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

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

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

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

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

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

The structure of the cerebral cortex

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

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

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

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

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

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

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

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

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

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

Areas of the cerebral cortex

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

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

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

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

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

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

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

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

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

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

Functions of the frontal lobe:

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

Composition of the cerebral cortex

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

Rice. 2. The cerebral cortex

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

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

A layer of pyramidal cells of small size.

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

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

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

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

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

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

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

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

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

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

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

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

The structure of the brain

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

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

Brain Functions

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

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

The cerebral cortex is 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, area 25 of the brain, as well as fields 12-16, 26, 27, 29-31 and many others) have not been fully studied.

Speech motor zone

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

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

Thickness

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

The cerebral cortex is part of most creatures on earth, but it is in humans that this area has reached the greatest development. Experts say that this contributed to the age-old labor activity that accompanies us throughout our lives.

In this article, we will look at the structure, as well as what the cerebral cortex is responsible for.

The cortical part of the brain plays the main functioning role for the human body as a whole and consists of neurons, their processes and glial cells. The cortex consists of stellate, pyramidal and spindle-shaped nerve cells. Due to the presence of warehouses, the cortical area occupies a fairly large surface.

The structure of the cerebral cortex includes a layered classification, which is divided into the following layers:

• Molecular. It has distinctive differences, which is reflected in the low cellular level. A low number of these cells, consisting of fibers, are closely interconnected
• External granular. The cellular substances of this layer are sent to the molecular layer
• layer of pyramidal neurons. It is the widest layer. Reached the greatest development in the precentral gyrus. The number of pyramidal cells increases within 20-30 microns from the outer zone of this layer to the inner
• Internal granular. Directly the visual cortex of the brain is the area where the inner granular layer has reached its maximum development.
• Internal pyramidal. It consists of large pyramidal cells. These cells are carried down to the molecular layer
• Layer of multimorphic cells. This layer is formed by nerve cells of a different nature, but mostly of a spindle-shaped type. The outer zone is characterized by the presence of larger cells. The cells of the internal section are characterized by a small size

If we consider the layered level more carefully, we can see that the cerebral cortex of the cerebral hemispheres takes on the projections of each of the levels occurring in different parts of the CNS.

Areas of the cerebral cortex

Features of the cellular structure of the cortical part of the brain is divided into structural units, namely: zones, fields, regions and subregions.

The cerebral cortex is classified into the following projection zones:

• Primary
• Secondary
• Tertiary

In the primary zone, certain neuron cells are located, to which a receptor impulse (auditory, visual) is constantly supplied. The secondary department is characterized by the presence of peripheral analyzer departments. The tertiary receives processed data from the primary and secondary zones, and is itself responsible for conditioned reflexes.

Also, the cerebral cortex is divided into a number of departments or zones that allow you to regulate many human functions.

Allocates the following zones:

• Sensory - areas in which the zones of the cerebral cortex are located:
  • visual
  • Auditory
  • Flavoring
  • Olfactory
• Motor. These are cortical areas, the stimulation of which can lead to certain motor reactions. They are located in the anterior central gyrus. Its damage can lead to significant motor impairment.
• Associative. These cortical regions are located next to the sensory areas. Impulses of nerve cells that are sent to the sensory zone form an exciting process of associative divisions. Their defeat entails severe impairment of the learning process and memory functions.

Functions of the lobes of the cerebral cortex

The cerebral cortex and subcortex perform a number of human functions. The lobes of the cerebral cortex themselves contain such necessary centers as:

• Motor, speech center (Broca's center). It is located in the lower region of the frontal lobe. Its damage can completely disrupt speech articulation, that is, the patient can understand what is being said to him, but cannot answer
• Auditory, speech center (Wernicke's center). Located in the left temporal lobe. Damage to this area can result in the person being unable to understand what the other person is saying, while still remaining able to express themselves. Also in this case, written speech is seriously impaired.

Speech functions are performed by sensory and motor areas. Its functions are related to written speech, namely reading and writing. The visual cortex and the brain regulate this function.

Damage to the visual center of the cerebral hemispheres leads to a complete loss of reading and writing skills, as well as to a possible loss of vision.

In the temporal lobe there is a center that is responsible for the memorization process. A patient with a lesion in this area cannot remember the names of certain things. However, he understands the very meaning and functions of the object and can describe them.

For example, instead of the word "cup", a person says: "this is where liquid is poured in order to then drink."

Pathologies of the cerebral cortex

There are a huge number of diseases that affect the human brain, including its cortical structure. Damage to the cortex leads to disruption of its key processes, and also reduces its performance.

The most common diseases of the cortical part include:

• Pick's disease. It develops in people in old age and is characterized by the death of nerve cells. At the same time, the external manifestations of this disease are almost identical to Alzheimer's disease, which can be seen at the stage of diagnosis, when the brain looks like a dried walnut. It is also worth noting that the disease is incurable, the only thing that therapy is aimed at is the suppression or elimination of symptoms.
• Meningitis. This infectious disease indirectly affects the parts of the cerebral cortex. It occurs as a result of damage to the cortex by infection with pneumococcus and a number of others. It is characterized by headaches, fever, pain in the eyes, drowsiness, nausea
• Hypertonic disease. With this disease, foci of excitation begin to form in the cerebral cortex, and outgoing impulses from this focus begin to constrict blood vessels, which leads to sharp jumps in blood pressure
• Oxygen starvation of the cerebral cortex (hypoxia). This pathological condition most often develops in childhood. It occurs due to a lack of oxygen or a violation of blood flow in the brain. Can lead to irreversible changes in neuronal tissue or death

Most pathologies of the brain and cortex cannot be determined based on the symptoms and external signs that appear. To identify them, you need to go through special diagnostic methods that allow you to explore almost any, even the most inaccessible places and subsequently determine the state of a particular area, as well as analyze its work.

The cortical area is diagnosed using various techniques, which we will discuss in more detail in the next chapter.

Conducting a survey

For high-precision examination of the cerebral cortex, methods such as:

• Magnetic resonance and computed tomography
• Encephalography
• Positron emission tomography
• Radiography

An ultrasound examination of the brain is also used, but this method is the least effective in comparison with the above methods. Of the advantages of ultrasound, the price and speed of the examination are distinguished.

In most cases, patients are diagnosed with cerebral circulation. For this, an additional series of diagnostics can be used, namely;

• Doppler ultrasound. Allows you to identify the affected vessels and changes in the speed of blood flow in them. The method is highly informative and absolutely safe for health.
• Rheoencephalography. The work of this method is to register the electrical resistance of tissues, which allows you to form a line of pulsed blood flow. Allows you to determine the state of blood vessels, their tone and a number of other data. Less informative than the ultrasonic method
• X-ray angiography. This is a standard X-ray examination, which is additionally carried out using intravenous administration of a contrast agent. Then the X-ray is taken. As a result of the spread of the substance throughout the body, all blood flows in the brain are highlighted on the screen.

These methods provide accurate information about the state of the brain, cortex and blood flow parameters. There are also other methods that are used depending on the nature of the disease, the patient's condition and other factors.

The human brain is the most complex organ, and many resources are spent on studying it. However, even in the era of innovative methods of its research, it is not possible to study certain parts of it.

The processing power of processes in the brain is so significant that even a supercomputer is not even close to the corresponding indicators.

The cerebral cortex and the brain itself are constantly being explored, as a result of which the discovery of various new facts about it becomes more and more. The most common discoveries:

• In 2017, an experiment was conducted in which a person and a supercomputer were involved. It turned out that even the most technically equipped equipment is able to simulate only 1 second of brain activity. It took 40 minutes to complete the task.
• The amount of human memory in an electronic unit of measurement of the amount of data is about 1000 terabytes.
• The human brain consists of more than 100 thousand vascular plexuses, 85 billion nerve cells. Also in the brain there are about 100 trillion. neural connections that process human memories. Thus, when learning something new, the structural part of the brain also changes.
• When a person wakes up, the brain accumulates an electric field with a power of 25 watts. This power is enough to light an incandescent lamp
• The mass of the brain is only 2% of the total mass of a person, however, the brain consumes about 16% of the energy in the body and more than 17% of oxygen
• The brain is 80% water and 60% fat. Therefore, to maintain normal brain function, a healthy diet is essential. Eat foods that contain omega-3 fatty acids (fish, olive oil, nuts) and drink the required amount of fluid daily
• Scientists have found that if a person "sits" on a diet, the brain begins to eat itself. And low levels of oxygen in the blood for several minutes can lead to undesirable consequences.
• Human forgetfulness is a natural process, and the destruction of unnecessary information in the brain allows it to remain flexible. Also, forgetfulness can occur artificially, for example, when drinking alcohol, which inhibits natural processes in the brain.

The activation of mental processes makes it possible to generate additional brain tissue that replaces the damaged one. Therefore, it is necessary to constantly develop mentally, which will significantly reduce the risk of dementia in old age.

Layer of gray matter covering the cerebral hemispheres of the cerebrum. The cerebral cortex is divided into four lobes: frontal, occipital, temporal, and parietal. The part of the cortex that covers most of the surface of the cerebral hemispheres is called the neocortex because it was formed during the final stages of human evolution. The neocortex can be divided into zones according to their functions. Different parts of the neocortex are associated with sensory and motor functions; the corresponding areas of the cerebral cortex are involved in the planning of movements (frontal lobes) or are associated with memory and perception (occipital lobes).

Cortex

Specificity. The upper layer of the cerebral hemispheres, consisting primarily of nerve cells with a vertical orientation (pyramidal cells), as well as bundles of afferent (centripetal) and efferent (centrifugal) nerve fibers. In neuroanatomical terms, it is characterized by the presence of horizontal layers that differ in width, density, shape and size of the nerve cells included in them.

Structure. The cerebral cortex is divided into a number of areas, for example, in the most common classification of cytoarchitectonic formations by K. Brodman, 11 areas and 52 fields are identified in the human cerebral cortex. Based on phylogenesis data, a new cortex, or neocortex, old, or archicortex, and ancient, or paleocortex, are distinguished. According to the functional criterion, three types of areas are distinguished: sensory areas that provide reception and analysis of afferent signals coming from specific relay nuclei of the thalamus, motor areas that have bilateral intracortical connections with all sensory areas for the interaction of sensory and motor areas, and associative areas that do not have direct afferent or efferent connections with the periphery, but associated with sensory and motor areas.

CORTEX

The surface covering the gray matter that forms the uppermost level of the brain. In an evolutionary sense, this is the newest neural formation, and approximately 9-12 billion of its cells are responsible for basic sensory functions, motor coordination and control, participation in the regulation of integrative, coordinated behavior and, most importantly, for the so-called "higher mental processes" of speech. , thinking, problem solving, etc.

CORTEX

English cerebral cortex) - the surface layer covering the cerebral hemispheres, formed mainly by vertically oriented nerve cells (neurons) and their processes, as well as bundles of afferent (centripetal) and efferent (centrifugal) nerve fibers. In addition, the cortex includes neuroglia cells.

A characteristic feature of the structure of C. g. m. is horizontal layering, due to the ordered arrangement of the bodies of nerve cells and nerve fibers. In K. m., 6 (according to some authors, 7) layers are distinguished, differing in width, arrangement density, shape and size of their constituent neurons. Due to the predominantly vertical orientation of the bodies and processes of neurons, as well as bundles of nerve fibers, K. m. has a vertical striation. For the functional organization of K. m., the vertical, columnar arrangement of nerve cells is of great importance.

The main type of nerve cells that make up the K. m. are pyramidal cells. The body of these cells resembles a cone, from the top of which one thick and long, apical dendrite departs; heading towards the surface of the K. g. m., it becomes thinner and fan-shaped divided into thinner terminal branches. Shorter basal dendrites and an axon depart from the base of the body of the pyramidal cell, heading to the white matter, located under the K. m., or branching within the cortex. The dendrites of pyramidal cells bear a large number of outgrowths, the so-called. spines, which take part in the formation of synaptic contacts with the endings of afferent fibers that come to K. m. from other sections of the cortex and subcortical formations (see Synapses). The axons of the pyramidal cells form the main efferent pathways coming from the C. g. m. The size of the pyramidal cells varies from 5-10 microns to 120-150 microns (Betz giant cells). In addition to pyramidal neurons, stellate, fusiform, and some other types of interneurons, which are involved in the reception of afferent signals and the formation of functional interneuronal connections, are part of the cgm.

Based on the peculiarities of the distribution in the layers of the cortex of nerve cells and fibers of various sizes and shapes, the entire territory of the K. g. fields that differ in their cellular structure and functional significance. The classification of cytoarchitectonic formations of K. g. m., proposed by K. Brodman, who divided the entire K. g. m. of a person into 11 regions and 52 fields, is generally accepted.

Based on the data of phylogenesis, K. g. m. is divided into new (neocortex), old (archicortex) and ancient (paleocortex). In the phylogenesis of the KGM, there is an absolute and relative increase in the territories of the new crust, with a relative decrease in the area of ​​the ancient and old. In humans, the new cortex accounts for 95.6%, while the ancient one occupies 0.6%, and the old one - 2.2% of the entire cortical territory.

Functionally, there are 3 types of areas in the cortex: sensory, motor, and associative.

Sensory (or projection) cortical zones receive and analyze afferent signals along fibers coming from specific relay nuclei of the thalamus. Sensory zones are localized in certain areas of the cortex: visual is located in the occipital (fields 17, 18, 19), auditory in the upper parts of the temporal region (fields 41, 42), somatosensory, analyzing the impulse coming from the receptors of the skin, muscles, joints, - in the region of the postcentral gyrus (fields 1, 2, 3). Olfactory sensations are associated with the function of phylogenetically older parts of the cortex (paleocortex) - the hippocampal gyrus.

The motor (motor) area - field 4 according to Brodman - is located on the precentral gyrus. The motor cortex is characterized by the presence in layer V of giant Betz pyramidal cells, the axons of which form the pyramidal tract, the main motor tract descending to the motor centers of the brain stem and spinal cord and providing cortical control of voluntary muscle contractions. The motor cortex has bilateral intracortical connections with all sensory areas, which ensures close interaction between sensory and motor areas.

association areas. The human cerebral cortex is characterized by the presence of a vast territory that does not have direct afferent and efferent connections with the periphery. These areas, connected through an extensive system of associative fibers with sensory and motor areas, are called associative (or tertiary) cortical areas. In the posterior cortex, they are located between the parietal, occipital, and temporal sensory areas, and in the anterior, they occupy the main surface of the frontal lobes. The associative cortex is either absent or poorly developed in all mammals up to primates. In humans, the posterior associative cortex occupies about half, and the frontal regions a quarter of the entire surface of the cortex. In terms of structure, they are distinguished by a particularly powerful development of the upper associative layers of cells in comparison with the system of afferent and efferent neurons. Their feature is also the presence of polysensory neurons - cells that perceive information from various sensory systems.

In the associative cortex there are also centers associated with speech activity (see Broca's center and Wernicke's center). Associative areas of the cortex are considered as structures responsible for the synthesis of incoming information, and as an apparatus necessary for the transition from visual perception to abstract symbolic processes.

Clinical neuropsychological studies show that damage to the posterior associative areas disrupts complex forms of orientation in space, constructive activity, makes it difficult to perform all intellectual operations that are carried out with the participation of spatial analysis (counting, perception of complex semantic images). With the defeat of speech zones, the ability to perceive and reproduce speech is impaired. Damage to the frontal areas of the cortex leads to the impossibility of implementing complex behavioral programs that require the selection of significant signals based on past experience and foreseeing the future. See Blocks of the brain, Cortpicalization, Brain, Nervous system, Development of the cerebral cortex, Neuro-psychological syndromes. (D. A. Farber.)