Functions of the human cerebral cortex. Cheat sheet: The structure and functions of the cerebral cortex

The brain is a mysterious organ that is constantly being studied by scientists and remains not fully explored. The structural system is not simple and is a combination of neuronal cells that are grouped into separate sections. The cerebral cortex is present in most animals and mammals, but it is in the human body that it has received greater development. This was facilitated by labor activity.

Why is the brain called gray matter or gray matter? It is grayish, but it has white, red and black colors. The gray substance represents different types of cells, and the white substance represents nervous matter. Red is blood vessels, and black is melanin pigment, which is responsible for the color of hair and skin.

The structure of the brain

The main body is divided into five main parts. The first part is oblong. It is an extension of the spinal cord, which controls communication with the activities of the body and is composed of a gray and white substance. The second, middle, includes four hillocks, of which two are responsible for auditory, and two for visual function. The third, posterior, includes the bridge and the cerebellum or cerebellum. Fourth, buffer hypothalamus and thalamus. Fifth, final, which forms two hemispheres.

The surface consists of grooves and brains covered with a shell. This department makes up 80% of the total weight of a person. Also, the brain can be divided into three parts cerebellum, stem and hemispheres. It is covered with three layers that protect and nourish the main organ. This is an arachnoid layer in which the cerebral fluid circulates, soft contains blood vessels, hard close to the brain and protects it from damage.

Brain Functions

Brain activity includes the basic functions of gray matter. These are sensory, visual, auditory, olfactory, tactile reactions and motor functions. However, all the main control centers are located in the oblong part, where the activities of the cardiovascular system, protective reactions and muscle activity are coordinated.

The motor pathways of the oblong organ create a crossing with a transition to the opposite side. This leads to the fact that receptors are first formed in the right region, after which impulses arrive in the left region. Speech is performed in the cerebral hemispheres. The posterior section is responsible for the vestibular apparatus.

The cerebral cortex is represented by a uniform layer of gray matter 1.3-4.5 mm thick, consisting of more than 14 billion nerve cells. Due to the folding of the bark, its surface reaches large sizes - about 2200 cm 2.

The thickness of the cortex consists of six layers of cells, which are distinguished by special staining and examination under a microscope. The cells of the layers are different in shape and size. From them, processes extend into the depths of the brain.

It was found that different areas - fields of the cerebral cortex differ in structure and function. Such fields (also called zones, or centers) are distinguished from 50 to 200. There are no strict boundaries between the zones of the cerebral cortex. They constitute an apparatus that provides reception, processing of incoming signals and a response to the received signals.

In the posterior central gyrus, behind the central sulcus, is located zone of skin and joint-muscular sensitivity. Here, signals are perceived and analyzed that occur when touching our body, when it is exposed to cold or heat, or pain effects.

In contrast to this zone - in the anterior central gyrus, in front of the central sulcus, is located motor zone. It revealed areas that provide movement of the lower extremities, muscles of the trunk, arms, head. When this zone is irritated by an electric current, contractions of the corresponding muscle groups occur. Wounds or other damage to the cortex of the motor zone entail paralysis of the muscles of the body.

In the temporal lobe is auditory zone. Impulses arising in the receptors of the cochlea of ​​the inner ear are received here and analyzed here. Irritations of parts of the auditory zone cause sensations of sounds, and when they are affected by the disease, hearing is lost.

visual area located in the cortex of the occipital lobes of the hemispheres. When it is irritated by an electric current during brain surgery, a person experiences sensations of flashes of light and darkness. If it is affected by any disease, it worsens and vision is lost.

Near the lateral furrow is located taste zone, where the sensations of taste are analyzed and formed based on the signals that occur in the receptors of the tongue. Olfactory the zone is located in the so-called olfactory brain, at the base of the hemispheres. When these areas are irritated during surgical operations or during inflammation, people smell or taste any substances.

Purely speech zone does not exist. It is represented in the cortex of the temporal lobe, the lower frontal gyrus on the left, and in areas of the parietal lobe. Their illnesses are accompanied by speech disorders.

First and second signal systems

The role of the cerebral cortex in the improvement of the first signaling system and the development of the second is invaluable. These concepts were developed by I.P. Pavlov. The signal system as a whole is understood as the totality of the processes of the nervous system that carry out the perception, processing of information and the body's response. It connects the body with the outside world.

First signal system

The first signal system determines the perception of sensory-specific images through the senses. It is the basis for the formation of conditioned reflexes. This system exists in both animals and humans.

In the higher nervous activity of man, a superstructure has developed in the form of a second signaling system. It is peculiar only to man and is manifested by verbal communication, speech, concepts. With the advent of this signal system, abstract thinking became possible, the generalization of the countless signals of the first signal system. According to I.P. Pavlov, words have turned into “signals of signals”.

Second signal system

The emergence of the second signaling system became possible due to the complex labor relations between people, since this system is a means of communication, collective labor. Verbal communication does not develop outside of society. The second signaling system gave rise to abstract (abstract) thinking, writing, reading, counting.

Words are also perceived by animals, but completely different from people. They perceive them as sounds, and not their semantic meaning, like people. Therefore, animals do not have a second signaling system. Both human signaling systems are interconnected. They organize human behavior in the broadest sense of the word. Moreover, the second changed the first signaling system, since the reactions of the first began to largely depend on the social environment. A person has become able to control his unconditioned reflexes, instincts, i.e. first signal system.

Functions of the cerebral cortex

Acquaintance with the most important physiological functions of the cerebral cortex indicates its extraordinary importance in life. The cortex, together with the subcortical formations closest to it, is a department of the central nervous system of animals and humans.

The functions of the cerebral cortex are the implementation of complex reflex reactions that form the basis of the higher nervous activity (behavior) of a person. It is no coincidence that she received the greatest development from him. The exceptional properties of the cortex are consciousness (thinking, memory), the second signal system (speech), high organization of work and life in general.

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 is 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 restoration.

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), proprioceptors (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 torso, 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 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 go to the motor neurons of the nuclei of the cranial nerves of the brainstem (corticobulbar tract), some to the neurons of the stem motor nuclei (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.

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 Broca's motor center of 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 to be 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, the function of which 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.

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 associative 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.

Shoshina Vera Nikolaevna

Therapist, education: Northern Medical University. Work experience 10 years.

Articles written

The brain of modern man and its complex structure is the greatest achievement of this species and its advantage, unlike other representatives of the living world.

The cerebral cortex is a very thin layer of gray matter that does not exceed 4.5 mm. It is located on the surface and sides of the cerebral hemispheres, covering them from above and along the periphery.

Anatomy of the cortex or cortex, complex. Each site performs its function and is of great importance in the implementation of nervous activity. This site can be considered the highest achievement of the physiological development of mankind.

Structure and blood supply

The cerebral cortex is a layer of gray matter cells that makes up approximately 44% of the total volume of the hemisphere. The area of ​​the cortex of an average person is about 2200 square centimeters. Structural features in the form of alternating furrows and convolutions are designed to maximize the size of the cortex and at the same time fit compactly within the cranium.

Interestingly, the pattern of convolutions and furrows is as individual as the prints of papillary lines on a person's fingers. Each individual is individual in pattern and.

The cortex of the hemispheres from the following surfaces:

1. Upper lateral. It adjoins the inner side of the bones of the skull (vault).
2. Lower. Its anterior and middle sections are located on the inner surface of the base of the skull, and the posterior ones rest on the cerebellum.
3. medial. It is directed to the longitudinal fissure of the brain.

The most protruding places are called poles - frontal, occipital and temporal.

The cerebral cortex is symmetrically divided into lobes:

• frontal;
• temporal;
• parietal;
• occipital;
• islet.

In the structure, the following layers of the human cerebral cortex are distinguished:

• molecular;
• external granular;
• layer of pyramidal neurons;
• internal granular;
• ganglionic, internal pyramidal or Betz cell layer;
• a layer of multiformate, polymorphic, or spindle-shaped cells.

Each layer is not a separate independent formation, but represents a single harmoniously functioning system.

Functional areas

Neurostimulation revealed that the cortex is divided into the following sections of the cerebral cortex:

1. Sensory (sensitive, projection). They receive incoming signals from receptors located in various organs and tissues.
2. Motor, outgoing signals sent to effectors.
3. Associative, processing and storing information. They evaluate previously obtained data (experience) and issue an answer based on them.

The structural and functional organization of the cerebral cortex includes the following elements:

• visual, located in the occipital lobe;
• auditory, occupying the temporal lobe and part of the parietal;
• vestibular is less studied and is still a problem for researchers;
• olfactory is on the bottom;
• taste is located in the temporal regions of the brain;
• the somatosensory cortex appears in the form of two areas - I and II, located in the parietal lobe.

Such a complex structure of the cortex suggests that the slightest violation will lead to consequences that affect many functions of the body and cause pathologies of varying intensity, depending on the depth of the lesion and the location of the site.

How is the cortex connected to other parts of the brain?

All areas of the human cortex do not exist in isolation, they are interconnected and form inextricable bilateral chains with deeper brain structures.

The most important and significant is the connection between the cortex and the thalamus. When the skull is injured, the damage is much more significant if the thalamus is also injured along with the cortex. Injuries to the cortex alone are found to be much smaller and have less significant consequences for the body.

Almost all connections from different parts of the cortex pass through the thalamus, which gives reason to combine these parts of the brain into the thalamocortical system. Interruption of connections between the thalamus and the cortex leads to the loss of functions of the corresponding part of the cortex.

Pathways from sensory organs and receptors to the cortes also run through the thalamus, with the exception of some olfactory pathways.

Interesting facts about the cerebral cortex

The human brain is a unique creation of nature, which the owners themselves, that is, people, have not yet learned to fully understand. It is not entirely fair to compare it with a computer, because now even the most modern and powerful computers cannot cope with the volume of tasks performed by the brain within a second.

We are accustomed to not paying attention to the usual functions of the brain associated with the maintenance of our daily life, but even the smallest failure occurred in this process, we would immediately feel it "in our own skin".

“Little gray cells,” as the unforgettable Hercule Poirot said, or from the point of view of science, the cerebral cortex is an organ that still remains a mystery to scientists. We found out a lot, for example, we know that the size of the brain does not affect the level of intelligence in any way, because the recognized genius - Albert Einstein - had a brain that was below average, about 1230 grams. At the same time, there are beings that have brains of a similar structure and even larger size, but have not yet reached the level of human development.

A striking example is the charismatic and intelligent dolphins. Some people believe that once in the deepest antiquity the tree of life split into two branches. Our ancestors went one way, and dolphins went the other way, that is, we may have had common ancestors with them.

A feature of the cerebral cortex is its indispensability. Although the brain is able to adapt to injury and even partially or completely restore its functionality, if part of the cortex is lost, the lost functions are not restored. Moreover, scientists were able to conclude that this part largely determines the personality of a person.

With an injury to the frontal lobe or the presence of a tumor here, after the operation and removal of the destroyed part of the cortex, the patient changes radically. That is, the changes concern not only his behavior, but also the personality as a whole. There have been cases when a good kind person turned into a real monster.

Based on this, some psychologists and criminologists have concluded that intrauterine damage to the cerebral cortex, especially its frontal lobe, leads to the birth of children with antisocial behavior, with sociopathic tendencies. These kids have a high chance of becoming a criminal and even a maniac.

CHM pathologies and their diagnostics

All violations of the structure and functioning of the brain and its cortex can be divided into congenital and acquired. Some of these lesions are incompatible with life, for example, anencephaly - the complete absence of the brain and acrania - the absence of cranial bones.

Other diseases leave a chance for survival, but are accompanied by mental disorders, such as encephalocele, in which part of the brain tissue and its membranes protrude outward through a hole in the skull. The same group also includes an underdeveloped small brain, accompanied by various forms of mental retardation (oligophrenia, idiocy) and physical development.

A rarer variant of the pathology is macrocephaly, that is, an increase in the brain. Pathology is manifested by mental retardation and convulsions. With it, the increase in the brain can be partial, that is, asymmetric hypertrophy.

Pathologies in which the cerebral cortex is affected are represented by the following diseases:

1. Holoprosencephaly is a condition in which the hemispheres are not separated and there is no full division into lobes. Children with such a disease are born dead or die on the first day after birth.
2. Agyria is the underdevelopment of the gyri, in which the functions of the cortex are impaired. Atrophy is accompanied by multiple disorders and leads to the death of the infant during the first 12 months of life.
3. Pachygyria is a condition in which the primary gyri are enlarged to the detriment of the others. At the same time, the furrows are short and straightened, the structure of the cortex and subcortical structures is disturbed.
4. Micropolygyria, in which the brain is covered with small convolutions, and the cortex does not have 6 normal layers, but only 4. The condition is diffuse and local. Immaturity leads to the development of plegia and muscle paresis, epilepsy, which develops in the first year, mental retardation.
5. Focal cortical dysplasia is accompanied by the presence in the temporal and frontal lobes of pathological areas with huge neurons and abnormal ones. Incorrect cell structure leads to increased excitability and seizures, accompanied by specific movements.
6. Heterotopia is an accumulation of nerve cells that, in the process of development, did not reach their place in the cortex. A solitary condition may appear after the age of ten, large accumulations cause seizures such as epileptic seizures and mental retardation.

Acquired diseases are mainly the consequences of serious inflammations, injuries, and also appear after the development or removal of a tumor - benign or malignant. Under such conditions, as a rule, the impulse emanating from the cortex to the corresponding organs is interrupted.

The most dangerous is the so-called prefrontal syndrome. This area is actually a projection of all human organs, therefore damage to the frontal lobe leads to memory, speech, movements, thinking, as well as partial or complete deformation and a change in the patient's personality.

A number of pathologies accompanied by external changes or deviations in behavior are easy to diagnose, others require more careful study, and removed tumors are subjected to histological examination to rule out a malignant nature.

Alarming indications for the procedure are the presence of congenital pathologies or diseases in the family, fetal hypoxia during pregnancy, asphyxia during childbirth, and birth trauma.

Methods for diagnosing congenital abnormalities

Modern medicine helps prevent the birth of children with severe malformations of the cerebral cortex. For this, screening is performed in the first trimester of pregnancy, which makes it possible to identify pathologies in the structure and development of the brain at the earliest stages.

In a baby born with suspected pathology, neurosonography is performed through the "fontanelle", and older children and adults are examined by conducting. This method allows not only to detect a defect, but also to visualize its size, shape and location.

If the family encountered hereditary problems associated with the structure and functioning of the cortex and the entire brain, a genetic consultation and specific examinations and analyzes are required.

The famous "gray cells" are the greatest achievement of evolution and the highest good for man. Damage can be caused not only by hereditary diseases and injuries, but also by acquired pathologies provoked by the person himself. Doctors urge you to take care of your health, give up bad habits, allow your body and brain to rest and not let your mind be lazy. Loads are useful not only for muscles and joints - they do not allow nerve cells to grow old and fail. The one who studies, works and loads his brain, suffers less from wear and tear and later comes to the loss of mental abilities.

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 organizing 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, brain 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, diseases, question to the doctor If the cerebral cortex has suffered, then with proper and adequate treatment it is possible to restore its functions.

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.