The cerebral cortex is divided into the ancient ( archicortex), old ( paleocortex) and new ( neocortex) on a phylogenetic basis, that is, in the order of occurrence in animals in the process of evolution. These areas of the cortex form extensive connections within the limbic system. In more phylogenetically ancient animals, the ancient and old cortex, like the entire Limbic system, was primarily responsible for smell. In humans, the limbic system performs much broader functions associated with the emotional and motivational sphere of behavior regulation. All three areas of the cortex are involved in the performance of these functions.

ancient bark along with other functions, it is related to the sense of smell and ensuring the interaction of brain systems. The ancient cortex includes the olfactory bulbs, which receive afferent fibers from the olfactory epithelium of the nasal mucosa; olfactory tracts located on the lower surface of the frontal lobe, olfactory tubercles, in which the secondary olfactory centers are located. This is the phylogenetically earliest part of the cortex, occupying adjacent areas of the frontal and temporal lobes on the lower and medial surfaces of the hemispheres.

old bark includes the cingulate gyrus, the hippocampus, and the amygdala.

Belt gyrus. It has numerous connections with the cortex and stem centers and acts as the main integrator various systems the brain that generates emotions.

The tonsil also forms extensive connections with the olfactory bulb. Through these connections, the sense of smell in animals is involved in the control of reproductive behavior.

In primates, including humans, damage to the amygdala reduces the emotional coloring of reactions, in addition, aggressive affects completely disappear in them. Electrical stimulation of the amygdala causes predominantly negative emotions- anger, rage, fear. Bilateral removal of tonsils sharply reduces the aggressiveness of animals. Calm animals, on the contrary, can become uncontrollably aggressive. In such animals, the ability to evaluate incoming information and correlate it with emotional behavior. The amygdala is involved in the process of identifying dominant emotions and motivations and choosing behavior in accordance with them. The amygdala is a powerful emotion modifier.

The hippocampus is located in the medial part of the temporal lobe. The hippocampus receives afferent inputs from the hippocampal gyrus (receives inputs from almost all areas of the neocortex and other parts of the GM), from the visual, olfactory and auditory systems. Damage to the hippocampus leads to characteristic memory and learning disabilities. The activity of the hippocampus is to consolidate memory - the transition short term memory in the long term. Damage to the hippocampus causes severe malabsorption new information, the formation of short-term and long-term memory. Therefore, the hippocampus, as well as other structures of the limbic system, significantly affects the functions of the neocortex and the learning process. This influence is carried out primarily through the creation emotional background, which largely affects the rate of formation of any conditioned reflex.

Pathways from the temporal cortex lead to the amygdala and hippocampus, transmitting information from the visual, auditory, and somatic sensory systems. Connections of the limbic system with the frontal lobes of the forebrain cortex have been established.

At new cortex greatest development size, differentiation of functions is observed in humans. The thickness of the new cortex ranges from 1.5 to 4.5 mm and is maximum in the anterior central gyrus. in the limbic system and in general nervous activity bark is engaged higher functions organization of activities.

Defeat frontal lobe causes emotional dullness, difficulty changing emotions. It is with the defeat of this area that the so-called frontal syndrome occurs. The prefrontal region and its associated subcortical structures (head of the caudate nucleus, mediodorsal nucleus of the thalamus) form the prefrontal system responsible for complex cognitive and behavioral functions. Pathways converge in the orbitofrontal cortex from the association areas of the cortex, the paralimbic areas of the cortex, and the limbic areas of the cortex. Thus, the prefrontal system and limbic system. Such an organization determines the involvement of the prefrontal system in complex forms behavior, where coordination of cognitive, emotional and motivational processes is necessary. Its integrity is necessary to assess the current situation, possible actions and their consequences, and thus for decision-making and development of programs of behavior.

Removal temporal lobes causes hypersexuality in monkeys, and their sexual activity can be directed even to inanimate objects. Finally, the postoperative syndrome is accompanied by the so-called mental blindness. Animals lose their ability correct assessment visual and auditory information, and this information is in no way associated with one's own emotional mood monkeys.

The temporal lobes are closely related to the structures of the hippocampus and amygdala and are also responsible for storing information and long-term memory and play key role in the process of converting short-term memory into long-term memory. The temporal cortex is also responsible for combining stored traces.

The neocortex is the rational brain

The newest outer part of the brain is the neocortex, or rational brain. This is the pinnacle of brain evolution, as well as the receptacle free will and conscious understanding. It is responsible for our higher cognitive functions (speaking, writing, problem solving) and also governs the analytical and mathematical thinking. The neocortex, also called the neocortex, or just the cortex for short, is made up of numerous folds and grooves, divided into right and left hemisphere. Right hemisphere is responsible for spatial imagination, creativity and abstract thinking, and the left thinks more linearly, rationally, using words. The emotional brain determines the significance, and the neocortex gives rational meaning to the feelings and emotions generated by the deeper, subconscious regions of the brain, trying to explain the causes and consequences of our sensations.

McLean called the cerebral cortex "the mother of creativity and the father of abstract thinking» . This part of the brain includes the prefrontal cortex, the most developed and difficult part the brain, which determines the difference between a person and other living beings. The prefrontal cortex enables us to plan behavior or create new possibilities by functioning as a mental stimulator of different realities, so that we can imagine and anticipate the consequences of our actions. The prefrontal cortex allows us to understand, without testing, that a device heavier than air can fly, and liver-flavored ice cream is a bad idea.

The prefrontal cortex is also responsible for logic and comparative analysis, which is illustrated by the dialogue in our head. As we walk past the store shelves inner voice reasoning, "Take this or that?" The ability to anticipate positive and negative outcomes provides the opportunity for conscious action and reasonable choice, guides moral choice such as when we suppress inappropriate physical needs. The prefrontal cortex also allows us to think first and act later, such as when the rational brakes kick in, preventing us from buying a BMW convertible, a $2,500 Gucci handbag, or eating another Godiva.

In addition, this part of the brain forms a sense of one's own "I", personality, a conscious idea of ​​oneself. It allows you to know that the reflection in the mirror is really you, and, being a repository of personality, determines our place in the social hierarchy and how we present ourselves to the world around us.

In the process of evolution, the rational brain appeared last, in thinking higher order he plays the lead role. He comprehends and arranges the world, rationally interprets objects, gives a conscious, subjective meaning to feelings and unconscious reactions. Nevertheless, this pinnacle of brain evolution has a minimal impact on our behavior and is far from always attracted and necessary for action.

When you solve a crossword puzzle, compare information on product labels, learn foreign language with the help of the Rosetta Stone program or decide to go to Las Vegas for a week, then you actively use your neocortex, or rational brain. We often refer to rational brain in marketing, when we tell the audience numbers and facts, for example, to compare brands. Although these logical facts are not in themselves the primary causes of motivation, they play important role in issuing permission to be guided in their actions by emotions or physical needs. Thus, in advertising and marketing, rational information plays a secondary, but nevertheless important role. However, in some cases, a rational approach, such as a persistent emphasis on economy, can work wonders for new brands that do not have a high emotional charge of competitors, who occupy a strong position in the market. A few years ago, when I was doing strategic planning for the telecommunications company MCI (now Verizon) at the New York branch of the Euro RSCG, the first thing I noticed was how smart, rational tools (such as tariff plans"Five Cents on Sundays" or "Friends and Family", discount offers for frequent callers) effectively challenged AT&T's monopoly, undermining its position. AT&T existed comfortably, positioning itself as a leading, well-known brand that helps maintain social connections, but MCI bet on economy.

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

(hemispheres) of the brain in the cranium occupy about 4/5 of the entire space. Their component is white matter, which includes long myelinated axons of nerve cells. FROM outside hemispheres are covered by 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 some zones, each of which is responsible for performing certain functions in the body (for the most part, these are reflex and instinctive activities and reactions).

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

Functions of the cortex

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

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

Most important functions the cerebral cortex are:

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

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

Some scientists are sure that the anterior parts of the cerebral hemispheres are responsible for the self-awareness of a person, for his specific character traits. It is a known fact that people whose anterior sections are affected to one degree or another experience certain difficulties with socialization, they practically do not pay attention to their appearance, they are not interested labor activity not interested in the opinions of others.

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

Layers of the cerebral cortex

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

• Molecular. This layer forms great amount dendritic formations, which are woven together in a chaotic manner. The neurites are oriented parallel, forming a layer of fibers. There are relatively few nerve cells here. It is believed that the main function of this layer is associative perception.
• External. A lot of nerve cells with processes are concentrated here. Neurons vary in shape. Nothing is known exactly about the functions of this layer.
• External pyramidal. Contains many nerve cells with processes that vary in size. Neurons are predominantly conical in shape. The dendrite is large.
• Internal granular. Includes not a large number of small neurons located at some distance. Between the nerve cells are fibrous grouped structures.
• Internal pyramidal. Nerve cells with processes that enter it are large and medium in size. Top part dendrites can come into contact with the molecular layer.
• Cover. Includes spindle-shaped nerve cells. The neurons in this structure are characterized by the fact that Bottom part nerve cells with processes reaches up to the white matter.

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

prefrontal cortex

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

The main functions of the prefrontal cortex are also commonly referred to as:

• Concentration of attention, focusing on obtaining only the information necessary for a person, ignoring outside thoughts and feelings.
• The ability to "reboot" consciousness, directing it in the right thought direction.
• Perseverance in the process of performing certain tasks, striving to obtain the intended result, despite the circumstances that arise.
• Analysis of the current situation.
• Critical thinking, which allows you to create a set of actions to search for verified and reliable data (checking the information received before using it).
• Planning, development of certain measures and actions to achieve the goals.
• Event forecasting.

Separately, the ability of this department to manage human emotions is noted. Here, the processes occurring in the limbic system are perceived and translated into specific emotions and feelings (joy, love, desire, grief, hatred, etc.).

Various structures of the cerebral cortex are attributed various functions. There is still no consensus on this issue. The international medical community is now coming to the conclusion that the cortex can be divided into several large zones, including cortical fields. Therefore, taking into account the functions of these zones, it is customary to distinguish three main departments.

Zone responsible for pulse processing

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

There is also a department that is responsible for receiving impulses and information from muscular system actively interacts with different layers of the cortex. It receives and processes all the impulses that come from the muscles.

If for some reason the cortex of the head is damaged in this area, then the person will experience problems with functioning. sensory system, problems with motor skills and the work of other systems that are associated with sensory centers. Outwardly, such violations will manifest themselves in the form of permanent arbitrary movements, convulsions ( varying degrees severity), partial or complete paralysis (in severe cases).

Sensory zone

This area is responsible for processing electrical signals to the brain. Several departments are located here at once, which ensure the susceptibility of the human brain to impulses coming from other organs and systems.

• Occipital (processes impulses coming from the visual center).
• Temporal (carries out the processing of information coming from the speech and auditory center).
• Hippocampus (analyzes impulses from the olfactory center).
• Parietal (processes data received from taste buds).

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

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

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

association zone

In the structure of the cerebral cortex there is also an associative zone, which provides contact between the signals of the neurons of the sensory zone and the motor center, and also gives the necessary feedback signals to these centers. The associative zone forms behavioral reflexes, takes part in the processes of their actual implementation. It occupies a significant (comparatively) part of the cerebral cortex, covering the departments included in both the frontal and posterior parts of the cerebral hemispheres (occipital, parietal, temporal).

The human brain is designed in such a way that in terms of associative perception, the posterior parts of the cerebral hemispheres are especially well developed (development occurs throughout life). They control speech (its understanding and reproduction).

If the anterior or posterior sections of the association zone are damaged, then this can lead to certain problems. For example, in case of defeat of the departments listed above, a person will lose the ability to correctly analyze the information received, will not be able to give the simplest forecasts for the future, start from the facts in the processes of thinking, use the experience gained earlier, deposited in the memory. There may also be problems with orientation in space, abstract thinking.

The cerebral cortex acts as a higher integrator of impulses, while emotions are concentrated in the subcortical zone (hypothalamus and other departments).

Different areas of the cerebral cortex are responsible for performing certain functions. You can consider and determine the difference in several ways: neuroimaging, comparing patterns of electrical activity, studying cell structure etc.

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

Many Brodmann fields were initially determined on the basis of the organization of neurons in them, but later their boundaries were refined in accordance with the correlation with different functions of the cerebral cortex. For example, the first, second, and third fields are defined as the primary somatosensory cortex, the fourth field is the primary motor cortex, and the seventeenth field is the primary visual cortex.

At the same time, some Brodmann fields (for example, area 25 of the brain, as well as fields 12-16, 26, 27, 29-31 and many others) have not been fully studied.

Speech motor zone

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

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

Thickness

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

Man is the only species on earth that is capable, in addition to satisfying the needs dictated by instincts, to carry out emotional, creative and mental activity. The uniqueness of people lies in the presence of vast, highly developed and complexly constructed areas of the brain, which have a generalized name neocortex. Therefore, in the study of man, as a species at the upper stage of evolution, the main directions are questions about the structure and functions of this part of the central nervous system.

General information

Neocortex (new cortex, isocortex or lat. Neocortex) is a region of the cerebral cortex, occupying about 96% of the surface of the hemispheres and having a thickness of 1.5 - 4 mm, which are responsible for the perception of the surrounding world, motor skills, thinking and speech.

The neocortex is made up of three main types of neurons - pyramidal, stellate, and fusiform. The first, the most numerous group, which makes up about 70-80% of the total amount in the brain. The proportion of stellate neurons is at the level of 15-25%, and spindle-shaped - about 5%.

The structure of the neocortex is almost homogeneous and consists of 6 horizontal layers and vertical columns of the cortex. The layers of the new cortex have the following structure:

1. Molecular, consisting of fibers and a small number of small stellate neurons. The fibers form a tangential plexus.
2. External granular, formed by small neurons of various shapes, which are associated with the molecular layer over all areas. At the very end of the layer are small pyramidal cells.
3. External pyramidal, consisting of small, medium and large pyramidal neurons. The processes of these cells can be associated with both layer 1 and white matter.
4. Internal granular, which consists mainly of stellate cells. This layer is characterized by a non-dense arrangement of neurons in it.
5. Internal pyramidal, formed by medium and large pyramidal cells, the processes of which are connected with all other layers.
6. Polymorphic, which is based on spindle-shaped neurons connected by processes with the 5th layer and white matter.

In addition, the new cortex is divided into regions, which in turn are subdivided into Brodmann fields. The following areas are distinguished:

1. Occipital (17,18 and 19 fields).
2. Upper parietal (5 and 7).
3. Lower parietal (39 and 40).
4. Postcentral (1, 2, 3 and 43).
5. Precentral (4 and 6).
6. Frontal (5, 9, 10, 11, 12, 32, 44, 45, 46 and 47).
7. Temporal (20, 21, 22, 37, 41 and 42).
8. Limbic (23, 24, 25 and 31).
9. Islet (13 and 14).

Cortex columns are a group of neurons that are perpendicular to the cerebral cortex. Within a small column, all cells perform the same task. But a hypercolumn, consisting of 50-100 minicolumns, can have either one or many functions.

neocortex functions

The new cortex is responsible for the execution of higher nerve functions(thinking, speech, processing information from the senses, creativity, etc.). Clinical Trials showed that each area of ​​the cerebral cortex is responsible for strictly certain functions. For example, human speech is controlled by the left frontal gyrus. However, if any of the areas is damaged, the neighboring one can take over its function, although this requires a long period time. Conventionally, there are three main groups of functions that the neocortex performs - sensory, motor and associative.

touch

This group includes a set of functions by which a person is able to perceive information from the senses.

Each feeling is analyzed by a separate area, but signals from others are also taken into account.

Signals from the skin are processed by the posterior central gyrus. Moreover, information from the lower extremities enters the upper part of the gyrus, from the body - to the middle, from the head and hands - to the lower. At the same time, only pain and temperature sensations are processed by the posterior central gyrus. The sense of touch is controlled by the upper parietal region.

Vision is controlled by the occipital region. Information is received in the 17th field, and in the 18th and 19th it is processed, that is, the color, size, shape and other parameters are analyzed.

Hearing is processed in the temporal region.

charm and taste sensations controlled by the hippocampal gyrus, which, unlike general structure The neocortex has only 3 horizontal layers.

It should be noted that in addition to the zones of direct reception of information from the senses, there are secondary ones next to them, in which the ratio of the received images with those stored in memory takes place. With damage to these areas of the brain, a person completely loses the ability to recognize incoming data.

Motor

This group includes the functions of the new cortex, with the help of which any movement of the human limbs is carried out. Motor skills are controlled and controlled by the precentral region. The lower limbs depend on the upper parts of the central gyrus, and the upper limbs depend on the lower ones. In addition to the precentral, the frontal, occipital and upper parietal regions are involved in the movement. An important feature performance of motor functions is that they cannot be performed without constant connections with sensory areas.

Associative

This group of functions of the neocortex is responsible for such complex elements of consciousness as thinking, planning, emotional control, memory, empathy and many others.

Associative functions are performed by the frontal, temporal and parietal regions.

In these parts of the brain, a reaction is formed to the data coming from the sense organs and command signals are sent to the motor and sensory zones.

To receive and control, all sensory and motor areas of the cerebral cortex are surrounded by associative fields, in which the analysis of the received information takes place. But at the same time, it should be taken into account that the data coming into these fields are already initially processed in sensory and motor areas. For example, if there is a malfunction in the work of such a site in the visual area, a person sees and understands that there is an object, but cannot name it and, accordingly, make a decision about his further behavior.

In addition, the frontal lobe of the cortex is very tightly connected to the limbic system, which allows it to control and manage emotional messages and reflexes. This enables a person to take place as a person.

The performance of associative functions in the neocortex is possible due to the fact that the neurons of this part of the central nervous system are able to preserve traces of excitation according to the feedback principle. long time(from a few years to a lifetime). This ability is memory, with the help of which associative links received information.

The role of the neocortex in emotions and stereogenesis

Emotions in humans initially appear in the limbic system of the brain. But in this case, they are represented by primitive concepts, which, getting into the new cortex, are processed with the help of an associative function. As a result, a person can operate with emotions on more high level, which makes it possible to introduce such concepts as joy, sadness, love, anger, etc.

Also, the neocortex has the ability to dampen strong bursts of emotion in the limbic system by sending calming signals to areas of high neuronal arousal. This leads to the fact that in a person the dominant role in behavior is played by the mind, and not by instinctive reflexes.

Differences from the old bark

The old cortex (archicortex) is an earlier emerging area of ​​the cerebral cortex than the neocortex. But in the process of evolution, the new crust became more developed and extensive. In this regard, the archicortex ceased to play a dominant role and became one of the constituent parts.

If we compare the old and the functions performed, then the first is assigned the role of execution congenital reflexes and motivation, and the second - the management of emotions and actions at a higher level.

In addition, the neocortex is much larger than old bark. So the first occupies about 96% percent of common surface hemispheres, and the size of the second - no more than 3%. This ratio shows that the archicortex cannot perform higher nervous functions.

Cortex. Neuronal organization of the neocortex. Function corticalization

New cortex (neocortex)- this is a layer of gray matter, the total area of ​​\u200b\u200bwhich reaches 2 thousand cm 2 due to folds; The neocortex covers the cerebral hemispheres and makes up about 70% of the total area of ​​the cortex. In the direction from the surface to the depth, the neocortex has 6 horizontal layers(see Fig. 72), archiocortex - 3, paleocortex - 4-5.

Functional layers of the new cerebral cortex.

I. molecular layer has few cells, but contains a large number of branching, ascending dendrites of pyramidal cells, on which fibers form synapses coming from the associative and nonspecific nuclei of the thalamus and regulating the level of excitability of the cortex.

Rice. 72. Structure of the cerebral cortex. I - molecular layer; II - outer granular layer; III - layer of pyramidal cells; IV - inner granular layer; V - layer of large pyramidal cells; VI - layer of spindle cells (polymorphic layer) (Guyton, 2008)

II. Outer granular layer contains mainly stellate cells and, in part, small pyramidal cells. The fibers of its cells are located mainly along the surface of the cortex, forming cortico-cortical connections.

III. pyramid layer formed primarily from pyramidal cells medium size, whose axons form cortico-cortical associations, as well as granular cells of the II layer.

IV. Inner granular layer formed by stellate cells that have synapses from neuronal fibers specific nuclei of the thalamus and metathalamus, bearing information from sensory receptors.

v. Ganglion layer represented by medium and large pyramidal cells. Moreover, Betz's giant pyramidal cells are located in the motor cortex, their axons form pyramidal pathways - corticobulbar and corticospinal motor pathways (pyramidal pathways).

VI. Layer of polymorphic cells, whose axons form corticothalamic pathways.

In layers I and IV of the new cortex, the perception and processing of incoming signals takes place. Neurons of II and III layers carry out cortico-cortical associative connections. Neurons of layers V and VI form descending pathways.

Functional Neural Columns new cerebral cortex. In the cerebral cortex there are functional associations of neurons located in a cylinder with a diameter of 0.5-1.0 mm, which includes all layers of the cortex and contains several hundred neurons ( neural columns). This, in particular, is evidenced by the electrophysiological studies of W. Mountcastle (1957) with the immersion of microelectrodes perpendicular to the surface of the somatosensory cortex. In this case, all neurons encountered on the way respond to a stimulus of only one type (for example, light). When the electrode was immersed at an angle, neurons of different sensibility came across in its path. Columns are found in the motor cortex and various areas of the sensory cortex. Column neurons can carry out self-regulation by the type of recurrent inhibition. Neighboring neuronal columns can partially overlap and interact with each other through the mechanism of lateral inhibition.

Function corticalization. Corticalization of functions is understood as an increase in the phylogenesis of the role of the cerebral cortex in the regulation of body functions and the subordination of the underlying parts of the central nervous system, in providing mental activity organism. For example, the regulation of locomotor motor functions(jumping, walking, running) and rectifying reflexes in lower vertebrates are completely provided by the brainstem, and the removal of the cerebral hemispheres practically does not change them. In cats, after transection of the trunk between the midbrain and diencephalon, locomotion is only partially preserved. Switching off the cerebral cortex in the experiment in monkeys and in pathological cases in humans leads to the loss of not only voluntary movements, locomotion, but also rectifying reflexes.