The structure and functions of the cerebral cortex. Functions of the areas of the cerebral cortex

The cerebral cortex is a multilevel brain structure in humans and many mammals, consisting of gray matter and located in the peripheral space of the hemispheres (the gray matter of the cortex covers them). Structure controls important functions and processes in the brain and other internal organs.

(hemispheres) of the brain in the cranium occupy about 4/5 of the entire space. Their component is white matter, which includes long myelinated axons of nerve cells. From the outside, the hemispheres are covered by the cerebral cortex, which also consists of neurons, as well as glial cells and non-myelinated fibers.

It is customary to divide the surface of the hemispheres into some zones, each of which is responsible for performing certain functions in the body (for the most part, these are reflex and instinctive activities and reactions).

There is such a thing - "ancient bark". It is evolutionarily the most ancient cloak structure of the cerebral cortex in all mammals. They also distinguish the “new cortex”, which in lower mammals is only outlined, and in humans it forms most of the cerebral cortex (there is also an “old cortex”, which is newer than the “ancient”, but older than the “new”).

Functions of the cortex

The human cerebral cortex is responsible for controlling a variety of functions that are used in various aspects of the life of the human body. Its thickness is about 3-4 mm, and the volume is quite impressive due to the presence of channels connecting with the central nervous system. How perception, processing of information, decision-making takes place through the electrical network with the help of nerve cells with processes.

Inside the cerebral cortex, various electrical signals are produced (the type of which depends on the current state of the person). The activity of these electrical signals depends on the well-being of a person. Technically, electrical signals of this type are described using frequency and amplitude indicators. More connections and localized in places that are responsible for providing the most complex processes. At the same time, the cerebral cortex continues to actively develop throughout a person’s life (at least until the moment when his intellect develops).

In the process of processing information entering the brain, reactions (mental, behavioral, physiological, etc.) are formed in the cortex.

The most important functions of the cerebral cortex are:

The interaction of internal organs and systems with the environment, as well as with each other, the correct course of metabolic processes within the body.
High-quality reception and processing of information received from the outside, awareness of the information received due to the flow of thinking processes. High sensitivity to any received information is achieved due to the large number of nerve cells with processes.
Support for the continuous relationship between various organs, tissues, structures and systems of the body.
Formation and correct work of human consciousness, the flow of creative and intellectual thinking.
Implementation of control over the activity of the speech center and processes associated with various mental and emotional situations.
Interaction with the spinal cord and other systems and organs of the human body.

The cerebral cortex in its structure has the anterior (frontal) sections of the hemispheres, which are currently the least studied by modern science. These areas are known to be virtually immune to external influences. For example, if these departments are affected by external electrical impulses, they will not give any reaction.

Some scientists are sure that the anterior parts of the cerebral hemispheres are responsible for the self-awareness of a person, for his specific character traits. It is a well-known fact that people in whom the anterior sections are affected to one degree or another experience certain difficulties with socialization, they practically do not pay attention to their appearance, they are not interested in labor activity, they are not interested in the opinions of others.

From the point of view of physiology, the importance of each department of the cerebral hemispheres is difficult to overestimate. Even those that are currently not fully understood.

Layers of the cerebral cortex

The cerebral cortex is formed by several layers, each of which has a unique structure and is responsible for performing certain functions. All of them interact with each other, performing a common job. It is customary to distinguish several main layers of the cortex:

Molecular. In this layer, a huge number of dendritic formations are formed, which are woven together in a chaotic manner. The neurites are oriented parallel, forming a layer of fibers. There are relatively few nerve cells here. It is believed that the main function of this layer is associative perception.
External. A lot of nerve cells with processes are concentrated here. Neurons vary in shape. Nothing is known exactly about the functions of this layer.
External pyramidal. Contains many nerve cells with processes that vary in size. Neurons are predominantly conical in shape. The dendrite is large.
Internal granular. Includes a small number of small neurons located at some distance. Between the nerve cells are fibrous grouped structures.
Internal pyramidal. Nerve cells with processes that enter it are large and medium in size. The upper part of the dendrites may be in contact with the molecular layer.
Cover. Includes spindle-shaped nerve cells. For neurons in this structure, it is characteristic that the lower part of the nerve cells with processes reaches up to the white matter.

The cerebral cortex includes various layers that differ in shape, location, and the functional component of their elements. In the layers there are neurons of pyramidal, spindle, stellar, branched types. Together they create more than fifty fields. Despite the fact that the fields do not have clearly defined boundaries, their interaction with each other makes it possible to regulate a huge number of processes associated with receiving and processing impulses (that is, incoming information), creating a response to the influence of stimuli.

The structure of the cortex is extremely complex and not fully understood, so scientists cannot say exactly how some elements of the brain work.

The level of a child's intellectual abilities is related to the size of the brain and the quality of blood circulation in the brain structures. Many children who had hidden birth injuries in the spinal region have a noticeably smaller cerebral cortex than their healthy peers.

prefrontal cortex

A large section of the cerebral cortex, which is presented in the form of anterior sections of the frontal lobes. With its help, control, management, focusing of any actions that a person performs are carried out. This department allows us to properly allocate our time. The well-known psychiatrist T. Goltieri described this site as a tool with which people set goals and develop plans. He was convinced that a properly functioning and well-developed prefrontal cortex is the most important factor in the effectiveness of an individual.

The main functions of the prefrontal cortex are also commonly referred to as:

Concentration of attention, focusing on obtaining only the information necessary for a person, ignoring outside thoughts and feelings.
The ability to "reboot" consciousness, directing it in the right thought direction.
Perseverance in the process of performing certain tasks, striving to obtain the intended result, despite the circumstances that arise.
Analysis of the current situation.
Critical thinking, which allows you to create a set of actions to search for verified and reliable data (checking the information received before using it).
Planning, development of certain measures and actions to achieve the goals.
Event forecasting.

Separately, the ability of this department to manage human emotions is noted. Here, the processes occurring in the limbic system are perceived and translated into specific emotions and feelings (joy, love, desire, grief, hatred, etc.).

Different structures of the cerebral cortex are assigned different functions. There is still no consensus on this issue. The international medical community is now coming to the conclusion that the cortex can be divided into several large zones, including cortical fields. Therefore, taking into account the functions of these zones, it is customary to distinguish three main departments.

Zone responsible for pulse processing

Impulses coming through the receptors of the tactile, olfactory, visual centers go exactly to this zone. Almost all reflexes associated with motor skills are provided by pyramidal neurons.

Here is the department that is responsible for receiving impulses and information from the muscular system, actively interacts with different layers of the cortex. It receives and processes all the impulses that come from the muscles.

If for some reason the head cortex is damaged in this area, then the person will experience problems with the functioning of the sensory system, problems with motor skills and the work of other systems that are associated with sensory centers. Outwardly, such violations will manifest themselves in the form of constant involuntary movements, convulsions (of varying severity), partial or complete paralysis (in severe cases).

Sensory area

This area is responsible for processing electrical signals to the brain. Several departments are located here at once, which ensure the susceptibility of the human brain to impulses coming from other organs and systems.

Occipital (processes impulses coming from the visual center).
Temporal (carries out the processing of information coming from the speech and auditory center).
Hippocampus (analyzes impulses from the olfactory center).
Parietal (processes data received from taste buds).

In the zone of sensory perception, there are departments that also receive and process tactile signals. The more neural connections there are in each department, the higher will be its sensory ability to receive and process information.

The departments noted above occupy about 20-25% of the entire cerebral cortex. If the area of sensory perception is somehow damaged, then a person may have problems with hearing, vision, smell, and touch. The received pulses will either not reach, or will be processed incorrectly.

Violations of the sensory zone will not always lead to the loss of some kind of feeling. For example, if the auditory center is damaged, this will not always lead to complete deafness. However, a person will almost certainly have certain difficulties with the correct perception of the received sound information.

association zone

In the structure of the cerebral cortex there is also an associative zone, which provides contact between the signals of the neurons of the sensory zone and the motor center, and also gives the necessary feedback signals to these centers. The associative zone forms behavioral reflexes, takes part in the processes of their actual implementation. It occupies a significant (comparatively) part of the cerebral cortex, covering the departments included in both the frontal and posterior parts of the cerebral hemispheres (occipital, parietal, temporal).

The human brain is designed in such a way that in terms of associative perception, the posterior parts of the cerebral hemispheres are especially well developed (development occurs throughout life). They control speech (its understanding and reproduction).

If the anterior or posterior sections of the association zone are damaged, then this can lead to certain problems. For example, in case of defeat of the departments listed above, a person will lose the ability to correctly analyze the information received, will not be able to give the simplest forecasts for the future, start from the facts in the processes of thinking, use the experience gained earlier, deposited in the memory. There may also be problems with orientation in space, abstract thinking.

The cerebral cortex acts as a higher integrator of impulses, while emotions are concentrated in the subcortical zone (hypothalamus and other departments).

Different areas of the cerebral cortex are responsible for performing certain functions. There are several methods to consider and determine the difference: neuroimaging, comparison of electrical activity patterns, studying the cellular structure, etc.

At the beginning of the 20th century, K. Brodmann (a German researcher in the anatomy of the human brain) created a special classification, dividing the cortex into 51 sections, basing his work on the cytoarchitectonics of nerve cells. Throughout the 20th century, the fields described by Brodmann were discussed, refined, renamed, but they are still used to describe the cerebral cortex in humans and large mammals.

Many Brodmann fields were initially determined on the basis of the organization of neurons in them, but later their boundaries were refined in accordance with the correlation with different functions of the cerebral cortex. For example, the first, second, and third fields are defined as the primary somatosensory cortex, the fourth field is the primary motor cortex, and the seventeenth field is the primary visual cortex.

At the same time, some Brodmann fields (for example, area 25 of the brain, as well as fields 12-16, 26, 27, 29-31 and many others) have not been fully studied.

Speech motor zone

A well-studied area of the cerebral cortex, which is also called the center of speech. The zone is conditionally divided into three major departments:

Broca's speech motor center. Forms a person's ability to speak. It is located in the posterior gyrus of the anterior part of the cerebral hemispheres. Broca's center and the motor center of speech motor muscles are different structures. For example, if the motor center is damaged in some way, then the person will not lose the ability to speak, the semantic component of his speech will not suffer, but the speech will cease to be clear, and the voice will become slightly modulated (in other words, the quality of pronunciation of sounds will be lost). If Broca's center is damaged, then the person will not be able to speak (just like a baby in the first months of life). Such disorders are called motor aphasia.
Wernicke's sensory center. It is located in the temporal region, is responsible for the functions of receiving and processing oral speech. If Wernicke's center is damaged, then sensory aphasia is formed - the patient will not be able to understand the speech addressed to him (and not only from another person, but also his own). The uttered by the patient will be a set of incoherent sounds. If there is a simultaneous defeat of the centers of Wernicke and Broca (usually this occurs with a stroke), then in these cases the development of motor and sensory aphasia is observed at the same time.
Center for the perception of written speech. It is located in the visual part of the cerebral cortex (field No. 18 according to Brodman). If it turns out to be damaged, then the person has agraphia - the loss of the ability to write.

Thickness

All mammals that have relatively large brain sizes (in general terms, not compared to body size) have a fairly thick cerebral cortex. For example, in field mice, its thickness is about 0.5 mm, and in humans - about 2.5 mm. Scientists also identify a certain dependence of the thickness of the bark on the weight of the animal.

Cortex - the highest department of the central nervous system, which ensures the functioning of the body as a whole in its interaction with the environment.

brain (cerebral cortex, neocortex) is a layer of gray matter, consisting of 10-20 billion and covering the large hemispheres (Fig. 1). The gray matter of the cortex makes up more than half of the total gray matter of the CNS. The total area of the gray matter of the cortex is about 0.2 m 2, which is achieved by the sinuous folding of its surface and the presence of furrows of different depths. The thickness of the cortex in its different parts ranges from 1.3 to 4.5 mm (in the anterior central gyrus). The neurons of the cortex are arranged in six layers oriented parallel to its surface.

In the areas of the cortex related to, there are zones with a three-layer and five-layer arrangement of neurons in the structure of the gray matter. These areas of the phylogenetically ancient cortex occupy about 10% of the surface of the cerebral hemispheres, the remaining 90% are the new cortex.

Rice. 1. Mole of the lateral surface of the cerebral cortex (according to Brodman)

The structure of the cerebral cortex

The cerebral cortex has a six-layer structure

Neurons of different layers differ in cytological features and functional properties.

molecular layer- the most superficial. It is represented by a small number of neurons and numerous branching dendrites of pyramidal neurons lying in deeper layers.

Outer granular layer formed by densely spaced numerous small neurons of various shapes. The processes of the cells of this layer form corticocortical connections.

Outer pyramidal layer consists of pyramidal neurons of medium size, the processes of which are also involved in the formation of corticocortical connections between adjacent areas of the cortex.

Inner granular layer similar to the second layer in terms of cell type and fiber arrangement. In the layer there are bundles of fibers that connect various parts of the cortex.

Signals from specific nuclei of the thalamus are carried to the neurons of this layer. The layer is very well represented in the sensory areas of the cortex.

Inner pyramidal layers formed by medium and large pyramidal neurons. In the motor area of the cortex, these neurons are especially large (50-100 microns) and are called giant, pyramidal Betz cells. The axons of these cells form fast-conducting (up to 120 m/s) fibers of the pyramidal tract.

Layer of polymorphic cells It is represented mainly by cells whose axons form corticothalamic pathways.

Neurons of the 2nd and 4th layers of the cortex are involved in the perception, processing of signals coming to them from the neurons of the associative areas of the cortex. Sensory signals from the switching nuclei of the thalamus come mainly to the neurons of the 4th layer, the severity of which is greatest in the primary sensory areas of the cortex. The neurons of the 1st and other layers of the cortex receive signals from other nuclei of the thalamus, the basal ganglia, and the brain stem. Neurons of the 3rd, 5th and 6th layers form efferent signals sent to other areas of the cortex and downstream to the underlying parts of the CNS. In particular, the neurons of the 6th layer form fibers that follow to the thalamus.

There are significant differences in the neuronal composition and cytological features of different parts of the cortex. According to these differences, Brodman divided the cortex into 53 cytoarchitectonic fields (see Fig. 1).

The location of many of these fields, identified on the basis of histological data, coincides in topography with the location of the cortical centers, identified on the basis of their functions. Other approaches to dividing the cortex into regions are also used, for example, based on the content of certain markers in neurons, according to the nature of neuronal activity, and other criteria.

The white matter of the cerebral hemispheres is formed by nerve fibers. Allocate association fibers, subdivided into arcuate fibers, but to which signals are transmitted between neurons of adjacent gyri and long longitudinal bundles of fibers that deliver signals to neurons of more distant parts of the hemisphere of the same name.

Commissural fibers - transverse fibers that transmit signals between neurons of the left and right hemispheres.

Projection fibers - conduct signals between the neurons of the cortex and other parts of the brain.

The listed types of fibers are involved in the creation of neural circuits and networks, the neurons of which are located at considerable distances from each other. There is also a special kind of local neural circuits in the cortex, formed by adjacent neurons. These neural structures are called functional cortical columns. Neuronal columns are formed by groups of neurons located one above the other perpendicular to the surface of the cortex. The belonging of neurons to the same column can be determined by the increase in their electrical activity in response to stimulation of the same receptive field. Such activity is recorded when the recording electrode is slowly moved in the cortex in a perpendicular direction. If the electrical activity of neurons located in the horizontal plane of the cortex is recorded, then an increase in their activity is noted when various receptive fields are stimulated.

The diameter of the functional column is up to 1 mm. The neurons of one functional column receive signals from the same afferent thalamocortical fiber. The neurons of adjacent columns are connected to each other by processes through which they exchange information. The presence of such interconnected functional columns in the cortex increases the reliability of perception and analysis of information coming to the cortex.

The efficiency of perception, processing and use of information by the cortex for the regulation of physiological processes is also ensured somatotopic principle of organization sensory and motor fields of the cortex. The essence of such an organization lies in the fact that in a certain (projective) area of the cortex, not any, but topographically outlined areas of the receptive field of the surface of the body, muscles, joints, or internal organs are represented. So, for example, in the somatosensory cortex, the surface of the human body is projected in the form of a scheme, when receptive fields of a specific area of the body surface are presented at a certain point in the cortex. Efferent neurons are represented in a strict topographical way in the primary motor cortex, the activation of which causes the contraction of certain muscles of the body.

The fields of the cortex are also inherent screen operating principle. In this case, the receptor neuron sends a signal not to a single neuron or to a single point of the cortical center, but to a network or field of neurons connected by processes. The functional cells of this field (screen) are columns of neurons.

The cerebral cortex, being formed at the later stages of the evolutionary development of higher organisms, to a certain extent subordinated to itself all the underlying parts of the CNS and is able to correct their functions. At the same time, the functional activity of the cerebral cortex is determined by the influx of signals to it from the neurons of the reticular formation of the brain stem and signals from the receptive fields of the sensory systems of the body.

Functional areas of the cerebral cortex

According to the functional basis, sensory, associative and motor areas are distinguished in the cortex.

Sensory (sensitive, projection) areas of the cortex

They consist of zones containing neurons, the activation of which by afferent impulses from sensory receptors or direct exposure to stimuli causes the appearance of specific sensations. These zones are present in the occipital (fields 17-19), parietal (zeros 1-3) and temporal (fields 21-22, 41-42) areas of the cortex.

In the sensory areas of the cortex, central projection fields are distinguished, providing a subtle, clear perception of sensations of certain modalities (light, sound, touch, heat, cold) and secondary projection fields. The function of the latter is to provide an understanding of the connection of the primary sensation with other objects and phenomena of the surrounding world.

The areas of representation of receptive fields in the sensory areas of the cortex largely overlap. A feature of the nerve centers in the area of secondary projection fields of the cortex is their plasticity, which is manifested by the possibility of restructuring specialization and restoring functions after damage to any of the centers. These compensatory abilities of the nerve centers are especially pronounced in childhood. At the same time, damage to the central projection fields after suffering a disease is accompanied by a gross violation of the functions of sensitivity and often the impossibility of its recovery.

visual cortex

The primary visual cortex (VI, field 17) is located on both sides of the spur groove on the medial surface of the occipital lobe of the brain. In accordance with the identification of alternating white and dark stripes on unstained sections of the visual cortex, it is also called the striate (striated) cortex. The neurons of the lateral geniculate body send visual signals to the neurons of the primary visual cortex, which receive signals from the ganglion cells of the retina. The visual cortex of each hemisphere receives visual signals from the ipsilateral and contralateral halves of the retina of both eyes, and their flow to the neurons of the cortex is organized according to the somatotopic principle. Neurons that receive visual signals from photoreceptors are topographically located in the visual cortex, similar to receptors in the retina. At the same time, the area of the macula of the retina has a relatively large zone of representation in the cortex than other areas of the retina.

The neurons of the primary visual cortex are responsible for visual perception, which, based on the analysis of input signals, is manifested by their ability to detect a visual stimulus, determine its specific shape and orientation in space. In a simplified way, it is possible to imagine the sensory function of the visual cortex in solving a problem and answering the question of what constitutes a visual object.

In the analysis of other qualities of visual signals (for example, location in space, movement, connection with other events, etc.), neurons of fields 18 and 19 of the extrastriate cortex, located adjacent to zero 17, take part. Information about the signals received by the sensory visual zones of the cortex, will be transferred for further analysis and use of vision to perform other brain functions in the associative areas of the cortex and other parts of the brain.

auditory cortex

It is located in the lateral sulcus of the temporal lobe in the region of the Heschl gyrus (AI, fields 41-42). The neurons of the primary auditory cortex receive signals from the neurons of the medial geniculate bodies. The fibers of the auditory pathways that conduct sound signals to the auditory cortex are organized tonotopically, and this allows cortical neurons to receive signals from certain auditory receptor cells in the organ of Corti. The auditory cortex regulates the sensitivity of auditory cells.

In the primary auditory cortex, sound sensations are formed and the individual qualities of sounds are analyzed to answer the question of what the perceived sound is. The primary auditory cortex plays an important role in the analysis of short sounds, intervals between sound signals, rhythm, sound sequence. A more complex analysis of sounds is carried out in the associative areas of the cortex adjacent to the primary auditory. Based on the interaction of neurons in these areas of the cortex, binaural hearing is carried out, the characteristics of pitch, timbre, sound volume, sound belonging are determined, and an idea of a three-dimensional sound space is formed.

vestibular cortex

It is located in the upper and middle temporal gyri (fields 21-22). Its neurons receive signals from the neurons of the vestibular nuclei of the brain stem, connected by afferent connections with the receptors of the semicircular canals of the vestibular apparatus. In the vestibular cortex, a feeling is formed about the position of the body in space and the acceleration of movements. The vestibular cortex interacts with the cerebellum (through the temporo-pontocerebellar pathway), participates in the regulation of body balance, adaptation of the posture to the implementation of purposeful movements. Based on the interaction of this area with the somatosensory and associative areas of the cortex, awareness of the body schema occurs.

Olfactory cortex

It is located in the region of the upper part of the temporal lobe (hook, zeros 34, 28). The cortex includes a number of nuclei and belongs to the structures of the limbic system. Its neurons are located in three layers and receive afferent signals from the mitral cells of the olfactory bulb, connected by afferent connections with olfactory receptor neurons. In the olfactory cortex, a primary qualitative analysis of odors is carried out and a subjective sense of smell, its intensity, and belonging is formed. Damage to the cortex leads to a decrease in the sense of smell or to the development of anosmia - loss of smell. With artificial stimulation of this area, there are sensations of various smells like hallucinations.

taste bark

It is located in the lower part of the somatosensory gyrus, directly anterior to the face projection area (field 43). Its neurons receive afferent signals from relay neurons of the thalamus, which are associated with neurons in the nucleus of the solitary tract of the medulla oblongata. The neurons of this nucleus receive signals directly from sensory neurons that form synapses on the cells of the taste buds. In the taste cortex, a primary analysis of the taste qualities of bitter, salty, sour, sweet is carried out, and on the basis of their summation, a subjective sensation of taste, its intensity, and belonging is formed.

Smell and taste signals reach the neurons of the anterior insular cortex, where, based on their integration, a new, more complex quality of sensations is formed that determines our relationship to the sources of smell or taste (for example, to food).

Somatosensory cortex

It occupies the region of the postcentral gyrus (SI, fields 1-3), including the paracentral lobule on the medial side of the hemispheres (Fig. 9.14). The somatosensory area receives sensory signals from thalamic neurons connected by spinothalamic pathways with skin receptors (tactile, temperature, pain sensitivity), proprioreceptors (muscle spindles, articular bags, tendons) and interoreceptors (internal organs).

Rice. 9.14. The most important centers and areas of the cerebral cortex

Due to the intersection of afferent pathways, signaling comes to the somatosensory zone of the left hemisphere from the right side of the body, respectively, to the right hemisphere from the left side of the body. In this sensory area of the cortex, all parts of the body are somatotopically represented, but the most important receptive zones of the fingers, lips, skin of the face, tongue, and larynx occupy relatively larger areas than the projections of such body surfaces as the back, front of the body, and legs.

The location of the representation of the sensitivity of body parts along the postcentral gyrus is often called the "inverted homunculus", since the projection of the head and neck is in the lower part of the postcentral gyrus, and the projection of the caudal part of the trunk and legs is in the upper part. In this case, the sensitivity of the legs and feet is projected onto the cortex of the paracentral lobule of the medial surface of the hemispheres. Within the primary somatosensory cortex there is a certain specialization of neurons. For example, field 3 neurons receive mainly signals from muscle spindles and mechanoreceptors of the skin, field 2 - from joint receptors.

The postcentral gyrus cortex is referred to as the primary somatosensory area (SI). Its neurons send processed signals to neurons in the secondary somatosensory cortex (SII). It is located posterior to the postcentral gyrus in the parietal cortex (fields 5 and 7) and belongs to the association cortex. SII neurons do not receive direct afferent signals from thalamic neurons. They are associated with SI neurons and neurons in other areas of the cerebral cortex. This makes it possible to carry out an integral assessment of signals entering the cortex along the spinothalamic pathway with signals coming from other (visual, auditory, vestibular, etc.) sensory systems. The most important function of these fields of the parietal cortex is the perception of space and the transformation of sensory signals into motor coordinates. In the parietal cortex, a desire (intention, impulse) to carry out a motor action is formed, which is the basis for the beginning of planning for the upcoming motor activity in it.

The integration of various sensory signals is associated with the formation of various sensations addressed to different parts of the body. These sensations are used both to form mental and other responses, examples of which can be movements with the simultaneous participation of the muscles of both sides of the body (for example, moving, feeling with both hands, grasping, unidirectional movement with both hands). The functioning of this area is necessary for recognizing objects by touch and determining the spatial location of these objects.

The normal function of the somatosensory areas of the cortex is an important condition for the formation of sensations such as heat, cold, pain and their addressing to a specific part of the body.

Damage to neurons in the area of the primary somatosensory cortex leads to a decrease in various types of sensitivity on the opposite side of the body, and local damage leads to a loss of sensitivity in a certain part of the body. Discriminatory sensitivity of the skin is especially vulnerable when the neurons of the primary somatosensory cortex are damaged, and the least sensitive is pain. Damage to neurons in the secondary somatosensory area of the cortex may be accompanied by a violation of the ability to recognize objects by touch (tactile agnosia) and skills in using objects (apraxia).

Motor areas of the cortex

About 130 years ago, researchers, applying point stimulation to the cerebral cortex with an electric current, found that the impact on the surface of the anterior central gyrus causes contraction of the muscles of the opposite side of the body. Thus, the presence of one of the motor areas of the cerebral cortex was discovered. Subsequently, it turned out that several areas of the cerebral cortex and its other structures are related to the organization of movements, and in the areas of the motor cortex there are not only motor neurons, but also neurons that perform other functions.

primary motor cortex

primary motor cortex located in the anterior central gyrus (MI, field 4). Its neurons receive the main afferent signals from the neurons of the somatosensory cortex - fields 1, 2, 5, premotor cortex and thalamus. In addition, cerebellar neurons send signals to the MI via the ventrolateral thalamus.

Efferent fibers of the pyramidal pathway begin from the pyramidal neurons Ml. Some of the fibers of this pathway follow the motor neurons of the nuclei of the cranial nerves of the brainstem (corticobulbar tract), some - to the neurons of the stem motor nuclei (the red nucleus, nuclei of the reticular formation, stem nuclei associated with the cerebellum) and some - to the inter- and motor neurons of the spinal cord. brain (corticospinal tract).

There is a somatotopic organization of the location of neurons in MI that control the contraction of different muscle groups of the body. The neurons that control the muscles of the legs and trunk are located in the upper parts of the gyrus and occupy a relatively small area, and the controlling muscles of the hands, especially the fingers, face, tongue and pharynx are located in the lower parts and occupy a large area. Thus, in the primary motor cortex, a relatively large area is occupied by those neural groups that control the muscles that carry out various, precise, small, finely regulated movements.

Since many Ml neurons increase electrical activity immediately before the onset of voluntary contractions, the primary motor cortex is assigned the leading role in controlling the activity of the motor nuclei of the trunk and spinal cord motoneurons and initiating voluntary, purposeful movements. Damage to the Ml field leads to muscle paresis and the impossibility of fine voluntary movements.

secondary motor cortex

Includes areas of the premotor and supplementary motor cortex (MII, field 6). premotor cortex located in field 6, on the lateral surface of the brain, anterior to the primary motor cortex. Its neurons receive afferent signals through the thalamus from the occipital, somatosensory, parietal associative, prefrontal areas of the cortex and cerebellum. The signals processed in it are sent by the neurons of the cortex along the efferent fibers to the motor cortex MI, a small number - to the spinal cord and a larger number - to the red nuclei, the nuclei of the reticular formation, the basal ganglia and the cerebellum. The premotor cortex plays a major role in the programming and organization of movements under the control of vision. The cortex is involved in the organization of posture and auxiliary movements for the actions carried out by the distal muscles of the limbs. Damage to the visual cortex often causes a tendency to re-execute the initiated movement (perseveration), even if the completed movement has reached the goal.

In the lower part of the premotor cortex of the left frontal lobe, immediately anterior to the region of the primary motor cortex, in which the neurons that control the muscles of the face are represented, is located speech area, or motor center of Broca's speech. Violation of its function is accompanied by a violation of the articulation of speech, or motor aphasia.

Additional motor cortex located in the upper part of field 6. Its neurons receive afferent signals from the somatossensor, parietal and prefrontal areas of the cerebral cortex. The signals processed in it are sent by the neurons of the cortex along the efferent fibers to the primary motor cortex MI, the spinal cord, and the stem motor nuclei. The activity of the neurons of the supplementary motor cortex increases earlier than that of the neurons of the MI cortex, and mainly in connection with the implementation of complex movements. At the same time, an increase in neural activity in the additional motor cortex is not associated with movements as such; for this, it is enough to mentally imagine a model of upcoming complex movements. The supplementary motor cortex is involved in the formation of a program of upcoming complex movements and in the organization of motor reactions to the specificity of sensory stimuli.

Since the neurons of the secondary motor cortex send many axons to the MI field, it is considered a higher structure in the hierarchy of motor centers for organizing movements, standing above the motor centers of the MI motor cortex. The nerve centers of the secondary motor cortex can influence the activity of motor neurons in the spinal cord in two ways: directly through the corticospinal pathway and through the MI field. Therefore, they are sometimes called supramotor fields, whose function is to instruct the centers of the MI field.

From clinical observations, it is known that maintaining the normal function of the secondary motor cortex is important for the implementation of precise hand movements, and especially for the performance of rhythmic movements. So, for example, if they are damaged, the pianist ceases to feel the rhythm and maintain the interval. The ability to perform opposite hand movements (manipulation with both hands) is impaired.

With simultaneous damage to the motor areas MI and MII of the cortex, the ability to fine coordinated movements is lost. Point irritations in these areas of the motor zone are accompanied by activation not of individual muscles, but of a whole group of muscles that cause directed movement in the joints. These observations led to the conclusion that the motor cortex is represented not so much by muscles as by movements.

prefrontal cortex

It is located in the region of field 8. Its neurons receive the main afferent signals from the occipital visual, parietal associative cortex, superior colliculi of the quadrigemina. The processed signals are transmitted via efferent fibers to the premotor cortex, superior colliculus, and stem motor centers. The cortex plays a decisive role in the organization of movements under the control of vision and is directly involved in the initiation and control of eye and head movements.

The mechanisms that implement the transformation of the idea of movement into a specific motor program, into bursts of impulses sent to certain muscle groups, remain insufficiently understood. It is believed that the idea of movement is formed due to the functions of the associative and other areas of the cortex, interacting with many brain structures.

Information about the intention of movement is transmitted to the motor areas of the frontal cortex. The motor cortex, through descending pathways, activates systems that ensure the development and use of new motor programs or the use of old ones that have already been worked out in practice and stored in memory. An integral part of these systems are the basal ganglia and the cerebellum (see their functions above). Movement programs developed with the participation of the cerebellum and basal ganglia are transmitted through the thalamus to the motor areas and, above all, to the primary motor cortex. This area directly initiates the execution of movements, connecting certain muscles to it and providing a sequence of changes in their contraction and relaxation. Cortical commands are transmitted to the motor centers of the brain stem, spinal motor neurons and motor neurons of the cranial nerve nuclei. In the implementation of movements, motor neurons play the role of the final path through which motor commands are transmitted directly to the muscles. Features of signal transmission from the cortex to the motor centers of the stem and spinal cord are described in the chapter on the central nervous system (brain stem, spinal cord).

Association areas of the cortex

In humans, the associative areas of the cortex occupy about 50% of the area of the entire cerebral cortex. They are located in the areas between the sensory and motor areas of the cortex. Associative areas do not have clear boundaries with secondary sensory areas, both in terms of morphological and functional features. Allocate parietal, temporal and frontal associative areas of the cerebral cortex.

Parietal association area of the cortex. It is located in fields 5 and 7 of the upper and lower parietal lobes of the brain. The area borders in front of the somatosensory cortex, behind - with the visual and auditory cortex. Visual, sound, tactile, proprioceptive, pain, signals from the memory apparatus and other signals can enter and activate the neurons of the parietal associative area. Some neurons are polysensory and can increase their activity when they receive somatosensory and visual signals. However, the degree of increase in the activity of neurons in the associative cortex in response to afferent signals depends on the current motivation, the attention of the subject, and information retrieved from memory. It remains insignificant if the signal coming from the sensory areas of the brain is indifferent to the subject, and increases significantly if it coincided with the existing motivation and attracted his attention. For example, when a monkey is presented with a banana, the activity of neurons in the associative parietal cortex remains low if the animal is full, and vice versa, activity increases sharply in hungry animals that like bananas.

The neurons of the parietal association cortex are connected by efferent connections with the neurons of the prefrontal, premotor, motor areas of the frontal lobe and cingulate gyrus. Based on experimental and clinical observations, it is generally accepted that one of the functions of the field 5 cortex is the use of somatosensory information for the implementation of purposeful voluntary movements and manipulation of objects. The function of the field 7 cortex is the integration of visual and somatosensory signals to coordinate eye movements and visually guided hand movements.

Violation of these functions of the parietal associative cortex in case of damage to its connections with the cortex of the frontal lobe or disease of the frontal lobe itself, explains the symptoms of the consequences of diseases localized in the region of the parietal associative cortex. They can be manifested by difficulty in understanding the semantic content of signals (agnosia), an example of which may be the loss of the ability to recognize the shape and spatial location of an object. The processes of transformation of sensory signals into adequate motor actions may be disturbed. In the latter case, the patient loses skills in the practical use of well-known tools and objects (apraxia), and he may develop an inability to perform visually guided movements (for example, moving a hand in the direction of an object).

Frontal association area of the cortex. It is located in the prefrontal cortex, which is part of the cortex of the frontal lobe, localized anterior to fields 6 and 8. The neurons of the frontal association cortex receive processed sensory signals via afferent connections from the neurons of the cortex of the occipital, parietal, temporal lobes of the brain and from the neurons of the cingulate gyrus. The frontal associative cortex receives signals about the current motivational and emotional states from the nuclei of the thalamus, limbic and other brain structures. In addition, the frontal cortex can operate with abstract, virtual signals. The associative frontal cortex sends efferent signals back to the brain structures from which they were received, to the motor areas of the frontal cortex, the caudate nucleus of the basal ganglia, and the hypothalamus.

This area of the cortex plays a primary role in the formation of higher mental functions of a person. It provides the formation of target settings and programs of conscious behavioral reactions, recognition and semantic evaluation of objects and phenomena, speech understanding, logical thinking. After extensive damage to the frontal cortex, patients may develop apathy, a decrease in the emotional background, a critical attitude towards their own actions and the actions of others, complacency, a violation of the possibility of using past experience to change behavior. The behavior of patients can become unpredictable and inadequate.

Temporal association area of the cortex. It is located in fields 20, 21, 22. Cortical neurons receive sensory signals from neurons in the auditory, extrastriate visual and prefrontal cortex, hippocampus and amygdala.

After a bilateral disease of the temporal association areas with involvement of the hippocampus or connections with it in the pathological process, patients may develop severe memory impairment, emotional behavior, inability to concentrate (absent-mindedness). Some people with damage to the lower temporal region, where the center of face recognition is supposedly located, may develop visual agnosia - the inability to recognize the faces of familiar people, objects, while maintaining vision.

On the border of the temporal, visual and parietal areas of the cortex in the lower parietal and posterior part of the temporal lobe, there is an associative area of the cortex, called sensory center of speech, or Wernicke's center. After its damage, a violation of the function of understanding speech develops while the speech motor function is preserved.

Direct irritation of certain parts of the cerebral cortex leads to muscle spasms corresponding to the part of the cortex - the projection motor zone. When the upper third of the anterior central gyrus is irritated, a spasm of the muscles of the leg occurs, the middle one - the arm, the lower one - the face, moreover, on the side opposite to the focus of irritation in the hemisphere.

These seizures are called partial (Jacksonian). They were discovered by the English neurologist D.H. Jackson (1835-1911). In the projection motor zone of each hemisphere of the brain, all the muscles of the opposite half of the body are represented.

The cerebral cortex (cortex cerebri, substantia corticalis; syn. cerebral cortex, cerebral cortex, mantle, cloak) - a layer of gray matter (1-5 mm thick) covering the cerebral hemispheres in mammals and humans; the highest department of the central nervous system, which regulates and coordinates all the vital functions of the body during its interaction with the environment, K. b. n. - the material substrate of higher nervous and mental activity (although this activity is the result of the work of the entire brain as a whole). At the person To. n. averages 44% of the volume of the hemispheres, its surface is up to 1670 cm 2.

Allocate ancient, old and new bark. The ancient and old cortex play a significant role in the regulation of vegetative functions, the implementation of instinctive behavior, and in the need-emotional sphere. The functions of the neocortex are diverse and depend on the cytoarchitectonic zones. The new cortex (hereinafter K. b. p.) plays an important role in cognitive processes, organizations of purposeful behavior, and in humans in the implementation of higher mental functions.

Allocate cortical projection zones(cm.) - primary and secondary , and associative (cm. Association areas) - tertiary and motor cortex . The basic principle of functional organization projection zones in the cortex is the principle of topical localization, which is based on clear anatomical connections between the individual perceiving elements of the periphery and the cortical cells of the projection zones.

Projection sensory zones, including primary and secondary cortical fields , receive and process information of a certain modality from the sense organs of the opposite half of the body (cortical ends of analyzers according to I.P. Pavlov). These include the visual cortex located in the occipital lobe, the auditory cortex in the temporal lobe, and the somato-sensory cortex in the parietal lobe.

Secondary, projection zones also receive sensory signals predominantly of one modality, its neural organization creates conditions for the perception of more complex signal features.

Associative cortical zones (tertiary)- make up 1/3 of the surface of the cerebral cortex in humans. Their role gradually increases in a number of vertebrates up to man. Having received maximum development in humans, A. to. they also adopted new, specifically human functions: speech, writing, intellect, etc. A. to. z. developed in the anterior hemispheres, occupying most of the frontal lobes (prefrontal cortex) and at the junction of the projections of the main analyzers: visual, auditory and skin-kinesthetic (posterior associative cortical zones). Nerve cells A. to. respond to stimuli of many modalities, and their responses arise not only to individual elements of the object, but also to its entire complexes.

motor cortex of each hemisphere, which occupies the posterior sections of the frontal lobe, controls and controls the motor actions of the opposite side of the body.

Functionally different areas of the cortex have a developed system of intracortical connections. Symmetrical cortical fields of both hemispheres are connected by fibers corpus callosum. The system of intracortical connections and bilateral connections with the underlying departments provide the possibility of forming functional systems, including structures of different levels.

Afferent and efferent projection zones of the cortex occupy a relatively small area. Most of the surface of the cortex is occupied by tertiary or interanalyzer zones, called associative.

The association zones of the cortex occupy a significant space between the frontal, occipital and temporal cortex (60-70% of the new cortex). They receive polymodal inputs from sensory areas. 52. Medial surface of the left hemisphere:

1 - precentral gyrus (motor zones); 2 - cingulate gyrus (part of the limbic system), responsible for visceral sensitivity; 3 - corpus callosum (main commissure); 4 - vault; 5 - frontal lobe; 6 - olfactory nerves, olfactory bulb and olfactory pathway; 7 - temporal lobe; 8 - hippocampus (part of the limbic system); 9 - primary projection visual field (field 17); 10 - secondary projection visual field (field 18);

11 - occipital lobe; 12 - parietal lobe; 13 - posterior central gyrus (somatosensory zones)

thirds of the cortex and thalamic associative nuclei and have exits to the motor areas of the cortex. Associative zones provide integration of sensory inputs and play an essential role in the processes of higher nervous and mental activity.

Reading functions are provided by the lexical center (the center of the lexicon). The center of the lexia is located in the angular gyrus.

Graphic analyzer, graphic center, writing function

Writing functions are provided by the graphic center (graphic center). The center of the graph is located in the posterior part of the middle frontal gyrus.

Counting Analyzer, Calculation Center, Counting Function

The functions of the account are provided by the counting center (calculation center). The center of calculation is located at the junction of the parieto-occipital region.

Praxis, praxis analyzer, praxis center

Praxis is the ability to perform purposeful motor acts. Praxis is formed in the process of human life, starting from infancy, and is provided by a complex functional system of the brain with the participation of the cortical fields of the parietal lobe (lower parietal lobule) and the frontal lobe, especially the left hemisphere in right-handed people. For normal praxis, the preservation of the kinesthetic and kinetic basis of movements, visual-spatial orientation, programming processes and control of purposeful actions are necessary. The defeat of the praxic system at one level or another is manifested by such a type of pathology as apraxia. The term "praxis" comes from the Greek word "praxis" which means "action". - this is a violation of a purposeful action in the absence of muscle paralysis and the preservation of its constituent elementary movements.

Gnostic center, center of gnosis

In the right hemisphere of the brain in right-handers, in the left hemisphere of the brain in left-handers, many gnostic functions are represented. With damage to the predominantly right parietal lobe, anosognosia, autopagnosia, and constructive apraxia may occur. The center of gnosis is also associated with ear for music, orientation in space, and the center of laughter.

memory, thinking

The most complex cortical functions are memory and thinking. These functions do not have a clear localization.

Memory, memory function

Various sections are involved in the implementation of the memory function. The frontal lobes provide active purposeful mnestic activity. The posterior gnostic sections of the cortex are associated with particular forms of memory - visual, auditory, tactile-kinesthetic. The speech zones of the cortex carry out the process of encoding incoming information into verbal logical-grammatical systems and verbal systems. The mediobasal regions of the temporal lobe, in particular the hippocampus, translate current impressions into long-term memory. The reticular formation ensures the optimal tone of the cortex, charging it with energy.

Thinking, the function of thinking

The function of thinking is the result of the integrative activity of the entire brain, especially the frontal lobes, which are involved in the organization of the purposeful conscious activity of a person, man, woman. Programming, regulation and control take place. At the same time, in right-handers, the left hemisphere is the basis of predominantly abstract verbal thinking, and the right hemisphere is mainly associated with concrete figurative thinking.

The development of cortical functions begins in the first months of a child's life and reaches its perfection by the age of 20.

In subsequent articles, we will focus on topical issues of neurology: areas of the cerebral cortex, areas of the cerebral hemispheres, visual, area of the cortex, auditory area of the cortex, motor motor and sensitive sensory areas, associative, projection areas, motor and functional areas, speech areas, primary areas cerebral cortex, associative, functional zones, frontal cortex, somatosensory zone, cortical tumor, absence of the cortex, localization of higher mental functions, problem of localization, cerebral localization, concept of dynamic localization of functions, research methods, diagnostics.

Cortex treatment

Sarclinic uses proprietary methods for restoring the work of the cerebral cortex. Treatment of the cerebral cortex in Russia in adults, adolescents, children, treatment of the cerebral cortex in Saratov in boys and girls, boys and girls, men and women allows you to restore lost functions. In children, the development of the cerebral cortex, the centers of the brain, is activated. In adults and children, atrophy and subatrophy of the cerebral cortex, cortical disturbance, inhibition in the cortex, excitation in the cortex, damage to the cortex, changes in the cortex, sore cortex, vasoconstriction, poor blood supply, irritation and dysfunction of the cortex, organic damage, stroke, detachment , damage, diffuse changes, diffuse irritation, death, underdevelopment, destruction, disease, question to the doctor If the cerebral cortex has suffered, then with proper and adequate treatment it is possible to restore its functions.

. There are contraindications. Specialist consultation is required.

Text: ® SARCLINIC | Sarclinic.com \ Sarlinic.ru Photo: MedusArt / Photogenika Photobank / photogenica.ru The people shown in the photo are models, do not suffer from the described diseases and / or all coincidences are excluded.

glial cells; it is located in some parts of the deep brain structures, the cortex of the cerebral hemispheres (as well as the cerebellum) is formed from this substance.

Each hemisphere is divided into five lobes, four of which (frontal, parietal, occipital and temporal) are adjacent to the corresponding bones of the cranial vault, and one (insular) is located deep in the fossa that separates the frontal and temporal lobes.

The cerebral cortex has a thickness of 1.5–4.5 mm, its area increases due to the presence of furrows; it is connected with other parts of the central nervous system, thanks to the impulses that neurons conduct.

The hemispheres make up approximately 80% of the total mass of the brain. They carry out the regulation of higher mental functions, while the brain stem is lower, which are associated with the activity of internal organs.

Three main regions are distinguished on the hemispheric surface:

convex upper lateral, which is adjacent to the inner surface of the cranial vault;
lower, with the anterior and middle sections located on the inner surface of the cranial base and the posterior ones in the region of the cerebellum;
the medial is located at the longitudinal fissure of the brain.

Features of the device and activities

The cerebral cortex is divided into 4 types:

ancient - occupies a little more than 0.5% of the entire surface of the hemispheres;
old - 2.2%;
new - more than 95%;
the average is about 1.5%.

The phylogenetically ancient cerebral cortex, represented by groups of large neurons, is pushed aside by the new one to the base of the hemispheres, becoming a narrow strip. And the old one, consisting of three cell layers, shifts closer to the middle. The main region of the old cortex is the hippocampus, which is the central department of the limbic system. The middle (intermediate) crust is a formation of a transitional type, since the transformation of old structures into new ones is carried out gradually.

The human cerebral cortex, unlike that of mammals, is also responsible for the coordinated work of internal organs. Such a phenomenon, in which the role of the cortex in the implementation of all the functional activities of the body increases, is called the corticalization of functions.

One of the features of the cortex is its electrical activity, which occurs spontaneously. Nerve cells located in this section have a certain rhythmic activity, reflecting biochemical, biophysical processes. Activity has a different amplitude and frequency (alpha, beta, delta, theta rhythms), which depends on the influence of numerous factors (meditation, sleep phases, stress, the presence of convulsions, neoplasms).

Structure

The cerebral cortex is a multilayer formation: each of the layers has its own specific composition of neurocytes, a specific orientation, and the location of processes.

The systematic position of neurons in the cortex is called "cytoarchitectonics", the fibers arranged in a certain order are called "myeloarchitectonics".

The cerebral cortex consists of six cytoarchitectonic layers.

Surface molecular, in which there are not very many nerve cells. Their processes are located in himself, and they do not go beyond.
The outer granular is formed from pyramidal and stellate neurocytes. The processes leave this layer and go to the next ones.
Pyramidal consists of pyramidal cells. Their axons go down where they end or form association fibers, and their dendrites go up to the second layer.
The internal granular is formed by stellate cells and small pyramidal. The dendrites go into the first layer, the lateral processes branch out within their own layer. Axons extend into the upper layers or into the white matter.
Ganglionic is formed by large pyramidal cells. Here are the largest neurocytes of the cortex. The dendrites are directed to the first layer or distributed in their own. Axons leave the cortex and begin to be fibers that connect various departments and structures of the central nervous system with each other.
Multiform - consists of various cells. Dendrites go to the molecular layer (some only up to the fourth or fifth layers). Axons are sent to the overlying layers or exit the cortex as association fibers.

The cerebral cortex is divided into regions - the so-called horizontal organization. There are 11 of them in total, and they include 52 fields, each of which has its own serial number.

Vertical organization

There is also a vertical division - into columns of neurons. In this case, small columns are combined into macro columns, which are called a functional module. At the heart of such systems are stellate cells - their axons, as well as their horizontal connections with the lateral axons of pyramidal neurocytes. All nerve cells in the vertical columns respond to the afferent impulse in the same way and together send an efferent signal. Excitation in the horizontal direction is due to the activity of transverse fibers that follow from one column to another.

He first discovered units that unite neurons of different layers vertically in 1943. Lorente de No - with the help of histology. Subsequently, this was confirmed using methods of electrophysiology on animals by W. Mountcastle.

The development of the cortex in fetal development begins early: as early as 8 weeks, the embryo has a cortical plate. First, the lower layers differentiate, and at 6 months, the unborn child has all the fields that are present in an adult. The cytoarchitectonic features of the cortex are fully formed by the age of 7, but the bodies of neurocytes increase even up to 18. For the formation of the cortex, coordinated movement and division of precursor cells from which neurons emerge are necessary. It has been established that this process is influenced by a special gene.

Horizontal organization

It is customary to divide the areas of the cerebral cortex into:

associative;
sensory (sensitive);
motor.

When studying localized areas and their functional characteristics, scientists used a variety of methods: chemical or physical stimulation, partial removal of brain areas, development of conditioned reflexes, registration of brain biocurrents.

sensitive

These areas occupy approximately 20% of the cortex. The defeat of such zones leads to a violation of sensitivity (reduction of vision, hearing, smell, etc.). The area of the zone directly depends on the number of nerve cells that perceive the impulse from certain receptors: the more there are, the higher the sensitivity. Allocate zones:

somatosensory (responsible for skin, proprioceptive, autonomic sensitivity) - it is located in the parietal lobe (postcentral gyrus);
visual, bilateral damage that leads to complete blindness - located in the occipital lobe;
auditory (located in the temporal lobe);
taste, located in the parietal lobe (localization - postcentral gyrus);
olfactory, bilateral violation of which leads to loss of smell (located in the hippocampal gyrus).

Violation of the auditory zone does not lead to deafness, but other symptoms appear. For example, the impossibility of distinguishing short sounds, the meaning of everyday noises (steps, pouring water, etc.) while maintaining the difference in pitch, duration, and timbre. Amusia can also occur, which consists in the inability to recognize, reproduce melodies, and also distinguish between them. Music can also be accompanied by unpleasant sensations.

Impulses traveling along afferent fibers from the left side of the body are perceived by the right hemisphere, and from the right side - by the left (damage to the left hemisphere will cause a violation of sensitivity on the right side and vice versa). This is due to the fact that each postcentral gyrus is connected to the opposite part of the body.

Motor

The motor areas, the irritation of which causes the movement of the muscles, are located in the anterior central gyrus of the frontal lobe. Motor areas communicate with sensory areas.

The motor pathways in the medulla oblongata (and partially in the spinal cord) form a decussation with a transition to the opposite side. This leads to the fact that the irritation that occurs in the left hemisphere enters the right half of the body, and vice versa. Therefore, damage to the cortex of one of the hemispheres leads to a violation of the motor function of the muscles on the opposite side of the body.

The motor and sensory areas, which are located in the region of the central sulcus, are combined into one formation - the sensorimotor zone.

Neurology and neuropsychology have accumulated a lot of information about how damage to these areas leads not only to elementary movement disorders (paralysis, paresis, tremors), but also to disturbances in voluntary movements and actions with objects - apraxia. When they appear, movements during writing may be disturbed, spatial representations may be disturbed, and uncontrolled patterned movements may appear.

Associative

These zones are responsible for linking the incoming sensory information with the one that was previously received and stored in memory. In addition, they allow you to compare information that comes from different receptors. The response to the signal is formed in the associative zone and transmitted to the motor zone. Thus, each associative area is responsible for the processes of memory, learning and thinking.. Large associative zones are located next to the corresponding functional sensory zones. For example, any associative visual function is controlled by the visual association area, which is located next to the sensory visual area.

Establishing the laws of the brain, analyzing its local disorders and checking its activity is carried out by the science of neuropsychology, which is located at the intersection of neurobiology, psychology, psychiatry and computer science.

Features of localization by fields

The cerebral cortex is plastic, which affects the transition of the functions of one department, if it is disturbed, to another. This is due to the fact that the analyzers in the cortex have a core, where the highest activity takes place, and a periphery, which is responsible for the processes of analysis and synthesis in a primitive form. Between the analyzer cores there are elements that belong to different analyzers. If the damage touches the nucleus, peripheral components begin to take responsibility for its activity.

Thus, the localization of functions possessed by the cerebral cortex is a relative concept, since there are no definite boundaries. However, cytoarchitectonics suggests the presence of 52 fields that communicate with each other through pathways:

associative (this type of nerve fibers is responsible for the activity of the cortex in the region of one hemisphere);
commissural (connect symmetrical areas of both hemispheres);
projection (contribute to the communication of the cortex, subcortical structures with other organs).

Table 1

		Relevant fields
Motor
sensitive
visual
Olfactory
Taste
Speech motor, which includes centers:	Wernicke, which allows you to perceive oral speech
	Broca - responsible for the movement of the tongue muscles; defeat threatens with a complete loss of speech
	Perception of speech in writing

So, the structure of the cerebral cortex involves considering it in a horizontal and vertical orientation. Depending on this, vertical columns of neurons and zones located in the horizontal plane are distinguished. The main functions performed by the cortex are reduced to the implementation of behavior, regulation of thinking, consciousness. In addition, it ensures the interaction of the body with the external environment and takes part in the control of the work of internal organs.