The parietal zone of the cerebral cortex. Zones and lobes of the cerebral cortex

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

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

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

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

Functions of the cortex

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

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

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

The most important functions of the cerebral cortex are:

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

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

Some scientists are sure that the anterior parts of the cerebral hemispheres are responsible for the self-awareness of a person, for his specific character traits. It is a 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 work activity, they are not interested in the opinions of others.

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

Layers of the cerebral cortex

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

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

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

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, zone 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.

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.

One of the most important organs that ensure the full functioning of the human body is the brain associated with the spinal cord and a network of neurons in various parts of the body. Thanks to this connection, synchronization of mental activity with motor reflexes and the area responsible for the analysis of incoming signals is ensured. The cerebral cortex is a layered formation in the horizontal direction. It consists of 6 different structures, each of them has a specific density, number and size of neurons. Neurons are nerve endings that perform the function of communication between parts of the nervous system during the passage of an impulse or as a reaction to the action of a stimulus. In addition to its horizontally layered structure, the cerebral cortex is permeated with many branches of neurons, located mostly vertically.

The vertical orientation of the branches of neurons forms a structure of a pyramidal shape or formation in the form of an asterisk. Many branches of short straight or branching types penetrate like layers of the cortex in the vertical direction, providing a connection between the various parts of the organ among themselves, and in the horizontal plane. In the direction of orientation of nerve cells, it is customary to distinguish centrifugal and centripetal directions of communication. In general, the physiological function of the cortex, in addition to providing the process of thinking and behavior, is to protect the cerebral hemispheres. In addition, according to scientists, as a result of evolution, the development and complication of the structure of the cortex took place. At the same time, a complication of the structure of the organ was observed as new connections were established between neurons, dendrites and axons. Characteristically, as the human intellect developed, the emergence of new neural connections occurred deep into the structure of the cortex from the outer surface to the areas located below.

Functions of the cortex

The cerebral cortex has an average thickness of 3 mm and a fairly large area due to the presence of connecting channels with the central nervous system. Perception, receipt of information, its processing, decision making and its implementation occur due to the many impulses passing through neurons like an electrical circuit. Depending on many factors, electrical signals up to 23 W are generated in the cortex. The degree of their activity is determined by the state of the person and is described by amplitude and frequency indicators. It is known that more connections are located in areas that provide more complex processes. At the same time, the cerebral cortex is not a complete structure and is in development throughout a person's life as his intellect develops. The receipt and processing of information entering the brain provides a number of physiological, behavioral, mental reactions due to the functions of the cortex, including:

• Ensuring the connection of organs and systems of the human body with the outside world and among themselves, the correct flow of metabolic processes.
• The correct perception of incoming information, its awareness through the process of thinking.
• Support the interaction of various tissues and structures that make up the organs of the human body.
• Formation and work of consciousness, intellectual and creative activity of a person.
• Control of speech activity and processes associated with mental activity.

It should be noted that the place and role of the anterior cortex in ensuring the functioning of the human body is insufficiently studied. These areas are known for their low sensitivity to external influences. For example, the action of electrical impulses on them did not cause a pronounced reaction. According to some experts, the functions of these areas of the cortex include the self-awareness of the individual, the presence and nature of its specific features. In people with damaged anterior areas of the cortex, processes of asocialization, loss of interests in the field of labor activity, their own appearance and opinion in the eyes of other people are observed. Other possible effects could be:

• loss of ability to concentrate;
• partial or complete loss of creative abilities;
• deep mental personality disorders.

The structure of the layers of the cerebral cortex

The functions performed by the body, such as coordination of the hemispheres, mental and labor activity, are largely due to the structure of its structure. Experts identify 6 different types of layers, the interaction between which ensures the operation of the system as a whole, among them:

• the molecular cover forms many chaotically intertwined dendritic formations with a low number of spindle-shaped cells responsible for the associative function;
• the outer cover is represented by many neurons of various shapes and high concentration, behind them are the outer boundaries of pyramidal structures;
• the outer cover of the pyramidal type consists of neurons of small and large sizes with a deeper location of the latter. The shape of these cells has a conical shape, a dendrite branches off from its top, having the greatest length and thickness, which, by dividing into smaller formations, connects neurons with gray matter. As they approach the cerebral cortex, the branchings are characterized by a smaller thickness and form a fan-shaped structure;
• the inner cover of the granular type consists of nerve cells with small dimensions, located at a certain distance, between which there are grouped structures of the fibrous type;
• the inner cover of the pyramidal shape consists of neurons of medium and large sizes, and the upper ends of the dendrites reach the level of the molecular cover;
• the cover, consisting of spindle-shaped neuron cells, is characterized by the fact that its part, located at the lowest point, reaches the level of white matter.

The various layers that make up the cortex differ from each other in the shape, location and purpose of their constituent structures. The relationship of neurons of stellate, pyramidal, branched and spindle-shaped types between different integuments form more than 5 dozen so-called fields. Despite the fact that there are no clear boundaries of the fields, their joint action allows you to regulate many processes associated with receiving nerve impulses, processing information and developing responses to a stimulus.

Areas of the cerebral cortex

According to the functions performed in the structure under consideration, three areas can be distinguished:

1. The zone associated with the processing of impulses received through the system of receptors from the organs of vision, smell, touch of a person. By and large, most of the reflexes associated with motor skills are provided by the cells of the pyramidal structure. Providing communication with muscle fibers and the spinal canal through dendritic structures and axons. The area responsible for receiving muscle information has well-established contacts between different layers of the cortex, which is important at the stage of correct interpretation of incoming impulses. If the cerebral cortex is affected in this area, it can lead to a breakdown in the coordinated work of sensory functions and motor activities. Visually, disorders of the motor department can manifest themselves in the reproduction of involuntary movements, twitches, convulsions, and in a more complex form lead to immobilization.
2. The area of ​​sensory perception is responsible for processing the incoming signals. By structure, it is an interconnected system of analyzers for setting feedback on the action of the stimulator. Experts identify a number of areas responsible for providing sensitivity to signals. Among them, the occipital provides visual perception, the temporal is associated with auditory receptors, the hippocampal zone with olfactory reflexes. The area responsible for the analysis of taste information is located in the region of the crown. The centers responsible for receiving and processing tactile signals are also localized there. Sensory ability is directly dependent on the number of neural connections in this area; in general, these zones occupy up to a fifth of the total volume of the cortex. Damage to this zone entails a distortion of perception, which does not allow the development of a response signal adequate to the stimulus acting on it. For example, disruption of the auditory zone does not necessarily lead to deafness, but can cause a number of effects that distort the correct perception of information. This may be expressed in the inability to capture the length or frequency of sound signals, their duration and timbre, the violation of the fixation of influences with a short duration of action.
3. The association zone makes contact between the signals received by neurons in the sensory area and the motor activity, which is a response. This area forms meaningful behavioral reflexes, ensures their practical implementation and occupies a large part of the cortex. According to the area of ​​localization, it is possible to distinguish the anterior areas located in the frontal parts and the posterior ones, which occupy the space between the zone of the temples, the crown and the back of the head. A person is characterized by a greater development of the posterior sections of the areas of associative perception. Associative centers play another important role, they ensure the implementation and perception of speech activity. Damage to the anterior associative area leads to a violation of the ability to perform analytical functions, forecasting based on available facts or previous experience. Violation of the posterior association zone makes it difficult for a person to orient himself in space. It also complicates the work of abstract three-dimensional thinking, construction and correct interpretation of complex visual models.

The consequences of damage to the cerebral cortex

Until the end, whether forgetfulness is one of the disorders associated with damage to the cerebral cortex has not been studied? Or these changes are connected with the normal functioning of the system according to the principle of destruction of unused links. Scientists have proven that due to the interconnection of neural structures with each other, if one of these areas is damaged, partial and even complete reproduction of its functions by other structures can be observed. In case of partial loss of the ability to perceive, process information or reproduce signals, the system may remain operational for some time, with limited functions. This happens due to the restoration of connections between the areas of neurons that have not been negatively affected according to the principle of the distribution system. However, the opposite effect is also possible, in which damage to one of the cortical zones can lead to a breakdown in several functions. In any case, a violation of the normal functioning of this important organ is a serious deviation, in the event of which it is necessary to immediately resort to the help of specialists in order to avoid further development of the disorder.

Among the most dangerous disorders in the functioning of this structure, one can single out atrophy associated with the processes of aging and the death of some neurons. The most used diagnostic methods are computed tomography and magnetic resonance imaging, encephalography, ultrasound studies, x-rays and angiography. It should be noted that modern diagnostic methods make it possible to identify pathological processes in the brain at a fairly early stage, with timely access to a specialist, depending on the type of disorder, there is a possibility of restoring impaired functions.

Reading strengthens neural connections:

In the KBP, areas with less defined functions are distinguished. So, a significant part of the frontal lobes, especially on the right side, can be removed without noticeable damage. However, if bilateral removal of the frontal areas is performed, severe mental disorders occur.

The projection zones of the analyzers are located in the cortex. According to their structure and functional significance, they were divided into 3 main groups of fields:

1. Primary fields (nuclear zones of analyzers).

2. Secondary fields

3. Tertiary fields.

Primary fields are associated with the sense organs and movement. They ripen early. Pavlov called them the nuclear zones of the analyzers. They carry out the primary analysis of individual stimuli that enter the cortex. If there is a violation of the primary fields to which information comes from the organ of vision or hearing, then cortical blindness or deafness occurs.

Secondary fields are the peripheral zones of the analyzers. They are located next to the primary and are connected with the senses through the primary fields. In these fields, generalization and further processing of information takes place. With the defeat of secondary fields, a person sees, hears, but does not recognize and does not understand the meaning of the signals.

Tertiary fields are analyzer overlap zones. They are located on the borders of the parietal, temporal and occipital regions, as well as in the anterior part of the frontal lobes. In the process of ontogenesis, they mature later than primary and secondary ones. The development of tertiary fields is associated with the formation of speech.

Areas of the left brain associated with speech, including making a speech (Broca's area), listening comprehension (Wernicke's zone), reading and writing (angular gyrus).

The diagram also shows motor, auditory and visual cortex.

These fields ensure the coordinated work of both hemispheres. Here the highest analysis and synthesis takes place, goals and tasks are developed. Tertiary fields have extensive connections.

Association zones

The connection of peripheral formations with the cortex.

The presence of structurally different fields in the CBP also implies their different functional significance. In the CBP, sensory, motor and associative areas are distinguished.

Sensory zones. Each hemisphere has two sensory areas:

Somatic (skin, muscle, joint sensitivity).

Visceral, this zone of the cortex receives impulses from the internal organs.

The somatic zone is located in the region of the postcentral gyrus. This zone receives information from the skin and the motor apparatus from the specific nuclei of the thalamus. The skin receptor system is projected onto the posterior central gyrus. The receptive fields of the skin of the lower extremities are projected onto the upper sections of this gyrus, the trunks onto the middle sections, and the arms and heads onto the lower sections. Removal of certain parts of this zone leads to loss of sensitivity in the relevant organs. A particularly large surface is occupied by the representation of the receptors of the hands, mimic muscles of the face, the vocal apparatus, and much less from the thigh, lower leg and torso, since fewer receptors are localized in these areas.

The second somatosensory zone is localized in the region of the Sylveian furrow. In this zone, integration and critical evaluation of information from specific nuclei of the thalamus takes place. For example, the visual zone is localized in the occipital lobe in the region of the spur groove. The auditory system is projected in the transverse temporal gyri (Geschl's gyrus).

The motor cortex is located in the anterior central gyrus. From here begins the pyramidal tract. Damage to this area of ​​the cortex leads to a violation of voluntary movements. Through associative pathways, the motor area is connected with other sensory areas of the opposite hemisphere.

All sensory and motor areas occupy less than 20% of the CBP surface. The rest of the cortex makes up the association area. Each association area of ​​the CPB is associated with several projection areas. The association areas of the cortex include parts of the parietal, frontal, and temporal lobes. The boundaries of associative fields are fuzzy. Its neurons are involved in the integration of various information. Here comes the highest analysis and synthesis of stimuli. As a result, complex elements of consciousness are formed. The parietal cortex is involved in assessing the biological significance of information and spatial perception. The frontal lobes (fields 9-14) together with the limbic system controls motivational behavior and carry out the programming of behavioral acts. If areas of the frontal lobes are destroyed, memory impairment occurs.

Localization of functions in the cerebral hemispheres. The cerebral cortex is divided into main zones, consisting of several cortical fields. Each of these zones performs a certain general function, and its constituent fields participate in the implementation of individual elements of this function in a specialized way. However, due to the conduction pathways, several zones of the cerebral hemispheres, certain subcortical centers, nuclei of the brain stem and segments of the spinal cord are involved in the implementation of individual links of higher and lower nervous activity.

With fine and precise specialization of certain groups of neurons, the brain and spinal cord function as a single whole. The mental functions of the brain are also not limited to individual areas of the cortex, but are the result of the joint activity of vast areas of the cerebral hemispheres and subcortical centers.

Rice. 123. Individual changes in the main fields of the neocortex of the cerebral hemispheres in three adults (A, B, C). Numbers-fields according to Brodman

The motor zone (field 4) is located in the anterior central gyrus along the central sulcus. In the upper quarter of the zone are the motor centers for the muscles of the legs.

Above are the neurons that innervate the muscles of the toes, and below are the hips and torso. The two middle quarters are occupied by the centers for the hands, above - the center of the muscles of the scapula, and below - the muscles of the fingers. And, finally, in the lower quarter of the anterior central gyrus are the centers of the muscles of the face and the speech apparatus.

As a result of the historical development of the human brain in the process of labor and speech, a particularly large place is occupied by groups of neurons that cause contraction of the muscles of the hand, mainly the thumb, and the muscles of the face, tongue and larynx. They receive centripetal fibers from proprioreceptors, which enter the spinal cord along the posterior roots, where they rise as part of the posterior column of the same side to the nuclei of the tender and sphenoid bundles of the medulla oblongata. The fibers of the second neurons emerge from these nuclei, forming a medial loop and, after crossing, reaching the nuclei of the thalamus opticus of the opposite side. From here, most of the centripetal fibers of the third neurons reach the posterior central gyrus and then enter the anterior central gyrus, and a smaller part enters it directly. Thus, the anterior central gyrus is connected to the posterior central gyrus by means of fibers passing through the conductive pathways of the cortex. Centrifugal motor fibers of pyramidal neurons emerge from the motor zone, which make up the pyramidal pathways; they reach the neurons of the anterior horns of the spinal cord. The motor area causes coordinated movements of skeletal muscles, predominantly on the opposite side of the body. It functions in conjunction with the subcortical centers - the striatum, as well as the Lewis body, the red nucleus and the substantia nigra.

The zone of musculoskeletal sensitivity (fields 1, 2, 3, 43 and partially 5 and 7) is located in the posterior central gyrus along the posterior central sulcus. In this zone, the granular layers of the cortex are especially strongly developed, to which centripetal fibers from skin receptors are suitable, which go as part of the same pathways as fibers from proprioreceptors. The location of the perceiving groups of neurons is the same as in the motor area. The largest surface is occupied by neurons that receive impulses from the receptors of the hand, face, tongue, and larynx. Field 7 is larger than other fields related to the sensitivity of the hand. The zone of musculoskeletal sensitivity is not completely separated from the motor zone, since in fields 3, 4 and 5 there is a combination of granular neurons with giant pyramidal neurons. Approximately 80% of motor neurons are located in the motor zone, and 20% are in the zone of skin-muscle sensitivity. Each hemisphere receives impulses mainly from receptors on the opposite side of the body, but also from receptors on the same side. This zone receives centripetal impulses mainly from the lateral and semilunar nuclei of the thalamus.

With lesions of certain areas of the posterior central gyrus, sensitivity is disturbed in certain areas of the skin. The loss of the ability to recognize objects by touch is referred to as tactile agnosia. In violation of the functions of the zone, there are disorders of touch, pain and temperature sensations of the skin and muscle-articular sensitivity. Incomplete damage to the zone causes a decrease in reception - hypoesthesia, and complete - its loss - anesthesia.

The frontal zone (fields 6, 5, 9, 10, 11, 44, 45, 46, 47) is located in the frontal lobe in front of the motor. It is divided into premotor and motor speech. The premotor zone (fields 6, 8, 9, 10, 11) regulates the tone of the skeletal muscles and coordinated movements of the body, orienting it in space. Field 46 is functionally connected with field 10, which is involved in the performance of motor conditioned reflexes. Centripetal impulses from the internal organs enter the premotor zone and a significant part of the centrifugal vegetative fibers comes from it. Therefore, damage to the premotor zone causes a violation of coordination of movements - ataxia and disorders of the functions of the cardiovascular, respiratory, digestive and other systems of internal organs.

The visual zone (fields 17, 18, 19) is located on the inner surface of the occipital lobe on both sides of the spur groove. In humans, it occupies 12% of the total surface of the cortex. Field 17 is located on the occipital pole; it is surrounded by field 18, which surrounds field 19, bordering the posterior limbic region, the upper and lower parietal regions. In field 17 - the central field of the visual zone, there are 16 times more neurons than in the central field of the auditory zone (field 41), and 10 times more neurons than in the central field of the motor zone (field 4). This indicates the leading importance of vision in the historical and individual development of man.

From the retina, 900 thousand - 1 million centripetal fibers of the optic nerves reach the lateral geniculate body, in which individual parts of the retina are accurately projected. The centripetal fibers of the neurons of the lateral geniculate body are sent to the visual zone, mainly to the main visual field 17. Other intermediate visual centers involved in the transmission of not visual impulses, but oculomotor impulses, are the thalamus and anterior tubercles of the quadrigemina.

Before entering the lateral geniculate body, the fibers of the optic nerve cross. Due to this decussation, as part of the visual path, heading to the visual zone of each hemisphere, 50% of the fibers of its side and 50% of the fibers of the opposite side. The visual zone of the left hemisphere receives visual impulses from the left halves of the retinas of both eyes, and to the zone of the right hemisphere - from the right halves of the retinas of both eyes. Therefore, the destruction of one of the visual zones causes blindness in the same halves of the retinas in both eyes - hemianopsia. In the optic nerves, in addition to centripetal fibers, there are also somewhat thicker centrifugal fibers to the muscles of the iris and centrifugal thin sympathetic fibers from the neurons of the subcortical centers. A small part of the centripetal fibers of the optic nerve is not interrupted in the subcortical formations, but goes directly to the cerebellum and the visual zones of the cerebral hemispheres.

The destruction of both fields 17 causes complete cortical blindness, the destruction of field 18 leads to loss of visual memory while maintaining vision, which is referred to as visual agnosia, and the destruction of field 19 leads to a loss of orientation in an unusual environment.

The auditory zone (fields 41, 42, 21, 22, 20, 37) is located on the surface of the temporal lobe, mainly the anterior transverse temporal gyrus and superior temporal gyrus. Field 41, located in the superior temporal gyrus and in the anterior part of the transverse gyrus, is a projection of the cochlear organ of Corti. From the organ of Corti, centripetal impulses pass through the spiral node along the cochlear nerve, which consists of about 30 thousand fibers. This node contains the first bipolar neurons of the auditory pathway. Further, the fibers of the first neurons transmit auditory impulses to the nuclei of the auditory nerve in the medulla oblongata, where the second neurons are located. The fibers of the nuclei of the auditory nerve communicate with the nuclei of the facial nerve in the medulla oblongata and the oculomotor nerve in the anterior tubercles of the midbrain. Therefore, with strong sounds, the muscles of the face, eyelids, auricle contract reflexively and eye movements are caused.

Most of the fibers of the nuclei of the auditory nerve intersect in the pons, and the smaller part passes on its side. Then the fibers of the auditory pathway enter the lateral lemniscal loop, which ends in the posterior tubercles of the quadrigemina and in the internal geniculate body, where the third neurons are located - their fibers conduct centripetal impulses to the auditory zone. There are also direct pathways connecting the nuclei of the auditory nerves with the cerebellum and the auditory zone. Most of the direct cerebellar tracts are formed by the vestibular nerve, and the smaller part by the cochlear nerve, which together make up the common trunk of the auditory nerve. The vestibular apparatus is also projected in the auditory zone.

Destruction of field 41 on one side causes deafness on the opposite side and hearing loss on one side, and destruction of fields 41 on both sides leads to complete cortical deafness. The destruction of field 22 in the anterior third of the superior temporal gyrus leads to musical deafness - the perception of the intensity of tone, timbre and rhythm of sounds is lost - auditory agnosia. The destruction of fields 21 and 20 in the middle and inferior temporal gyrus causes ataxia - a disorder of balance and coordination of movements.

In the auditory zone, there is also a speech-auditory center.

Olfactory and gustatory zones. The olfactory zone is located in the ancient cortex, which receives centripetal impulses from the olfactory cells. In addition to the olfactory function, it also performs a taste function and is involved in the activities of the digestive, excretory and reproductive systems. The hippocampus was previously thought to have an olfactory function. It is now believed that, together with the limbic system, the hypothalamic region of the diencephalon and pituitary gland, the midbrain and medulla oblongata, and especially the reticular formation, the hippocampus is involved in general motor reactions and autonomic reflexes during emotions. The taste zone proper is probably located in area 43, which is located in the lower part of the posterior central gyrus.

The limbic gyrus (posterior field 23 and anterior field 24) and the insular cortex (fields 13 and 14) are involved in higher nervous activity.

All zones of the cortex are not isolated, but are interconnected by conductive pathways.

Speech centers (fields 44, 45, 46, 39, 40, 42, 22.37). The motor center of speech is located in the lower part of the anterior central gyrus in field 44. In most right-handers, the area of ​​\u200b\u200bfield 44 in the left hemisphere is larger than in the right hemisphere. Field 44 causes complex contractions of the speech muscles necessary to pronounce words. With the destruction of this field, a person cannot speak, but can produce the simplest contractions of the speech muscles - scream and sing. This is motor, motor aphasia, which in some cases manifests itself in the absence of contractions of the muscles of the tongue and the rest of the speech muscles. Since in these cases the auditory center of speech is not damaged, the understanding of the speech of others is preserved. When field 44 is affected, not only oral speech is often disturbed, but also inner speech or the ability to formulate thoughts in words without pronouncing them, on the basis of accumulated sound images that have a certain semantic content. At the same time, reading to oneself is difficult, the ability to write arbitrarily and under dictation is upset, but the copying of letters when writing is preserved. In right-handers, motor aphasia is observed when the left hemisphere is affected, and left-handers - in the right.

Rice. 129. Localization of speech centers:
1 - motor, 2 - auditory, 3 - visual

In front of field 44 is field 45, which regulates the construction of grammatically correct combinations of words and singing. If this field is damaged due to loss of memory for pronunciation techniques, singing is upset. Facial expressions and gestures, which give speech its expressiveness, are carried out thanks to impulses coming from field 46 to fields 44 and 45, to the fields of the premotor region and to the subcortical centers.

The auditory, or sensory, speech center is located in the posterior section of the left superior temporal gyrus in field 42, which understands the word when it is heard. If the field is destroyed, the ability to understand the meaning of words is lost, but their perception as sounds is preserved - sensory aphasia, or speech deafness. At the same time, due to a lack of understanding of one's own speech, excessive talkativeness is sometimes observed - logorrhoea, or verbal diarrhea. In the back part of the field 22, the connections of sound images of words with all perceiving zones are fixed, in which ideas about objects and phenomena arise. Therefore, damage to this field also causes sensory aphasia.

Fields 39 and 40, located in the parietal lobe next to field 22, carry out the understanding of the meaning of combinations of words or phrases. Therefore, their defeat leads to a speech disorder, which is called semantic (semantic) aphasia. With the defeat of field 39, due to the loss of the ability to recognize letters and numbers and understand the meaning of visible written images of words and numbers, the ability to read aloud, write and count is lost. The defeat of field 40 causes a loss of the ability to write, since there is no orientation of movements in space and their sequence is disturbed. This lack of ability to produce systemic, purposeful movements (apraxia) does not exclude the possibility of correctly performing individual hand movements that are not related to writing. Consequently, the process of writing in right-handed people is carried out by the temporal, lower parietal and lower frontal regions of the left hemisphere. When field 37 is affected, memory loss for words is caused - amnestic aphasia.

Thus, the large hemispheres of the brain as a whole are involved in the implementation of the function of speech, but a special role is played by individual fields of the cortex. In right-handers, as a result of the predominant development of the functions of the right hand and the right half of the body, the most complex mental functions of the left hemisphere of the brain are especially developed.

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