Cerebral cortex. Zones and lobes of the cerebral cortex

16.10.2019 -

The cerebral cortex is a multi-level 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). The structure controls important functions and processes occurring in the brain and other internal organs.

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

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

There is such a thing as “ancient bark”. This is the evolutionarily most ancient structure of the telencephalon of the cerebral cortex in all mammals. They also distinguish the “new cortex,” which in lower mammals is only outlined, but in humans forms the majority of the cerebral cortex (there is also the “old cortex,” which is newer than the “ancient” one, but older than the “new one”).

Functions of the cortex

The human cerebral cortex is responsible for controlling many functions that are used in different aspects of the human body. Its thickness is about 3-4 mm, and its volume is quite impressive due to the presence of channels connecting the central nervous system. How perception, information processing, and decision-making occur through an electrical network using nerve cells with processes.

Various electrical signals are produced within the cerebral cortex (the type of which depends on the current state of the person). The activity of these electrical signals depends on the person’s well-being. Technically, electrical signals of this type are described in terms of frequency and amplitude. A greater number of connections are localized in places that are responsible for ensuring the most complex processes. At the same time, the cerebral cortex continues to actively develop throughout a person’s life (at least until 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:

Interaction internal organs and systems with environment, and also with each other, correct flow metabolic processes inside 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 information received is achieved through large quantity nerve cells with processes.
Supporting a continuous relationship between various organs, tissues, structures and systems of the body.
Formation and proper functioning of human consciousness, the flow of creative and intellectual thinking.
Exercising control over the activity of the speech center and processes associated with various mental and emotional situations.
Interaction with spinal cord and other systems and organs of the human body.

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

Some scientists are confident that the anterior sections of the cerebral hemispheres are responsible for a person’s self-awareness and his specific character traits. It is a known fact that people whose anterior regions 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 a physiological point of view, the importance of each section of the cerebral hemispheres is difficult to overestimate. Even those that have not yet been fully studied.

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 specific functions. They all interact with each other, doing 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 parallel oriented and form 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. Many nerve cells with processes are concentrated here. Neurons vary in shape. Nothing is known yet about the exact functions of this layer.
The outer one is pyramidal. Contains many nerve cells with processes that vary in size. Neurons are predominantly conical in shape. The dendrite is large.
Internal grainy. Includes a small number of neurons small size, which are located at some distance. Between the nerve cells there are fibrous grouped structures.
Internal pyramidal. Nerve cells with processes that enter into it are large and medium in size. Top part dendrites can come into contact with the molecular layer.
Cover. Includes spindle-shaped nerve cells. What is characteristic of neurons in this structure is that Bottom part nerve cells with processes reach the white matter.

The cerebral cortex includes various layers that differ in shape, location, and functional components of their elements. The layers contain pyramidal, spindle, stellate, and branched neurons. 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 receiving and processing impulses (that is, incoming information), creating 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 have had hidden birth injuries in the spinal area have a noticeably smaller cerebral cortex than their healthy peers.

Prefrontal cortex

A large section of the cerebral cortex, which is represented in the form of the anterior sections of the frontal lobes. With its help, control, management, and focusing of any actions that a person performs are carried out. This department allows us to properly distribute our time. The famous psychiatrist T. Galtieri described this area as a tool with which people set goals and develop plans. He was confident that a properly functioning and well-developed prefrontal cortex - most important factor personal effectiveness.

The main functions of the prefrontal cortex also include:

Concentration, focusing on obtaining only the information a person needs, ignoring other thoughts and feelings.
The ability to “reboot” consciousness, directing it in the right thinking direction.
Perseverance in the process of performing certain tasks, the desire to achieve the intended result, despite the emerging circumstances.
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 set goals.
Forecasting events.

The ability of this department to control human emotions is especially 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 attributed various functions. There is still no consensus on this issue. The international medical community now comes 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 sections.

Area responsible for processing pulses

Impulses arriving through tactile, olfactory, visual centers, they go exactly to this zone. Almost all reflexes associated with motor skills are provided by pyramidal neurons.

This is also where the department is located, which is responsible for receiving impulses and information from the outside muscular system, actively interacts with different layers of the cortex. It receives and processes all impulses that come from the muscles.

If for some reason the scalp 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 functioning of other systems that are associated with sensory centers. Externally, such disorders will manifest themselves in the form of constant involuntary movements, convulsions ( varying degrees severity), partial or complete paralysis (in severe cases).

Sensory zone

This area is responsible for processing electrical signals entering the brain. There are several departments located here that ensure the human brain’s sensitivity to impulses coming from other organs and systems.

Occipital (processes impulses coming from the visual center).
Temporal (processes information coming from the speech-hearing center).
Hippocampus (analyzes impulses coming from the olfactory center).
Parietal (processes data received from taste buds).

In the zone sensory perception there are departments that also receive and process tactile signals. The more there will be neural connections in each department, the higher will be its sensory ability to receive and process information.

The sections noted above occupy about 20-25% of the entire cerebral cortex. If the sensory perception area is somehow damaged, a person may have problems with hearing, vision, smell, and the sensation of touch. The received impulses will either not arrive or will be processed incorrectly.

Not always violations of the sensory zone will lead to the loss of some sense. For example, if the auditory center is damaged, this will not always lead to complete deafness. However, a person will almost certainly have some difficulties with the correct perception of the sound information received.

Association zone

The structure of the cerebral cortex also contains an associative zone, which ensures contact between the signals of neurons in the sensory zone and the motor center, and also provides the necessary feedback signals to these centers. The associative zone forms behavioral reflexes and takes part in the processes of their actual implementation. It occupies a significant (comparatively) part of the cerebral cortex, covering sections 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 parts of the association zone are damaged, this can lead to certain problems. For example, if the departments listed above are damaged, a person will lose the ability to competently analyze the information received, will not be able to make simple forecasts for the future, will not be able to build on facts in the thinking process, or will be unable to use previously acquired experience that is stored in memory. There may also be problems with spatial orientation and 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 specific functions. You can examine and determine the difference using several methods: neuroimaging, comparison of electrical activity patterns, study cellular structure etc.

At the beginning of the 20th century, K. Brodmann (a German researcher of human brain anatomy) created a special classification, dividing the cortex into 51 sections, basing his work on the cytoarchitecture of nerve cells. Throughout the 20th century, the fields described by Brodmann were discussed, refined, and renamed, but they are still used to describe the cerebral cortex in humans and large mammals.

Many Brodmann fields were initially defined based on the organization of neurons within them, but later their boundaries were refined in accordance with correlations with various 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.

However, 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 area

A well-studied area of the cerebral cortex, which is also commonly called the speech center. The zone is conventionally divided into three large sections:

Broca's speech motor center. Forms a person's ability to speak. Located in the posterior gyrus of the anterior part of the cerebral hemispheres. Broca's center and the motor center of the speech motor muscles are different structures. For example, if the motor center is damaged in some way, then a person will not lose the ability to speak, the semantic component of his speech will not suffer, but speech will cease to be clear, and the voice will become poorly modulated (in other words, the quality of pronunciation of sounds will be lost). If Broca's center is damaged, the person will not be able to speak (just like a baby in the first months of life). Such disorders are commonly called motor aphasia.
Wernicke's sensory center. Located in the temporal region, responsible for the functions of receiving and processing oral speech. If Wernicke's center is damaged, sensory aphasia will form - the patient will not be able to understand speech addressed to him (and not only from another person, but also his own). What the patient says will be a collection of incoherent sounds. If simultaneous damage to Wernicke's and Broca's centers occurs (usually this occurs during a stroke), then in these cases the development of motor and sensory aphasia is observed simultaneously.
Center of perception writing. Located in the visual part of the cerebral cortex (field No. 18 according to Brodmann). If it turns out to be damaged, then the person experiences agraphia - loss of the ability to write.

Thickness

All mammals that have relatively large brains (in a general sense, not in comparison with body size) have a fairly thick cerebral cortex. For example, in field mice its thickness is about 0.5 mm, and in humans it is about 2.5 mm. Scientists also highlight a certain dependence of the thickness of the bark on the weight of the animal.

Cerebral cortex , a layer of gray matter 1-5 mm thick covering the cerebral hemispheres of mammals and humans. This part of the brain, which developed late in the evolution of the animal kingdom, plays exclusively important role in the implementation of mental, or higher nervous activity, although this activity is the result of the brain as a whole. Thanks to two-way communications with lower-level departments nervous system, the cortex can be involved in the regulation and coordination of all body functions. In humans, the cortex makes up on average 44% of the volume of the entire hemisphere as a whole. Its surface reaches 1468-1670 cm2.

Structure of the cortex . A characteristic feature of the structure of the cortex is the oriented, horizontal-vertical distribution of its constituent nerve cells across layers and columns; Thus, the cortical structure is characterized by a spatially ordered arrangement of functioning units and connections between them. The space between the bodies and processes of cortical nerve cells is filled with neuroglia and a vascular network (capillaries). Cortical neurons are divided into 3 main types: pyramidal (80-90% of all cortical cells), stellate and fusiform. The main functional element of the cortex is the afferent-efferent (i.e., perceiving centripetal and sending centrifugal stimuli) long-axon pyramidal neuron. Stellate cells are characterized by poor development of dendrites and powerful development axons that do not extend beyond the diameter of the cortex and cover groups of pyramidal cells with their branches. Stellate cells play the role of perceiving and synchronizing elements capable of coordinating (simultaneously inhibiting or exciting) spatially close groups of pyramidal neurons. The cortical neuron is characterized by a complex submicroscopic structure. Cortical areas of different topography differ in the density of cells, their size and other characteristics of the layer-by-layer and columnar structure. All these indicators determine the architecture of the cortex, or its cytoarchitectonics. The largest divisions of the cortex are the ancient (paleocortex), old (archicortex), new (neocortex) and interstitial cortex. The surface of the new cortex in humans occupies 95.6%, old 2.2%, ancient 0.6%, interstitial 1.6%.

If we imagine the cerebral cortex as a single cover (cloak) covering the surface of the hemispheres, then the main central part of it will be the new cortex, while the ancient, old and intermediate will take place on the periphery, i.e., along the edges of this cloak. The ancient cortex in humans and higher mammals consists of a single cell layer, indistinctly separated from the underlying subcortical nuclei; the old bark is completely separated from the latter and is represented by 2-3 layers; the new cortex consists, as a rule, of 6-7 layers of cells; interstitial formations - transitional structures between the fields of the old and new cortex, as well as the ancient and new cortex - from 4-5 layers of cells. The neocortex is divided into the following areas: precentral, postcentral, temporal, inferior parietal, superior parietal, temporo-parietal-occipital, occipital, insular and limbic. In turn, areas are divided into subareas and fields. The main type of direct and feedback connections of the new cortex are vertical bundles of fibers that bring information from subcortical structures to the cortex and send it from the cortex to these same subcortical formations. Along with vertical connections, there are intracortical - horizontal - bundles of associative fibers passing through the various levels cortex and in the white matter under the cortex. Horizontal beams are most characteristic of layers I and III of the cortex, and in some fields for layer V.

Horizontal bundles ensure the exchange of information both between fields located on adjacent gyri and between distant areas of the cortex (for example, frontal and occipital).

Functional features of the cortex are determined by the above-mentioned distribution of nerve cells and their connections across layers and columns. Convergence (convergence) of impulses from various organs feelings. According to modern ideas, such a convergence of heterogeneous excitations is a neurophysiological mechanism of integrative activity of the brain, i.e., analysis and synthesis of the body’s response activity. It is also significant that the neurons are combined into complexes, apparently realizing the results of the convergence of excitations on individual neurons. One of the main morpho-functional units of the cortex is a complex called a column of cells, which passes through all cortical layers and consists of cells located at one perpendicular to the surface of the cortex. The cells in the column are closely connected to each other and receive a common afferent branch from the subcortex. Each column of cells is responsible for the perception of predominantly one type of sensitivity. For example, if at the cortical end of the skin analyzer one of the columns reacts to touching the skin, then the other reacts to the movement of the limb in the joint. IN visual analyzer functions of visual image perception are also distributed across columns. For example, one of the columns perceives the movement of an object in the horizontal plane, the adjacent one in the vertical plane, etc.

The second complex of cells of the neocortex - the layer - is oriented in the horizontal plane. It is believed that small cell layers II and IV consist mainly of perceptive elements and are “entrances” to the cortex. Large cell layer V is the exit from the cortex to the subcortex, and the middle cell layer III is associative, connecting different cortical zones.

The localization of functions in the cortex is characterized by dynamism due to the fact that, on the one hand, there are strictly localized and spatially delimited zones of the cortex associated with the perception of information from certain body feelings, and on the other hand, the cortex is a single apparatus in which individual structures are closely connected and, if necessary, can be interchanged (the so-called plasticity of cortical functions). In addition, at any given moment, cortical structures (neurons, fields, areas) can form coordinated complexes, the composition of which changes depending on specific and nonspecific stimuli that determine the distribution of inhibition and excitation in the cortex. Finally, there is a close interdependence between functional state cortical zones and the activity of subcortical structures. Cortical territories differ sharply in their functions. Much of the ancient crust is included in the system olfactory analyzer. The old and interstitial cortex, being closely related to the ancient cortex both by systems of connections and evolutionarily, are not directly related to smell. They are part of the system responsible for the regulation of vegetative reactions and emotional states. The new cortex is a set of final links of various perceptive (sensory) systems (cortical ends of analyzers).

It is customary to distinguish projection, or primary, and secondary fields, as well as tertiary fields, or associative zones, in the zone of a particular analyzer. Primary fields receive information mediated through the smallest number of switches in the subcortex (in the visual thalamus, or thalamus, diencephalon). The surface of peripheral receptors is, as it were, projected onto these fields. In the light of modern data, projection zones cannot be considered as devices that perceive point-to-point stimulation. In these zones, certain parameters of objects are perceived, i.e., images are created (integrated), since these areas of the brain respond to certain changes in objects, their shape, orientation, speed of movement, etc.

Cortical structures play a primary role in learning in animals and humans. However, the formation of some simple conditioned reflexes, mainly from internal organs, can be ensured by subcortical mechanisms. These reflexes can also be formed on lower levels development when there is no cortex yet. Complex conditioned reflexes, underlying integral acts of behavior, require the preservation of cortical structures and the participation of not only the primary zones of the cortical ends of the analyzers, but also the associative - tertiary zones. Cortical structures are also directly related to memory mechanisms. Electrical stimulation of certain areas of the cortex (for example, the temporal cortex) evokes complex patterns of memories in people.

Feature activity of the cortex - its spontaneous electrical activity, recorded as an electroencephalogram (EEG). In general, the cortex and its neurons have rhythmic activity, which reflects the biochemical and biophysical processes occurring in them. This activity has a varied amplitude and frequency (from 1 to 60 Hz) and changes under the influence of various factors.

The rhythmic activity of the cortex is irregular, however, based on the frequency of potentials, several can be distinguished different types its (alpha, beta, delta and theta rhythms). The EEG undergoes characteristic changes during many physiological and pathological conditions(various phases of sleep, with tumors, seizures, etc.). The rhythm, i.e. frequency, and amplitude of the bioelectric potentials of the cortex are set by subcortical structures that synchronize the work of groups of cortical neurons, which creates the conditions for their coordinated discharges. This rhythm is associated with the apical (apical) dendrites of pyramidal cells. The rhythmic activity of the cortex is influenced by influences coming from the senses. Thus, a flash of light, a click or a touch on the skin causes the so-called in the corresponding areas. a primary response consisting of a series of positive waves (downward deflection of the electron beam on the oscilloscope screen) and a negative wave (upward deflection of the beam). These waves reflect the activity of the structures of a given area of the cortex and change in its different layers.

Phylogeny and ontogeny of the cortex . The cortex is a product of long evolutionary development, during which the ancient cortex first appears, arising in connection with the development of the olfactory analyzer in fish. With the emergence of animals from water onto land, the so-called. a mantle-shaped part of the cortex, completely separate from the subcortex, which consists of old and new cortex. The formation of these structures in the process of adaptation to the complex and diverse conditions of terrestrial existence is associated (with the improvement and interaction of various perceiving and propulsion systems. In amphibians, the cortex is represented by the ancient and rudiment of the old bark; in reptiles, the ancient and old bark is well developed and the rudiment of the new bark appears. Greatest development the neocortex reaches in mammals, and among them in primates (monkeys and humans), proboscideans (elephants) and cetaceans (dolphins, whales). Due to the uneven growth of individual structures of the new cortex, its surface becomes folded, covered with grooves and convolutions. The improvement of the telencephalon cortex in mammals is inextricably linked with the evolution of all parts of the central nervous system. This process is accompanied by an intensive growth of direct and feedback connections connecting cortical and subcortical structures. Thus, at higher stages of evolution, the functions of subcortical formations begin to be controlled by cortical structures. This phenomenon is called corticolization of functions. As a result of corticolization, the brain stem forms a single complex with the cortical structures, and damage to the cortex at higher stages of evolution leads to disruption of the vital functions of the body. The association zones undergo the greatest changes and increase during the evolution of the neocortex, while the primary sensory fields decrease in relative size. The growth of the new cortex leads to the displacement of the old and ancient cortex onto the lower and middle surfaces of the brain.

The cortical plate appears relatively early in the process of intrauterine development of a person - at the 2nd month. The lower layers of the cortex (VI-VII) are distinguished first, then the higher ones (V, IV, III and II;) By 6 months, the embryo already has all the cytoarchitectonic fields of the cortex characteristic of an adult. After birth, three turning points can be distinguished in the growth of the cortex: at the 2-3rd month of life, at 2.5-3 years and at 7 years. By the last period, the cytoarchitecture of the cortex is fully formed, although the cell bodies of neurons continue to increase until 18 years of age. The cortical zones of the analyzers complete their development earlier, and the degree of their increase is less than that of the secondary and tertiary zones. There is great diversity in the timing of maturation of cortical structures in different individuals, which coincides with the variety of timing of maturation functional features bark. Thus, individual (ontogenesis) and historical (phylogeny) development of the cortex is characterized by similar patterns.

On the topic : structure of the cerebral cortex

Prepared

The cortex is the most complex highly differentiated part of the central nervous system. It is divided morphologically into 6 layers, which differ in the content of neurons and the position of neural variables. There are 3 types of neurons - pyramidal, stellate (astrocytes), spindle-shaped, which are interconnected.

The main role in afferent function and excitation switching processes belongs to astrocytes. They have short but strongly branching axons that do not extend beyond the gray matter. Shorter and more branching dendrites. They participate in the processes of perception, irritation and unification of the activity of pyramidal neurons.

Bark layers:

Molecular (zonal)

External granular

Small and medium pyramids

Internal grainy

Ganglionic (layer of large pyramids)

Layer of polymorphic cells

Pyramidal neurons perform the efferent function of the cortex and connect neurons in cortical areas that are distant from each other. Pyramidal neurons include Betz's pyramids (giant pyramidal ones), they are located in the anterior central gyrus. The longest axonal processes are found in Betz's pyramids. A characteristic feature of pyramidal cells is their perpendicular orientation. The axon extends downwards, and the dendrites extend upwards.

Each neuron can have from 2 to 5 thousand synaptic contacts. This suggests that control cells are greatly influenced by other neurons in other areas, which allows them to coordinate the motor response in response to environmental influences.

Spindle-shaped cells are characteristic of layers 2 and 4. In humans, these layers are most widely expressed. They perform an associative function, connecting cortical zones with each other when solving various problems.

The structural organizing unit is the cortical column - a vertical interconnected module, all cells of which are functionally connected to each other and form a common receptor field. It has several inputs and several outputs. Columns that have similar functions are combined into macro columns.

The CBP develops immediately after birth, and until the age of 18 the number of elementary connections in the CBP increases.

The size of the cells contained in the cortex, the thickness of the layers, and their connection with each other determine the cytoarchitectonics of the cortex.

Broadman and Fog.

Cytoarchitectonic field is a region of the cortex that is different from others, but similar inside. Each field has its own specifics. Currently, there are 52 main fields, but some fields are missing in humans. In humans, areas are identified that have corresponding fields.

The bark bears the imprint of phylogenetic development. It is divided into 4 main types, which differ from each other in the differentiation of neural layers: paleocortex - an ancient cortex related to olfactory functions: olfactory bulb, olfactory tract, olfactory sulcus; archeocortex - old cortex, includes areas of the medial surface around the corpus callosum: cingulate gyrus, hippocampus, amygdala; mesocortex – intermediate cortex: outer-inferior surface of the insula; neocortex - new cortex, only in mammals, 85% of the entire cortex of the CBP, lies on the convexital and lateral surfaces.

The paleocortx and archeocortex are the limbic system.

Connections between the cortex and subcortical formations are carried out by several types of pathways:

Associative fibers - only within 1 hemisphere, they connect neighboring gyri in the form of arcuate fascicles, or neighboring lobes. their purpose is to ensure the holistic functioning of one hemisphere in the analysis and synthesis of multimodal excitations.

Projection fibers – connect peripheral receptors with the CGM. They have different inputs, as a rule, they intersect, they are all switched in the thalamus. The task is to transmit a monomodal impulse to the corresponding primary zone of the cortex.

Integrative-starting fibers (integrative pathways) – start from the motor areas. These are descending efferent pathways, they have crosshairs at different levels, the application zone is muscle commands.

Commissural fibers – ensure the holistic collaboration of the 2 hemispheres. Located in corpus callosum, optic chiasm, thalamus and at the level of 4-cholomium. The main task is to connect equal convolutions of different hemispheres.

Limbic-reticular fibers – connect the energy-regulating zones of the medulla oblongata with the CBP. The task is to maintain the general active/passive background of the brain.

2 body control systems: the reticular formation and the limbic system. These systems are modulating - they strengthen/weaken impulses. This block has several levels of response: physiological, psychological, behavioral.

Human is the superficial layer that covers the cerebral hemisphere and is predominantly formed by vertically oriented nerve cells (the so-called neurons), as well as their processes and efferent (centrifugal), afferent bundles (centripetal) and nerve fibers.

In addition, the composition of the cortex also includes cells, as well as neuroglia.

A very significant feature of the structure is the horizontal dense layering, which is primarily due to the entire ordered arrangement of each body of nerve cells and fibers. There are 6 main layers, which mainly differ in their own width, the overall density of its location, the size and shape of all the constituent external neurons.

Mainly, precisely because of their vertical orientation of the processes, these bundles of all the different nerve fibers, as well as the bodies of neurons, which have vertical striations. And for a complete functional organization the human cerebral cortex, and the columnar, vertical location of absolutely all internal nerve cells on the surface of the cerebral cortex zone is of great importance here.

The main type of all the main nerve cells that make up the cerebral cortex are special pyramidal cells. The body of these cells resembles an ordinary cone, from the height of which one long and thick apical dendrite begins to extend. An axon and shorter basal dendrites also extend from the base of the body of this pyramidal cell, heading into the full-fledged white matter, which is located directly under the cerebral cortex, or branching in the cortex.

All dendrites of the pyramid cells bear a fairly large number of spines and outgrowths, which take the most active part in the full formation of synaptic contacts at the end of afferent fibers that come to the cerebral cortex from other subcortical formations and parts of the cortex. The axons of these cells are capable of forming efferent main pathways that go directly from the C.G.M. The sizes of all pyramidal cells can vary from 5 to 150 microns (150 are Betz giant cells). In addition to pyramidal neurons K.G.M. it contains some fusiform and stellate types of interneurons, which are involved in the reception of incoming afferent signals, as well as the formation of interneuron functional connections.

Features of the cerebral cortex

Based on various phylogenetic data, the cerebral cortex is divided into ancient (paleocortex), old (archicortex) and new (neocortex). In the phylogeny of K.G.M. There is a relative universal increase in the territory of the new crustal surface with a slight decrease in the area of the old and ancient one.

Functionally, the areas of the cerebral cortex are divided into 3 types: associative, motor and sensory. In addition, the cerebral cortex is also responsible for the corresponding areas.

What is the cerebral cortex responsible for?

In addition, it is important to note that the entire cerebral cortex, in addition to all of the above, is responsible for everything. The zones of the cerebral cortex contain neurons of various structures, including stellate, small and large pyramidal, basket-shaped, fusiform and others. In functional terms, all main neurons are divided into the following types:

Intercalary neurons (fusiform, small pyramidal and others). Interneurons have subdivisions and can be either inhibitory or excitatory (small and large basket neurons, neurons with brush-shaped neurons and candelabra-shaped axons)
Afferent (these are the so-called stellate cells) - to which impulses arrive from all specific pathways, and various specific sensations arise. It is these cells that transmit impulses directly to efferent and intercalary neurons. Groups of polysensory neurons respectively receive different impulses from visual cusps associative nuclei
Efferent neurons (they are called large pyramidal cells) - impulses from these cells go to the so-called periphery, where they provide a certain type of activity

Neurons, as well as processes on the surface of the cerebral cortex, are also arranged in six layers. Neurons that perform the same reflex functions are located strictly one above the other. Thus, individual columns are considered the main structural unit of the surface of the cerebral cortex. And the most pronounced connection is between the third, fourth and fifth stages of the K.G.M. layers.

Cortical pads

The following factors can also be considered evidence of the presence of columns in the cerebral cortex:
When introducing various microelectrodes into the C.G.M. the impulse is recorded (registered) strictly perpendicularly under the full impact of a similar reflex reaction. And when the electrodes are inserted in a strictly horizontal direction, characteristic impulses for various reflex reactions are recorded. Basically, the diameter of one column is 500 µm. All neighboring columns are tightly connected in all functional terms, and are also often located with each other in close reciprocal relationships (some inhibit, others excite).

When stimuli act on a response, many columns are also involved and a perfect synthesis and analysis of stimuli occurs - this is the principle of screening.

Since the cerebral cortex grows in the periphery, then all the superficial layers of the cerebral cortex have full attitude and to all signaling systems. These superficial layers consist of a very large number of nerve cells (about 15 billion) and together with their processes, with the help of which the possibility of such unlimited closure functions and broad associations is created - this is the essence of the entire activity of the second signaling system. But with all this, the second s.s. works with other systems.

Attention!

30.07.2013

Formed by neurons, it is a layer of gray matter that covers the cerebral hemispheres. Its thickness is 1.5 - 4.5 mm, the area of an adult is 1700 - 2200 cm 2. Myelinated fibers forming the white matter of the telencephalon connect the cortex with the rest departments of the Moscow . Approximately 95 percent of the surface of the hemispheres is neocortex, or neocortex, which is phylogenetically considered the most recent formation of the brain. The archiocortex (old cortex) and paleocortex (ancient cortex) have a more primitive structure, they are characterized by a fuzzy division into layers (weak stratification).

The structure of the cortex.

The neocortex is formed by six layers of cells: the molecular lamina, the outer granular lamina, the outer pyramidal lamina, the internal granular and pyramidal lamina, and the multiforme lamina. Each layer is distinguished by the presence of nerve cells of a certain size and shape.

The first layer is a molecular plate, which is formed by a small number of horizontally oriented cells. Contains branching dendrites of pyramidal neurons of the underlying layers.

The second layer is the outer granular plate, consisting of the bodies of stellate neurons and pyramidal cells. This also includes a network of thin nerve fibers.

The third layer, the outer pyramidal plate, consists of the bodies of pyramidal neurons and processes that do not form long pathways.

The fourth layer, the internal granular plate, is formed by densely spaced stellate neurons. Thalamocortical fibers are adjacent to them. This layer includes bundles of myelin fibers.

The fifth layer, the inner pyramidal lamina, is formed mainly by large pyramidal Betz cells.

The sixth layer is a multiform plate, consisting of a large number of small polymorphic cells. This layer smoothly passes into the white matter of the cerebral hemispheres.

Furrows cortex Each hemisphere is divided into four lobes.

The central sulcus begins on the inner surface, descends down the hemisphere and separates frontal lobe from parietal. The lateral groove originates from the lower surface of the hemisphere, rises obliquely to the top and ends in the middle of the superolateral surface. The parieto-occipital sulcus is localized in the posterior part of the hemisphere.

Frontal lobe.

The frontal lobe has the following structural elements: frontal pole, precentral gyrus, superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus, pars tegmental, triangular and orbital. The precentral gyrus is the center of all motor acts: starting from elementary functions and ending with complex ones comprehensive actions. The richer and more differentiated the action, the large area occupies this center. Intellectual activity is controlled by the lateral sections. The medial and orbital surfaces are responsible for emotional behavior and autonomic activity.

Parietal lobe.

Within its boundaries there are the postcentral gyrus, intraparietal sulcus, paracentral lobule, superior and inferior parietal lobules, supramarginal and angular gyri. Somatic sensitive cortex located in the postcentral gyrus; a significant feature of the arrangement of functions here is somatotopic division. The entire remaining parietal lobe is occupied by the association cortex. It is responsible for recognizing somatic sensitivity and its relationship with various forms sensory information.

Occipital lobe.

It is the smallest in size and includes the semilunar and calcarine sulci, the cingulate gyrus and a wedge-shaped area. The cortical center of vision is located here. Thanks to which a person can perceive visual images, recognize and evaluate them.

Temporal lobe.

On the lateral surface, three temporal gyri can be distinguished: superior, middle and inferior, as well as several transverse and two occipitotemporal gyri. Here, in addition, there is the hippocampal gyrus, which is considered the center of taste and smell. The transverse temporal gyrus is a control zone auditory perception and interpretation of sounds.

Limbic complex.

Unites a group of structures that are located in the marginal zone of the cerebral cortex and thalamus diencephalon. It's limbic cortex, dentate gyrus, amygdala, septal complex, mammillary bodies, anterior nuclei, olfactory bulbs, bundles of connective myelin fibers. Main function This complex is the control of emotions, behavior and stimuli, as well as memory functions.

Basic dysfunctions of the cortex.

Main disorders to which cortex, divided into focal and diffuse. The most common focal ones are:

Aphasia is a disorder or complete loss of speech function;

Anomia – inability to name various objects;

Dysarthria is a disorder of articulation;

Prosody is a violation of the rhythm of speech and the placement of stress;

Apraxia is the inability to perform habitual movements;

Agnosia is the loss of the ability to recognize objects using sight or touch;

Amnesia is a memory disorder that is expressed by a slight or complete inability to reproduce information received by a person in the past.

Diffuse disorders include: stupor, stupor, coma, delirium and dementia.