Cerebral cortex structure. Cheat sheet: Structure and functions of the cerebral cortex

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 sections 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 hemianopsia. 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 cerebral cortex is the outer layer of nervous tissue in the brain of humans and other mammalian species. The cerebral cortex is divided by a longitudinal fissure (lat. Fissura longitudinalis) into two large parts, which are called the cerebral hemispheres or hemispheres - right and left. Both hemispheres are connected below by the corpus callosum (lat. Corpus callosum). The cerebral cortex plays a key role in the performance of brain functions such as memory, attention, perception, thinking, speech, consciousness.

In large mammals, the cerebral cortex is collected in the mesenteries, giving a larger surface area in the same volume of the skull. The ripples are called convolutions, and between them lie furrows and deeper ones - cracks.

Two-thirds of the human brain is hidden in grooves and fissures.

The cerebral cortex has a thickness of 2 to 4 mm.

The cortex is formed by gray matter, which consists mainly of cell bodies, mainly astrocytes, and capillaries. Therefore, even visually, the cortical tissue differs from the white matter, which lies deeper and consists mainly of white myelin fibers - the axons of neurons.

The outer part of the cortex, the so-called neocortex (lat. Neocortex), the most evolutionarily young part of the cortex in mammals, has up to six cell layers. Neurons of different layers are interconnected in cortical mini-columns. Various areas of the cortex, known as Brodmann's areas, differ from each other in cytoarchitectonics (histological structure) and functional role in sensitivity, thinking, consciousness and cognition.

Development

The cerebral cortex develops from the embryonic ectoderm, namely, from the anterior part of the neural plate. The neural plate folds and forms the neural tube. The ventricular system arises from the cavity inside the neural tube, and neurons and glia arise from the epithelial cells of its walls. From the frontal part of the neural plate, the forebrain, the cerebral hemispheres and then the cortex are formed

The growth zone of cortical neurons, the so-called “S” zone, is located next to the ventricular system of the brain. This zone contains progenitor cells that later in the process of differentiation become glial cells and neurons. Glial fibers, formed in the first divisions of precursor cells, are radially oriented, span the thickness of the cortex from the ventricular zone to the pia mater (lat. Pia mater) and form “rails” for the migration of neurons outward from the ventricular zone. These daughter nerve cells become pyramidal cells of the cortex. The development process is clearly regulated in time and is guided by hundreds of genes and energy regulation mechanisms. During development, a layer-by-layer structure of the cortex is formed.

Cortical development between 26 and 39 weeks (human embryo)

Cell layers

Each of the cell layers has a characteristic density of nerve cells and connections with other areas. There are direct connections between different areas of the cortex and indirect connections, for example, through the thalamus. One typical pattern of cortical lamination is the strip of Gennari in the primary visual cortex. This strand is visually whiter than the tissue, visible to the naked eye at the base of the calcarine groove (lat. Sulcus calcarinus) in the occipital lobe (lat. Lobus occipitalis). The stria Gennari consists of axons that carry visual information from the thalamus to the fourth layer of the visual cortex.

Staining columns of cells and their axons allowed neuroanatomists at the beginning of the twentieth century. make a detailed description of the layer-by-layer structure of the cortex in different species. After the work of Corbinian Brodmann (1909), neurons in the cortex were grouped into six main layers - from the outer ones, adjacent to the pia mater; to the internal ones, bordering the white matter:

1. Layer I, the molecular layer, contains a few scattered neurons and consists primarily of vertically (apically) oriented dendrites of pyramidal neurons and horizontally oriented axons and glial cells. During development, this layer contains Cajal-Retzius cells and subpial cells (cells located immediately under the granular layer. Spinous astrocytes are also sometimes found here. The apical tufts of dendrites are considered to be of great importance for reciprocal connections (“feedback”) in the cerebral cortex, and are involved in the functions of associative learning and attention.
2. Layer II, the outer granular layer, contains small pyramidal neurons and numerous stellate neurons (whose dendrites extend from different sides of the cell body, forming a star shape).
3. Layer III, the outer pyramidal layer, contains predominantly small and medium pyramidal and nonpyramidal neurons with vertically oriented intracortical ones (those within the cortex). Cell layers I to III are the main targets of intrapulmonary afferents, and layer III is the main source of cortico-cortical connections.
4. Layer IV, the internal granular layer, contains various types of pyramidal and stellate neurons and serves as the main target of thalamocortical (thalamus to cortex) afferents.
5. Layer V, the inner pyramidal layer, contains large pyramidal neurons, the axons of which leave the cortex and project to subcortical structures (such as the basal ganglia. In the primary motor cortex, this layer contains Betz cells, the axons of which extend through the internal capsule, brainstem and spinal cord and form the corticospinal pathway, which controls voluntary movements.
6. Layer VI, the polymorphic or multiforme layer, contains few pyramidal neurons and many polymorphic neurons; Efferent fibers from this layer go to the thalamus, establishing a reverse (reciprocal) connection between the thalamus and the cortex.

The outer surface of the brain, on which the areas are designated, is supplied with blood by cerebral arteries. The area indicated in blue corresponds to the anterior cerebral artery. The portion of the posterior cerebral artery is indicated in yellow

The cortical layers are not simply stacked one on one. There are characteristic connections between the different layers and the cell types within them that permeate the entire thickness of the cortex. The basic functional unit of the cortex is considered to be the cortical minicolumn (a vertical column of neurons in the cerebral cortex that runs through its layers. The minicolumn includes from 80 to 120 neurons in all areas of the brain except the primary visual cortex of primates).

Areas of the cortex without the fourth (internal granular) layer are called agranular; those with a rudimentary granular layer are called disgranular. The speed of information processing within each layer is different. So in II and III it is slow, with a frequency (2 Hz), while in layer V the oscillation frequency is much faster - 10-15 Hz.

Cortical zones

Anatomically, the cortex can be divided into four parts, which have names corresponding to the names of the skull bones that cover:

• Frontal lobe (brain), (lat. Lobus frontalis)
• Temporal lobe (lat. Lobus temporalis)
• Parietal lobe, (lat. Lobus parietalis)
• Occipital lobe, (lat. Lobus occipitalis)

Taking into account the features of the laminar (layer-by-layer) structure, the cortex is divided into neocortex and alocortex:

• Neocortex (lat. Neocortex, other names - isocortex, lat. Isocortex and neopallium, lat. Neopallium) is part of the mature cerebral cortex with six cellular layers. The exemplar neocortical areas are Brodmann Area 4, also known as primary motor cortex, primary visual cortex, or Brodmann Area 17. The neocortex is divided into two types: isocortex (the true neocortex, examples of which Brodmann Areas 24, 25, and 32 are only discussed) and prosocortex, which is represented, in particular, by Brodmann area 24, Brodmann area 25 and Brodmann area 32
• Alocortex (lat. Allocortex) - part of the cortex with the number of cell layers less than six, is also divided into two parts: paleocortex (lat. Paleocortex) with three layers, archicortex (lat. Archicortex) of four to five, and the adjacent perialocortex (lat. periallocortex). Examples of areas with such a layered structure are the olfactory cortex: the vaulted gyrus (lat. Gyrus fornicatus) with the hook (lat. Uncus), the hippocampus (lat. Hippocampus) and structures close to it.

There is also a “transitional” (between the alocortex and neocortex) cortex, which is called paralimbic, where cell layers 2,3 and 4 merge. This zone contains the proisocortex (from the neocortex) and the perialocortex (from the alocortex).

Cortex. (according to Poirier fr. Poirier.). Livooruch - groups of cells, on the right - fibers.

Paul Brodmann

Different areas of the cortex are involved in performing different functions. This difference can be seen and recorded in various ways - by comparing lesions in certain areas, comparing patterns of electrical activity, using neuroimaging techniques, studying cellular structure. Based on these differences, researchers classify cortical areas.

The most famous and cited for a century is the classification created in 1905-1909 by the German researcher Corbinian Brodmann. He divided the cerebral cortex into 51 regions based on the cytoarchitecture of neurons, which he studied in the cerebral cortex using Nissl staining of cells. Brodmann published his maps of cortical areas in humans, apes, and other species in 1909.

Brodmann's fields have been actively and in detail discussed, debated, clarified, and renamed for almost a century and remain the most widely known and frequently cited structures of the cytoarchitectonic organization of the human cerebral cortex.

Many of the Brodmann fields, initially defined solely by their neuronal organization, were later associated by correlation with various cortical functions. For example, Fields 3, 1 & 2 are the primary somatosensory cortex; area 4 is the primary motor cortex; field 17 is primary visual cortex, and fields 41 and 42 are more correlated with primary auditory cortex. Determining the correspondence of the processes of Higher Nervous Activity to areas of the cerebral cortex and linking them to specific Brodmann fields is carried out using neurophysiological studies, functional magnetic resonance imaging and other techniques (as this was, for example, done with linking Broca’s areas of speech and language to Brodmann fields 44 and 45). However, functional imaging can only approximately determine the localization of brain activation in Brodmann's fields. And to accurately determine their boundaries in each individual brain, a histological examination is needed.

Some of the important Brodmann fields. Where: Primary somatosensory cortex - primary somatosensory cortex Primary motor cortex - primary motor (motor) cortex; Wernicke’s area - Wernicke’s area; Primary visual area - primary visual area; Primary auditory cortex - primary auditory cortex; Broca's area - Broca's area.

Bark thickness

In mammalian species with large brain sizes (in absolute terms, not just relative to body size), the cortex tends to be thicker. The range, however, is not very large. Small mammals such as shrews have a neocortex thickness of approximately 0.5 mm; and species with the largest brains, such as humans and cetaceans, are 2.3-2.8 mm thick. There is a roughly logarithmic relationship between brain weight and cortical thickness.

Magnetic resonance imaging (MRI) of the brain makes it possible to measure intravital cortical thickness and correlate it with body size. The thickness of different areas varies, but in general, the sensory (sensitive) areas of the cortex are thinner than the motor (motor) areas. One study showed the dependence of cortical thickness on intelligence level. Another study showed greater cortical thickness in migraine sufferers. However, other studies show the absence of such a connection.

Convolutions, grooves and fissures

Together, these three elements - Convolutions, sulci and fissures - create a large surface area of ​​the brain of humans and other mammals. When looking at the human brain, it is noticeable that two-thirds of the surface is hidden in grooves. Both grooves and fissures are depressions in the cortex, but they vary in size. The sulcus is a shallow groove that surrounds the gyri. The fissure is a large groove that divides the brain into parts, as well as into two hemispheres, such as the medial longitudinal fissure. However, this distinction is not always clear-cut. For example, the lateral fissure is also known as the lateral fissure and as the "Sylvian fissure" and the "central fissure", also known as the Central fissure and as the "Rolandic fissure".

This is very important in conditions where the size of the brain is limited by the internal size of the skull. An increase in the surface of the cerebral cortex using a system of convolutions and sulci increases the number of cells that are involved in the performance of brain functions such as memory, attention, perception, thinking, speech, consciousness.

Blood supply

The supply of arterial blood to the brain and cortex, in particular, occurs through two arterial basins - the internal carotid and vertebral arteries. The terminal section of the internal carotid artery branches into branches - the anterior cerebral and middle cerebral arteries. In the lower (basal) parts of the brain, arteries form a circle of Willis, due to which arterial blood is redistributed between the arterial basins.

Middle cerebral artery

The middle cerebral artery (lat. A. Cerebri media) is the largest branch of the internal carotid artery. Poor circulation in it can lead to the development of ischemic stroke and middle cerebral artery syndrome with the following symptoms:

1. Paralysis, plegia or paresis of the opposite muscles of the face and arms
2. Loss of sensory sensitivity in the opposite muscles of the face and arm
3. Damage to the dominant hemisphere (often left) of the brain and the development of Broca's aphasia or Wernicke's aphasia
4. Damage to the non-dominant hemisphere (often the right) of the brain leads to unilateral spatial agnosia on the remote affected side
5. Infarcts in the area of ​​the middle cerebral artery lead to deviation conjugation, when the pupils of the eyes move towards the side of the brain lesion.

Anterior cerebral artery

The anterior cerebral artery is a smaller branch of the internal carotid artery. Having reached the medial surface of the cerebral hemispheres, the anterior cerebral artery goes to the occipital lobe. It supplies the medial areas of the hemispheres to the level of the parieto-occipital sulcus, the area of ​​the superior frontal gyrus, the area of ​​the parietal lobe, as well as areas of the lower medial sections of the orbital gyri. Symptoms of her defeat:

1. Paresis of the leg or hemiparesis with a predominant lesion of the leg on the opposite side.
2. Blockage of the paracentral branches leads to monoparesis of the foot, reminiscent of peripheral paresis. Urinary retention or incontinence may occur. Reflexes of oral automatism and grasping phenomena, pathological foot bending reflexes appear: Rossolimo, Bekhterev, Zhukovsky. Changes in mental state occur due to damage to the frontal lobe: decreased criticism, memory, unmotivated behavior.

Posterior cerebral artery

A paired vessel that supplies blood to the posterior parts of the brain (occipital lobe). Has an anastomosis with the middle cerebral artery. Its lesions lead to:

1. Homonymous (or upper quadrant) hemianopsia (loss of part of the visual field)
2. Metamorphopsia (impaired visual perception of the size or shape of objects and space) and visual agnosia,
3. Alexia,
4. Sensory aphasia,
5. Transient (transient) amnesia;
6. Tubular vision
7. Cortical blindness (while maintaining reaction to light),
8. Prosopagnosia,
9. Disorientation in space
10. Loss of topographic memory
11. Acquired achromatopsia - deficiency of color vision
12. Korsakoff's syndrome (impaired working memory)
13. Emotional and affective disorders

The cerebral cortex is present in the structure of the body of many creatures, but in humans it has reached its perfection. Scientists claim that this became possible thanks to the centuries-old labor activity that accompanies us constantly. Unlike animals, birds or fish, a person constantly develops his capabilities and this improves his brain activity, including the functions of the cerebral cortex.

But let's approach this gradually, first looking at the structure of the cortex, which is undoubtedly very fascinating.

Internal structure of the cerebral cortex

The cerebral cortex contains more than 15 billion nerve cells and fibers. Each of them has a different shape, and form several unique layers responsible for specific functions. For example, the functionality of the cells of the second and third layers is to transform excitation and correctly redirect it to certain parts of the brain. And, for example, centrifugal impulses represent the performance of the fifth layer. Let's look at each layer more carefully.

The numbering of the layers of the brain starts from the surface and goes deeper:

1. The molecular layer has a fundamental difference in its low level of cells. There is a very limited number of them, consisting of nerve fibers closely interconnected with each other.
2. The granular layer is otherwise called the outer layer. This is due to the presence of an inner layer.
3. The pyramidal level is named after its structure because it has a pyramidal structure of neurons that vary in size.
4. Granular layer No. 2 is called internal.
5. Pyramid level No. 2 is similar to the third level. Its composition is pyramid-shaped neurons of medium and large size. They penetrate down to the molecular level because it contains apical dendrites.
6. The sixth layer is fusiform cells, also known as “fusiform” cells, which gradually pass into the white matter of the brain.

If we consider these levels in more depth, it turns out that the cerebral cortex takes on the projections of each level of excitation that occurs in different parts of the central nervous system and is called “lower”. They, in turn, are transported to the brain along the nerve pathways of the human body.

Presentation: "Localization of higher mental functions in the cerebral cortex"

Thus, the cerebral cortex is the organ of higher nervous activity in humans, and regulates absolutely all nervous processes occurring in the body.

And this happens due to the peculiarities of its structure, and it is divided into three zones: associative, motor and sensory.

Modern understanding of the structure of the cerebral cortex

It is worth noting that there is a slightly different idea of ​​its structure. According to it, there are three zones that are distinguished from each other not only by their structure, but also by their functional purpose.

• The primary zone (motor), in which its specialized and highly differentiated nerve cells are located, receive impulses from auditory, visual and other receptors. This is a very important area, damage to which can lead to serious disorders of motor and sensory function.
• The secondary (sensory) zone is responsible for information processing functions. In addition, its structure consists of the peripheral sections of the analyzer nuclei, which establish correct connections between stimuli. Its defeat threatens a person with a serious perception disorder.
• The associative, or tertiary zone, its structure allows it to be excited by impulses coming from receptors of the skin, hearing, etc. It forms a person’s conditioned reflexes, helping to cognize the surrounding reality.

Presentation: "Cerebral cortex"

Main functions

How does the cerebral cortex of humans and animals differ? Because its purpose is to summarize all departments and control work. These functions are provided by billions of neurons with a diverse structure. These include types such as intercalary, afferent and efferent. Therefore, it will be relevant to consider each of these types in more detail.

The intercalary type of neurons have, at first glance, mutually exclusive functions, namely, inhibition and excitation.

The afferent type of neurons is responsible for impulses, or rather for their transmission. Efferent, in turn, provide a specific area of ​​human activity and are classified as the periphery.

Of course, this is medical terminology and it is worth abstracting from it by specifying the functionality of the human cerebral cortex in simple folk language. So, the cerebral cortex is responsible for the following functions:

• The ability to correctly establish connections between internal organs and tissues. And even more than that, it makes her perfect. This possibility is based on the conditioned and unconditioned reflexes of the human body.
• Organization of relationships between the human body and the environment. In addition, it controls the functionality of organs, corrects their work and is responsible for metabolism in the human body.
• He is 100% responsible for ensuring that thinking processes are correct.
• And the final, but no less important function is the highest level of nervous activity.

Having become familiar with these functions, we come to understand that it has allowed each person and the entire family as a whole to learn to control the processes that occur in the body.

Presentation: "Structural and functional characteristics of the sensory cortex"

Academician Pavlov, in his numerous studies, more than once pointed out that it is the cortex that is both the manager and distributor of human and animal activities.

But it is also worth noting that the cerebral cortex has ambiguous functions. This is mainly manifested in the work of the central gyrus and frontal lobes, which are responsible for muscle contraction on the side completely opposite to this irritation.

In addition, its different parts are responsible for different functions. For example, the occipital lobes are for visual, and the temporal lobes are for auditory functions:

• To be more specific, the occipital lobe of the cortex is actually a projection of the retina of the eye, which is responsible for its visual functions. If any disturbance occurs in it, a person may lose orientation in an unfamiliar environment and even suffer complete, irreversible blindness.
• The temporal lobe is an area of ​​auditory reception that receives impulses from the cochlea of ​​the inner ear, that is, it is responsible for its auditory functions. Damage to this part of the cortex threatens a person with complete or partial deafness, which is accompanied by a complete misunderstanding of words.
• The lower lobe of the central gyrus is responsible for brain analyzers or, in other words, taste perception. It receives impulses from the oral mucosa and its damage threatens the loss of all taste sensations.
• And finally, the anterior part of the cerebral cortex, in which the piriform lobe is located, is responsible for olfactory reception, that is, the functions of the nose. Impulses come into it from the nasal mucosa; if it is affected, the person will lose his sense of smell.

There is no need to remind once again that a person is at the highest stage of development.

This confirms the structure of a particularly developed frontal region, which is responsible for work activity and speech. It is also important in the process of forming human behavioral reactions and its adaptive functions.

There are many studies, including the work of the famous academician Pavlov, who worked with dogs, studying the structure and function of the cerebral cortex. All of them prove the advantages of humans over animals, precisely due to its special structure.

True, we should not forget that all parts are in close contact with each other and depend on the work of each of its components, so human perfection is the key to the functioning of the brain as a whole.

From this article, the reader has already understood that the human brain is complex and still poorly understood. However, it is a perfect device. By the way, few people know that the processing power of processes in the brain is so high that the most powerful computer in the world is powerless next to it.

Here are some more interesting facts that scientists published after a series of tests and studies:

• 2017 was marked by an experiment in which a hyper-powerful PC tried to simulate only 1 second of brain activity. The test took about 40 minutes. The result of the experiment was that the computer failed to complete the task.
• The memory capacity of the human brain can accommodate the n-number bt, which is expressed as 8432 zeros. This is approximately 1,000 Tb. As an example, the national British archive stores historical information for the last 9 centuries and its volume is only 70 Tb. Feel how significant the difference is between these numbers.
• The human brain contains 100 thousand kilometers of blood vessels, 100 billion neurons (a figure equal to the number of stars in our entire galaxy). In addition, the brain contains one hundred trillion neural connections that are responsible for the formation of memories. Thus, when you learn something new, the structure of the brain changes.
• During awakening, the brain accumulates a power of 23 W in the electric field - this is enough to light the Ilyich lamp.
• By weight, the brain consists of 2% of the total mass, but it uses approximately 16% of the energy in the body and more than 17% of the oxygen contained in the blood.
• Another interesting fact is that the brain consists of 75% water, and its structure is somewhat similar to Tofu cheese. And 60% of the brain is fat. In view of this, healthy and proper nutrition is necessary for the correct functioning of the brain. Eat fish, olive oil, seeds or nuts every day - and your brain will work long and clearly.
• Some scientists, after conducting a series of studies, noticed that when dieting, the brain begins to “eat” itself. And low oxygen levels for five minutes can lead to irreversible consequences.
• Surprisingly, a human being is not able to tickle himself, because... the brain tunes in to external stimuli and, in order not to miss these signals, the actions of the person himself are slightly ignored.
• Forgetting is a natural process. That is, eliminating unnecessary data allows the central nervous system to be flexible. And the effect of alcoholic drinks on memory is explained by the fact that alcohol inhibits processes.
• The brain's response to alcohol-containing drinks is six minutes.

Activating the intellect allows the production of additional brain tissue, which compensates for those that are sick. In view of this, it is recommended to engage in development, which in the future will save you from a weak mind and various mental disorders.

Indulge in new activities - these are the best for brain development. For example, communicating with people who are superior to you in one or another intellectual area is a powerful means of developing your intellect.

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

The vertical direction of the neuron branches forms a pyramidal or asterisk-shaped structure. Many branches of short straight or branching types penetrate both the layers of the cortex in the vertical direction, ensuring the connection of various parts of the organ with each other, and in the horizontal plane. Based on the direction of nerve cell orientation, it is customary to distinguish between centrifugal and centripetal directions of communication. In general, the physiological function of the cortex, in addition to supporting the process of thinking and behavior, is to protect the cerebral hemispheres. In addition, according to scientists, as a result of evolution, the structure of the cortex developed and became more complex. At the same time, a complication of the structure of the organ was observed as new connections were established between neurons, dendrites and axons. It is characteristic that as human intelligence developed, the emergence of new neural connections occurred deep into the structure of the cortex from the outer surface to areas located below.

Functions of the cortex

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

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

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

• loss of concentration;
• partial or complete loss of creative abilities;
• deep mental personality disorders.

The structure of the layers of the cerebral cortex

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

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

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

Areas of the cerebral cortex

Based on the functions performed in the structure under consideration, three areas can be distinguished:

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

Consequences of damage to the cerebral cortex

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

Among the most dangerous disturbances in the functioning of this structure is atrophy associated with the processes of aging and death of some neurons. The most used diagnostic methods are computer and magnetic resonance imaging, encephalography, ultrasound studies, X-rays and angiography. It should be noted that modern diagnostic methods make it possible to identify pathological processes in the functioning of the brain at a fairly early stage; if you contact a specialist in a timely manner, depending on the type of disorder, there is a possibility of restoration of impaired functions.

Reading strengthens neural connections:

A 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 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; corresponding areas of the cerebral cortex are involved in motor planning (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 the width, density, shape and size of the nerve cells included in them.

Structure. The cerebral cortex is divided into a number of regions, for example, in the most common classification of cytoarchitectonic formations by K. Brodman, 11 regions and 52 fields are identified in the human cerebral cortex. Based on phylogenetic data, the new cortex, or neocortex, the old, or archicortex, and the ancient, or paleocortex, are distinguished. According to the functional criterion, three types of areas are distinguished: sensory areas, which provide the reception and analysis of afferent signals coming from specific relay nuclei of the thalamus, motor areas, which have bilateral intracortical connections with all sensory areas for the interaction of sensory and motor areas, and associative areas, which 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, which forms the uppermost level of the brain. In an evolutionary sense, it is the newest neural formation, and its approximately 9-12 billion cells are responsible for basic sensory functions, motor coordination and control, participation in the regulation of integrative, coordinated behavior and, most importantly, the so-called “higher mental processes” of speech , thinking, problem solving, etc.

CORTEX

English cerebral cortex) - the superficial layer covering the cerebral hemispheres, is 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 neuroglial cells.

A characteristic feature of the structure of the blood cell is horizontal layering, caused by the ordered arrangement of nerve cell bodies and nerve fibers. In the K. g. m. there are 6 (according to some authors, 7) layers, differing in width, 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, the K. g. m. has vertical striations. For the functional organization of the circulatory system, the vertical, columnar arrangement of nerve cells is of great importance.

The main type of nerve cells that make up the K. g. m. are pyramidal cells. The body of these cells resembles a cone, from the apex of which one thick and long apical dendrite extends; heading towards the surface of the K. g. m., it becomes thinner and fan-shapedly divided into thinner terminal branches. From the base of the body of the pyramidal cell, shorter basal dendrites and an axon extend, heading into the white matter located under the K. g. 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 coming to the K. g.m. from other parts of the cortex and subcortical formations (see Synapses). The axons of pyramidal cells form the main efferent pathways coming from the K. g.m. The sizes of pyramidal cells vary from 5-10 microns to 120-150 microns (Betz giant cells). In addition to pyramidal neurons, the circulatory system includes stellate, fusiform, and some other types of interneurons that participate in the reception of afferent signals and the formation of functional interneuron connections.

Based on the characteristics of the distribution of nerve cells and fibers of different sizes and shapes in the layers of the cortex, the entire territory of the cerebral cortex is divided into a number of regions (for example, occipital, frontal, temporal, etc.), and the latter into more detailed cytoarchitectonic regions fields that differ in their cellular structure and functional significance. The generally accepted classification of cytoarchitectonic formations of the human hematopoietic system is proposed by K. Brodmann, who divided the entire human hemodynamic system into 11 regions and 52 fields.

Based on phylogenetic data, the cosmos is divided into new (neocortex), old (archicortex), and ancient (paleocortex). In the phylogenesis of the K. g.m., 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 crust. In humans, the neocortex accounts for 95.6%, while the ancient occupies 0.6%, and the old 2.2% of the total 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 region (fields 17, 18, 19), auditory in the upper parts of the temporal region (fields 41, 42), somatosensory, analyzing impulses coming from receptors of the skin, muscles, joints, - in the area 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 - Brodmann's area 4 - is located on the precentral gyrus. The motor cortex is characterized by the presence in layer V of Betz giant 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.

Associative 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 parts of the cortex they are located between the parietal, occipital and temporal sensory areas, and in the anterior parts they occupy the main surface of the frontal lobes. The association cortex is either absent or poorly developed in all mammals up to primates. In humans, the posterior association cortex occupies approximately half, and the frontal areas a quarter of the entire surface of the cortex. In structure, they are distinguished by the 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.

The associative cortex also contains 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 when the posterior associative areas are damaged, complex forms of orientation in space and constructive activity are disrupted, and the performance of all intellectual operations that are carried out with the participation of spatial analysis (counting, perception of complex semantic images) becomes difficult. When speech zones are damaged, the ability to perceive and reproduce speech is impaired. Damage to the frontal cortex leads to the impossibility of implementing complex behavioral programs that require the selection of significant signals based on past experience and anticipation of the future. See Brain blocks, Cortpicalization, Brain, Nervous system, Development of the cerebral cortex, Neuropsychological syndromes. (D. A. Farber.)