CORTEX (cortexencephali) - all surfaces of the cerebral hemispheres, covered with a cloak (pallium), formed by gray matter. Together with other departments of c. n. With. the bark is involved in the regulation and coordination of all body functions, plays an extremely important role in mental, or higher nervous activity (see).
In accordance with the stages of evolutionary development of c. n. With. the bark is divided into old and new. The old cortex (archicortex - the old cortex itself and paleocortex - the ancient cortex) is a phylogenetically older formation than the new cortex (neocortex), which appeared during the development of the cerebral hemispheres (see Architectonics of the cerebral cortex, Brain).
Morphologically, K. m. is formed by nerve cells (see), their processes and neuroglia (see), which has a support-trophic function. In primates and humans in the cortex, there are approx. 10 billion neurocytes (neurons). Depending on the shape, pyramidal and stellate neurocytes are distinguished, which are characterized by great diversity. The axons of pyramidal neurocytes are sent to the subcortical white matter, and their apical dendrites - to the outer layer of the cortex. Star-shaped neurocytes have only intracortical axons. Dendrites and axons of stellate neurocytes branch abundantly near the cell bodies; some of the axons approach the outer layer of the cortex, where, following horizontally, they form a dense plexus with the tops of the apical dendrites of pyramidal neurocytes. Along the surface of the dendrites there are reniform outgrowths, or spines, which represent the region of axodendritic synapses (see). The cell body membrane is the area of axosomatic synapses. In each area of the cortex there are many input (afferent) and output (efferent) fibers. Efferent fibers go to other areas K. of m, to subcrustal educations or to the motive centers of a spinal cord (see). Afferent fibers enter the cortex from the cells of the subcortical structures.
The ancient cortex in humans and higher mammals consists of a single cell layer, poorly differentiated from the underlying subcortical structures. Actually the old bark consists of 2-3 layers.
The new bark has a more complex structure and takes (in humans) approx. 96% of the entire surface of K. g. m. Therefore, when they talk about K. g. m., they usually mean a new bark, which is divided into the frontal, temporal, occipital and parietal lobes. These lobes are divided into areas and cytoarchitectonic fields (see Architectonics of the cerebral cortex).
The thickness of the cortex in primates and humans varies from 1.5 mm (on the surface of the gyri) to 3-5 mm (in the depth of the furrows). On the sections painted across Nissl, the layered structure of bark is visible, a cut depends on grouping of neurocytes at its different levels (layers). In the bark, it is customary to distinguish 6 layers. The first layer is poor in cell bodies; the second and third - contain small, medium and large pyramidal neurocytes; the fourth layer is the zone of stellate neurocytes; the fifth layer contains giant pyramidal neurocytes (giant pyramidal cells); the sixth layer is characterized by the presence of multiform neurocytes. However, the six-layer organization of the cortex is not absolute, since in reality in many parts of the cortex there is a gradual and uniform transition between layers. The cells of all layers, located on the same perpendicular with respect to the surface of the cortex, are closely connected with each other and with subcortical formations. Such a complex is called a column of cells. Each such column is responsible for the perception of predominantly one type of sensitivity. For example, one of the columns of the cortical representation of the visual analyzer perceives the movement of an object in a horizontal plane, the neighboring one - in a vertical one, etc.
Similar cell complexes of the neocortex have a horizontal orientation. It is assumed that, for example, small cell layers II and IV consist mainly of receptive cells and are “entrances” to the cortex, large cell layer V is an “exit” from the cortex to subcortical structures, and middle cell layer III is associative, connects different areas of the cortex.
Thus, several types of direct and feedback connections between the cellular elements of the cortex and subcortical formations can be distinguished: vertical bundles of fibers that carry information from subcortical structures to the cortex and back; intracortical (horizontal) bundles of associative fibers passing at different levels of the cortex and white matter.
The variability and originality of the structure of neurocytes indicate the extreme complexity of the apparatus of intracortical switching and the methods of connections between neurocytes. This feature of the structure of K. g. m should be considered as morfol, the equivalent of its extreme reactivity and funkts, plasticity, providing it with higher nervous functions.
An increase in the mass of the cortical tissue occurred in a limited space of the skull, so the surface of the cortex, which was smooth in lower mammals, was transformed into convolutions and furrows in higher mammals and humans (Fig. 1). It was with the development of the cortex already in the last century that scientists associated such aspects of brain activity as memory (see), intelligence, consciousness (see), thinking (see), etc.
I. P. Pavlov defined 1870 as the year "from which scientific fruitful work on the study of the cerebral hemispheres begins." This year, Fritsch and Gitzig (G. Fritsch, E. Hitzig, 1870) showed that electrical stimulation of certain areas of the anterior section of the CG of dogs causes a contraction of certain groups of skeletal muscles. Many scientists believed that when stimulated by K. m., the “centers” of voluntary movements and motor memory are activated. However still Ch. Sherrington preferred to avoid funkts, interpretations of this phenomenon and was limited only by the statement that the area of bark, irritation a cut causes reduction of muscle groups, is intimately connected with a spinal cord.
Directions of experimental researches K. of m of the end of the last century were almost always connected with problems a wedge, neurology. On this basis, experiments were started with partial or complete decortication of the brain (see). The first complete decortication in a dog was made by Goltz (F. L. Goltz, 1892). The decorticated dog turned out to be viable, but many of its most important functions were sharply impaired - vision, hearing, orientation in space, coordination of movements, etc. partial extirpations of the cortex suffered from the absence of an objective criterion for their evaluation. The introduction of the conditioned reflex method into the practice of experimenting with extirpations opened up a new era in studies of the structural and functional organization of CG m.
Simultaneously with the discovery of the conditioned reflex, the question arose about its material structure. Since the first attempts to develop a conditioned reflex in decorticated dogs failed, I. P. Pavlov came to the conclusion that C. g. m. is an "organ" of conditioned reflexes. However, further studies showed the possibility of developing conditioned reflexes in decorticated animals. It was found that conditioned reflexes are not disturbed during vertical cuts of various areas of the K. g. m. and their separation from subcortical formations. These facts, along with electrophysiological data, gave reason to consider the conditioned reflex as a result of the formation of a multichannel connection between various cortical and subcortical structures. The shortcomings of the method of extirpation for studying the significance of C. g. m in the organization of behavior prompted the development of methods for reversible, functional, exclusion of the cortex. Buresh and Bureshova (J. Bures, O. Buresova, 1962) applied the phenomenon of the so-called. spreading depression by applying potassium chloride or other irritants to one or another part of the cortex. Since depression does not spread through the furrows, this method can only be used on animals with a smooth surface K. g. m. (rats, mice).
Other way funkts, switching off K. g. m. - its cooling. The method developed by N. Yu. Belenkov et al. (1969), consists in the fact that, in accordance with the shape of the surface of the cortical areas scheduled for shutdown, capsules are made that are implanted over the dura mater; during the experiment, a cooled liquid is passed through the capsule, as a result of which the temperature of the cortex under the capsule decreases to 22–20°C. The assignment of biopotentials with the help of microelectrodes shows that at such a temperature, the impulse activity of neurons stops. The cold decortication method used in hron, experiments on animals demonstrated the effect of an emergency shutdown of the new cortex. It turned out that such a switch-off stops the implementation of previously developed conditioned reflexes. Thus, it was shown that K. g. m. is a necessary structure for the manifestation of a conditioned reflex in an intact brain. Consequently, the observed facts of the development of conditioned reflexes in surgically decorticated animals are the result of compensatory rearrangements occurring in the time interval from the moment of the operation to the beginning of the study of the animal in hron, experiment. The compensatory phenomena take place and in case funkts, switching-offs of a new bark. Just like cold shutdown, acute shutdown of the neocortex in rats with the help of spreading depression sharply disrupts conditioned reflex activity.
A comparative evaluation of the effects of complete and partial decortication in various animal species showed that monkeys endure these operations more difficult than cats and dogs. The degree of dysfunction during extirpation of the same areas of the cortex is different in animals at different stages of evolutionary development. For example, the removal of temporal regions in cats and dogs impairs hearing less than in monkeys. Similarly, vision after removal of the occipital lobe of the cortex is affected to a greater extent in monkeys than in cats and dogs. On the basis of these data there was an idea of corticolization of functions in the course of evolution of c. n. N of page, according to Krom phylogenetically earlier links of a nervous system pass to lower level of hierarchy. At the same time, K. g. m. plastically rebuilds the functioning of these phylogenetically older structures in accordance with the influence of the environment.
Cortical projections of afferent systems K. of m represent specialized end stations of ways from sensory organs. Efferent pathways go from K. m. to the motor neurons of the spinal cord as part of the pyramidal tract. They originate mainly from the motor area of the cortex, which in primates and humans is represented by the anterior central gyrus, located anterior to the central sulcus. Behind the central sulcus is the somatosensory area K. m. - the posterior central gyrus. Individual parts of the skeletal muscles are corticolized to varying degrees. The lower limbs and trunk are represented least differentiated in the anterior central gyrus, the representation of the muscles of the hand occupies a large area. An even larger area corresponds to the musculature of the face, tongue and larynx. In the posterior central gyrus, in the same ratio as in the anterior central gyrus, afferent projections of body parts are presented. It can be said that the organism is, as it were, projected into these convolutions in the form of an abstract "homunculus", which is characterized by an extreme preponderance in favor of the anterior segments of the body (Fig. 2 and 3).
In addition, the cortex includes associative, or non-specific, areas that receive information from receptors that perceive irritations of various modalities, and from all projection zones. The phylogenetic development of C. g. m. is characterized primarily by the growth of associative zones (Fig. 4) and their separation from projection zones. In lower mammals (rodents), almost the entire cortex consists of projection zones alone, which simultaneously perform associative functions. In humans, the projection zones occupy only a small part of the cortex; everything else is reserved for associative zones. It is assumed that associative zones play a particularly important role in the implementation of complex forms in c. n. d.
In primates and humans, the frontal (prefrontal) region reaches the greatest development. It is phylogenetically the youngest structure directly related to the highest mental functions. However, attempts to project these functions to separate areas of the frontal cortex have not been successful. Obviously, any part of the frontal cortex can be included in the implementation of any of the functions. The effects observed during the destruction of various parts of this area are relatively short-lived or often completely absent (see Lobectomy).
The confinement of separate structures of K. of m to certain functions, considered as a problem of localization of functions, remains till now one of the most difficult problems of neurology. Noting that in animals, after the removal of the classical projection zones (auditory, visual), conditioned reflexes to the corresponding stimuli are partially preserved, I. P. Pavlov hypothesized the existence of a "core" of the analyzer and its elements, "scattered" throughout the C. g. With the help microelectrode research methods (see) it was succeeded to register activity of the specific neurocytes responding to incentives of a certain touch modality in various areas K. of m. Superficial assignment of bioelectric potentials reveals distribution of primary evoked potentials on the considerable areas K. of m - outside of the corresponding projection zones and cytoarchitectonic fields. These facts, along with the poly-functionality of disorders during the removal of any sensory area or its reversible shutdown, indicate a multiple representation of functions in the C. g. m. Motor functions are also distributed over large areas of the C. g. m. tract, are located not only in the motor areas, but also beyond them. In addition to sensory and motor cells, in K. m. there are also intermediate cells, or interneurocytes, which make up the bulk of K. g. m. and concentrated ch. arr. in association areas. Multimodal excitations converge on interneurocytes.
Experimental data indicate, thus, the relativity of the localization of functions in C. g. m., the absence of cortical "centers" reserved for one or another function. The least differentiated in funkts, the relation are the associative areas possessing especially expressed properties of plasticity and interchangeability. However, it does not follow from this that the associative regions are equipotential. The principle of equipotentiality of the cortex (the equivalence of its structures), expressed by Lashley (K. S. Lashley) in 1933 on the basis of the results of extirpations of a poorly differentiated rat cortex, as a whole cannot be extended to the organization of cortical activity in higher animals and humans. I. P. Pavlov contrasted the principle of equipotentiality with the concept of dynamic localization of functions in C.G.M.
The solution to the problem of the structural and functional organization of C. g. m. is largely hampered by the identification of the localization of symptoms of extirpations and stimulations of certain cortical zones with the localization of the functions of C. g. m. This question already concerns the methodological aspects of neurophysiol, experiment, since from a dialectical point From the point of view of any structural-functional unit in the form in which it appears in each given study, it is a fragment, one of the aspects of the existence of the whole, a product of the integration of structures and connections of the brain. For example, the position that the function of motor speech is "localized" in the lower frontal gyrus of the left hemisphere is based on the results of damage to this structure. At the same time, electrical stimulation of this "center" of speech never causes an act of articulation. It turns out, however, that the utterance of entire phrases can be induced by stimulation of the rostral thalamus, which sends afferent impulses to the left hemisphere. Phrases caused by such stimulation have nothing to do with arbitrary speech and are not adequate to the situation. This highly integrated stimulation effect indicates that ascending afferent impulses are transformed into a neuronal code effective for the higher coordination mechanism of motor speech. In the same way, complexly coordinated movements caused by stimulation of the motor area of the cortex are organized not by those structures that are directly exposed to irritation, but by neighboring or spinal and extrapyramidal systems excited along descending pathways. These data show that there is a close relationship between the cortex and subcortical formations. Therefore, it is impossible to oppose cortical mechanisms to the work of subcortical structures, but it is necessary to consider specific cases of their interaction.
With electrical stimulation of individual cortical areas, the activity of the cardiovascular system, the respiratory apparatus, went. - kish. a path and other visceral systems. K. M. Bykov also substantiated the influence of CGM on the internal organs by the possibility of the formation of visceral conditioned reflexes, which, along with vegetative shifts with various emotions, was put by him as the basis for the concept of the existence of cortico-visceral relations. The problem of cortico-visceral relations is solved in terms of studying the modulation by the cortex of the activity of subcortical structures that are directly related to the regulation of the internal environment of the body.
An essential role is played by communications K. of m with a hypothalamus (see).
The level of activity of K. m. is mainly determined by ascending influences from the reticular formation (see) of the brain stem, which is controlled by cortico-fugal influences. The effect of the last has dynamic character and is a consequence of the current afferent synthesis (see). Studies using electroencephalography (see), in particular corticography (i.e., the assignment of biopotentials directly from K. g. m.), It would seem that they confirmed the hypothesis about the closure of the temporary connection between the foci of excitations that occur in the cortical projections of the signal and unconditioned stimuli in the process of formation of a conditioned reflex. However, it turned out that as the behavioral manifestations of the conditioned reflex become stronger, the electrographic signs of the conditioned connection disappear. This crisis of the technique of electroencephalography in the knowledge of the mechanism of the conditioned reflex was overcome in the studies of M. N. Livanov et al. (1972). They showed that the spread of excitation along C. g. m. and the manifestation of a conditioned reflex depend on the level of distant synchronization of biopotentials removed from spatially remote points of C. g. m. An increase in the level of spatial synchronization is observed with mental stress (Fig. 5). In this state, synchronization areas are not concentrated in certain areas of the cortex, but are distributed over its entire area. Correlation relations cover points of the entire frontal cortex, but at the same time, increased synchrony is also recorded in the precentral gyrus, in the parietal region, and in other parts of the C. g. m.
The brain consists of two symmetrical parts (hemispheres) interconnected by commissures consisting of nerve fibers. Both hemispheres of the brain are united by the largest commissure - the corpus callosum (see). Its fibers connect identical points of the K. g. m. The corpus callosum ensures the unity of the functioning of both hemispheres. When it is cut, each hemisphere begins to function independently of one another.
In the process of evolution, the human brain acquired the property of lateralization, or asymmetry (see). Each of its hemispheres specialized to perform certain functions. In most people, the left hemisphere is dominant, providing the function of speech and control over the action of the right hand. The right hemisphere is specialized for the perception of form and space. At the same time funkts, differentiation of hemispheres is not absolute. However, extensive damage to the left temporal lobe is usually accompanied by sensory and motor speech disorders. Obviously, lateralization is based on innate mechanisms. However, the potential of the right hemisphere in organizing the function of speech can manifest itself when the left hemisphere is damaged in newborns.
There are reasons to consider lateralization as an adaptive mechanism that developed as a result of the complication of brain functions at the highest stage of its development. Lateralization prevents the interference of various integrative mechanisms in time. It is possible that cortical specialization counteracts the incompatibility of various functional systems (see), facilitates decision-making about the purpose and mode of action. The integrative activity of the brain is not limited, therefore, to the external (summative) integrity, understood as the interaction of the activities of independent elements (be it neurocytes or entire brain formations). Using the example of the development of lateralization, one can see how this integral, integrative activity of the brain itself becomes a prerequisite for the differentiation of the properties of its individual elements, endowing them with functionality and specificity. Consequently, the funkts, the contribution of each individual structure of the C. g. m., in principle, cannot be assessed in isolation from the dynamics of the integrative properties of the whole brain.
Pathology
The cerebral cortex is rarely affected in isolation. Signs of its defeat to a greater or lesser extent usually accompany the pathology of the brain (see) and are part of its symptoms. Usually patol, not only K. of m, but also white matter of hemispheres is surprised by processes. Therefore, pathology K. of m is usually understood as its primary lesion (diffuse or local, without a strict boundary between these concepts). The most extensive and intense lesion of K. m. is accompanied by the disappearance of mental activity, a complex of both diffuse and local symptoms (see Apallic syndrome). Along with nevrol, symptoms of damage to the motor and sensitive spheres, symptoms of damage to various analyzers in children is a delay in the development of speech and even the complete impossibility of the formation of the psyche. In this case, changes in cytoarchitectonics are observed in the form of a violation of layering, up to its complete disappearance, foci of loss of neurocytes with their replacement by growths of glia, heterotopia of neurocytes, pathology of the synaptic apparatus and other pathomorphol changes. Lesions of K. m. hereditary and degenerative diseases of the brain, disorders of cerebral circulation, etc.
Studying of EEG at localization patol, the center in K. of m reveals dominance of focal slow waves which are considered as a correlate of guarding braking more often (U. Walter, 1966). Weak expressiveness of slow waves in the field patol, the center is a useful diagnostic sign in a preoperative assessment of a condition of patients. As N. P. Bekhtereva's researches (1974) carried out jointly with neurosurgeons showed, the absence of slow waves in the area patol, the focus is an unfavorable prognostic sign of the consequences of surgical intervention. For an assessment patol, K.'s state of m also the test for interaction of EEG in a zone of focal defeat with the caused activity is used in response to positive and differentiating conditional irritants. The bioelectric effect of such an interaction can be both an increase in focal slow waves, and a weakening of their severity or an increase in frequent oscillations such as pointed beta waves.
Bibliography: Anokhin P.K. Biology and neurophysiology of the conditioned reflex, M., 1968, bibliogr.; Belenkov N. Yu. Structural integration factor in brain activity, Usp. fiziol, sciences, t. 6, century. 1, p. 3, 1975, bibliogr.; Bekhtereva N. P. Neurophysiological aspects of human mental activity, L., 1974; Gray Walter, The Living Brain, trans. from English, M., 1966; Livanov MN Spatial organization of brain processes, M., 1972, bibliogr.; Luria A. R. Higher cortical functions of a person and their disturbances in local lesions of the brain, M., 1969, bibliogr.; Pavlov I.P. Complete works, vol. 3-4, M.-L., 1951; Penfield V. and Roberts L. Speech and brain mechanisms, trans. from English, L., 1964, bibliography; Polyakov G. I. Fundamentals of the systematics of neurons in the neocortex of the human brain, M., 1973, bibliogr.; Cytoarchitectonics of the human cerebral cortex, ed. S. A. Sarkisova and others, p. 187, 203, M., 1949; Sade J. and Ford D. Fundamentals of neurology, trans. from English, p. 284, M., 1976; M a s t e g t o n R. B. a. B e r k 1 e y M. A. Brain function, Ann. Rev. Psychol., at. 25, p. 277, 1974, bibliogr.; S h about 1 1 D. A. The organization of cerebral cortex, L.-N. Y., 1956, bibliogr.; Sperry R. W. Hemisphere deconnection and unity in conscious awareness, Amer. Psychol., v. 23, p. 723, 1968.
H. Yu. Belenkov.
30.07.2013
Formed by neurons, it is a layer of gray matter that covers the cerebral hemispheres. Its thickness is 1.5 - 4.5 mm, the area in an adult is 1700 - 2200 cm 2. Myelinated fibers that form the white matter of the telencephalon connect the cortex to the rest departments of the . Approximately 95 percent of the surface of the hemispheres is the neocortex, or neocortex, which is phylogenetically considered the latest formation of the brain. Archiocortex (old cortex) and paleocortex (ancient cortex) have a more primitive structure, they are characterized by a fuzzy division into layers (weak stratification).
The structure of the bark.
The neocortex is formed by six layers of cells: the molecular lamina, the outer granular lamina, the outer pyramidal lamina, the inner granular and pyramidal laminae, and the lamina multiforme. Each layer is distinguished by the presence of nerve cells of a certain size and shape.
The first layer is the molecular plate, which is formed by a small number of horizontally oriented cells. Contains branching dendrites of pyramidal neurons of the underlying layers.
The second layer is the outer granular plate, consisting of the bodies of stellate neurons and pyramidal cells. This also includes a network of thin nerve fibers.
The third layer - the outer pyramidal plate consists of the bodies of pyramidal neurons and processes that do not form long pathways.
The fourth layer - the inner granular plate is formed by densely spaced stellate neurons. They are adjacent to thalamocortical fibers. This layer includes bundles of myelin fibers.
The fifth layer - the inner pyramidal plate is formed mainly by large Betz pyramidal cells.
The sixth layer is a multiform plate, consisting of a large number of small polymorphic cells. This layer smoothly passes into the white matter of the cerebral hemispheres.
Furrows cortex each of the hemispheres is divided into four lobes.
The central sulcus begins on the inner surface, descends down the hemisphere and separates the frontal lobe from the parietal. The lateral groove originates from the lower surface of the hemisphere, rises obliquely to the top and ends in the middle of the upper lateral surface. The parietal-occipital sulcus is localized in the back of the hemisphere.
Frontal lobe.
The frontal lobe has the following structural elements: frontal pole, precentral gyrus, superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus, operculum, triangular and orbital parts. The precentral gyrus is the center of all motor acts: from elementary functions to complex complex actions. The richer and more differentiated the action, the larger the zone occupied by the given center. Intellectual activity is controlled by the lateral divisions. The medial and orbital surfaces are responsible for emotional behavior and autonomic activity.
Parietal lobe.
Within its limits, the postcentral gyrus, intraparietal sulcus, paracentral lobule, superior and inferior parietal lobules, supramarginal and angular gyrus are distinguished. Somatic sensitive cortex is located in the postcentral gyrus, an essential feature of the location of functions here is the somatotopic dissection. The entire remaining parietal lobe is occupied by the associative cortex. It is responsible for the recognition of somatic sensitivity and its relationship with various forms of sensory information.
Occipital lobe.
It is the smallest in size and includes the lunate and spur sulci, the cingulate gyrus and the wedge-shaped area. Here is the cortical center of vision. Thanks to this, a person can perceive visual images, recognize and evaluate them.
The temporal share.
On the lateral surface, three temporal gyri can be distinguished: superior, middle, and inferior, as well as several transverse and two occipitotemporal gyri. Here, in addition, is the gyrus of the hippocampus, which is considered the center of taste and smell. The transverse temporal gyrus is a zone that controls auditory perception and interpretation of sounds.
limbic complex.
It unites a group of structures that are located in the marginal zone of the cerebral cortex and the visual mound of the diencephalon. It's limbic cortex, dentate gyrus, amygdala, septal complex, mastoid bodies, anterior nuclei, olfactory bulbs, bundles of connective myelin fibers. The main function of this complex is the control of emotions, behavior and stimuli, as well as memory functions.
The main violations of the functions of the cortex.
The main disorders to which cortex, divided into focal and diffuse. Of the focal, the most common are:
Aphasia - a disorder or complete loss of speech function;
Anomia - the inability to name various objects;
Dysarthria - articulation disorder;
Prosody - violation of the rhythm of speech and placement of stresses;
Apraxia - inability to perform habitual movements;
Agnosia - the loss of the ability to recognize objects with the help of sight or touch;
Amnesia is a memory impairment, which is expressed by a slight or complete inability to reproduce information received by a person in the past.
Diffuse disorders include: stunning, stupor, coma, delirium, and dementia.
Localization of functions in the cerebral hemispheres. The cerebral cortex is divided into main zones, consisting of several cortical fields. Each of these zones performs a certain general function, and its constituent fields participate in the implementation of individual elements of this function in a specialized way. However, due to the conduction pathways, several zones of the cerebral hemispheres, certain subcortical centers, nuclei of the brain stem and segments of the spinal cord are involved in the implementation of individual links of higher and lower nervous activity.
With fine and precise specialization of certain groups of neurons, the brain and spinal cord function as a single whole. The mental functions of the brain are also not limited to individual areas of the cortex, but are the result of the joint activity of vast areas of the cerebral hemispheres and subcortical centers.
Rice. 123. Individual changes in the main fields of the neocortex of the cerebral hemispheres in three adults (A, B, C). Numbers-fields according to Brodman
The motor zone (field 4) is located in the anterior central gyrus along the central sulcus. In the upper quarter of the zone are the motor centers for the muscles of the legs.
Above are the neurons that innervate the muscles of the toes, and below are the hips and torso. The two middle quarters are occupied by the centers for the hands, above - the center of the muscles of the scapula, and below - the muscles of the fingers. And, finally, in the lower quarter of the anterior central gyrus are the centers of the muscles of the face and the speech apparatus.
As a result of the historical development of the human brain in the process of labor and speech, a particularly large place is occupied by groups of neurons that cause contraction of the muscles of the hand, mainly the thumb, and the muscles of the face, tongue and larynx. They receive centripetal fibers from proprioreceptors, which enter the spinal cord along the posterior roots, where they rise as part of the posterior column of the same side to the nuclei of the tender and sphenoid bundles of the medulla oblongata. The fibers of the second neurons emerge from these nuclei, forming a medial loop and, after crossing, reaching the nuclei of the thalamus opticus of the opposite side. From here, most of the centripetal fibers of the third neurons reach the posterior central gyrus and then enter the anterior central gyrus, and a smaller part enters it directly. Thus, the anterior central gyrus is connected to the posterior central gyrus by means of fibers passing through the conductive pathways of the cortex. Centrifugal motor fibers of pyramidal neurons emerge from the motor zone, which make up the pyramidal pathways; they reach the neurons of the anterior horns of the spinal cord. The motor area causes coordinated movements of skeletal muscles, predominantly on the opposite side of the body. It functions in conjunction with the subcortical centers - the striatum, as well as the Lewis body, the red nucleus and the substantia nigra.
With lesions of certain areas of the anterior central gyrus, voluntary movements of individual muscle groups are disturbed. Incomplete damage to the zone causes a violation of movements - paresis, and its complete destruction - paralysis.
The zone of musculoskeletal sensitivity (fields 1, 2, 3, 43 and partially 5 and 7) is located in the posterior central gyrus along the posterior central sulcus. In this zone, the granular layers of the cortex are especially strongly developed, to which centripetal fibers from skin receptors are suitable, which go as part of the same pathways as fibers from proprioreceptors. The location of the perceiving groups of neurons is the same as in the motor area. The largest surface is occupied by neurons that receive impulses from the receptors of the hand, face, tongue, and larynx. Field 7 is larger than other fields related to the sensitivity of the hand. The zone of musculoskeletal sensitivity is not completely separated from the motor zone, since in fields 3, 4 and 5 there is a combination of granular neurons with giant pyramidal neurons. Approximately 80% of motor neurons are located in the motor zone, and 20% are in the zone of skin-muscle sensitivity. Each hemisphere receives impulses mainly from receptors on the opposite side of the body, but also from receptors on the same side. This zone receives centripetal impulses mainly from the lateral and semilunar nuclei of the thalamus.
With lesions of certain areas of the posterior central gyrus, sensitivity is disturbed in certain areas of the skin. The loss of the ability to recognize objects by touch is referred to as tactile agnosia. In violation of the functions of the zone, there are disorders of touch, pain and temperature sensations of the skin and muscle-articular sensitivity. Incomplete damage to the zone causes a decrease in reception - hypoesthesia, and complete - its loss - anesthesia.
The frontal zone (fields 6, 5, 9, 10, 11, 44, 45, 46, 47) is located in the frontal lobe in front of the motor lobe. It is divided into premotor and motor speech. The premotor zone (fields 6, 8, 9, 10, 11) regulates the tone of the skeletal muscles and coordinated movements of the body, orienting it in space. Field 46 is functionally connected with field 10, which is involved in the performance of motor conditioned reflexes. Centripetal impulses from the internal organs enter the premotor zone and a significant part of the centrifugal vegetative fibers comes from it. Therefore, damage to the premotor zone causes a violation of coordination of movements - ataxia and disorders of the functions of the cardiovascular, respiratory, digestive and other systems of internal organs.
The visual zone (fields 17, 18, 19) is located on the inner surface of the occipital lobe on both sides of the spur groove. In humans, it occupies 12% of the total surface of the cortex. Field 17 is located on the occipital pole; it is surrounded by field 18, which surrounds field 19, bordering the posterior limbic region, the upper and lower parietal regions. In field 17 - the central field of the visual zone, there are 16 times more neurons than in the central field of the auditory zone (field 41), and 10 times more neurons than in the central field of the motor zone (field 4). This indicates the leading importance of vision in the historical and individual development of man.
From the retina, 900 thousand - 1 million centripetal fibers of the optic nerves reach the lateral geniculate body, in which individual parts of the retina are precisely projected. The centripetal fibers of the neurons of the lateral geniculate body are sent to the visual zone, mainly to the main visual field 17. Other intermediate visual centers involved in the transmission of not visual impulses, but oculomotor impulses, are the thalamus and anterior tubercles of the quadrigemina.
Before entering the lateral geniculate body, the fibers of the optic nerve intersect. Due to this decussation, as part of the visual path, heading to the visual zone of each hemisphere, 50% of the fibers of its side and 50% of the fibers of the opposite side. The visual zone of the left hemisphere receives visual impulses from the left halves of the retinas of both eyes, and to the zone of the right hemisphere - from the right halves of the retinas of both eyes. Therefore, the destruction of one of the visual zones causes blindness in the same halves of the retinas in both eyes - hemianopia. In the optic nerves, in addition to centripetal fibers, there are also somewhat thicker centrifugal fibers to the muscles of the iris and centrifugal thin sympathetic fibers from the neurons of the subcortical centers. A small part of the centripetal fibers of the optic nerve is not interrupted in the subcortical formations, but goes directly to the cerebellum and the visual zones of the cerebral hemispheres.
The destruction of both fields 17 causes complete cortical blindness, the destruction of field 18 leads to loss of visual memory while maintaining vision, which is referred to as visual agnosia, and the destruction of field 19 leads to a loss of orientation in an unusual environment.
The auditory zone (fields 41, 42, 21, 22, 20, 37) is located on the surface of the temporal lobe, mainly the anterior transverse temporal gyrus and superior temporal gyrus. Field 41, located in the superior temporal gyrus and in the anterior part of the transverse gyrus, is a projection of the cochlear organ of Corti. From the organ of Corti, centripetal impulses pass through the spiral node along the cochlear nerve, which consists of about 30 thousand fibers. This node contains the first bipolar neurons of the auditory pathway. Further, the fibers of the first neurons transmit auditory impulses to the nuclei of the auditory nerve in the medulla oblongata, where the second neurons are located. The fibers of the nuclei of the auditory nerve communicate with the nuclei of the facial nerve in the medulla oblongata and the oculomotor nerve in the anterior tubercles of the midbrain. Therefore, with strong sounds, the muscles of the face, eyelids, auricle contract reflexively and eye movements are caused.
Most of the fibers of the nuclei of the auditory nerve intersect in the pons, and the smaller part passes on its side. Then the fibers of the auditory pathway enter the lateral lemniscal loop, which ends in the posterior tubercles of the quadrigemina and in the internal geniculate body, where the third neurons are located - their fibers conduct centripetal impulses to the auditory zone. There are also direct pathways connecting the nuclei of the auditory nerves with the cerebellum and the auditory zone. Most of the direct cerebellar tracts are formed by the vestibular nerve, and the smaller part by the cochlear nerve, which together make up the common trunk of the auditory nerve. The vestibular apparatus is also projected in the auditory zone.
Destruction of field 41 on one side causes deafness on the opposite side and hearing loss on one side, and destruction of fields 41 on both sides leads to complete cortical deafness. The destruction of field 22 in the anterior third of the superior temporal gyrus leads to musical deafness - the perception of the intensity of tone, timbre and rhythm of sounds is lost - auditory agnosia. The destruction of fields 21 and 20 in the middle and inferior temporal gyrus causes ataxia - a disorder of balance and coordination of movements.
In the auditory zone, there is also a speech-auditory center.
Olfactory and gustatory zones. The olfactory zone is located in the ancient cortex, which receives centripetal impulses from the olfactory cells. In addition to the olfactory function, it also performs a taste function and is involved in the activities of the digestive, excretory and reproductive systems. The hippocampus was previously thought to have an olfactory function. It is now believed that, together with the limbic system, the hypothalamic region of the diencephalon and pituitary gland, the midbrain and medulla oblongata, and especially the reticular formation, the hippocampus is involved in general motor reactions and autonomic reflexes during emotions. The taste zone proper is probably located in area 43, which is located in the lower part of the posterior central gyrus.
The limbic gyrus (posterior field 23 and anterior field 24) and the insular cortex (fields 13 and 14) are involved in higher nervous activity.
All zones of the cortex are not isolated, but are interconnected by conductive pathways.
Speech centers (fields 44, 45, 46, 39, 40, 42, 22.37). The motor center of speech is located in the lower part of the anterior central gyrus in field 44. In most right-handers, the area of \u200b\u200bfield 44 in the left hemisphere is larger than in the right hemisphere. Field 44 causes complex contractions of the speech muscles necessary to pronounce words. With the destruction of this field, a person cannot speak, but can produce the simplest contractions of the speech muscles - scream and sing. This is motor, motor aphasia, which in some cases manifests itself in the absence of contractions of the muscles of the tongue and the rest of the speech muscles. Since in these cases the auditory center of speech is not damaged, the understanding of the speech of others is preserved. When field 44 is affected, not only oral speech is often disturbed, but also inner speech or the ability to formulate thoughts in words without pronouncing them, on the basis of accumulated sound images that have a certain semantic content. At the same time, reading to oneself is difficult, the ability to write arbitrarily and under dictation is upset, but the copying of letters when writing is preserved. In right-handers, motor aphasia is observed when the left hemisphere is affected, and left-handers - in the right.
Rice. 129. Localization of speech centers:
1 - motor, 2 - auditory, 3 - visual
In front of field 44 is field 45, which regulates the construction of grammatically correct combinations of words and singing. If this field is damaged due to loss of memory for pronunciation techniques, singing is upset. Facial expressions and gestures, which give speech its expressiveness, are carried out thanks to impulses coming from field 46 to fields 44 and 45, to the fields of the premotor region and to the subcortical centers.
The auditory, or sensory, speech center is located in the posterior section of the left superior temporal gyrus in field 42, which understands the word when it is heard. If the field is destroyed, the ability to understand the meaning of words is lost, but their perception as sounds is preserved - sensory aphasia, or speech deafness. At the same time, due to a lack of understanding of one's own speech, excessive talkativeness is sometimes observed - logorrhoea, or verbal diarrhea. In the back part of the field 22, the connections of sound images of words with all perceiving zones are fixed, in which ideas about objects and phenomena arise. Therefore, damage to this field also causes sensory aphasia.
Fields 39 and 40, located in the parietal lobe next to field 22, carry out the understanding of the meaning of combinations of words or phrases. Therefore, their defeat leads to a speech disorder, which is called semantic (semantic) aphasia. With the defeat of field 39, due to the loss of the ability to recognize letters and numbers and understand the meaning of visible written images of words and numbers, the ability to read aloud, write and count is lost. The defeat of field 40 causes a loss of the ability to write, since there is no orientation of movements in space and their sequence is disturbed. This lack of ability to produce systemic, purposeful movements (apraxia) does not exclude the possibility of correctly performing individual hand movements that are not related to writing. Consequently, the process of writing in right-handed people is carried out by the temporal, lower parietal and lower frontal regions of the left hemisphere. When field 37 is affected, memory loss for words is caused - amnestic aphasia.
Thus, the large hemispheres of the brain as a whole are involved in the implementation of the function of speech, but a special role is played by individual fields of the cortex. In right-handers, as a result of the predominant development of the functions of the right hand and the right half of the body, the most complex mental functions of the left hemisphere of the brain are especially developed.
Related content:
Cortex
brain: cortex (cerebral cortex) - the upper layer of the cerebral hemispheres, consisting primarily of nerve cells with a vertical orientation (pyramidal cells), as well as bundles of afferent (centripetal) and efferent (centrifugal) nerve fibers. In neuroanatomical terms, it is characterized by the presence of horizontal layers that differ in width, density, shape and size of the nerve cells included in them.
The cerebral cortex is divided into a number of areas: for example, in the most common classification of cytoarchitectonic formations by K. Brodman, 11 areas and 52 fields are identified in the human cortex. On the basis of the phylogenesis database, a new cortex, or neocortex, is distinguished; old, or archicortex; and ancient, or paleocortex. According to functional criteria, three types of areas are distinguished: sensory zones that provide reception and analysis of afferent signals coming from specific relay nuclei of the thalamus; motor zones, having bilateral intracortical connections with all sensory areas for the interaction of sensory and motor zones; and associative zones, which do not have direct afferent or efferent connections with the periphery, but are associated with sensory and motor zones.
Dictionary of practical psychologist. - M.: AST, Harvest. S. Yu. Golovin. 1998 .
Anatomical and physiological subsystem of the nervous system.
Specificity.The upper layer of the cerebral hemispheres, consisting primarily of nerve cells with a vertical orientation (pyramidal cells), as well as bundles of afferent (centripetal) and efferent (centrifugal) nerve fibers. In neuroanatomical terms, it is characterized by the presence of horizontal layers that differ in width, density, shape and size of the nerve cells included in them.
Structure.The cerebral cortex is divided into a number of areas, for example, in the most common classification of cytoarchitectonic formations by K. Brodman, 11 areas and 52 fields are identified in the human cerebral cortex. Based on phylogenesis data, a new cortex, or neocortex, old, or archicortex, and ancient, or paleocortex, are distinguished. According to the functional criterion, three types of areas are distinguished: sensory areas that provide reception and analysis of afferent signals coming from specific relay nuclei of the thalamus, motor areas that have bilateral intracortical connections with all sensory areas for the interaction of sensory and motor areas, and associative areas that do not have direct afferent or efferent connections with the periphery, but associated with sensory and motor areas.
Psychological Dictionary. THEM. Kondakov. 2000 .
CORTEX
(English) cerebral cortex) - the superficial layer covering the cerebral hemispheres brain, is formed mainly by vertically oriented nerve cells (neurons) and their processes, as well as bundles afferent(centripetal) And efferent(centrifugal) nerve fibers. In addition, neuroglial cells are part of the cortex.
A characteristic feature of the structure of C. g. m. is horizontal layering, due to the ordered arrangement of the bodies of nerve cells and nerve fibers. In K. m., 6 (according to some authors, 7) layers are distinguished, differing in width, arrangement density, shape and size of their constituent neurons. Due to the predominantly vertical orientation of the bodies and processes of neurons, as well as bundles of nerve fibers, K. m. has a vertical striation. For the functional organization of K. m., the vertical, columnar arrangement of nerve cells is of great importance.
The main type of nerve cells that make up the K. m. are pyramidal cells. The body of these cells resembles a cone, from the top of which one thick and long, apical dendrite departs; heading towards the surface of the K. g. m., it becomes thinner and fan-shaped divided into thinner terminal branches. Shorter basal dendrites extend from the base of the pyramidal cell body and , heading into the white matter, located under the K. g. m., or branching within the bark. The dendrites of pyramidal cells bear a large number of outgrowths, the so-called. spines, which take part in the formation of synaptic contacts with the endings of afferent fibers that come to K. g. m. from other parts of the cortex and subcortical formations (see. ). The axons of the pyramidal cells form the main efferent pathways coming from the C. g. m. The size of the pyramidal cells varies from 5-10 microns to 120-150 microns (Betz giant cells). In addition to pyramidal neurons, the composition of K. g. m includes stellate,fusiform and some other types of interneurons involved in the reception of afferent signals and the formation of functional interneuronal connections.
Based on the peculiarities of the distribution in the layers of the cortex of nerve cells and fibers of various sizes and shapes, the entire territory of the K. g. regions(for example, occipital, frontal, temporal, etc.), and the latter - into more fractional cytoarchitectonic fields, differing in their cellular structure and functional significance. The classification of cytoarchitectonic formations of K. g. m., proposed by K. Brodman, who divided the entire K. g. m. of a person into 11 regions and 52 fields, is generally accepted.
Based on phylogenesis data, K. g. m. is divided into a new one ( neocortex), old ( archicortex) and ancient ( paleocortex). In the phylogenesis of the KGM, there is an absolute and relative increase in the territories of the new crust, with a relative decrease in the area of the ancient and old. In humans, the new cortex accounts for 95.6%, while the ancient one occupies 0.6%, and the old one - 2.2% of the entire cortical territory.
Functionally, there are 3 types of areas in the cortex: sensory, motor, and associative.
Touch(or projection) cortical zones receive and analyze afferent signals along the fibers coming from specific relay nuclei of the thalamus. Sensory zones are localized in certain areas of the cortex: visual located in the occipital (fields 17, 18, 19), auditory in the upper parts of the temporal region (fields 41, 42), somatosensory, analyzing the impulse coming from the receptors of the skin, muscles, joints - in the region of the postcentral gyrus (fields 1, 2, 3). Olfactory sensations are associated with the function of phylogenetically older sections of the cortex (paleocortex) - the hippocampal gyrus.
Motor(motor) area - field 4 according to Brodman - is located on the precentral gyrus. The motor cortex is characterized by the presence in layer V of giant Betz pyramidal cells, the axons of which form the pyramidal tract, the main motor tract descending to the motor centers of the brain stem and spinal cord and providing cortical control of voluntary muscle contractions. The motor cortex has bilateral intracortical connections with all sensory areas, which ensures close interaction between sensory and motor areas.
association areas. The human cerebral cortex is characterized by the presence of a vast territory that does not have direct afferent and efferent connections with the periphery. These areas, connected through an extensive system of associative fibers with sensory and motor areas, are called associative (or tertiary) cortical areas. In the posterior cortex, they are located between the parietal, occipital, and temporal sensory areas, and in the anterior, they occupy the main surface of the frontal lobes. The associative cortex is either absent or poorly developed in all mammals up to primates. In humans, the posterior associative cortex occupies about half, and the frontal regions a quarter of the entire surface of the cortex. In terms of structure, they are distinguished by a particularly powerful development of the upper associative layers of cells in comparison with the system of afferent and efferent neurons. Their feature is also the presence of polysensory neurons - cells that perceive information from various sensory systems.
The associative cortex also contains centers associated with speech activity (see Fig. And ). Associative areas of the cortex are considered as structures responsible for the synthesis of incoming information, and as an apparatus necessary for the transition from visual perception to abstract symbolic processes.
Clinical neuropsychological studies show that damage to the posterior associative areas disrupts complex forms of orientation in space, constructive activity, and makes it difficult to perform all intellectual operations that are carried out with the participation of spatial analysis (counting, perception of complex semantic images). With the defeat of speech zones, the ability to perceive and reproduce speech is impaired. Damage to the frontal areas of the cortex leads to the impossibility of implementing complex behavioral programs that require the selection of significant signals based on past experience and foreseeing the future. Cm. , , , , , . (D. A. Farber.)
Big psychological dictionary. - M.: Prime-EVROZNAK. Ed. B.G. Meshcheryakova, acad. V.P. Zinchenko. 2003 .
Cortex
Layer of gray matter covering the cerebral hemispheres of the cerebrum. The cerebral cortex is divided into four lobes: frontal, occipital, temporal, and parietal. The part of the cortex that covers most of the surface of the cerebral hemispheres is called the neocortex because it was formed during the final stages of human evolution. The neocortex can be divided into zones according to their functions. Different parts of the neocortex are associated with sensory and motor functions; the corresponding parts of the cerebral cortex are involved in planning movements (frontal lobes) or are associated with memory and perception ().
Psychology. AND I. Dictionary-reference book / Per. from English. K. S. Tkachenko. - M.: FAIR-PRESS. Mike Cordwell. 2000 .
See what the "cerebral cortex" is in other dictionaries:
CORTEX- BRAIN CORTEX, the outer layer of the cerebral hemispheres covered with deep convolutions. The cortex, or "gray matter", is the most complexly organized part of the brain; its purpose is the perception of sensations, control ... ... Scientific and technical encyclopedic dictionary
Cortex- the upper layer of the cerebral hemispheres, consisting primarily of nerve cells with a vertical orientation (pyramidal cells), as well as bundles of afferent, centripetal and efferent, centrifugal nerve fibers. IN … Psychological Dictionary
cortex- honey. The brain is the most voluminous of the elements of the central nervous system. It consists of two lateral parts, hemispheres of the brain, connected one to the other, and of the underlying elements. It weighs about 1200 g. The two hemispheres of the brain ... ... Universal additional practical explanatory dictionary by I. Mostitsky
Cortex- Thin (2 mm) outer shell of the cerebral hemispheres. The human cerebral cortex is the center of higher cognitive processes and processing of sensorimotor information ... Psychology of sensations: a glossary
cortex- Cortex / cerebral hemispheres. The surface layer of the brain in higher vertebrates and humans ... Dictionary of many expressions
Cortex- Central nervous system (CNS) I. Neck nerves. II. Thoracic nerves. III. Lumbar nerves. IV. sacral nerves. V. Coccygeal nerves. / 1. Brain. 2. Diencephalon. 3. Midbrain. 4. Bridge. 5. Cerebellum. 6. Medulla oblongata. 7. ... ... Wikipedia
CORTEX- The surface covering the gray matter, which forms the uppermost level of the brain. In an evolutionary sense, this is the newest nerve formation, and its approximately 9 12 billion cells are responsible for the main sensory functions, ... ... Explanatory Dictionary of Psychology
cortex- see bark... Big Medical Dictionary
Cerebral Cortex, Cerebral Cortex- having a complex structure, the outer layer of the cerebrum, which accounts for up to 40% of the weight of the entire brain and which contains approximately 15 billion neurons (see Gray matter). The cerebral cortex is directly responsible for the psyche ... ... medical terms
BRAIN CORTEX, BRAIN CORTEX- (cerebral cortex) having a complex structure, the outer layer of the large brain, which accounts for up to 40% of the weight of the entire brain and which contains approximately 15 billion neurons (see Gray matter). The cerebral cortex is directly responsible for ... ... Explanatory Dictionary of Medicine
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- How emotions affect abstract thinking and why mathematics is incredibly precise. How the cerebral cortex is arranged, why its capabilities are limited and how emotions, complementing the work of the cortex, allow people, A. G. Sverdlik. Mathematics, unlike other disciplines, is universal and extremely accurate. It creates the logical structure of all natural sciences. The incomprehensible efficiency of mathematics, as in its time ... Buy for 638 UAH (only Ukraine)
- How emotions affect abstract thinking and why mathematics is incredibly precise. How the cerebral cortex is arranged, why its capabilities are limited and how emotions, complementing the work of the cortex, allow a person to make scientific discoveries, A. G. Sverdlik. Mathematics, unlike other disciplines, is universal and extremely accurate. It creates the logical structure of all natural sciences. "The incomprehensible efficiency of mathematics", as in its time...
In the KBP, areas with less defined functions are distinguished. So, a significant part of the frontal lobes, especially on the right side, can be removed without noticeable damage. However, if bilateral removal of the frontal areas is performed, severe mental disorders occur.
The projection zones of the analyzers are located in the cortex. According to their structure and functional significance, they were divided into 3 main groups of fields:
1. Primary fields (nuclear zones of analyzers).
2. Secondary fields
3. Tertiary fields.
Primary fields are associated with the sense organs and movement. They ripen early. Pavlov called them the nuclear zones of the analyzers. They carry out the primary analysis of individual stimuli that enter the cortex. If there is a violation of the primary fields to which information comes from the organ of vision or hearing, then cortical blindness or deafness occurs.
Secondary fields are the peripheral zones of the analyzers. They are located next to the primary and are connected with the senses through the primary fields. In these fields, generalization and further processing of information takes place. With the defeat of secondary fields, a person sees, hears, but does not recognize and does not understand the meaning of the signals.
Tertiary fields are analyzer overlap zones. They are located on the borders of the parietal, temporal and occipital regions, as well as in the anterior part of the frontal lobes. In the process of ontogenesis, they mature later than primary and secondary ones. The development of tertiary fields is associated with the formation of speech.
Areas of the left brain associated with speech, including making a speech (Broca's area), listening comprehension (Wernicke's zone), reading and writing (angular gyrus).
The diagram also shows motor, auditory and visual cortex.
These fields ensure the coordinated work of both hemispheres. Here the highest analysis and synthesis takes place, goals and tasks are developed. Tertiary fields have extensive connections.
Association zones
The connection of peripheral formations with the cortex.
The presence of structurally different fields in the CBP also implies their different functional significance. In the CBP, sensory, motor and associative areas are distinguished.
Sensory zones. Each hemisphere has two sensory areas:
Somatic (skin, muscle, joint sensitivity).
Visceral, this zone of the cortex receives impulses from the internal organs.
The somatic zone is located in the region of the postcentral gyrus. This zone receives information from the skin and the motor apparatus from the specific nuclei of the thalamus. The skin receptor system is projected onto the posterior central gyrus. The receptive fields of the skin of the lower extremities are projected onto the upper sections of this gyrus, the trunks onto the middle sections, and the arms and heads onto the lower sections. Removal of certain parts of this zone leads to loss of sensitivity in the relevant organs. A particularly large surface is occupied by the representation of the receptors of the hands, mimic muscles of the face, the vocal apparatus, and much less from the thigh, lower leg and torso, since fewer receptors are localized in these areas.
The second somatosensory zone is localized in the region of the Sylveian furrow. In this zone, integration and critical evaluation of information from specific nuclei of the thalamus takes place. For example, the visual zone is localized in the occipital lobe in the region of the spur groove. The auditory system is projected in the transverse temporal gyri (Geschl's gyrus).
The motor cortex is located in the anterior central gyrus. From here begins the pyramidal tract. Damage to this area of the cortex leads to a violation of voluntary movements. Through associative pathways, the motor area is connected with other sensory areas of the opposite hemisphere.
All sensory and motor areas occupy less than 20% of the CBP surface. The rest of the cortex makes up the association area. Each association area of the CPB is associated with several projection areas. The association areas of the cortex include parts of the parietal, frontal, and temporal lobes. The boundaries of associative fields are fuzzy. Its neurons are involved in the integration of various information. Here comes the highest analysis and synthesis of stimuli. As a result, complex elements of consciousness are formed. The parietal cortex is involved in assessing the biological significance of information and spatial perception. The frontal lobes (fields 9-14) together with the limbic system controls motivational behavior and carry out the programming of behavioral acts. If areas of the frontal lobes are destroyed, memory impairment occurs.
