields, determined by the nature and number of neurons, the thickness of the layers, etc. The presence of structurally different fields also implies their different functional purpose.

Taking into account the functional features of the field of the new cortex, they are divided into primary, secondary and tertiary or associative. Primary and secondary fields unite the sections of the cortex associated with the functioning of certain sensory systems.

1) Primary (projection) fields receive and process information from any sensory system. Here is carried out primary analysis sensory information within the same modality (for example, for visual - color, illumination, shape). Modality - a type of sensory sensations - auditory, visual, olfactory, etc.

Primary sensory and motor fields are strictly localized. Below are some of them.

In the cortex of the postcentral gyrus and the superior parietal lobule, there are nerve cells that form core of proprioceptive and general sensitivity(temperature, pain and tactile). Motor Analyzer Core is located in the motor area of ​​the cortex, which includes the precentral gyrus and the paracentral lobule of the medial surface of the hemisphere. The size and location of the projection zones of various organs in the somatosensory and motor cortex depends on their functional significance.

In the depth of the lateral sulcus, on the surface of the middle part of the superior temporal gyrus facing the insula, there is auditory analyzer core. The cortex of the middle temporal gyrus contains nucleus of the vestibular analyzer.

The core of the visual analyzer located on the medial surface of the occipital lobe, on both sides of the spur groove.

speech centers are located in the left hemisphere in right-handed people, and in the right hemisphere in left-handed people. Motor Speech Analyzer Core(speech pronunciation) is located in the posterior sections of the inferior frontal gyrus ( Broca's center). The core of the auditory speech analyzer(speech perception) is closely connected with the cortical auditory center and is located in the posterior sections of the superior temporal gyrus, on its surface facing the lateral sulcus ( Venicke zone). Close to the nucleus of the visual analyzer is the core of the visual analyzer of written speech.

Cortical departments taste and olfactory analyzers are located on the lower surface of the temporal lobe, in the seahorse gyrus and the hook on the lower surface of the temporal lobe.

2) Secondary fields are located above the primary ones and occupy a large area. In addition to sensitive ones, they receive fibers from motivational and emotional centers, memory structures, etc. They are characteristic identification sensory images within the same modality (for example, recognition of an object - a nail, a screw, a rod, a dowel, a heel, a mushroom, a nipple, a needle). Damage to the secondary fields can lead to sensory agnosia (impaired recognition processes): visual, auditory, olfactory, gustatory, as well as sensory aphasia (impaired speech recognition).

3) Tertiary or associative fields occupy more than 50% of the entire surface of the hemispheres and are the youngest (in evolutionary terms). Tertiary fields are closely related to the associative nuclei of the thalamus. Associative zones provide contacts between the projection zones of individual analyzers and integrate their activities. They take part in multisensory processing of information, the formation of responses and the implementation of complex forms of behavior. In addition, there are other types of convergence: sensory-biological (manifested in the convergence to individual neurons of the cerebral cortex of afferent excitations of any sensory modality and motivational excitations associated with various biological states of the body (pain, hunger, etc.), multibiological and efferent- afferent The main association areas are parieto-occipital(primarily a function of perception) and frontal(organization and control of behavioral, mainly motor, reactions). The anterior frontal section are morphological substrate of mental activity (consciousness, thinking, learning, memory, emotions).