Ancient, old and new cortex - relationship and role in the integrative mechanisms of the brain. Structures of the limbic system and neocortex

Neocortex - evolutionarily the youngest part of the crust, occupying most the surface of the hemispheres. Its thickness in humans is approximately 3 mm.

The cellular composition of the neocorhex is very diverse, but about three quarters of the neurons of the cortex are pyramidal neurons (pyramids), in connection with which one of the main classifications of neurons of the cortex divides them into pyramidal and non-iramidal (fusiform, stellate, granular, candelabra cells, Martinotti cells, etc. .). Another classification is related to the length of the axon (see paragraph 2.4). Longaxon Golgi I cells are mainly pyramids and spindles, their axons can exit from the cortex, the rest of the cells are shortaxon Golgi II cells.

Cortical neurons also differ in the size of the cell body: the size of ultra-small neurons is 6x5 microns, the size of giant ones is more than 40 x 18. The largest neurons are Betz pyramids, their size is 120 x 30-60 microns.

Pyramidal neurons (see Fig. 2.6, G) have the shape of a body in the form of a pyramid, the top of which is directed upwards. An apical dendrite departs from this apex and rises into the overlying cortical layers. Basal dendrites extend from the rest of the soma. All dendrites have spines. A long axon departs from the base of the cell, forming numerous collaterals, including recurrent ones, which bend and rise up. Stellate cells have no apical dendrite; spines on dendrites are absent in most cases. In fusiform cells, two large dendrites extend from opposite poles of the body, there are also small dendrites extending from the rest of the body. Dendrites have spines. The axon is long, with little branching.

During embryonic development, the new cortex necessarily goes through the stage of a six-layer structure; with maturation in some areas, the number of layers may decrease. The deeper layers are phylogenetically older, the outer layers are younger. Each layer of the cortex is characterized by its own neuronal composition and thickness, which is different areas crust may differ from each other.

We list new crust layers(Figure 9.8).

I layer - molecular- the outermost, contains no a large number of neurons and is mainly composed of fibers running parallel to the surface. Also, dendrites of neurons located in the underlying layers rise here.

Layer II - outer granular, or outer granular, - consists mainly of small pyramidal neurons and a small number of medium-sized stellate cells.

III layer - outer pyramidal - the widest and thickest layer, contains mainly small and medium-sized pyramidal and stellate neurons. Large and giant pyramids are located in the depths of the layer.

IV layer - internal granular, or internal granular, - consists mainly of small neurons of all varieties, there are also a few large pyramids.

V layer - inner pyramidal, or ganglionic, characteristic feature which is the presence of large and in some areas (mainly in fields 4 and 6; Fig. 9.9; subparagraph 9.3.4) - giant pyramidal neurons (Betz pyramids). The apical dendrites of the pyramids, as a rule, reach layer I.

VI layer - polymorphic, or multiforme, - contains predominantly spindle-shaped neurons, as well as cells of all other forms. This layer is divided into two sublayers, which a number of researchers consider as independent layers, speaking in this case about a seven-layer crust.

Rice. 9.8.

a- neurons are colored entirely; b- only the bodies of neurons are painted; v- painted

only outgrowths of neurons

Main functions each layer is also different. Layers I and II carry out connections between neurons of different layers of the cortex. Callosal and associative fibers mainly come from the pyramids of layer III and come to layer II. The main afferent fibers entering the cortex from the thalamus terminate in layer IV neurons. Layer V is mainly associated with the system of descending projection fibers. The axons of the pyramids of this layer form the main efferent pathways of the cerebral cortex.

In most cortical areas, all six layers are equally well expressed. Such a crust is called homotypic. However, in some fields during development, the severity of the layers may change. This bark is called heterotypic. It is of two types:

granular (zeros 3, 17, 41; Fig. 9.9), in which the number of neurons in the outer (II) and especially in the inner (IV) granular layers is greatly increased, as a result of which the IV layer is divided into three sublayers. This cortex is characteristic of the primary sensory zones (see below);

Agranular (fields 4 and 6, or motor and premotor cortex; Fig. 9.9), in which, on the contrary, there is a very narrow layer II and practically no IV, but very wide pyramidal layers, especially the inner one (V).

Which are only outlined in lower mammals, and in humans they constitute the main part of the cortex. The new cortex is located in the upper layer of the cerebral hemispheres, has a thickness of 2-4 millimeters and is responsible for higher nervous functions - sensory perception, execution of motor commands, conscious thinking and, in humans, speech.

Anatomy

The new cortex contains two main types of neurons: pyramidal neurons (~ 80% of neurons in the neocortex) and interneurons (~ 20% of neurons in the neocortex).

The structure of the neocortex is relatively uniform (hence the alternative name: isocortex). In humans, it has six horizontal layers of neurons, differing in the type and nature of connections. Vertically, neurons are grouped into so-called cortex columns. At the beginning of the 20th century, Brodman showed that in all mammals, the new cortex contains 6 horizontal layers of neurons.

Principle of operation

A fundamentally new theory of the algorithmic work of the new crust was developed in Menlo Park, California, USA (Silicon Valley), by Jeff Hawkins. The theory of hierarchical temporary memory has been implemented in software in the form of a computer algorithm, which is available for use under a license from numenta.com.

• The same algorithm processes all the senses.
• The function of a neuron contains memory in time, something like cause-and-effect relationships, hierarchically forming into larger and larger objects from smaller ones.

Functions

The neocortex is embryo derived from the dorsal telencephalon, which is part of the forebrain. The neocortex is divided into areas delimited by cranial sutures that serve different functions. For example, the occipital lobe contains the primary visual cortex, and the temporal lobe contains the primary auditory cortex. Further subdivisions or regions of the neocortex are responsible for more specific cognitive processes. In humans, the frontal lobe contains areas dedicated to abilities that are enhanced or unique to our species, such as complex language processing localized in the prefrontal cortex. In humans and other primates, social and emotional processing is localized in the orbitofrontal cortex.

The neocortex has been shown to play an important role in sleep, memory and learning. Semantic memories appear to be stored in the neocortex, in particular in the anterolateral temporal lobe of the neocortex. The neocortex is also responsible for transmitting sensory information to the basal nuclei. The pulsation rate of neurons in the neocortex also affects slow sleep.

The role that the neocortex plays in neurological processes directly related to human behavior is not yet fully understood. To understand the role of the neocortex in human cognition of the world, computer model brain that modeled the electrochemistry of the neocortex - "Blue Brain project" Project "Blue Brain". The project was created to improve understanding of the processes of perception, learning, memory and gain additional knowledge about mental disorders.

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). The 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 myelin axons nerve cells... On the outside, the hemispheres are covered with the cerebral cortex, which also consists of neurons, as well as glial cells and myelin-free 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 reflex and instinctive activities and reactions).

There is such a concept - "ancient crust". This is evolutionarily the most ancient structure of the cloak of the telencephalon of the cerebral cortex in all mammals. They also distinguish the "new cortex", which is only outlined in lower mammals, but in humans it forms a large part 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 many functions that are used in various aspects of the human body's life. Its thickness is about 3-4 mm, and its volume is quite impressive due to the presence of channels connecting with the central nervous system. As in the electrical network, perception, information processing, decision making with the help of nerve cells with processes take place.

Inside the cerebral cortex, various electrical signals are generated (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. 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 (at least until the moment when his intellect develops).

In the process of processing information entering the brain, reactions (mental, behavioral, physiological, etc.) are formed in the cortex.

The most important functions of the cerebral cortex are:

• Interaction of internal organs and systems with environment as well as 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 due to the large number of nerve cells with processes.
• Support for continuous interconnection between various organs, tissues, structures and systems of the body.
• Formation and correct work human consciousness, the flow of creative and intellectual thinking.
• Control over the activity of the speech center and the 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 on this moment studied by modern science to the least extent. These areas are known to be practically immune to external influences. For example, if these departments are influenced by external electrical impulses, they will not give any reaction.

Some scientists are sure that the front sections of the cerebral hemispheres are responsible for a person's self-awareness, for his specific character traits. It is a known fact that people whose front 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 opinion of others.

From the point of view of physiology, the importance of each section of the cerebral hemispheres is difficult to overestimate. Even those that have not been fully studied at the moment.

The 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, performing common work... It is customary to distinguish several main layers of the bark:

• Molecular. This layer is formed great amount dendritic formations, which are intertwined in a chaotic manner. The neurites are oriented parallel to each other and form an interlayer 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. The exact functions of this layer are still unknown.
• External pyramidal. Contains many nerve cells with processes that vary in size. Neurons are predominantly conical in shape. Dendrite has big sizes.
• Internal granular. Includes a small number of neurons small size that are located at some distance. Fibrous grouped structures are located between nerve cells.
• 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. For neurons in this structure, it is characteristic that the lower part of the nerve cells with processes reaches up to the white matter.

The cerebral cortex includes various layers that differ in shape, location, functional component of their elements. The layers contain neurons of pyramidal, spindle, stellar, branchy species. Together they create over 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 certain 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 with latent birth injuries in the spine have a significantly smaller cerebral cortex than their healthy peers.

Prefrontal cortex

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

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

• Focusing on, focusing on getting only necessary for a person information, ignoring third-party thoughts and feelings.
• The ability to "reboot" the mind, directing it in the right mental channel.
• Persistence in the process of performing certain tasks, striving to obtain the intended result, despite the emerging circumstances.
• Analysis of the current situation.
• Critical thinking, allowing 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 set goals.
• Forecasting events.

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

Different functions are attributed to different structures of the cerebral cortex. There is still no consensus on this issue. The international medical community currently concludes 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.

Area 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 the muscular system, actively interacts with different layers of the cortex. It receives and processes all the impulses that come from the muscles.

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

Sensory zone

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

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

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

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

Violations of the sensory zone will not always lead to the loss of some 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.

Associative 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 return signals to these centers. The associative zone forms behavioral reflexes, takes part in the processes of their actual implementation. Occupies a significant (comparatively) part of the cerebral cortex, covering the sections included in both the frontal and the 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 front or back sections of the associative zone are damaged, then this can lead to certain problems. For example, in case of defeat of the above departments, a person will lose the ability to competently analyze the information received, will not be able to make the simplest predictions for the future, start from the facts in the processes of thinking, and use the experience gained earlier, deposited in memory. There may also be problems with orientation in space, abstract thinking.

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

Different areas of the cerebral cortex are responsible for certain functions. There are several methods to consider and determine the difference: neuroimaging, comparison of patterns of electroactivity, study of cell structure, etc.

At the beginning of the 20th century, K. Brodmann (a German researcher of 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 Brodman were discussed, refined, renamed, but they are still used to describe the cerebral cortex in humans and large mammals.

Many of Brodmann's fields were initially determined based on 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 of Brodmann's fields (for example, zone 25 of the brain, as well as fields 12-16, 26, 27, 29-31 and many others) are not fully understood.

Reciprocating zone

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

1. Broca's propulsion 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 the person will not lose the ability to speak, the semantic component of his speech will not suffer, however, the speech will cease to be clear, and the voice will become low-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 an infant in the first months of life). Such disorders are usually called motor aphasia.
2. Wernicke's sensory center. Located in the temporal region, responsible for receiving and processing functions 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). What the patient says will be a collection of incoherent sounds. If there is a simultaneous defeat of the Wernicke and Broca centers (this usually occurs with a stroke), then in these cases the development of motor and sensory aphasia is observed at the same time.
3. Written Speech Perception Center. It is located in the visual part of the cerebral cortex (field number 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 a relatively large brain size (in the general sense, and not in comparison with body size) 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.

In this article, we will talk about the limbic system, the neocortex of their history, and their main functions.

Limbic system

The limbic system of the brain is a collection of complex neuroregulatory structures in the brain. This system is not limited to just a few functions - it performs a huge number of tasks that are most important for a person. The purpose of the limbus is the regulation of higher mental functions and special processes of the higher nervous activity ranging from simple charm and wakefulness to cultural emotions, memory and sleep.

History of origin

The limbic system of the brain was formed long before the neocortex began to form. it oldest the hormonal-instinctive structure of the brain, which is responsible for the survival of the subject. Over a long evolution, you can form 3 main goals of the system for survival:

• Dominance is a manifestation of superiority in a variety of ways
• Food - Subject's food
• Reproduction - transferring your genome to the next generation

Because man has animal roots, a limbic system is present in the human brain. Initially, Homo sapiens possessed only affects that affect the physiological state of the body. Over time, communication was formed by the type of shouting (vocalization). Individuals who knew how to convey their state with the help of emotions survived. Over time, the emotional perception of reality was more and more formed. Such evolutionary layering allowed people to unite into groups, groups into tribes, tribes into settlements, and the latter into whole nations. For the first time, the limbic system was discovered by the American researcher Paul McLean back in 1952.

System structure

Anatomically, the limbus includes areas of the paleocortex (ancient cortex), archicortex (old cortex), part of the neocortex (new cortex), and some structures of the subcortex (caudate nucleus, amygdala, pallidum). The listed names of various types of the crust indicate their formation at the specified time of evolution.

Weight specialists in the field of neurobiology, they were engaged in the question of which structures belong to the limbic system. The latter includes many structures:

In addition, the system is closely related to the reticular formation system (the structure responsible for brain activation and wakefulness). The outline of the anatomy of the limbic complex rests on the gradual layering of one part on another. So, the cingulate gyrus lies on top, and then downward:

• corpus callosum;
• arch;
• mamillary body;
• amygdala;
• hippocampus.

A distinctive feature of the visceral brain is its rich connection with other structures, consisting of complex pathways and two-way connections. Such a branched system of branches forms a complex vicious circles, which creates conditions for prolonged circulation of excitation in the limbus.

Functional limbic system

The visceral brain actively receives and processes information from the outside world. What is the limbic system responsible for? Limbus- one of those structures that works in real time, allowing the body to effectively adapt to conditions external environment.

The human limbic system in the brain performs the following functions:

• Formation of emotions, feelings and experiences. Through the prism of emotions, a person subjectively evaluates objects and the phenomenon of the environment.
• Memory. This function is carried out by the hippocampus, which is located in the structure of the limbic system. Mnestic processes are provided by the processes of reverberation - the circular movement of excitation in the closed neural circuits of the sea horse.
• Selection and correction of a model of suitable behavior.
• Learning, retraining, fear and aggression;
• Developing spatial skills.
• Defensive and foraging behavior.
• Expressiveness of speech.
• Acquisition and maintenance of various phobias.
• The work of the olfactory system.
• Reaction of caution, preparation for action.
• Regulation of sexual and social behavior. There is a concept of emotional intelligence - the ability to recognize the emotions of the people around you.

At expressing emotions there is a reaction that manifests itself in the form of: changes in blood pressure, skin temperature, respiratory rate, pupil response, sweating, hormonal response, and much more.

Perhaps there is a question among women about how to turn on the limbic system in men. but answer simple: nothing. In all men, the limbus is fully functional (except for patients). This is justified by evolutionary processes, when a woman in almost all time periods of history was engaged in raising a child, which includes a deep emotional return, and, consequently, a deep development of the emotional brain. Unfortunately, men can no longer reach the development of a woman's level limbus.

The development of the limbic system in infants largely depends on the type of upbringing and the general attitude towards it. A stern gaze and a cold smile are not conducive to the development of a limbic complex, unlike a strong hug and a sincere smile.

5interactions with the neocortex

The neocortex and the limbic system are tightly connected by many pathways. Thanks to this combination, these two structures make up one whole of the human mental sphere: they combine the mental component with the emotional one. The new cortex acts as a regulator of animal instincts: before performing any action spontaneously evoked by emotions, human thought, as a rule, undergoes a series of cultural and moral inspections. In addition to controlling emotions, the neocortex has a supportive effect. The feeling of hunger arises in the depths of the limbic system, and already the higher cortical centers that regulate behavior search for food.

Sigmund Freud, the father of psychoanalysis, did not bypass such brain structures in his time. The psychologist argued that any neurosis is formed under the yoke of suppression of sexual and aggressive instincts. Of course, at the time of his work, there was still no data on the limbus, but the great scientist guessed about such brain devices. So, the more cultural and moral layers (super Ego - neocortex) an individual had, the more his primary animal instincts are suppressed (Id - limbic system).

Violations and their consequences

Based on the fact that the limbic system is responsible for many functions, this very many can succumb to various damage. The limbus, like other structures of the brain, can be subject to injury and other harmful factors, including hemorrhagic tumors.

The syndromes of the limbic system are rich in number, the main ones are as follows:

Dementia- dementia. The development of diseases such as Alzheimer's and Pick's syndrome is associated with atrophy of the limbic complex systems, and especially in the localization of the hippocampus.

Epilepsy... Organic disorders of the hippocampus lead to the development of epilepsy.

Pathological anxiety and phobias. Dysfunction of the amygdala leads to mediator imbalance, which, in turn, is accompanied by a disorder of emotions, which includes anxiety. Phobia, on the other hand, is an irrational fear in relation to a harmless object. In addition, imbalances in neurotransmitters trigger depression and mania.

Autism... At its core, autism is a deep and serious maladjustment in society. The limbic system's inability to recognize the emotions of others has dire consequences.

Reticular formation(or reticular formation) is a nonspecific formation of the limbic system responsible for the activation of consciousness. After deep sleep, people wake up thanks to the work of this structure. In cases of its damage, the human brain is exposed to various disorders of switching off consciousness, including absence and syncope.

Neocortex

The new cortex is a part of the brain found in higher mammals. The rudiments of the neocortex are also observed in lower milk-sucking animals, but they do not reach high development. In humans, the isocortex is the lion's share of the total cerebral cortex, with an average thickness of up to 4 millimeters. The area of ​​the neocortex reaches 220 thousand square meters. mm.

History of origin

At the moment, the neocortex is the highest stage of human evolution. Scientists managed to study the first manifestations of the new bark from representatives of reptiles. The last animals that did not have a new bark in the chain of development were birds. And only developed man possesses.

Evolution is a complex and lengthy process. Every kind of creature goes through a harsh evolutionary process. If a species of an animal could not adapt to a changeable external environment, the species lost its existence. Why is man was able to adapt and survive to this day?

Being in favorable conditions living (warm climate and protein food), the descendants of humans (before the Neanderthals) had no choice but to eat and reproduce (thanks to the developed limbic system). Because of this, the mass of the brain, by the standards of the duration of evolution, gained a critical mass in a short period of time (several million years). By the way, the mass of the brain in those days was 20% more than that of a modern person.

However, all good things come to an end sooner or later. With the change of climate, the descendants had to change their place of residence, and with it, and start looking for food. Having a huge brain, descendants began to use it for finding food, and then for social involvement, because it turned out that by uniting in groups according to certain criteria of behavior, it was easier to survive. For example, in a group where everyone shared food with other members of the group, they had a better chance of survival (Someone picked berries well, others hunted, etc.).

From this moment began separate evolution on the brain separate from the evolution of the whole body. Since then appearance the person has not changed much, but the composition of the brain differs dramatically.

What does it consist of

The new cortex of the cerebral hemispheres is an accumulation of nerve cells that form a complex. Anatomically, 4 types of cortex are divided, depending on its localization -, occipital,. Histologically, the cortex consists of six balls of cells:

• Molecular ball;
• outer granular;
• pyramidal neurons;
• internal granular;
• ganglionic layer;
• muliform cells.

What functions does

The human neocortex is classified into three functional areas:

• Sensory... This zone is responsible for the higher processing of the received stimuli from the external environment. So, ice becomes cold when information about the temperature enters the parietal region - there is no cold on the finger, but there is only an electrical impulse.
• Associative zone... This area of ​​the cortex is responsible for the communication between the motor cortex and the sensory cortex.
• Motor area... All conscious movement is formed in this part of the brain.
  In addition to these functions, the new cortex provides higher mental activity: intelligence, speech, memory and behavior.

Output

Summing up, the following can be highlighted:

• Due to two main, fundamentally different, structures of the brain, a person has a duality of consciousness. Two different thoughts are formed in the brain over each action:
  • “I want” - the limbic system (instinctive behavior). The limbic system occupies 10% of the total brain mass, low energy consumption
  • "It is necessary" - neocortex ( social behavior). The neocortex occupies up to 80% of the total brain mass, high energy consumption and limited metabolic rate

By origin, the cerebral cortex is divided into ancient (pleocortex), old (archecortex) and new (neocortex). The ancient cortex includes structures associated with the analysis of olfactory stimuli; it includes olfactory bulbs, tracts, and tubercles. The old cortex includes the cingulate cortex, hippocampal cortex, dentate gyrus, and amygdala. The ancient and old cortex forms the olfactory brain. In addition to smell, the olfactory brain provides alertness and attention reactions, takes part in the regulation of autonomic functions, plays a role in the formation of sexual, food, defensive instinctive behavior, and the provision of emotions.

All other structures of the cortex belong to the neocortex, which occupies about 96% of the total area of ​​the entire cortex.

The location of nerve cells in the cortex is denoted by the term "cytoarchitectonics". And the conductive fibers - "myeloarchitectonics".

The new cortex consists of 6 cell layers that differ in cell composition, neural connections, and functions. In the areas of the ancient bark and old bark, only 2-3 layers of cells come to light. Neurons of four upper layers the neocortex mainly process information from other departments nervous system... The main centrifugal layer is layer 5. The axons of its cells form the main descending pathways of the cerebral cortex, they conduct signals that control the work of the stem structures and the spinal cord.

Layer 1 is the outermost, molecular layer. It contains mainly nerve fibers deeper located neurons. In addition, it contains a small number of small cells. The fibers of the molecular layer form bonds between different areas bark

2nd layer - outer granular. It contains a large number of small multipolar neurons. Part of the ascending dendrites from the third layer ends in this layer.

3rd layer - outer pyramidal. It is the widest, contains mainly medium and less often small and large pyramidal neurons. Dendrites of neurons from this layer are sent to the second layer.

4th layer - inner granular. Comprises a large number small granular, as well as medium and large stellate cells. They are divided into two sublayers: 4a and 4b.

5th layer - ganglionic, or inner pyramidal. It is characterized by the presence of large pyramidal neurons. Their upward dendrites reach the molecular layer, while the basal and collateral axons are distributed in the fifth layer.

Layer 6 is polymorphic. It contains, along with cells of other forms, fusiform neurons. The shapes of other cells are very diverse: they have triangular, pyramidal, oval and polygonal shapes.