So, the area of ​​the cerebral cortex of one human hemisphere is about 800 - 2200 square meters. cm, thickness -- 1.5?5 mm. Most of the bark (2/3) lies deep in the furrows and is not visible from the outside. Thanks to this organization of the brain in the process of evolution, it was possible to significantly increase the area of ​​the cortex with a limited volume of the skull. The total number of neurons in the cortex can reach 10 - 15 billion.

The cerebral cortex itself is heterogeneous, therefore, in accordance with phylogeny (by origin), ancient cortex (paleocortex), old cortex (archicortex), intermediate (or middle) cortex (mesocortex) and new cortex (neocortex) are distinguished.

Ancient bark

Ancient bark, (or paleocortex)- This is the most simply structured cerebral cortex, which contains 2–3 layers of neurons. According to a number of famous scientists such as H. Fenish, R. D. Sinelnikov and Ya. R. Sinelnikov, indicating that the ancient cortex corresponds to the area of ​​the brain that develops from the piriform lobe, and the components of the ancient cortex are the olfactory tubercle and the surrounding cortex, including area of ​​the anterior perforated substance. The composition of the ancient cortex includes the following structural formations such as the prepiriform, periamygdala region of the cortex, the diagonal cortex and the olfactory brain, including the olfactory bulbs, the olfactory tubercle, the septum pellucidum, the nuclei of the septum pellucidum and the fornix.

According to M. G. Prives and a number of some scientists, the olfactory brain is topographically divided into two sections, including a number of formations and convolutions.

1. peripheral section (or olfactory lobe), which includes formations lying at the base of the brain:

olfactory bulb;

olfactory tract;

olfactory triangle (within which the olfactory tubercle is located, i.e., the apex of the olfactory triangle);

internal and lateral olfactory gyri;

internal and lateral olfactory stripes (the fibers of the internal stripe end in the subcallosal field of the paraterminal gyrus, the septum pellucidum and the anterior perforated substance, and the fibers of the lateral stripe end in the parahippocampal gyrus);

anterior perforated space or substance;

diagonal stripe, or Broca's stripe.

2. The central section includes three convolutions:

parahippocampal gyrus (hippocampal gyrus, or seahorse gyrus);

dentate gyrus;

cingulate gyrus (including its anterior part - the uncus).

Old and intermediate bark

Old bark (or archicortex)-- this cortex appears later than the ancient cortex and contains only three layers of neurons. It consists of the hippocampus (seahorse or Ammon's horn) with its base, the dentate gyrus and the cingulate gyrus. cortex brain neuron

Intermediate bark (or mesocortex)-- which is a five-layer cortex that separates the new cortex (neocortex) from the ancient cortex (paleocortex) and old cortex (archicortex) and because of this the middle cortex is divided into two zones:

• 1. peripaleocortical;
• 2. periarchiocortical.

According to V. M. Pokrovsky and G. A. Kuraev, the mesocortex includes the ostracic gyrus, as well as the parahippocampal gyrus in the entorhinal region bordering the old cortex and the prebase of the hippocampus.

According to R. D. Sinelnikov and Ya. R. Sinelnikov, the intermediate cortex includes such formations as the lower part of the insular lobe, the parahippocampal gyrus and the lower part of the limbic region of the cortex. But it is necessary to understand that the limbic region is understood as part of the new cortex of the cerebral hemispheres, which occupies the cingulate and parahippocampal gyri. There is also an opinion that the intermediate cortex is an incompletely differentiated zone of the insular cortex (or visceral cortex).

Due to the ambiguity of this interpretation of structures related to the ancient and old cortex, it has led to the advisability of using a combined concept as archiopaleocortex.

The structures of the archiopaleocortex have multiple connections, both among themselves and with other brain structures.

New crust

New bark (or neocortex)- phylogenetically, i.e. in its origin - this is the most recent formation of the brain. Due to the later evolutionary emergence and rapid development of the new cerebral cortex in its organization of complex forms of higher nervous activity and its highest hierarchical level, which is vertically coordinated with the activity of the central nervous system, constituting the most features of this part of the brain. The features of the neocortex have attracted and continue to hold the attention of many researchers studying the physiology of the cerebral cortex for many years. Currently, old ideas about the exclusive participation of the neocortex in the formation of complex forms of behavior, including conditioned reflexes, have been replaced by the idea of ​​it as the highest level of thalamocortical systems functioning together with the thalamus, limbic and other brain systems. The neocortex is involved in the mental experience of the external world - its perception and the creation of its images, which are preserved for a more or less long time.

A feature of the structure of the neocortex is the screen principle of its organization. The main thing in this principle - the organization of neural systems is the geometric distribution of projections of higher receptor fields on a large surface of the neuronal field of the cortex. Also characteristic of the screen organization is the organization of cells and fibers that run perpendicular to the surface or parallel to it. This orientation of cortical neurons provides opportunities for combining neurons into groups.

As for the cellular composition in the neocortex, it is very diverse, the size of neurons is approximately from 8–9 μm to 150 μm. The vast majority of cells belong to two types: pararamid and stellate. The neocortex also contains spindle-shaped neurons.

In order to better examine the features of the microscopic structure of the cerebral cortex, it is necessary to turn to architectonics. Under the microscopic structure, cytoarchitectonics (cellular structure) and myeloarchitectonics (fibrous structure of the cortex) are distinguished. The beginning of the study of the architectonics of the cerebral cortex dates back to the end of the 18th century, when in 1782 Gennari first discovered the heterogeneity of the structure of the cortex in the occipital lobes of the hemispheres. In 1868, Meynert divided the diameter of the cerebral cortex into layers. In Russia, the first researcher of the bark was V. A. Betz (1874), who discovered large pyramidal neurons in the 5th layer of the cortex in the area of ​​the precentral gyrus, named after him. But there is another division of the cerebral cortex - the so-called Brodmann field map. In 1903, the German anatomist, physiologist, psychologist and psychiatrist K. Brodmann published a description of fifty-two cytoarchitectonic fields, which are areas of the cerebral cortex that differ in their cellular structure. Each such field differs in size, shape, location of nerve cells and nerve fibers and, of course, different fields are associated with different functions of the brain. Based on the description of these fields, a map of 52 Brodman fields was compiled

NEOCORTEX NEOCORTEX

(from neo... and lat. cortex - bark, shell), new bark, neopallium, basic. part of the cerebral cortex. N. carries out the highest level of coordination of brain function and the formation of complex forms of behavior. In the process of evolution, N. first appears in reptiles, in which it is small in size and has a relatively simple structure (the so-called lateral cortex). The N. has a typical multilayer structure only in mammals, in which it consists of 6-7 layers of cells (pyramidal, stellate, fusiform) and is divided into lobes: frontal, parietal, temporal, occipital and mediobasal. In turn, the lobes are divided into regions, subregions and fields, differing in their cellular structure and connections with the deep parts of the brain. Along with projection (vertical) fibers, N.'s neurons form associative (horizontal) fibers, which in mammals and especially in humans are collected in anatomically distinct bundles (for example, the occipital-frontal bundle), providing simultaneous coordinated activity of various types. zones N. The N. consists of the most complexly constructed associative cortex, the edges in the process of evolution experience the greatest increase, while the primary sensory fields of the N. are relatively reduced. (see CEREBRAL CORTICAL HEMISPHERES).

.(Source: “Biological Encyclopedic Dictionary.” Editor-in-chief M. S. Gilyarov; Editorial Board: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected - M.: Sov. Encyclopedia, 1986.)

See what "NEOCORTEX" is in other dictionaries:

Neocortex...

New cortex (synonyms: neocortex, isocortex) (lat. neocortex) new areas of the cerebral cortex, which in lower mammals are only outlined, but in humans they form the main part of the cortex. The new cortex is located in the upper layer of the hemispheres... ... Wikipedia

neocortex- 3.1.15 neocortex: The new cerebral cortex, which ensures the implementation of intellectual mental activity by human thinking. 3.1.16 Source… Dictionary-reference book of terms of normative and technical documentation

- (neocortex; neo + lat. cortex bark) see New bark ... Large medical dictionary

neocortex- y, h. Evolutionary innovation and complexity of the nerve tissues that form the forehead, thus the scronae and other parts of the brain... Ukrainian Tlumach Dictionary

NEOCORTEX (NEW CORTEX)- Evolutionarily the newest and most complex of nerve tissues. The frontal, parietal, temporal and occipital lobes of the brain consist of the neocortex... Explanatory dictionary of psychology

Arches, paleo, neocortex... Spelling dictionary-reference book

cortex- cerebral cortex: 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... ... Great psychological encyclopedia

The term cortex refers to any outer layer of brain cells. The mammalian brain has three types of cortex: the pyriform cortex, which has olfactory functions; the old cortex (archicortex), which makes up the main. Part… … Psychological Encyclopedia

Cortex. Neural organization of the neocortex. Corticalization of functions

New cortex (neocortex)- this is a layer of gray matter, the total area of ​​which reaches 2 thousand cm 2 due to folds; The neocortex covers the cerebral hemispheres and makes up about 70% of the total area of ​​the cortex. In the direction from the surface to the depths, the neocortex has 6 horizontal layers(see Fig. 72), archiocortex - 3, paleocortex - 4-5.

Functional layers of the neocortex.

I. Molecular layer has few cells, but contains a large number of branching, ascending dendrites of pyramidal cells, on which fibers form synapses coming from the associative and nonspecific nuclei of the thalamus and regulating the level of excitability of the cortex.

Rice. 72. Structure of the cerebral cortex. I – molecular layer; II – outer granular layer; III – layer of pyramidal cells; IV – internal granular layer; V – layer of large pyramidal cells; VI – spindle cell layer (polymorphic layer) (Guyton, 2008)

II. Outer granular layer contains mainly stellate cells and partly small pyramidal cells. The fibers of its cells are located mainly along the surface of the cortex, forming cortico-cortical connections.

III. Pyramid layer formed mainly from medium-sized pyramidal cells, the axons of which form cortico-cortical associative connections, as well as granular cells of layer II.

IV. Inner granular layer formed by stellate cells on which there are synapses from neuron fibers specific nuclei of the thalamus and metathalamus, carrying information from receptors of sensory systems.

V. Ganglion layer represented by medium and large pyramidal cells. Moreover, Betz giant pyramidal cells are located in the motor cortex, their axons form pyramidal tracts - corticobulbar and corticospinal motor tracts (pyramidal tracts).

VI. Layer of polymorphic cells, whose axons form corticothalamic tracts.

In layers I and IV of the neocortex, perception and processing of incoming signals occurs. Neurons of layers II and III carry out cortico-cortical associative connections. Neurons of layers V and VI form descending pathways.

Functional neural columns neocortex. In the cerebral cortex there are functional associations of neurons located in a cylinder with a diameter of 0.5-1.0 mm, including all layers of the cortex and containing several hundred neurons ( neural speakers). This, in particular, is evidenced by the electrophysiological studies of V. Mountcastle (1957) with the immersion of microelectrodes perpendicular to the surface of the somatosensory cortex. In this case, all neurons encountered along the way respond to only one type of stimulus (for example, light). When the electrode was immersed at an angle, neurons of different sensory sensitivity came across its path. Columns are found in the motor cortex and various areas of the sensory cortex. Neurons of the column can carry out self-regulation according to the type of recurrent inhibition. Adjacent neural columns can partially overlap and also interact with each other through the mechanism of lateral inhibition.

Corticalization of functions. Corticalization of functions is understood as an increase in phylogenesis of the role of the cerebral cortex in the regulation of body functions and the subordination of the underlying parts of the central nervous system in ensuring the mental activity of the body. For example, the regulation of locomotor motor functions (jumping, walking, running) and righting reflexes in lower vertebrates is completely ensured by the brain stem, and the removal of the cerebral hemispheres practically does not change them. In cats, after cutting the trunk between the midbrain and diencephalon, locomotion is only partially preserved. Switching off the cerebral cortex in experiments in monkeys and in pathological cases in humans leads to the loss of not only voluntary movements and locomotion, but also righting reflexes.

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

In phylogenetic terms, the cerebral cortex is the youngest neural 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 crust inwards, 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 located parallel to the surface. Afferent fibers coming from the associative and nonspecific nuclei of the thalamus form synapses on these dendrites.

Outer granular layer. Composed mainly of stellate and partly 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 medium-sized pyramidal cells. The axons of these cells, like granule cells of the 2nd layer, form corticocortical associative connections.

Inguinal granular layer. The nature of the cells (stellate cells) and the arrangement of their fibers 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, therefore, 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 predominantly by spindle-shaped cells, the axons of which form the corticothalamic tracts.

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

Histological evidence shows that the elementary neural circuits involved in information processing are located perpendicular to the surface of the cortex. Moreover, they are located in such a way that they cover all layers of the cortex. Such associations of neurons were called by scientists neural columns. Adjacent neural columns can partially overlap and also interact with each other.

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

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

Sensory cortical areas – zones into which sensory stimuli are projected. 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 (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 predominantly of unimodal neurons and form sensations of the same quality. In the primary sensory zones there is usually a clear spatial (topographic) representation of body parts and their receptor fields.

Around the primary sensory areas are less localized secondary sensory areas, whose multimodal 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 on the opposite side of the body from tactile, pain, temperature receptors, interoceptive sensitivity and sensitivity of the musculoskeletal system from muscle, joint, 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 body and legs is in the superomedial 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).

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

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

(section of the brain in the frontal plane)

In the depths of the lateral sulcus is located auditory cortex(cortex of Heschl's transverse temporal gyri). 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: different parts of the organ of Corti are represented in different areas of the cortex. 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 a “body schema” and regulate the functions of the cerebellum (temporopontine-cerebellar tract).

Another area of ​​the neocortex is located in the occipital cortex. This primary visual area. Here there is a topical representation of retinal receptors. In this case, each point of the retina corresponds to its own section of the visual cortex. Due to the incomplete decussation of the visual pathways, the same halves of the retina are projected into the visual area of ​​each hemisphere. The presence of a retinal projection in both eyes in each hemisphere is the basis of binocular vision. Irritation of the cerebral cortex in this area leads to the appearance of light sensations. Located near the primary visual area secondary visual area. Neurons in this area are multimodal 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 recognition arise. Irritation of this area of ​​the cortex causes visual hallucinations, obsessive sensations, and 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 transferred for further processing to the associative cortex.

Association cortical areas (intersensory, interanalyzer), includes areas of the neocortex that 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 defined, which is due to the secondary projection zones, the functional properties of which are transitional between the properties of the primary projection and associative zones. The association 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 almost 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 occurred. As a result of this, the associative cortex is a powerful apparatus for the convergence of various sensory excitations, allowing complex processing of information about the external and internal environment of the body and using it to carry out higher mental functions.

Based on thalamocortical projections, two associative systems of the brain are distinguished:

thalamoparietal;

Thalomotemporal.

Thalamotparietal system is represented by associative zones of the parietal cortex, receiving the main afferent inputs from the posterior group of associative nuclei of the thalamus (lateral posterior nucleus and pillow). The parietal associative 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 thalamoparietal 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. The center of stereognosis is located in the parietal cortex (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 consciousness of a three-dimensional model of the body (“body diagram”).

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

Thalamobic 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 programs of goal-directed behavior, especially in a new environment for a person. The implementation of this function is based on other functions of the talomoloby system, such as:

the formation of a 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 a person’s higher emotions associated with his social activities and creativity;

ensuring probabilistic forecasting, which is expressed in changes in behavior in response to changes in environmental conditions and dominant motivation;

self-control of actions by constantly comparing the result of an 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, an acceptor of the result of an action).

As a result of a prefrontal lobotomy performed for medical reasons, in which the connections between the frontal lobe and the thalamus intersect, the development of “emotional dullness”, a lack of motivation, strong intentions and plans based on prediction, is observed. Such people become rude, tactless, they have a tendency to repeat certain motor acts, although the changed situation requires the performance of completely different actions.

Along with the thalamoparietal and thalamofrontal systems, some scientists propose to distinguish the thalamotemporal system. However, the concept of the thalamotemporal system has not yet received confirmation and sufficient scientific elaboration. Scientists note a certain role for the temporal cortex. Thus, some associative centers (for example, stereognosis and praxis) also include areas of the temporal cortex. Wernicke's auditory speech center is located in the temporal cortex, located in the posterior parts 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 that of others. In the middle part of the superior temporal gyrus there is a center for recognizing musical sounds and their combinations. At the border of the temporal, parietal and occipital lobes there is a center for reading written speech, which ensures the recognition and storage of images of written speech.

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

Motor cortex areas . The concept of the motor cortex of the cerebral hemispheres began to form in the 80s of the 19th century, 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, it is customary to distinguish two motor areas in the motor cortex: primary and secondary.

IN primary motor cortex(precentral gyrus) there are neurons innervating the motor neurons of the muscles of the face, trunk and limbs. It has a clear topography of the projections of the body muscles. In this case, the projections of the muscles of the lower extremities and trunk are located in the upper parts of the precentral gyrus and occupy a relatively small area, and the projections 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 varied 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. When this cortical area is damaged, the ability to make fine coordinated movements of the limbs, especially the fingers, is lost.

Secondary motor cortex. Located on the lateral surface of the hemispheres, in front of the precentral gyrus (premotor cortex). It carries out higher motor functions associated with planning and coordination of voluntary movements. The premotor cortex receives the bulk of the efferent impulses from the basal ganglia and 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). In the premotor cortex there are motor centers associated with human social functions: in the posterior section of the middle frontal gyrus there is a center for written speech, in the posterior section of the inferior frontal gyrus there is a center for motor speech (Broca's center), as well as a musical motor center that determines the tone of speech and ability sing.

The motor cortex is often called the agranular cortex because its granular layers are poorly defined, but the layer containing Betz's giant pyramidal cells is more pronounced. Neurons of the motor cortex 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 neurons and their associated interneurons are located vertically relative to the surface of the cortex. Such nearby neural complexes that perform similar functions are called functional motor speakers. Pyramidal neurons of the motor column can excite or inhibit motor neurons of the brainstem and spinal centers. Adjacent columns functionally overlap, and pyramidal neurons that regulate the activity of one muscle are located, as a rule, 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 percentral gyrus, and 20 million fibers of the corticobulbar tract, starting from the cortex of the lower third of the precentral gyrus. Through the motor cortex and pyramidal tracts, voluntary simple and complex goal-directed motor programs are carried out (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 tracts cross. But a small part of them remains uncrossed, which helps compensate for impaired movement functions in unilateral lesions. The premotor cortex also carries out its functions through the pyramidal tracts (motor writing skills, turning the head and eyes in the opposite direction, etc.).

To cortical extrapyramidal pathways These include the corticobulbar and corticoreticular tracts, which begin in approximately the same area as the pyramidal tracts. The fibers of the corticobulbar tract end on the neurons of the red nuclei of the midbrain, from which the rubrospinal tracts proceed. The fibers of the corticoreticular tracts end on the neurons of the medial nuclei of the reticular formation of the pons (the medial reticulospinal tracts extend from them) and on the neurons of the reticular giant cell nuclei of the medulla oblongata, from which the lateral reticulospinal tracts begin. Through these pathways, tone and posture are regulated, providing precise, targeted movements. Cortical extrapyramidal tracts 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 directed movements, it can be noted that the urge (motivation) to move is created in the frontal system, the intention of movement - in the associative cortex of the cerebral hemispheres, the program of movements - 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 Interhemispheric relationships manifest themselves 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 French physicians M. Dax and P. Broca showed that human 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-hemisphere dominance, which formed evolutionarily as a result of work activity and is a specific property of his brain. In the 20th century, as a result of the use of various clinical techniques (especially when studying patients with split brains - transection of the corpus callosum was carried out), it was shown that in a number of psychophysiological functions in humans, not the left, but the right hemisphere dominates. Thus, the concept of partial dominance of the hemispheres arose (its author is R. Sperry).

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

In the sensory sphere, the role of the right and left hemispheres is best demonstrated in visual perception. The right hemisphere perceives the visual image holistically, in all details at once, it more easily solves the problem of distinguishing objects and recognizing visual images of objects that are difficult to describe in words, creating the prerequisites for concrete sensory thinking. The left hemisphere evaluates the visual image as dissected. Familiar objects are easier to recognize and problems of object similarity are solved, visual images are devoid of specific details and have a high degree of abstraction, and 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 activities of the two hemispheres.

Joint 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.

Clinical studies have shown that in addition to transverse commissural fibers, which provide interconnection between the hemispheres of the brain, also longitudinal and vertical commissural fibers.

Questions for self-control:

General characteristics of the new cortex.

Functions of the neocortex.

The structure of the new cortex.

What are neural columns?

What areas of the cortex are identified by scientists?

Characteristics of the sensory cortex.

What are primary sensory areas? Their characteristics.

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 associative area of ​​the cortex.

Characteristics of associative systems of the brain.

What is the thalamoparietal system? Its functions.

What is the thalamic system? Its functions.

General characteristics of the motor cortex.

Primary motor cortex; its characteristics.

Secondary motor cortex; its characteristics.

What are functional motor speakers?

Characteristics of cortical pyramidal and extrapyramidal tracts.

Which are only outlined in lower mammals, but in humans they form the main part of the cortex. The neocortex is located in the upper layer of the cerebral hemispheres, has a thickness of 2-4 millimeters and is responsible for higher nervous functions - sensory perception, execution of motor commands, conscious thinking and, in humans, speech.

Anatomy

The neocortex contains two main types of neurons: pyramidal neurons (~80% of neocortical neurons) and interneurons (~20% of neocortical neurons).

The structure of the neocortex is relatively homogeneous (hence the alternative name: “isocortex”). In humans, it has six horizontal layers of neurons, differing in the type and nature of connections. Vertically, neurons are combined into so-called cortex columns. At the beginning of the 20th century, Brodmann showed that in all mammals the neocortex has 6 horizontal layers of neurons.

Principle of operation

A fundamentally new theory of the algorithmic functioning of the neocortex was developed in Menlo Park, California, USA (Silicon Valley), by Jeff Hawkins. The theory of hierarchical temporary memory was implemented in software in the form of a computer algorithm, which is available for use under a license on the website numenta.com.

• The same algorithm processes all senses.
• The function of a neuron involves memory in time, something like cause-and-effect relationships, hierarchically developing into larger and larger objects from smaller ones.

Functions

The neocortex is embryonically derived from the dorsal telencephalon, which is part of the forebrain. The neocortex is divided into regions delimited by cranial sutures that serve different functions. For example, the occipital lobe contains the primary visual cortex, while the temporal lobe contains the primary auditory cortex. Further subdivisions or areas of the neocortex are responsible for more specific cognitive processes. In humans, the frontal lobe contains areas dedicated to abilities that are enhanced or unique to our species, such as complex language processing located in the prefrontal cortex. In humans and other primates, social and emotional processing is localized in the orbitofrontal cortex.

The neocortex has been shown to play an important role in sleep, memory and learning. Semantic memories appear to be stored in the neocortex, specifically in the anterolateral temporal lobe of the neocortex. The neocortex is also responsible for transmitting sensory information to the basal ganglia. The firing rate of neurons in the neocortex also influences slow-wave sleep.

The role that the neocortex plays in neurological processes directly related to human behavior is not yet fully understood. To understand the role of the neocortex in human cognition of the world, a computer model of the brain was created that simulated the electrochemistry of the neocortex - the Blue Brain project. The project was created to improve understanding of the processes of perception, learning, memory and to obtain additional knowledge about mental disorders.