The cerebral cortex is divided into. The structure and functions of the cerebral cortex. Outer granular layer

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

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 made up of pyramidal neurons medium size, the processes of which are also involved in the formation of corticocortical connections between neighboring 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.

Efficiency of perception, processing and use of information by the cortex for regulation physiological processes also provided 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, forming in the later stages evolutionary development higher organisms, to a certain extent subordinated to itself all the underlying parts of the central nervous system 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), 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 various kinds sensation on the opposite side of the body, and local damage - to loss of sensation 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. Part of the fibers of this path goes to the motor neurons of the nuclei of the cranial nerves of the brainstem (corticobulbar tract), part - to the neurons of the stem motor nuclei (red nucleus, nuclei of the reticular formation, stem nuclei associated with the cerebellum) and part - to the inter- and motor neurons spinal cord(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. Motor neurons in the implementation of movements play a role 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, understanding of speech, 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.

The cerebral cortex is the highest department of the central nervous system, which provides a perfect organization of human behavior. In fact, it predetermines consciousness, participates in the management of thinking, helps to ensure the relationship with the outside world and the functioning of the body. It establishes interaction with the outside world through reflexes, which allows you to properly adapt to new conditions.

The specified department is responsible for the work of the brain itself. On top of certain areas interconnected with the organs of perception, zones have formed that have subcortical white matter. They are important in complex data processing. Due to the appearance of such an organ in the brain, the next stage begins, at which the significance of its functioning increases significantly. This department is an organ that expresses the individuality and conscious activity of the individual.

General information about GM bark

It is a surface layer up to 0.2 cm thick, which covers the hemispheres. It provides for vertically oriented nerve endings. This organ contains centripetal and centrifugal nerve processes, neuroglia. Each share of this department is responsible for certain functions:

• - auditory function and sense of smell;
• occipital - visual perception;
• parietal - touch and taste buds;
• frontal - speech, motor activity, complex thought processes.

In fact, the cortex predetermines the conscious activity of the individual, participates in the control of thinking, and interacts with the outside world.

Anatomy

The functions performed by the cortex are often determined by its anatomical structure. The structure has its character traits expressed in different number layers, dimensions, anatomy of the nerve endings that form the organ. Experts distinguish the following types of layers that interact with each other and help the system as a whole function:

• molecular layer. Helps to create chaotically connected dendritic formations with a small number of spindle-shaped cells and causing associative activity.
• outer layer. Expressed by neurons with different outlines. After them, the external contours of structures that have a pyramidal shape are localized.
• The outer layer is pyramidal. Assumes the presence of neurons of different sizes. In shape, these cells are similar to a cone. From above comes the dendrite, which has the largest dimensions. connected by dividing into minor formations.
• grainy layer. Provides for nerve endings of small size, localized apart.
• pyramid layer. Assumes the presence of neural circuits with different dimensions. The upper processes of neurons are able to reach the initial layer.
• An integument containing neural connections resembling a spindle. Some of them, located at the lowest point, can reach the level of white matter.
• frontal lobe
• Plays a key role in conscious activity. Participates in memorization, attention, motivation and other tasks.

It provides for the presence of 2 paired lobes and occupies 2/3 of the entire brain. The hemispheres control opposite sides of the body. So, the left lobe regulates the work of the muscles of the right side and vice versa.

The frontal parts are important in subsequent planning, including management and decision making. In addition, they perform the following functions:

• Speech. Facilitates the expression of thought processes in words. Damage to this area can affect perception.
• Motility. Gives the opportunity to influence motor activity.
• comparative processes. Facilitates the classification of objects.
• Memorization. Each area of ​​the brain is important in the process of memorization. The frontal part forms long-term memory.
• Personal formation. It makes it possible to interact with impulses, memory and other tasks that form the main characteristics of the individual. The defeat of the frontal lobe radically changes the personality.
• Motivation. Most of the sensory nerve processes are located in the frontal part. Dopamine contributes to the maintenance of the motivational component.
• Attention control. If the frontal parts are not able to control attention, then an attention deficit syndrome is formed.

parietal lobe

It covers the upper and lateral parts of the hemisphere, and is also separated by a central groove. The functions that this site performs differ for the dominant and non-dominant sides:

• Dominant (mainly left). Responsible for the possibility of understanding the structure of the whole through the ratio of its components and for the synthesis of information. In addition, it enables the implementation of interrelated movements that are required to obtain a specific result.
• Non-dominant (predominantly right). A center that processes the data coming from the back of the head and provides a 3-dimensional perception of what is happening. The defeat of this area leads to the inability to recognize objects, faces, landscapes. Since visual images are processed in the brain separately from the data coming from other sense organs. In addition, the side takes part in the orientation in human space.

Both parietal parts are involved in the perception of temperature changes.

temporal

It implements a complex mental function - speech. It is located on both hemispheres from the side in the lower part, closely interacting with nearby departments. This part of the cortex has the most pronounced contours.

The temporal areas process auditory impulses, converting them into a sound image. They are important in providing verbal communication skills. Directly in this department, the recognition of the heard information takes place, the choice of language units for semantic expression.

To date, it has been confirmed that the occurrence of difficulties with smell in an elderly patient signals the emerging Alzheimer's disease.

A small area inside the temporal lobe () controls long-term memory. The temporal part directly accumulates memories. The dominant department interacts with verbal memory, the non-dominant one contributes to the visual memorization of images.

Simultaneous damage to two lobes leads to a serene state, loss of the ability to identify external images and increased sexuality.

Island

The islet (closed lobule) is located deep in the lateral furrow. The islet is separated from adjacent sections by a circular groove. The upper section of the closed lobule is divided into 2 parts. Here the taste analyzer is projected.

Forming the bottom of the lateral groove, the closed lobule is a protrusion, the upper part of which is directed outward. The islet is separated by a circular groove from the nearby lobes, which form the tegmentum.

The upper section of the closed lobule is divided into 2 parts. In the first, the precentral sulcus is localized, and the anterior central gyrus is located in the middle of them.

Furrows and convolutions

They are depressions and folds in the middle of them, which are localized on the surface of the cerebral hemispheres. Furrows contribute to an increase in the cortex of the hemispheres, without increasing the volume of the cranium.

The significance of these areas lies in the fact that two-thirds of the entire cortex is located deep in the furrows. There is an opinion that the hemispheres develop differently in different departments, as a result of this, the tension will also be uneven in specific areas. This can lead to the formation of folds or convolutions. Other scientists believe that the initial development of the furrows is of great importance.

The anatomical structure of the organ in question is distinguished by a variety of functions.

Each department of this body has a specific purpose, being a kind of level of influence.

Thanks to them, all the functioning of the brain is carried out. Violations in the work of a certain area can lead to malfunctions in the activity of the entire brain.

Pulse processing zone

This area contributes to the processing of nerve signals coming through the visual receptors, smell, touch. Most of the reflexes associated with motor skills will be provided by pyramidal cells. The zone that provides the processing of muscle data is characterized by a well-coordinated interconnection of all layers of the organ, which is of key importance at the stage of the appropriate processing of nerve signals.

If the cerebral cortex is affected in this area, then disturbances can occur in the coordinated functioning of the functions and actions of perception, which are inextricably linked with motor skills. Outwardly, disorders in the motor part manifest themselves during involuntary motor activity, convulsions, severe manifestations that lead to paralysis.

Sensory area

This area is responsible for processing impulses entering the brain. In its structure, it is a system of interaction of analyzers to establish a relationship with the stimulator. Experts distinguish 3 departments responsible for the perception of impulses. These include the occipital, which provides processing of visual images; temporal, which is associated with hearing; hippocampal area. The part that is responsible for processing these taste stimulants is located near the crown of the head. Here are the centers that are responsible for receiving and processing tactile impulses.

Sensory ability directly depends on the number of neural connections in this area. Approximately these sections occupy up to a fifth of the total size of the cortex. Damage to this area provokes improper perception, which will not allow the production of a counter impulse that would be adequate to the stimulus. For example, a disturbance in the functioning of the auditory zone does not cause deafness in all cases, but it can provoke some effects that distort the normal perception of data.

association zone

This department facilitates the contact between the impulses received by the neural connections in the sensory department and the motility, which is a counter signal. This part forms meaningful behavioral reflexes, and also takes part in their implementation. According to the location, the anterior zones are distinguished, located in the frontal parts, and the posterior ones, which have taken an intermediate position in the middle of the temples, the crown and the occipital region.

The individual is characterized by strongly developed posterior associative zones. These centers have a special purpose, guaranteeing the processing of speech impulses.

Pathological changes in the work of the anterior associative area lead to failures in analysis, prediction, based on previously experienced sensations.

Disorders in the functioning of the posterior associative area complicates spatial orientation, slows down abstract thought processes, the construction and identification of complex visual images.

The cerebral cortex is responsible for the functioning of the brain. This caused changes in the anatomical structure of the brain itself, as its work became much more complicated. On top of certain areas interconnected with the organs of perception and the motor apparatus, departments were formed that have associative fibers. They are necessary for the complex processing of data entering the brain. As a result of the formation of this organ, a new stage begins, where its significance increases significantly. This department is considered the body that expresses individual characteristics man and his conscious activity.

The cerebral cortex is the youngest formation of the central nervous system. The activity of the cerebral cortex is based on the principle conditioned reflex, therefore it is called conditioned reflex. It provides a quick connection with the external environment and adaptation of the body to changing environmental conditions.

Deep grooves divide each cerebral hemisphere into frontal, temporal, parietal, occipital lobes and insula. The islet is located deep in the Sylvian furrow and is closed from above by parts of the frontal and parietal lobes of the brain.

The cerebral cortex is divided into the ancient ( archiocortex), old (paleocortex) and new (neocortex). The ancient cortex, along with other functions, is related to the sense of smell and ensuring the interaction of brain systems. The old cortex includes the cingulate gyrus, the hippocampus. In the new cortex, the greatest development of size, differentiation of functions is noted in humans. The thickness of the new bark is 3-4 mm. The total area of ​​the cortex of an adult is 1700-2000 cm 2, and the number of neurons - 14 billion (if they are arranged in a row, a chain 1000 km long is formed) - is gradually depleted and by old age is 10 billion (more than 700 km). The cortex contains pyramidal, stellate, and fusiform neurons.

Pyramidal neurons have different sizes, their dendrites carry a large number of spines: the axon of the pyramidal neuron goes through the white matter to other areas of the cortex or structures of the central nervous system.

stellate neurons have short, well-branched dendrites and a short axon that provides neuronal connections within the cerebral cortex itself.

spindle neurons provide vertical or horizontal interconnections of neurons of different layers of the cortex.

The structure of the cerebral cortex

The cortex contains a large number of glial cells that perform supporting, metabolic, secretory, and trophic functions.

The outer surface of the cortex is divided into four lobes: frontal, parietal, occipital, and temporal. Each lobe has its own projection and associative areas.

The cerebral cortex has a six-layer structure (Fig. 1-1):

• molecular layer(1) light, composed of nerve fibers and has a small number of nerve cells;
• outer granular layer(2) consists of stellate cells, which determine the duration of the circulation of excitation in the cerebral cortex, i.e. related to memory
• pyramid mark layer(3) is formed from small pyramidal cells and, together with layer 2, provides cortical-cortical connections of various convolutions of the brain;
• inner granular layer(4) consists of stellate cells, specific thalamocortical pathways end here, i.e. pathways starting from receptor-analyzers.
• inner pyramidal layer(5) consists of giant pyramidal cells, which are the output neurons, their axons go to the brainstem and spinal cord;
• layer of polymorphic cells(6) consists of heterogeneous triangular and spindle-shaped cells that form corticothalamic pathways.

I - afferent pathways from the thalamus: STA - specific thalamic afferents; NTA - nonspecific thalamic afferents; EMF - efferent motor fibers. The numbers indicate the layers of the cortex; II - pyramidal neuron and the distribution of endings on it: A - non-specific afferent fibers from the reticular formation and; B — recurrent collaterals from axons of pyramidal neurons; B — commissural fibers from mirror cells of the opposite hemisphere; D - specific afferent fibers from the sensory nuclei of the thalamus

Rice. 1-1. Connections of the cerebral cortex.

The cellular composition of the cortex in terms of the diversity of morphology, functions, and forms of communication is unparalleled in other parts of the CNS. The neuronal composition, the distribution over the layers in different areas of the cortex are different. This made it possible to isolate 53 cytoarchitectonic fields in the human brain. The division of the cerebral cortex into cytoarchitectonic fields is more clearly formed as its function improves in phylogenesis.

The functional unit of the cortex is a vertical column about 500 µm in diameter. Column - zone of distribution of branches of one ascending (afferent) thalamocortical fiber. Each column contains up to 1000 neural ensembles. The excitation of one column inhibits neighboring columns.

The ascending path passes through all cortical layers (specific path). The non-specific pathway also passes through all cortical layers. The white matter of the hemispheres is located between the cortex and the basal ganglia. It consists of a large number of fibers running in different directions. These are the pathways of the telencephalon. There are three types of paths.

• projection- connects the cortex with the diencephalon and other parts of the central nervous system. These are ascending and descending paths;
• commissural - its fibers are part of the cerebral commissures that connect the corresponding parts of the left and right hemispheres. They are part of the corpus callosum;
• associative - connects areas of the cortex of the same hemisphere.

Areas of the cerebral cortex

According to the characteristics of the cellular composition, the surface of the cortex is divided into structural units following order: zones, regions, sub-regions, fields.

The zones of the cerebral cortex are divided into primary, secondary and tertiary projection zones. They contain specialized nerve cells, which receive impulses from certain receptors (auditory, visual, etc.). Secondary zones are peripheral sections of the analyzer cores. The tertiary zones receive processed information from the primary and secondary zones of the cerebral cortex and play an important role in the regulation of conditioned reflexes.

In the gray matter of the cerebral cortex, sensory, motor and associative zones are distinguished:

• sensory areas of the cerebral cortex - areas of the cortex in which the central sections of the analyzers are located:
  visual zone - occipital lobe of the cerebral cortex;
  auditory zone - temporal lobe of the cerebral cortex;
  zone of taste sensations - the parietal lobe of the cerebral cortex;
  zone of olfactory sensations - the hippocampus and the temporal lobe of the cerebral cortex.

Somatosensory zone located in the posterior central gyrus, nerve impulses from the proprioreceptors of muscles, tendons, joints and impulses from temperature, tactile and other skin receptors come here;

• motor areas of the cerebral cortex areas of the cortex, upon stimulation of which motor reactions appear. They are located in the anterior central gyrus. When it is damaged, significant movement disorders are observed. The paths along which the impulses go from the cerebral hemispheres to the muscles form a cross, therefore, when the motor zone of the right side of the cortex is stimulated, the muscles of the left side of the body contract;
• associative zones - areas of the cortex adjacent to the sensory areas. Nerve impulses entering the sensory zones lead to the excitation of the associative zones. Their peculiarity is that excitation can occur when impulses are received from various receptors. The destruction of associative zones leads to serious learning and memory impairments.

Speech function is associated with sensory and motor areas. Motor center of speech (Broca's center) located in the lower part of the left frontal lobe, when it is destroyed, the speech articulation; while the patient understands speech, but he can not speak.

Auditory Speech Center (Wernicke Center) located in the left temporal lobe of the cerebral cortex, when it is destroyed, verbal deafness occurs: the patient can speak, express his thoughts orally, but does not understand someone else's speech; hearing is preserved, but the patient does not recognize the words, written speech is disturbed.

Speech functions associated with written speech - reading, writing - are regulated visual center of speech located on the border of the parietal, temporal and occipital lobes of the cerebral cortex. His defeat leads to the impossibility of reading and writing.

The temporal lobe contains the center responsible for memorization layer. A patient with a lesion in this area does not remember the names of objects, he needs to prompt the right words. Forgetting the name of the object, the patient remembers its purpose, properties, therefore, describes their qualities for a long time, tells what is done with this object, but cannot name it. For example, instead of the word “tie”, the patient says: “this is what they put on the neck and tie with a special knot so that it is beautiful when they go to visit.”

Functions of the frontal lobe:

• management of innate behavioral responses with the help of accumulated experience;
• coordination of external and internal motivations of behavior;
• development of a strategy of behavior and a program of action;
• mental characteristics of the individual.

Composition of the cerebral cortex

The cerebral cortex is the highest structure of the central nervous system and consists of nerve cells, their processes and neuroglia. The cortex contains stellate, fusiform and pyramidal neurons. Due to the presence of folds, the bark has a large surface area. The ancient cortex (archicortex) and the new cortex (neocortex) are distinguished. The bark consists of six layers (Fig. 2).

Rice. 2. The cerebral cortex

The upper molecular layer is formed mainly by the dendrites of the pyramidal cells of the underlying layers and the axons of the nonspecific nuclei of the thalamus. On these dendrites, synapses are formed by afferent fibers coming from the associative and nonspecific nuclei of the thalamus.

The outer granular layer is formed by small stellate cells and partly by small pyramidal cells. The fibers of the cells of this layer are located mainly along the surface of the cortex, forming cortico-cortical connections.

A layer of pyramidal cells of small size.

Inner granular layer formed by stellate cells. It ends with afferent thalamocortical fibers, starting from the receptors of the analyzers.

The inner pyramidal layer consists of large pyramidal cells involved in the regulation of complex forms of movement.

The multiform layer consists of verstenoid cells that form the corticothalamic pathways.

According to their functional significance, the neurons of the cortex are divided into sensory, perceiving afferent impulses from the nuclei of the thalamus and receptors of sensory systems; motor, sending impulses to the subcortical nuclei, intermediate, middle, medulla oblongata, cerebellum, reticular formation and spinal cord; and intermediate, which carry out the connection between the neurons of the cerebral cortex. The neurons of the cerebral cortex are in a state of constant excitation, which does not disappear even during sleep.

In the cerebral cortex, sensory neurons receive impulses from all receptors of the body through the nuclei of the thalamus. And each organ has its own projection or cortical representation, located in certain areas of the cerebral hemispheres.

There are four sensory and four motor areas in the cerebral cortex.

Motor cortex neurons receive afferent impulses through the thalamus from muscle, joint, and skin receptors. The main efferent connections of the motor cortex are carried out through the pyramidal and extrapyramidal pathways.

Animals have the most developed frontal area of ​​the cortex and its neurons are involved in providing goal-directed behavior. If this portion of the bark is removed, the animal becomes lethargic, drowsy. In the temporal region, the site of auditory reception is localized, and nerve impulses from the receptors of the cochlea of ​​the inner ear arrive here. The area of ​​visual reception is located in the occipital lobes of the cerebral cortex.

The parietal region, the extranuclear zone, plays an important role in the organization of complex forms of higher nervous activity. Here are scattered elements of the visual and skin analyzers, inter-analyzer synthesis is carried out.

Associative zones are located next to the projection zones, which carry out the connection between the sensory and motor zones. The associative cortex takes part in the convergence of various sensory excitations, which allows complex processing of information about the external and internal environment.

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 concept - 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 at the moment modern science least studied. 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 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 common work. 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 the receipt and processing of impulses (that is, incoming information), the creation of 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 damage to 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 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:

1. 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.
2. 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.
3. 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.

The brain is the main human organ that controls all its vital functions, determines its personality, behavior and consciousness. Its structure is extremely complex and is a combination of billions of neurons grouped into departments, each of which performs its own functions of the cerebral cortex.

The human brain is made up of several sections. Each of them performs its function, ensuring the vital activity of the body.

Table 1. Main departments.

Name	Description
Oblong	This part is a continuation of the spinal cord. It consists of nuclei of gray matter and paths from white. It is this part that determines the connection between the brain and the body.
Average	It consists of 4 tubercles, two of which are responsible for vision and two for hearing.
Rear	The hindbrain includes the pons and cerebellum. This is a small department in the back of the head, which weighs within 140 grams. Consists of two hemispheres fastened together.
Intermediate	Consists of thalamus, hypothalamus.
Finite	This section forms both hemispheres of the brain, connected by the corpus callosum. The surface is full of convolutions and furrows covered with bark. The hemispheres are divided into lobes: frontal, parietal, temporal and occipital.

The last section occupies more than 80% of the total mass of the organ. Also, the body can be divided into 3 parts: the cerebellum, the trunk and the cerebral hemispheres.

In this case, the entire brain has a coating in the form of a shell, divided into three components:

• Cobweb (cerebrospinal fluid circulates through it)
• Soft (adjacent to the brain and full of blood vessels)
• Hard (contacts the skull and protects the brain from damage)

All components are important in the regulation of life and have a specific function. But the centers of regulation of activity are located in the cortex.

The human brain consists of many departments, each of which has a complex structure and performs a specific role. The largest of them is the final one, which consists of hemispheres. All this is covered with three shells that provide protective and nourishing functions.

Learn about the structure and functions of the brain from the proposed video.

What functions does

The brain and its cortex perform a number of important functions.

Brain

It is difficult to list all the functions, because this is an extremely complex organ. This includes all aspects of the life of the human body. However, it is possible to single out the main functions performed by the brain.

The functions of the main organ include all the feelings of a person. These are sight, hearing, taste, smell and touch. All of them are performed in the cerebral cortex. It is also responsible for many other aspects of life, including motor function.

Human speech is performed in the cerebral hemispheres, namely in the centers of Broca and Wernicke. The hemispheres also perform many other functions.

In addition, diseases can occur against the background of external infections. The same meningitis that occurs due to infections of pneumococcus, meningococcus and the like. The development of the disease is characterized by pain in the head, fever, pain in the eyes and many other symptoms such as weakness, nausea and drowsiness.

Many diseases that develop in the brain and its cortex have not yet been studied. Therefore, their treatment is hampered by a lack of information. So it is recommended to consult a doctor at the first non-standard symptoms, which will prevent the disease by diagnosing it at an early stage.

There are many diseases of the cerebral cortex. Among them are infectious diseases, ailments against the background of other diseases of the body, as well as diseases with an unclear cause. But most of them can be cured with medicine. Therefore, it is recommended not to delay if you feel unwell and undergo an examination of the cortex, which is carried out in many clinics.

Ultrasound is also used for analysis, although this research method is less effective. However, it is inexpensive and fast, as it does not require any preparation on the part of the patient. There is no need to move the patient.

The structure of the brain can also be determined by the x-ray of the skull. Diseases of the brain and its cortex can affect the structure of bone tissue, which will immediately be reflected in the study. This mainly refers to dropsy of the brain, its underdevelopment and other similar ailments.

Also, in the diagnosis of the brain, a study of cerebral circulation is performed. It is done through three procedures:

• Doppler ultrasound. Allows you to determine the narrowed vessels and changes in the speed of blood flow in them. It gives extensive information about the work of cerebral circulation and is not harmful to the body.
• The second option is rheocephalography. This is a less informative method that registers the electrical resistance of tissues, which allows you to create a line of pulsed blood flow. Such studies will determine the state of the vessels, their tone and other data.
• The last method is the use of x-ray angiography. This is a small surgical operation when a catheter filled with a special substance is inserted into one of the arteries. After that, an x-ray is taken. As a result, all movements of the injected substance following the blood flow are visible on it.

Video with MRI results of the head organ:

These examination methods will provide information about the state of the brain, its cortex and blood circulation. This will provide sufficient information for the diagnosis of diseases and their successful treatment. But there are other research methods that are used depending on the patient's condition and assumptions about the disease.

The human brain is a complex organ with many components and functions. However, its most complex part is the cortex, in which a person's self-consciousness is determined and all his feelings are processed. The structure of the cortex is no less complex, it is divided into several layers and lobes that perform their role. Often there are diseases of this area, but they are still poorly understood. They can be diagnosed through special examinations.

Dec 26, 2015 Violetta Doctor