The structure of the forebrain cortex. Structure and functions of the cerebral cortex

Modern scientists know for certain that thanks to the functioning of the brain, such abilities as awareness of signals received from the external environment, mental activity, and memorization of thoughts are possible.

The ability of an individual to realize his own relationships with other people is directly related to the process of excitation of neural networks. Moreover, we are talking specifically about those neural networks that are located in the cortex. It represents the structural basis of consciousness and intelligence.

In this article we will look at how the cerebral cortex is structured; the areas of the cerebral cortex will be described in detail.

Neocortex

The cortex contains about fourteen billion neurons. It is thanks to them that the main zones function. The vast majority of neurons, up to ninety percent, form the neocortex. It is part of the somatic NS and its highest integrative department. The most important functions of the cerebral cortex are the perception, processing, and interpretation of information that a person receives with the help of various senses.

In addition, the neocortex controls the complex movements of the human body's muscle system. It contains centers that take part in the process of speech, memory storage, and abstract thinking. Most of the processes that occur in it form the neurophysical basis of human consciousness.

What other parts does the cerebral cortex consist of? We will consider the areas of the cerebral cortex below.

Paleocortex

It is another large and important section of the cortex. Compared to the neocortex, the paleocortex has a simpler structure. The processes that take place here are rarely reflected in consciousness. The higher vegetative centers are localized in this section of the cortex.

Connection of the cortex with other parts of the brain

It is important to consider the connection that exists between the underlying parts of the brain and the cerebral cortex, for example, with the thalamus, pons, medial pons, and basal ganglia. This connection is carried out using large bundles of fibers that form the internal capsule. Bundles of fibers are represented by wide layers, which are composed of white matter. They contain a huge number of nerve fibers. Some of these fibers provide transmission of nerve signals to the cortex. The rest of the bundles transmit nerve impulses to the nerve centers located below.

How is the cerebral cortex structured? The areas of the cerebral cortex will be presented below.

Structure of the cortex

The largest part of the brain is its cortex. Moreover, cortical zones are only one type of parts distinguished in the cortex. In addition, the cortex is divided into two hemispheres - right and left. The hemispheres are connected to each other by bundles of white matter that form the corpus callosum. Its function is to ensure coordination of the activities of both hemispheres.

Classification of cerebral cortex zones by their location

Despite the fact that the cortex has a huge number of folds, in general the location of its individual convolutions and grooves is constant. The main ones are a guideline for identifying areas of the cortex. Such zones (lobes) include occipital, temporal, frontal, parietal. Although they are classified by location, each has its own specific functions.

Auditory cortex

For example, the temporal zone is the center in which the cortical section of the hearing analyzer is located. If damage to this part of the cortex occurs, deafness may occur. In addition, Wernicke's speech center is located in the auditory zone. If it is damaged, then the person loses the ability to perceive oral speech. A person perceives it as simple noise. Also in the temporal lobe there are neural centers that belong to the vestibular apparatus. If they are damaged, the sense of balance is disrupted.

Speech areas of the cerebral cortex

Speech areas are concentrated in the frontal lobe of the cortex. The speech motor center is also located here. If damage occurs in the right hemisphere, then the person loses the ability to change the timbre and intonation of his own speech, which becomes monotonous. If damage to the speech center occurs in the left hemisphere, then articulation and the ability to articulate speech and singing disappear. What else does the cerebral cortex consist of? The areas of the cerebral cortex have different functions.

Visual zones

In the occipital lobe there is a visual zone, in which there is a center that responds to our vision as such. The perception of the world around us occurs precisely with this part of the brain, and not with the eyes. It is the occipital cortex that is responsible for vision, and damage to it can lead to partial or complete loss of vision. The visual area of the cerebral cortex is examined. What's next?

The parietal lobe also has its own specific functions. It is this zone that is responsible for the ability to analyze information that relates to tactile, temperature and pain sensitivity. If damage occurs to the parietal region, the brain's reflexes are disrupted. A person cannot recognize objects by touch.

Motor zone

Let's talk about the motor zone separately. It should be noted that this zone of the cortex does not correlate in any way with the lobes discussed above. It is part of the cortex containing direct connections to motor neurons in the spinal cord. This name is given to neurons that directly control the activity of the muscles of the body.

The main motor area of the cerebral cortex is located in a gyrus called the precentral gyrus. This gyrus is a mirror image of the sensory area in many aspects. Between them there is contralateral innervation. To put it another way, the innervation is directed to the muscles that are located on the other side of the body. The exception is the facial area, which is characterized by bilateral control of the muscles located on the jaw and lower part of the face.

Slightly below the main motor zone is an additional zone. Scientists believe that it has independent functions that are associated with the process of outputting motor impulses. The supplementary motor area has also been studied by specialists. Experiments carried out on animals show that stimulation of this zone provokes the occurrence of motor reactions. The peculiarity is that such reactions occur even if the main motor area has been isolated or completely destroyed. It is also involved in motor planning and speech motivation in the dominant hemisphere. Scientists believe that if the accessory motor is damaged, dynamic aphasia can occur. Brain reflexes suffer.

Classification according to the structure and functions of the cerebral cortex

Physiological experiments and clinical trials, which were carried out at the end of the nineteenth century, made it possible to establish the boundaries between the areas to which different receptor surfaces are projected. Among them are sensory organs that are directed to the outside world (skin sensitivity, hearing, vision), receptors embedded directly in the organs of movement (motor or kinetic analyzers).

Cortical areas in which various analyzers are located can be classified according to structure and function. So, there are three of them. These include: primary, secondary, tertiary zones of the cerebral cortex. The development of the embryo involves the formation of only primary zones, characterized by simple cytoarchitecture. Next comes the development of secondary ones, tertiary ones develop last. Tertiary zones are characterized by the most complex structure. Let's look at each of them in a little more detail.

Central fields

Over many years of clinical research, scientists have managed to accumulate significant experience. Observations made it possible to establish, for example, that damage to various fields, within the cortical sections of different analyzers, can have a far different impact on the overall clinical picture. If we consider all these fields, then among them we can single out one that occupies a central position in the nuclear zone. This field is called central or primary. It is located simultaneously in the visual zone, in the kinesthetic zone, and in the auditory zone. Damage to the primary field entails very serious consequences. A person cannot perceive and carry out the most subtle differentiation of stimuli that affect the corresponding analyzers. How else are areas of the cerebral cortex classified?

Primary zones

In the primary zones there is a complex of neurons that is most predisposed to providing bilateral connections between the cortical and subcortical zones. It is this complex that connects the cerebral cortex with various sensory organs in the most direct and shortest way. In this regard, these zones have the ability to identify stimuli in a very detailed manner.

An important common feature of the functional and structural organization of the primary areas is that they all have a clear somatic projection. This means that individual peripheral points, for example, skin surfaces, retina, skeletal muscles, cochleae of the inner ear, have their own projection into strictly limited, corresponding points, which are located in the primary zones of the cortex of the corresponding analyzers. In this regard, they were given the name projection zones of the cerebral cortex.

Secondary zones

In another way, these zones are called peripheral. This name was not given to them by chance. They are located in the peripheral parts of the cortex. Secondary zones differ from the central (primary) zones in their neural organization, physiological manifestations and architectural features.

Let's try to figure out what effects occur if the secondary zones are affected by an electrical stimulus or if they are damaged. The effects that arise mainly concern the most complex types of processes in the psyche. In the event that damage occurs to the secondary zones, the elementary sensations remain relatively intact. Basically, there are disturbances in the ability to correctly reflect mutual relationships and entire complexes of elements that make up the various objects that we perceive. For example, if the secondary zones of the visual and auditory cortex are damaged, then the emergence of auditory and visual hallucinations can be observed, which unfold in a certain temporal and spatial sequence.

Secondary areas are of significant importance in the implementation of mutual connections between stimuli, which are allocated with the help of primary areas of the cortex. In addition, they play a significant role in the integration of functions that are carried out by the nuclear fields of different analyzers as a result of combining into complex complexes of receptions.

Thus, secondary zones are of particular importance for the implementation of mental processes in more complex forms that require coordination and which are associated with a detailed analysis of the relationships between objective stimuli. During this process, specific connections are established, which are called associative. Afferent impulses entering the cortex from receptors of various external sensory organs reach secondary fields through many additional switches in the association nucleus of the thalamus, which is also called the thalamus optic. Afferent impulses going to the primary zones, in contrast to impulses going to the secondary zones, reach them via a shorter route. It is implemented through a relay core in the visual thalamus.

We figured out what the cerebral cortex is responsible for.

What is the thalamus?

Fibers from the thalamic nuclei reach each lobe of the cerebral hemispheres. The thalamus is a visual thalamus located in the central part of the forebrain; it consists of a large number of nuclei, each of which transmits impulses to certain areas of the cortex.

All signals that enter the cortex (with the exception of olfactory signals) pass through the relay and integrative nuclei of the visual thalamus. From the nuclei of the thalamus, fibers are directed to sensory areas. The taste and somatosensory zones are located in the parietal lobe, the auditory sensory zone is in the temporal lobe, and the visual zone is in the occipital lobe.

Impulses to them come, respectively, from the ventro-basal complexes, medial and lateral nuclei. Motor areas are connected to the ventral and ventrolateral nuclei of the thalamus.

EEG desynchronization

What happens if a person who is in a state of complete rest is exposed to a very strong stimulus? Naturally, a person will fully concentrate on this stimulus. The transition of mental activity, which occurs from a state of rest to a state of activity, is reflected on the EEG by the beta rhythm, which replaces the alpha rhythm. Fluctuations become more frequent. This transition is called EEG desynchronization; it appears as a result of sensory stimulation entering the cortex from nonspecific nuclei located in the thalamus.

Activating reticular system

The diffuse nervous system consists of nonspecific nuclei. This system is located in the medial sections of the thalamus. It is the anterior part of the activating reticular system, which regulates the excitability of the cortex. A variety of sensory signals can activate this system. Sensory signals can be both visual and olfactory, somatosensory, vestibular, auditory. The activating reticular system is a channel that transmits signal data to the superficial layer of the cortex through nonspecific nuclei located in the thalamus. Excitation of the ARS is necessary for a person to be able to maintain a state of wakefulness. If disturbances occur in this system, comatose sleep-like states may occur.

Tertiary zones

There are functional relationships between the analyzers of the cerebral cortex, which have an even more complex structure than that described above. During the growth process, the fields of the analyzers overlap each other. Such overlap zones that form at the ends of the analyzers are called tertiary zones. They are the most complex types of combining the activities of the auditory, visual, and skin-kinesthetic analyzers. Tertiary zones are located outside the boundaries of the analyzers’ own zones. In this regard, their damage does not have a pronounced effect.

Tertiary zones are special cortical areas in which scattered elements of different analyzers are collected. They occupy a very vast territory, which is divided into regions.

The upper parietal region integrates the movements of the whole body with the visual analyzer and forms a body diagram. The inferior parietal region combines generalized forms of signaling that are associated with differentiated object and speech actions.

No less important is the temporo-parietal-occipital region. She is responsible for the complex integration of auditory and visual analyzers with oral and written speech.

It is worth noting that, compared to the first two zones, the tertiary zones are characterized by the most complex interaction chains.

If we rely on all the material presented above, we can conclude that the primary, secondary, and tertiary zones of the human cortex are highly specialized. Separately, it is worth emphasizing the fact that all three cortical zones that we considered, in a normally functioning brain, together with systems of connections and subcortical formations, function as a single differentiated whole.

We examined in detail the zones and sections of the cerebral cortex.

The cortex works in conjunction with other structures. This part of the organ has certain features associated with its specific activity. The main basic function of the cortex is to analyze information received from the organs and store the received data, as well as their transmission to other parts of the body. The cerebral cortex communicates with information receptors, which act as receivers of signals entering the brain.

Among the receptors there are sensory organs, as well as organs and tissues that carry out commands, which, in turn, are transmitted from the cortex.

For example, visual information coming from is sent along nerves through the cortex to the occipital zone, which is responsible for vision. If the image is not static, it is analyzed in the parietal zone, in which the direction of movement of the observed objects is determined. The parietal lobes are also involved in the formation of articulate speech and a person’s perception of his location in space. The frontal lobes of the cerebral cortex are responsible for the higher psyches involved in the formation of personality, character, abilities, behavioral skills, creative inclinations, etc.

Lesions of the cerebral cortex

When one or another part of the cerebral cortex is damaged, disturbances occur in the perception and functioning of certain sensory organs.

With lesions of the frontal lobe of the brain, mental disorders occur, which most often manifest themselves in serious impairment of attention, apathy, weakened memory, sloppiness and a feeling of constant euphoria. A person loses some personal qualities and develops serious behavioral deviations. Frontal ataxia often occurs, which affects standing or walking, difficulty moving, problems with accuracy, and the occurrence of hit-and-miss phenomena. The phenomenon of grasping may also occur, which consists of obsessively grasping objects surrounding a person. Some scientists associate the appearance of epileptic seizures precisely after injury to the frontal lobe.

When the frontal lobe is damaged, a person’s mental abilities are significantly impaired.

With lesions of the parietal lobe, memory disorders are observed. For example, astereognosis may occur, which manifests itself in the inability to recognize an object by touch when closing the eyes. Apraxia often appears, manifested in a violation of the formation of a sequence of events and the building of a logical chain for performing a motor task. Alexia is characterized by the inability to read. Acalculia is an impairment of the ability to process numbers. There may also be impaired perception of one's own body in space and an inability to understand logical structures.

The affected temporal lobes are responsible for hearing and perception disorders. With lesions of the temporal lobe, the perception of oral speech is impaired, attacks of dizziness, hallucinations and seizures, mental disorders and excessive irritation begin. Injuries to the occipital lobe cause visual hallucinations and disturbances, the inability to recognize objects when looking at them, and distorted perception of the shape of an object. Sometimes photoms appear - flashes of light that occur when the inner part of the occipital lobe is irritated.

The human brain has a small top layer, approximately 0.4 cm thick. This is the cerebral cortex. It serves to perform a large number of functions used in various aspects of life. This direct influence of the cortex most often affects human behavior and consciousness.

The cerebral cortex has an average thickness of approximately 0.3 cm and a rather impressive volume due to the presence of connecting channels with the central nervous system. Information is perceived, processed, and a decision is made due to a large number of impulses that pass through neurons, as if along an electrical circuit. Depending on various conditions, electrical signals are produced in the cerebral cortex. The level of their activity can be determined by a person’s well-being and described using amplitude and frequency indicators. There is a fact that many connections are localized in areas that are involved in complex processes. In addition to the above, the human cerebral cortex is not considered complete in its structure and develops throughout the entire period of life in the process of forming human intelligence. When receiving and processing information signals that enter the brain, a person is provided with reactions of a physiological, behavioral, and mental nature due to the functions of the cerebral cortex. These include:

The interaction of organs and systems in the body with the environment and with each other, the proper course of metabolic processes.
Proper reception and processing of information signals, their awareness through mental processes.
Maintaining the interconnection of the different tissues and structures that make up the organs in the human body.
Education and functioning of consciousness, intellectual and creative work of the individual.
Control over speech activity and processes that are associated with psycho-emotional situations.

It is necessary to say about the incomplete study of the place and significance of the anterior parts of the cerebral cortex in ensuring the functioning of the human body. It is known about such zones that they are low susceptibility to external influences. For example, the impact of an electrical impulse on these areas does not manifest itself in bright reactions. According to some scientists, their functions are self-awareness, the presence and nature of specific features. People with lesions in the anterior cortex have problems with socialization, they lose interest in the world of work, and they lack attention to their appearance and the opinions of others. Other possible effects:

loss of ability to concentrate;
creative skills are partially or completely lost;
deep psycho-emotional disorders of the individual.

Layers of bark

The functions performed by the cortex are often determined by the structure of the structure. The structure of the cerebral cortex is distinguished by its characteristics, which are expressed in a different number of layers, sizes, topography and structure of the nerve cells that form the cortex. Scientists distinguish several different types of layers, which, interacting with each other, contribute to the complete functioning of the system:

molecular layer: it creates a large number of chaotically woven dendritic formations with a small content of spindle-shaped cells that are responsible for associative functioning;
outer layer: expressed by a large number of neurons, which have a varied shape and high content. Behind them are the outer limits of the structures, shaped like a pyramid;
the outer layer is pyramidal in appearance: it contains neurons of small and significant dimensions while the larger ones are located deeper. These cells resemble a cone in shape; a dendrite extends from the top point, which has maximum dimensions; neurons containing gray matter are connected through division into small formations. As they approach the cerebral cortex, the branches are thin and form a structure resembling a fan;
the inner layer is granular in appearance: it contains nerve cells that are small in size, located at a certain distance, between them there are grouped structures of a fibrous appearance;
inner layer of pyramidal type: includes neurons that have medium and large dimensions. The upper ends of the dendrites can reach the molecular layer;
a covering that contains spindle-shaped neuron cells. It is characteristic of them that the part of them that is at the lowest point can reach the level of the white matter.

The various layers that the cerebral cortex includes differ from each other in shape, location and purpose of the elements of their structure. The combined action of neurons in the form of a star, pyramid, spindle and branched species between various layers forms more than 50 fields. Despite the fact that there are no clear limits for the fields, their interaction makes it possible to regulate a large number of processes that are associated with the reception of nerve impulses, information processing and the formation of a counter reaction to stimuli.

The structure of the cerebral cortex is quite complex and has its own characteristics, expressed in a different number of covers, dimensions, topography and structure of cells that form layers.

Cortical areas

The localization of functions in the cerebral cortex is viewed differently by many experts. But most researchers have come to the conclusion that the cerebral cortex can be divided into several main areas, which include cortical fields. Based on the functions performed, this structure of the cerebral cortex is divided into 3 areas:

Area associated with pulse processing

This area is associated with the processing of impulses that come through receptors from the visual system, smell, and touch. The main part of the reflexes that are associated with motor skills is provided by pyramidal-shaped cells. The area responsible for receiving muscle information has a smooth interaction between the various layers of the cerebral cortex, which plays a special role at the stage of proper processing of incoming impulses. When the cerebral cortex is damaged in this area, it provokes disorders in the well-functioning sensory functions and actions that are inextricable from motor skills. Externally, malfunctions in the motor department can manifest themselves with involuntary movements, convulsive twitching, and severe forms leading to paralysis.

Sensory zone

This area is responsible for processing signals that enter the brain. By its structure, it is a system of interaction between analyzers in order to establish feedback on the effect of the stimulant. Scientists have identified several areas that are responsible for sensitivity to impulses. These include the occipital, which provides visual processing; The temporal lobe is associated with hearing; hippocampal area - with the sense of smell. The area that is responsible for processing information from taste stimulants is located near the crown of the head. There, the centers responsible for receiving and processing tactile signals are localized. Sensory ability directly depends on the number of neural connections in a given area. Approximately these zones can occupy up to 1/5 of the total size of the cortex. Damage to such a zone will lead to incorrect perception, which will not make it possible to produce a counter signal adequate to the stimulus influencing it. For example, a malfunction in the auditory zone does not always provoke deafness, but can cause certain effects that distort the proper perception of information. This is expressed in the inability to grasp the length or frequency of a sound, its duration and timbre, failures in recording effects with a short duration of action.

Association zone

This zone makes possible contact between the signals that are received by neurons in the sensory part and motor activity, which is a counter reaction. This department forms meaningful reflexes of behavior, participates in ensuring their actual implementation, and is largely covered by the cerebral cortex. According to the areas of location, the anterior sections are distinguished, which are located near the frontal parts, and the posterior sections, occupying the space between the temples, crown and back of the head. Humans are characterized by a strong development of the posterior parts of the areas of associative perception. These centers are important in ensuring the implementation and processing of speech activity. Damage to the anterior associative area provokes disruptions in the ability to perform analytical functions, forecasting, based on facts or early experience. A malfunction in the posterior association zone complicates orientation in space, slows down abstract three-dimensional thinking, construction and proper interpretation of difficult visual models.

Features of neurological diagnostics

In the process of neurological diagnostics, much attention is paid to movement and sensitivity disorders. Therefore, it is much easier to detect malfunctions in the conductive ducts and initial zones than damage to the associative cortex. It must be said that neurological symptoms may be absent even with extensive damage to the frontal, parietal or temporal area. It is necessary that the assessment of cognitive functions be as logical and consistent as neurological diagnostics.

This type of diagnosis is aimed at fixed relationships between the function of the cerebral cortex and structure. For example, during the period of damage to the striate cortex or optic tract, in the vast majority of cases there is contralateral homonymous hemianopia. In a situation where the sciatic nerve is damaged, the Achilles reflex is not observed.

Initially, it was believed that the functions of the associative cortex could operate in this way. There was an assumption that there are centers of memory, spatial perception, word processing, therefore, through special tests it is possible to determine the localization of damage. Later, opinions emerged regarding distributed neural systems and the functional orientation within their boundaries. These ideas suggest that distributed systems are responsible for the complex cognitive functions of the cortex - intricate neural circuits, within which cortical and subcortical formations are located.

Consequences of damage

Experts have proven that due to the interconnection of neural structures with each other, in the process of damage to one of the above areas, partial or complete functioning of other structures is observed. As a result of incomplete loss of the ability to perceive, process information or reproduce signals, the system is capable of remaining operational for a certain period of time, having limited functions. This can happen due to the restoration of relationships between undamaged areas of neurons using the distribution system method.

But there is a possibility of the opposite effect, during which damage to one of the parts of the cortex leads to impairment of a number of functions. Be that as it may, a failure in the normal functioning of such an important organ is considered a dangerous deviation, the formation of which should promptly seek help from doctors in order to avoid the subsequent development of disorders. The most dangerous malfunctions in the functioning of such a structure include atrophy, which is associated with the aging and death of some neurons.

The most commonly used examination methods by people are CT and MRI, encephalography, diagnostics using ultrasound, X-rays and angiography. It must be said that current research methods make it possible to detect pathology in the functioning of the brain at a preliminary stage, if you consult a doctor in time. Depending on the type of disorder, it is possible to restore damaged functions.

The cerebral cortex is responsible for brain activity. This leads to changes in the structure of the human brain itself, since its functioning has become much more complex. On top of the brain zones associated with the sensory organs and the motor system, zones were formed that were very densely endowed with associative fibers. Such areas are needed for complex processing of information received by the brain. As a result of the formation of the cerebral cortex, the next stage comes, at which the role of its work increases sharply. The human cerebral cortex is an organ that expresses individuality and conscious activity.

The central nervous system is the part of the body responsible for our perception of the outside world and ourselves. It regulates the functioning of the entire body and, in fact, is the physical substrate of what we call “I”. The main organ of this system is the brain. Let's look at how the parts of the brain are structured.

Functions and structure of the human brain

This organ is primarily made up of cells called neurons. These nerve cells produce electrical impulses that enable the nervous system to function.

The work of neurons is ensured by cells called neuroglia - they make up almost half of the total number of cells in the central nervous system.

Neurons, in turn, consist of a body and processes of two types: axons (transmitting impulses) and dendrites (receiving impulses). The bodies of nerve cells form a tissue mass, which is commonly called gray matter, and their axons are woven into nerve fibers and represent white matter.

Over the course of evolution, the brain has become one of the most important organs in the entire body. Occupying only one fiftieth of the total body weight, it consumes a fifth of all oxygen entering the blood.

To protect it, nature has created a whole arsenal of various means. Externally, the parts of the brain are protected by the cranium, under which there are three more membranes of the brain:

Solid. It is a thin film, one side adjacent to the bone tissue of the skull, and the other directly to the cortex.
Soft. It consists of loose tissue and tightly envelops the surface of the hemispheres, going into all the cracks and grooves. Its function is to supply blood to the organ.
Arachnoid. It is located between the first and second membranes and exchanges cerebrospinal fluid (cerebrospinal fluid). Liquor is a natural shock absorber that protects the brain from damage when moving.

Next, let's take a closer look at how the human brain works. According to morpho-functional characteristics, the brain is also divided into three parts. The lowermost section is called rhomboid. Where the rhomboid part begins, the spinal cord ends - it passes into the medulla oblongata and posterior (pons and cerebellum).

Next comes the midbrain, which unites the lower parts with the main nerve center - the anterior section. The latter includes the telencephalon (cerebral hemispheres) and diencephalon. The key functions of the cerebral hemispheres are the organization of higher and lower nervous activity.

Finite brain

This part has the largest volume (80%) compared to the rest. It consists of two cerebral hemispheres, the corpus callosum connecting them, and the olfactory center.

The large hemispheres of the brain, left and right, are responsible for the formation of all thought processes. Here there is the greatest concentration of neurons and the most complex connections between them are observed. In the depths of the longitudinal groove, which divides the hemispheres, there is a dense concentration of white matter - the corpus callosum. It consists of complex plexuses of nerve fibers that intertwine different parts of the nervous system.

Within the white matter are clusters of neurons called the basal ganglia. The close location to the “transport junction” of the brain allows these formations to regulate muscle tone and carry out instant reflex-motor reactions. In addition, the basal ganglia are responsible for the formation and operation of complex automatic actions, partially repeating the functions of the cerebellum.

Cortex

This small superficial layer of gray matter (up to 4.5 mm) is the youngest formation in the central nervous system. It is the cerebral cortex that is responsible for the work of higher nervous activity in humans.

Research has made it possible to determine which areas of the cortex were formed relatively recently during evolutionary development, and which were present in our prehistoric ancestors:

neocortex - the new outer part of the cortex, which is its main part;
archicortex - an older formation responsible for human instinctive behavior and emotions;
The paleocortex is the most ancient area involved in the control of autonomic functions. In addition, it helps maintain the internal physiological balance of the body.

Despite its seemingly small volume, the cerebral cortex has an area of about four square meters.

This is possible thanks to the convolutions and grooves, which in addition also divide the hemispheres into lobes, each of which has different functions:

Frontal lobes

The largest lobes of the cerebral hemispheres, responsible for complex motor functions. In the frontal lobes of the brain, planning of voluntary movements occurs, and speech centers are also located here. It is in this part of the cortex that volitional control of behavior is exercised. If the frontal lobes are damaged, a person loses control over his actions, behaves antisocially and simply inappropriately.

Occipital lobes

Closely related to visual function, they are responsible for the processing and perception of optical information. That is, they transform the entire set of light signals that enter the retina into meaningful visual images.

Parietal lobes

They carry out spatial analysis and process most sensations (touch, pain, “muscle feeling”). In addition, it promotes the analysis and integration of various information into structured fragments - the ability to feel one’s own body and its sides, the ability to read, count and write.

Temporal lobes

In this department, audio information is analyzed and processed, which ensures the function of hearing and the perception of sounds. The temporal lobes are involved in recognizing the faces of different people, as well as facial expressions and emotions. Here information is structured for permanent storage, and thus long-term memory is realized.

In addition, the temporal lobes contain speech centers, damage to which leads to the inability to perceive spoken language.

Insula

It is considered responsible for the formation of consciousness in a person. In moments of compassion, empathy, listening to music and the sounds of laughter and crying, active work of the insular lobe is observed. This is also where the processing of feelings of aversion to dirt and unpleasant odors, including imaginary stimuli, takes place.

Diencephalon

The diencephalon serves as a kind of filter for neural signals - it receives all incoming information and decides where it should go. Consists of the lower and posterior parts (thalamus and epithalamus). In this department, the endocrine function is also realized, i.e. hormonal metabolism.

The lower part consists of the hypothalamus. This small, dense bundle of neurons has a tremendous impact on the entire body. In addition to regulating body temperature, the hypothalamus controls sleep and wake cycles. It also releases hormones that are responsible for the sensations of hunger and thirst. As a pleasure center, the hypothalamus regulates sexual behavior.

It is also directly connected to the pituitary gland and converts nervous activity into endocrine activity. The functions of the pituitary gland, in turn, are to regulate the functioning of all glands of the body. Electrical signals go from the hypothalamus to the pituitary gland of the brain, “ordering” the production of which hormones should be started and which ones should be stopped.

The diencephalon also includes:

Thalamus - it is this part that performs the functions of a “filter”. Here, signals coming from visual, auditory, taste and tactile receptors undergo primary processing and are distributed to the appropriate departments.
Epithalamus - produces the hormone melatonin, which regulates wakefulness cycles, participates in the process of puberty, and controls emotions.

Midbrain

First of all, it regulates auditory and visual reflex activity (constriction of the pupil in bright light, turning the head towards a source of loud sound, etc.). After processing in the thalamus, the information goes to the midbrain.

Here its further processing takes place and the process of perception begins, the formation of a meaningful sound and optical image. In this department, eye movements are synchronized and binocular vision is ensured.

The midbrain includes the peduncles and quadrigeminal region (two auditory and two visual colliculi). Inside there is a cavity of the midbrain that unites the ventricles.

Medulla

This is an ancient formation of the nervous system. The functions of the medulla oblongata are to ensure breathing and heartbeat. If this area is damaged, the person dies - oxygen stops flowing into the blood, which is no longer pumped by the heart. In the neurons of this department, protective reflexes such as sneezing, blinking, coughing and vomiting begin.

The structure of the medulla oblongata resembles an elongated onion. It contains the nuclei of gray matter: the reticular formation, the nuclei of several cranial nerves, as well as neural ganglia. The pyramid of the medulla oblongata, consisting of pyramidal nerve cells, performs a conducting function, uniting the cerebral cortex and the spinal region.

The most important centers of the medulla oblongata:

breathing regulation
regulation of blood circulation
regulation of a number of functions of the digestive system

Hindbrain: pons and cerebellum

The structure of the hindbrain includes the pons and the cerebellum. The function of the bridge is very similar to its name, since it consists mainly of nerve fibers. The cerebral pons is essentially a “highway” through which signals travel from the body to the brain and impulses travel from the nerve center to the body. Along the ascending pathways, the brain bridge passes into the midbrain.

The cerebellum has a much wider range of capabilities. The functions of the cerebellum are to coordinate body movements and maintain balance. Moreover, the cerebellum not only regulates complex movements, but also contributes to the adaptation of the motor system to various disorders.

For example, experiments using an invertoscope (special glasses that invert the image of the surrounding world) have shown that it is the functions of the cerebellum that are responsible for the fact that when wearing the device for a long time, a person not only begins to navigate in space, but also sees the world correctly.

Anatomically, the cerebellum follows the structure of the cerebral hemispheres. The outside is covered with a layer of gray matter, under which there is an accumulation of white matter.

Limbic system

The limbic system (from the Latin word limbus - edge) is a set of formations surrounding the upper part of the trunk. The system includes the olfactory centers, hypothalamus, hippocampus and reticular formation.

The main functions of the limbic system are the body's adaptation to changes and the regulation of emotions. This education promotes the creation of lasting memories through associations between memory and sensory experiences. The close connection between the olfactory tract and the emotional centers is why smells evoke such strong and clear memories in us.

If we list the main functions of the limbic system, then it is responsible for the following processes:

Smell
Communication
Memory: short-term and long-term
Restful sleep
Performance of departments and bodies
Emotions and motivational component
Intellectual activity
Endocrine and vegetative
Partially involved in the formation of food and sexual instinct

CORTEX (cortex brain) - all surfaces of the cerebral hemispheres, covered with a cloak (pallium) formed by gray matter. Together with other departments of the c. n. With. the cortex is involved in the regulation and coordination of all functions of the body, plays an extremely important role in mental or higher nervous activity (see).

In accordance with the stages of evolutionary development of c. n. With. The bark is divided into old and new. The old cortex (archicortex - the actual old cortex and paleocortex - the ancient cortex) is a phylogenetically more ancient formation than the new cortex (neocortex), which appeared during the development of the cerebral hemispheres (see Architectonics of the cerebral cortex, Brain).

Morphologically, K. g. m. is formed by nerve cells (see), their processes and neuroglia (see), which has a supporting-trophic function. In primates and humans, the cortex contains approx. 10 billion neurocytes (neurons). Depending on their shape, pyramidal and stellate neurocytes are distinguished, which are characterized by great diversity. The axons of pyramidal neurocytes are directed into the subcortical white matter, and their apical dendrites are directed into the outer layer of the cortex. Stellate neurocytes have only intracortical axons. Dendrites and axons of stellate neurocytes branch abundantly near the cell bodies; Some of the axons approach the outer layer of the cortex, where they, following horizontally, form a dense plexus with the apices of the apical dendrites of pyramidal neurocytes. Along the surface of the dendrites there are kidney-shaped outgrowths, or spines, which represent the area of axodendritic synapses (see). The cell body membrane is the region of axosomatic synapses. Each area of the cortex has many input (afferent) and output (efferent) fibers. Efferent fibers go to other areas of the K. g. m., to subcortical formations or to the motor centers of the spinal cord (see). Afferent fibers enter the cortex from cells of subcortical structures.

The ancient cortex in humans and higher mammals consists of a single cell layer, poorly differentiated from the underlying subcortical structures. Actually, the old bark consists of 2-3 layers.

The new cortex has a more complex structure and occupies (in humans) approx. 96% of the entire surface of the K. g. m. Therefore, when they talk about the K. g. m., they usually mean the new cortex, which is divided into the frontal, temporal, occipital and parietal lobes. These lobes are divided into regions and cytoarchitectonic fields (see Architectonics of the cerebral cortex).

The thickness of the cortex in primates and humans varies from 1.5 mm (on the surface of the gyri) to 3-5 mm (in the depth of the sulci). Nissl-stained sections show a layered structure of the cortex, which depends on the grouping of neurocytes at its different levels (layers). It is customary to distinguish 6 layers in the bark. The first layer is poor in cell bodies; the second and third - contain small, medium and large pyramidal neurocytes; the fourth layer is the zone of stellate neurocytes; the fifth layer contains giant pyramidal neurocytes (giant pyramidal cells); the sixth layer is characterized by the presence of multiform neurocytes. However, the six-layer organization of the cortex is not absolute, since in fact, in many parts of the cortex there is a gradual and uniform transition between layers. Cells of all layers, located on the same perpendicular to the surface of the cortex, are closely connected with each other and with the subcortical formations. Such a complex is called a column of cells. Each such column is responsible for the perception of predominantly one type of sensitivity. For example, one of the columns of the cortical representation of the visual analyzer perceives the movement of an object in the horizontal plane, the neighboring one - in the vertical, etc.

Similar complexes of neocortical cells have a horizontal orientation. It is assumed that, for example, small-cell layer II and IV consist mainly of receptive cells and are “entrances” to the cortex, large-cell layer V is the “exit” from the cortex to the subcortical structures, and middle-cell layer III is associative and connects with each other. different zones of the cortex.

Thus, we can distinguish several types of direct and feedback connections between the cellular elements of the cortex and subcortical formations: vertical bundles of fibers that carry information from the subcortical structures to the cortex and back; intracortical (horizontal) bundles of associative fibers passing at various levels of the cortex and white matter.

The variability and originality of the structure of neurocytes indicate the extreme complexity of intracortical switching apparatuses and methods of connections between neurocytes. This structural feature of the K. g. m. should be considered as a morphol, the equivalent of its extreme reactivity and functionality, plasticity, providing it with higher nervous functions.

The increase in the mass of cortical tissue occurred in a limited space of the skull, so the surface of the cortex, smooth in lower mammals, was transformed into convolutions and grooves in higher mammals and humans (Fig. 1). It was with the development of the cortex that already in the last century scientists associated such aspects of brain activity as memory (q.v.), intelligence, consciousness (q.v.), thinking (q.v.), etc.

I. P. Pavlov defined 1870 as the year “from which scientific fruitful work on the study of the cerebral hemispheres begins.” This year, Fritsch and Hitzig (G. Fritsch, E. Hitzig, 1870) showed that electrical stimulation of certain areas of the anterior section of the canine muscle causes contraction of certain groups of skeletal muscles. Many scientists believed that when the brain is irritated, the “centers” of voluntary movements and motor memory are activated. However, even C. Sherrington preferred to avoid the functional interpretation of this phenomenon and limited himself to only the statement that the area of the cortex, irritation of the cut causes a contraction of muscle groups, is intimately connected with the spinal cord.

The directions of experimental research of K. g.m. of the end of the last century were almost always associated with problems of wedge, neurology. On this basis, experiments were begun with partial or complete decortication of the brain (see). Goltz (F. L. Goltz, 1892) was the first to perform complete decortication in a dog. The decorticated dog turned out to be viable, but many of its most important functions were severely impaired - vision, hearing, orientation in space, coordination of movements, etc. Before I. P. Pavlov discovered the phenomenon of the conditioned reflex (see), the interpretation of experiments with both complete and partial extirpations of the cortex suffered from the lack of an objective criterion for their evaluation. The introduction of the conditioned reflex method into the practice of experiments with extirpations opened a new era in the study of the structural and functional organization of blood cells.

Simultaneously with the discovery of the conditioned reflex, the question arose about its material structure. Since the first attempts to develop a conditioned reflex in decorticated dogs failed, I. P. Pavlov came to the conclusion that the coronary gland is the “organ” of conditioned reflexes. However, further research showed the possibility of developing conditioned reflexes in decorticated animals. It was found that conditioned reflexes are not disturbed by vertical transections of various areas of the cerebral cortex and their separation from subcortical formations. These facts, along with electrophysiological data, gave reason to consider the conditioned reflex as a result of the formation of a multichannel connection between various cortical and subcortical structures. The shortcomings of the extirpation method for studying the significance of K. g.m. in the organization of behavior prompted the development of methods for reversible, functional, shutdown of the cortex. Buresh and Bureshova (J. Bures, O. Buresova, 1962) applied the phenomenon of the so-called. spreading depression by applying potassium chloride or other irritants to one or another part of the cortex. Since depression does not spread through the furrows, this method can only be used on animals with a smooth surface of the K. g. m. (rats, mice).

Another way to function, turn off the K.G.M. is its cooling. The method developed by N. Yu. Belenkov et al. (1969), is that in accordance with the shape of the surface of the cortical areas planned for switching off, capsules are made that are implanted above the dura mater; During the experiment, a cooled liquid is passed through the capsule, as a result of which the temperature of the cortex under the capsule decreases to 22-20°. Removal of biopotentials using microelectrodes shows that at this temperature the impulse activity of neurons stops. The method of cold decortication, used in chronic experiments on animals, demonstrated the effect of emergency shutdown of the neocortex. It turned out that such a shutdown stops the implementation of previously developed conditioned reflexes. Thus, it was shown that the K. g. m. is a necessary structure for the manifestation of a conditioned reflex in the intact brain. Consequently, the observed facts of the development of conditioned reflexes in surgically decorticated animals are the result of compensatory changes that occur in the time interval from the moment of surgery to the beginning of the study of the animal in the chronic experiment. Compensatory phenomena also occur in the case of functional shutdowns of the neocortex. Just like cold shutdown, acute shutdown of the neocortex in rats by spreading depression dramatically disrupts conditioned reflex activity.

A comparative assessment of the effects of complete and partial decortication in various animal species showed that monkeys tolerate these operations more severely than cats and dogs. The degree of dysfunction during extirpation of the same cortical zones is different in animals at different stages of evolutionary development. For example, removal of the temporal regions in cats and dogs impairs hearing function less than in monkeys. Similarly, after removal of the occipital cortex, vision is affected more in monkeys than in cats and dogs. Based on these data, the idea of corticolization of functions in the process of evolution of c. n. p., according to Krom, phylogenetically earlier links of the nervous system move to a lower level of the hierarchy. At the same time, K. g.m. plastically rearranges the functioning of these phylogenetically older structures in accordance with the influence of the environment.

Cortical projections of the afferent systems of the brain are specialized terminal stations of the pathways from the sensory organs. From the K. g. m. to the motor neurons of the spinal cord as part of the pyramidal tract there are efferent pathways. They originate primarily from the motor area of the cortex, the edges of primates and humans are represented by the anterior central gyrus, located anterior to the central sulcus. Posterior to the central sulcus is the somatosensory area K. g. m. - the posterior central gyrus. Individual areas of skeletal muscle are corticolized to varying degrees. The lower limbs and trunk are represented least differentiated in the anterior central gyrus; a large area is occupied by the muscles of the hand. An even larger area corresponds to the muscles of the face, tongue and larynx. In the posterior central gyrus, afferent projections of body parts are represented in the same ratio as in the anterior central gyrus. We can say that the organism is, as it were, projected into these convolutions in the form of an abstract “homunculus”, which is characterized by an extreme preponderance in favor of the anterior segments of the body (Fig. 2 and 3).

In addition, the cortex includes associative, or nonspecific, areas that receive information from receptors that perceive stimuli of various modalities, and from all projection zones. The phylogenetic development of K. g.m. is characterized primarily by the growth of associative zones (Fig. 4) and their separation from projection zones. In lower mammals (rodents), almost the entire cortex consists of projection zones alone, which simultaneously perform associative functions. In humans, projection zones occupy only a small part of the cortex; everything else is reserved for associative zones. It is assumed that associative zones play a particularly important role in the implementation of complex forms. n. d.

In primates and humans, the frontal (prefrontal) region reaches the greatest development. This is phylogenetically the youngest structure, directly related to the highest mental functions. However, attempts to project these functions onto individual areas of the frontal cortex are unsuccessful. Obviously, any part of the frontal cortex can be involved in any of the functions. The effects observed when various parts of this area are destroyed are relatively short-lived or often completely absent (see Lobectomy).

The association of individual structures of the blood muscle with certain functions, considered as a problem of localization of functions, remains to this day one of the most difficult problems of neurology. Noting that in animals, after the removal of the classical projection zones (auditory, visual), conditioned reflexes to the corresponding stimuli are partially preserved, I. P. Pavlov hypothesized the existence of a “core” of the analyzer and its elements, “scattered” throughout the brain. Using microelectrode research methods (see), it was possible to register in various areas of the brain the activity of specific neurocytes that respond to stimuli of a certain sensory modality. Superficial removal of bioelectric potentials reveals the distribution of primary evoked potentials over significant areas of the brain, outside the corresponding projection zones and cytoarchitectonic fields. These facts, along with the multi-functionality of disturbances when any sensory area is removed or its reversible shutdown, indicate multiple representation of functions in the circulatory system. Motor functions are also distributed over large areas of the circulatory system. Thus, neurocytes, the processes of which form a pyramidal tract, are located not only in the motor areas, but also beyond them. In addition to sensory and motor cells, in the K. g. m. there are also intermediate cells, or interneurocytes, which make up the bulk of the K. g. m. and concentrated hl. arr. in associative areas. Multimodal excitations converge on interneurocytes.

Experimental data indicate, therefore, the relativity of the localization of functions in the K. g.m., the absence of cortical “centers” reserved for one or another function. The least differentiated in functional terms are the associative areas, which have especially pronounced properties of plasticity and interchangeability. This, however, does not imply that the associative regions are equipotential. The principle of equipotentiality of the cortex (equivalence of its structures), expressed by K. S. Lashley in 1933 based on the results of extirpations of the poorly differentiated rat cortex, in general cannot be extended to the organization of cortical activity in higher animals and humans. I. P. Pavlov contrasted the principle of equipotentiality with the concept of dynamic localization of functions in quantum mechanics.

The solution to the problem of the structural and functional organization of the K. g. m. is in many ways difficult to identify the localization of symptoms of extirpations and stimulation of certain cortical zones with the localization of the functions of the K. g. m. This question concerns the methodological aspects of neurophysiology, experiment, since from a dialectical point From our point of view, any structural and functional unit in the form in which it appears in each given study is a fragment, one of the aspects of the existence of the whole, a product of the integration of brain structures and connections. For example, the position that the function of motor speech is “localized” in the inferior frontal gyrus of the left hemisphere is based on the results of damage to this structure. At the same time, electrical stimulation of this “center” of speech never causes an act of articulation. It turns out, however, that the utterance of entire phrases can be caused by stimulation of the rostral thalamus, which sends afferent impulses to the left hemisphere. Phrases caused by such stimulation have nothing to do with voluntary speech and are not adequate to the situation. This highly integrated stimulation effect suggests that ascending afferent impulses are transformed into a neuronal code effective for the higher coordination mechanism of motor speech. In the same way, complexly coordinated movements caused by irritation of the motor area of the cortex are organized not by those structures that are directly exposed to irritation, but by neighboring or spinal and extrapyramidal systems excited along descending pathways. These data show that there is a close connection between the cortex and subcortical formations. Therefore, cortical mechanisms cannot be opposed to the work of subcortical structures, but specific cases of their interaction must be considered.

With electrical stimulation of individual cortical areas, the activity of the cardiovascular system, respiratory system, and gastrointestinal tract changes. tract and other visceral systems. K. M. Bykov also substantiated the influence of K. g. m. on internal organs by the possibility of the formation of visceral conditioned reflexes, which, along with vegetative shifts during various emotions, was the basis for the concept of the existence of cortico-visceral relations. The problem of cortico-visceral relations is solved in terms of studying the modulation by the cortex of the activity of subcortical structures that are directly related to the regulation of the internal environment of the body.

A significant role is played by the connections of K. g. m. with the hypothalamus (see).

The level of activity of K. g. m. is mainly determined by ascending influences from the reticular formation (see) of the brain stem, which is controlled by corticofugal influences. The effect of the latter is dynamic in nature and is a consequence of the current afferent synthesis (see). Studies using electroencephalography (see), in particular corticography (i.e., the removal of biopotentials directly from the K. g.m.), would seem to confirm the hypothesis about the closure of the temporary connection between the foci of excitations arising in the cortical projections of the signal and unconditioned stimuli in the process of formation of a conditioned reflex. However, it turned out that as the behavioral manifestations of the conditioned reflex become stronger, the electrographic signs of the conditioned connection disappear. This crisis of the electroencephalography technique in understanding the mechanism of the conditioned reflex was overcome in the studies of M. N. Livanov et al. (1972). They showed that the spread of excitation along the K. g.m. and the manifestation of the conditioned reflex depends on the level of distant synchronization of biopotentials removed from spatially distant points of the K. g.m. An increase in the level of spatial synchronization is observed with mental stress (Fig. 5). In this state, areas of synchronization are not concentrated in certain areas of the cortex, but are distributed over its entire area. Correlation relationships cover points throughout the frontal cortex, but at the same time, increased synchrony is also recorded in the precentral gyrus, in the parietal region, and in other areas of the brain muscle.

The brain consists of two symmetrical parts (hemispheres), interconnected by commissures consisting of nerve fibers. Both hemispheres of the brain are united by the largest commissure - the corpus callosum (see). Its fibers connect identical points of the circulatory system. The corpus callosum ensures the unity of the functioning of both hemispheres. When it is cut, each hemisphere begins to function independently of one another.

In the process of evolution, the human brain acquired the property of lateralization, or asymmetry (see). Each hemisphere was specialized to perform certain functions. In most people, the left hemisphere is dominant, providing speech function and control of the action of the right hand. The right hemisphere is specialized for the perception of shape and space. At the same time, the functional differentiation of the hemispheres is not absolute. However, extensive damage to the left temporal lobe is usually accompanied by sensory and motor speech impairments. It is obvious that lateralization is based on innate mechanisms. However, the potential capabilities of the right hemisphere in organizing speech function can manifest themselves when the left hemisphere is damaged in newborns.

There are reasons to consider lateralization as an adaptive mechanism that developed as a result of the complication of brain functions at the highest stage of its development. Lateralization prevents the interference of different integrative mechanisms over time. It is possible that cortical specialization counteracts the incompatibility of various functional systems (see), facilitates decision-making about the goal and method of action. The integrative activity of the brain is not limited, i.e., to external (summative) integrity, understood as the interaction of the activities of independent elements (whether neurocytes or entire brain formations). Using the example of the development of lateralization, one can see how this holistic, integrative activity of the brain itself becomes a prerequisite for differentiating the properties of its individual elements, endowing them with functionality and specificity. Consequently, the functional contribution of each individual structure of the brain cannot, in principle, be assessed in isolation from the dynamics of the integrative properties of the whole brain.

Pathology

The cerebral cortex is rarely affected in isolation. Signs of its damage, to a greater or lesser extent, usually accompany brain pathology (see) and are part of its symptoms. Usually patol, the processes affect not only K. g. m., but also the white matter of the hemispheres. Therefore, the pathology of K. g.m. is usually understood as its predominant lesion (diffuse or local, without a strict boundary between these concepts). The most extensive and intense lesion of the K. g. m. is accompanied by the disappearance of mental activity, a complex of both diffuse and local symptoms (see Apallic syndrome). Along with neurol, symptoms of damage to the motor and sensory spheres, symptoms of damage to various analyzers in children are a delay in speech development and even the complete impossibility of mental development. In K. g.m., changes in cytoarchitectonics are observed in the form of disruption of layering, up to its complete disappearance, foci of loss of neurocytes with their replacement by glial growths, heterotopia of neurocytes, pathology of the synaptic apparatus and other pathomorphological changes. Lesions of K. g. m. are observed with various congenital anomalies of the brain in the form of anencephaly, microgyria, microcephaly, with various forms of oligophrenia (see), as well as with a variety of infections and intoxications with damage to the nervous system, with traumatic brain injuries, with hereditary and degenerative brain diseases, cerebrovascular accidents, etc.

Studying the EEG when localizing patol, a focus in K. g. m. more often reveals the predominance of focal slow waves, which are considered as a correlate of protective inhibition (W. Walter, 1966). Weak expression of slow waves in the area of the patol lesion is a useful diagnostic sign in the preoperative assessment of the condition of patients. As studies by N.P. Bekhtereva (1974), conducted jointly with neurosurgeons, showed, the absence of slow waves in the area of pathol, the focus is an unfavorable prognostic sign of the consequences of surgical intervention. To assess patol, the state of K. g.m., a test for the interaction of the EEG in the zone of focal lesion with evoked activity in response to positive and differentiating conditioned stimuli is also used. The bioelectric effect of such interaction can be both an increase in focal slow waves, and a weakening of their severity or an increase in frequent oscillations such as pointed beta waves.

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N. Yu. Belenkov.