How many nerve layers does the neocortex have? Cortex

The cerebral cortex is divided into ancient ( archicortex), old ( paleocortex) and new ( neocortex) according to phylogenetic characteristics, that is, according to the order of occurrence in animals during the process of evolution. These cortical areas 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 the sense of smell. In humans, the limbic system performs much broader functions related to the emotional and motivational sphere of behavior regulation. All three areas of the cortex are involved in performing these functions.

Ancient bark along with other functions, it is related to 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 secondary olfactory centers are located. This is phylogenetically the 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 cortex, hippocampus and amygdala.

Cingulate gyrus. It has numerous connections with the cortex and brainstem centers and acts as the main integrator of various brain systems that form emotions.

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

In primates, including humans, damage to the amygdala is reduced emotional coloring reactions, in addition, their aggressive affects completely disappear. Electrical stimulation of the amygdala causes predominantly negative emotions– anger, rage, fear. Bilateral removal of tonsils dramatically 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 is impaired. 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 temporal lobe. The hippocampus gets afferent inputs from the hippocampal gyrus (receives inputs from almost all areas of the neocortex and other parts of the brain), from the visual, olfactory and auditory systems. Damage to the hippocampus leads to characteristic memory and learning disorders. The activity of the hippocampus is to consolidate memory - the transition of short-term memory to long-term memory. Damage to the hippocampus causes severe disruption of learning new information, formation of short-term and long-term memory. Consequently, the hippocampus, as well as other structures of the limbic system, significantly influences the functions of the neocortex and learning processes. This influence is carried out primarily through the creation of an emotional background, which is largely reflected in the rate of formation of any conditioned reflex.

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

U neocortex The greatest development of size and differentiation of functions is observed in humans. The thickness of the neocortex 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 The cortex deals with the highest functions of organizing activity.

Defeat frontal lobe causes emotional dullness and difficulty changing emotions. It is when this area is damaged that the so-called frontal syndrome occurs. The prefrontal region and associated subcortical structures (the head of the caudate nucleus, the mediodorsal nucleus of the thalamus) form the prefrontal system, which is responsible for complex cognitive and behavioral functions. In the orbitofrontal cortex, pathways from the association cortical areas, paralimbic cortical areas, and limbic cortical areas converge. Thus, this is where the prefrontal system and the limbic system intersect. This organization determines the involvement of the prefrontal system in complex forms of behavior where coordination of cognitive, emotional and motivational processes is necessary. Its integrity is necessary for assessing the current situation, possible actions and their consequences, and thereby for making decisions and developing behavioral programs.

Removal temporal lobes causes hypersexuality in monkeys, and their sexual activity can be directed even towards inanimate objects. Finally, postoperative syndrome is accompanied by the so-called mental blindness. Animals lose the ability to correctly evaluate visual and auditory information, and this information is in no way connected with the monkeys’ own emotional state.

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

The cerebral cortex is the center of higher nervous (mental) activity in humans and controls the performance of a huge number of vital functions and processes. It covers the entire surface of the cerebral hemispheres and occupies about half of their volume.

The cerebral hemispheres occupy about 80% of the volume of the cranium, and consist of white matter, the basis of which consists of long myelinated axons of neurons. The outside of the hemisphere is covered by gray matter or the cerebral cortex, consisting of neurons, unmyelinated fibers and glial cells, which are also contained in the thickness of the sections of this organ.

The surface of the hemispheres is conventionally divided into several zones, the functionality of which is to control the body at the level of reflexes and instincts. It also contains the centers of higher mental activity of a person, ensuring consciousness, assimilation of received information, allowing adaptation in the environment, and through it, at the subconscious level, through the hypothalamus, the autonomic nervous system (ANS) is controlled, which controls the organs of circulation, respiration, digestion, excretion , reproduction, and metabolism.

In order to understand what the cerebral cortex is and how its work is carried out, it is necessary to study the structure at the cellular level.

Functions

The cortex occupies most of the cerebral hemispheres, and its thickness is not uniform over the entire surface. This feature is due to the large number of connecting channels with the central nervous system (CNS), which ensure the functional organization of the cerebral cortex.

This part of the brain begins to form during fetal development and is improved throughout life, through receiving and processing signals coming from environment. Thus, it is responsible for performing the following brain functions:

• connects the organs and systems of the body with each other and the environment, and also ensures an adequate response to changes;
• processes incoming information from motor centers using mental and cognitive processes;
• consciousness and thinking are formed in it, and intellectual work is also realized;
• controls speech centers and processes that characterize the psycho-emotional state of a person.

In this case, data is received, processed, and stored thanks to a significant number of impulses passing through and generated in neurons connected by long processes or axons. The level of cell activity can be determined by the physiological and mental state of the body and described using amplitude and frequency indicators, since the nature of these signals is similar to electrical impulses, and their density depends on the area in which the psychological process occurs.

It is still unclear how the frontal part of the cerebral cortex affects the functioning of the body, but it is known that it is little susceptible to processes occurring in the external environment, therefore all experiments with the influence electrical impulses to this part of the brain do not find a clear response in the structures. However, it is noted that people whose frontal part is damaged experience problems communicating with other individuals, cannot realize themselves in any work activity, and they are indifferent to their appearance and outside opinions. Sometimes there are other violations in the performance of the functions of this body:

• lack of concentration on everyday objects;
• manifestation of creative dysfunction;
• disorders of a person’s psycho-emotional state.

The surface of the cerebral cortex is divided into 4 zones, outlined by the most distinct and significant convolutions. Each part controls the basic functions of the cerebral cortex:

1. parietal zone - responsible for active sensitivity and musical perception;
2. the primary visual area is located in the occipital part;
3. temporal or temporal is responsible for speech centers and the perception of sounds coming from external environment, in addition, participates in the formation of emotional manifestations such as joy, anger, pleasure and fear;
4. The frontal zone controls motor and mental activity, and also controls speech motor skills.

Features of the structure of the cerebral cortex

The anatomical structure of the cerebral cortex determines its characteristics and allows it to perform the functions assigned to it. The cerebral cortex has the following number of distinctive features:

• neurons in its thickness are arranged in layers;
• nerve centers are located in a specific place and are responsible for the activity of a certain part of the body;
• the level of activity of the cortex depends on the influence of its subcortical structures;
• it has connections with all underlying structures of the central nervous system;
• presence of different fields cellular structure, which is confirmed by histological examination, while each field is responsible for performing some higher nervous activity;
• the presence of specialized associative areas makes it possible to establish a cause-and-effect relationship between external stimuli and the body’s response to them;
• the ability to replace damaged areas with nearby structures;
• This part of the brain is capable of storing traces of neuronal excitation.

The large hemispheres of the brain consist mainly of long axons, and also contain in their thickness clusters of neurons that form the largest nuclei of the base, which are part of the extrapyramidal system.

As already mentioned, the formation of the cerebral cortex occurs during intrauterine development, and at first the cortex consists of the lower layer of cells, and already at 6 months of the child all structures and fields are formed in it. The final formation of neurons occurs by the age of 7, and the growth of their bodies is completed at 18 years.

An interesting fact is that the thickness of the cortex is not uniform over its entire length and includes a different number of layers: for example, in the area of ​​the central gyrus it reaches its maximum size and has all 6 layers, and sections of the old and ancient cortex have 2 and 3 layers. x layer structure, respectively.

The neurons of this part of the brain are programmed to restore the damaged area through synoptic contacts, so each of the cells actively tries to restore damaged connections, which ensures the plasticity of neural cortical networks. For example, when the cerebellum is removed or dysfunctional, the neurons connecting it with the terminal section begin to grow into the cerebral cortex. In addition, the plasticity of the cortex also manifests itself under normal conditions, when the process of learning a new skill occurs or as a result of pathology, when the functions performed by the damaged area are transferred to neighboring areas of the brain or even hemispheres.

The cerebral cortex has the ability to preserve traces of neuronal excitation long time. This feature allows you to learn, remember and respond with a certain reaction of the body to external stimuli. This is how the formation of a conditioned reflex occurs, the neural pathway of which consists of 3 series-connected apparatuses: an analyzer, a closing apparatus of conditioned reflex connections and a working device. Weakness of the closure function of the cortex and trace manifestations can be observed in children with severe mental retardation, when the formed conditioned connections between neurons are fragile and unreliable, which entails difficulties in learning.

The cerebral cortex includes 11 areas consisting of 53 fields, each of which is assigned its own number in neurophysiology.

Regions and zones of the cortex

The cortex is a relatively young part of the central nervous system, developing from the terminal part of the brain. The evolutionary development of this organ occurred in stages, so it is usually divided into 4 types:

1. The archicortex or ancient cortex, due to the atrophy of the sense of smell, has turned into the hippocampal formation and consists of the hippocampus and its associated structures. With its help, behavior, feelings and memory are regulated.
2. The paleocortex, or old cortex, makes up the bulk of the olfactory area.
3. The neocortex or new cortex has a layer thickness of about 3-4 mm. It is a functional part and performs higher nervous activity: it processes sensory information, gives motor commands, and also forms conscious thinking and human speech.
4. The mesocortex is an intermediate version of the first 3 types of cortex.

Physiology of the cerebral cortex

The cerebral cortex has a complex anatomical structure and includes sensory cells, motor neurons and internerons, which have the ability to stop the signal and be excited depending on the received data. The organization of this part of the brain is built according to the columnar principle, in which the columns are divided into micromodules that have a homogeneous structure.

The basis of the micromodule system is made up of stellate cells and their axons, while all neurons react equally to the incoming afferent impulse and also send an efferent signal synchronously in response.

The formation of conditioned reflexes that ensure the full functioning of the body occurs due to the connection of the brain with neurons located in various parts body, and the cortex ensures synchronization of mental activity with the motor skills of organs and the area responsible for analyzing incoming signals.

Signal transmission in the horizontal direction occurs through transverse fibers located in the thickness of the cortex, and transmit the impulse from one column to another. Based on the principle of horizontal orientation, the cerebral cortex can be divided into the following areas:

• associative;
• sensory (sensitive);
• motor.

When studying these zones, various methods of influencing the neurons included in its composition were used: chemical and physical stimulation, partial removal of areas, as well as the development of conditioned reflexes and registration of biocurrents.

The associative zone connects incoming sensory information with previously acquired knowledge. After processing, it generates a signal and transmits it to the motor zone. In this way, it is involved in remembering, thinking, and learning new skills. Association areas of the cerebral cortex are located in proximity to the corresponding sensory area.

The sensitive or sensory area occupies 20% of the cerebral cortex. It also consists of several components:

• somatosensory, located in the parietal zone, is responsible for tactile and autonomic sensitivity;
• visual;
• auditory;
• taste;
• olfactory.

Impulses from the limbs and organs of touch on the left side of the body enter along afferent pathways to the opposite lobe of the cerebral hemispheres for subsequent processing.

Neurons of the motor zone are excited by impulses received from muscle cells and are located in the central gyrus of the frontal lobe. The mechanism of data receipt is similar to the mechanism of the sensory zone, since the motor pathways form an overlap in the medulla oblongata and follow to the opposite motor zone.

Convolutions, grooves and fissures

The cerebral cortex is formed by several layers of neurons. Characteristic feature This part of the brain has a large number of wrinkles or convolutions, due to which its area is many times greater than the surface area of ​​​​the hemispheres.

Cortical architectonic fields determine the functional structure of areas of the cerebral cortex. All of them are different in morphological characteristics and regulate different functions. In this way, 52 different fields are identified, located in certain areas. According to Brodmann, this division looks like this:

1. The central sulcus separates the frontal lobe from the parietal region; the precentral gyrus lies in front of it, and the posterior central gyrus lies behind it.
2. The lateral groove separates the parietal zone from the occipital zone. If you separate its side edges, you can see a hole inside, in the center of which there is an island.
3. The parieto-occipital sulcus separates the parietal lobe from the occipital lobe.

The core of the motor analyzer is located in the precentral gyrus, while the upper parts of the anterior central gyrus belong to the muscles of the lower limb, and the lower parts belong to the muscles of the oral cavity, pharynx and larynx.

The right-sided gyrus forms a connection with the motor system of the left half of the body, the left-sided one - with the right side.

The posterior central gyrus of the 1st lobe of the hemisphere contains the core of the tactile sensation analyzer and is also connected with the opposite part of the body.

Cell layers

The cerebral cortex carries out its functions through neurons located in its thickness. Moreover, the number of layers of these cells may differ depending on the area, the dimensions of which also vary in size and topography. Experts distinguish the following layers of the cerebral cortex:

1. The surface molecular layer is formed mainly from dendrites, with a small inclusion of neurons, the processes of which do not leave the boundaries of the layer.
2. The external granular consists of pyramidal and stellate neurons, the processes of which connect it with the next layer.
3. The pyramidal layer is formed by pyramidal neurons, the axons of which are directed downward, where they break off or form associative fibers, and their dendrites connect this layer with the previous one.
4. The internal granular layer is formed by stellate and small pyramidal neurons, the dendrites of which extend into the pyramidal layer, and its long fibers extend into the upper layers or descend down into the white matter of the brain.
5. The ganglion consists of large pyramidal neurocytes, their axons extend beyond the cortex and connect various structures and sections of the central nervous system with each other.

The multiform layer is formed by all types of neurons, and their dendrites are oriented into the molecular layer, and axons penetrate the previous layers or extend beyond the cortex and form associative fibers that form a connection between gray matter cells and the rest of the functional centers of the brain.

Video: Cerebral cortex

Anatomy

The neocortex contains two main types of neurons: pyramidal neurons (~80% of neocortical neurons) and interneurons (~20% of neocortical neurons).

The structure of the neocortex is relatively homogeneous (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 combined into so-called cortex columns. In dolphins, the neocortex has 3 horizontal layers of neurons.

Principle of operation

Fundamentally new theory The algorithms for the operation of the neocortex were developed in Menlo Park, California, USA (Silicon Valley), by Jeff Hawkins. The theory of hierarchical temporary memory was implemented in software in the form of a computer algorithm, which is available for use under a license on the website numenta.com.

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

see also

• Ancient bark

Links

• W. Mountcastle “The Organizing Principle of Brain Function: An Elementary Module and a Distributed System”
• Translation into Russian of the article “Hierarchical temporary memory” from the site Numenta.com

Wikimedia Foundation. 2010.

See what “New crust” is in other dictionaries:

NEOCORTEX (NEW CORTEX)- Evolutionarily the newest and most complex of nerve tissues. The frontal, parietal, temporal and occipital lobes of the brain consist of the neocortex... Dictionary in psychology

- (cortex hemispheria cerebri), pallium, or cloak, a layer of gray matter (1–5 mm) covering the hemispheres of the cerebrum of mammals. This part of the brain, which developed late in evolution, plays an extremely important role in... ... Biological encyclopedic dictionary

Bark: Wiktionary has an entry for “bark.” In biology: Bark is the outer part of a tree trunk. Bark of large n... Wikipedia

cortex- cerebral cortex: cortex (cerebral cortex) the upper layer of the cerebral hemispheres, consisting primarily of nerve cells with a vertical orientation (pyramidal cells), as well as bundles of afferent (centripetal) and efferent... ... Great psychological encyclopedia

A layer of gray matter 1–5 mm thick covering the cerebral hemispheres of mammals and humans. This part of the brain (See Cerebrum), which developed in the later stages of the evolution of the animal kingdom, plays exclusively... ... Great Soviet Encyclopedia

Large brain (cortex cerebri, PNA, LNH; substantia corticalis, BNA, JNA; synonym: C. cerebral hemispheres, C. brain, mantle, cloak) surface layer cerebral hemispheres, formed by its gray matter; plays an important role in... Medical encyclopedia

- (cortex cerebri) gray matter located on the surface of the cerebral hemispheres and consisting of nerve cells (neurons), neuroglia, interneuron connections of the cortex, as well as blood vessels. K.b. m. contains central (cortical) sections... ... Medical encyclopedia

Topic 14

Physiology of the brain

PartV

New crust cerebral hemispheres

The new cortex (neocortex) is a layer of gray matter with a total area of ​​1500-2200 cm2, covering the cerebral hemispheres of the telencephalon. It makes up about 40% of the brain's mass. The cortex contains about 14 billion neurons and about 140 billion glial cells. The cerebral cortex is phylogenetically the youngest neural structure. In humans, it carries out the highest regulation of body functions and psychophysiological processes that provide various forms of behavior.

Structural and functional characteristics of the cortex. The cerebral cortex consists of six horizontal layers located in the direction from the surface to the depth.

Molecular layer has very few cells, but a large number of branching dendrites of pyramidal cells, forming a plexus located parallel to the surface. Afferent fibers coming from the associative and nonspecific nuclei of the thalamus form synapses on these dendrites.

Outer granular layer composed mainly of stellate and partly small pyramidal cells. The fibers of the cells of this layer are located mainly along the surface of the cortex, forming corticocortical connections.

Outer pyramidal layer consists predominantly of medium-sized pyramidal cells. The axons of these cells, like granule cells of layer II, form corticocortical associative connections.

Inner granular layer the nature of the cells and the arrangement of their fibers is similar to the outer granular layer. On the neurons of this layer, afferent fibers form synaptic endings, coming from neurons of specific nuclei of the thalamus and, consequently, from receptors of sensory systems.

Inner pyramidal layer formed by medium and large pyramidal cells, with Betz's giant pyramidal cells located in the motor cortex. The axons of these cells form the efferent corticospinal and corticobulbar motor pathways.

Layer of polymorphic cells formed predominantly by spindle cells, the axons of which form the corticothalamic tract.

▓ Afferent and efferent connections of the cortex. In layers I and IV, perception and processing of signals entering the cortex occur. Neurons of layers II and III carry out corticocortical associative connections. The efferent pathways leaving the cortex are formed mainly in layers V – VI. A more detailed division of the cortex into various fields was carried out on the basis of cytoarchitectonic characteristics (shape and arrangement of neurons) by K. Brodman, who identified 11 areas, including 52 fields, many of which are characterized by functional and neurochemical features. According to Brodmann, the frontal area includes fields 8, 9, 10, 11, 12, 44, 45, 46, 47. The precentral region includes fields 4 and 6, and the postcentral region includes fields 1, 2, 3, and 43. The parietal region includes fields 5, 7, 39, 40, and the occipital region 17 18 19. The temporal region consists of a very large number of cytoarchitectonic fields: 20, 21, 22, 36, 37, 38, 41, 42, 52.

Fig.1. Cytoarchitectonic fields of the human cerebral cortex (according to K. Brodman): a – outer surface of the hemisphere; b – inner surface of the hemisphere.

Histological evidence shows that the elementary neural circuits involved in information processing are located perpendicular to the surface of the cortex. In the motor and various zones of the sensory cortex there are neural columns with a diameter of 0.5-1.0 mm, which represent a functional association of neurons. Neighboring neural columns can partially overlap, and also interact with each other through the mechanism of lateral inhibition and carry out self-regulation according to the type of recurrent inhibition.

In phylogenesis, the role of the cerebral cortex in the analysis and regulation of body functions and the subordination of the underlying parts of the central nervous system increases. This process is called corticolization functions.

The function localization problem has three concepts:

The principle of narrow localization is that all functions are placed in one, separate structure.

The concept of equipotentialism – different cortical structures are functionally equivalent.

The principle of multifunctionality of cortical fields. The property of multifunctionality allows this structure to be included in providing various forms activity, while realizing the basic, genetically inherent function. The degree of multifunctionality of different cortical structures is not the same: for example, in the fields of the associative cortex it is higher than in the primary sensory fields, and in the cortical structures it is higher than in the stem ones. Multifunctionality is based on the multichannel entry of afferent excitation into the cerebral cortex, the overlap of afferent excitations, especially at the thalamic and cortical levels, the modulating influence of various structures (nonspecific thalamus, basal ganglia) on cortical functions, the interaction of cortical-subcortical and intercortical pathways of excitation.

One of the largest options for the functional division of the new cerebral cortex is the separation of sensory, associative and motor areas in it.

Sensory areas of the cerebral cortex. Sensory cortical areas are areas to which sensory stimuli are projected. The sensory areas of the cortex are otherwise called: the projection cortex or the cortical sections of the analyzers. They are located mainly in the parietal, temporal and occipital lobes. Afferent pathways to the sensory cortex come predominantly from specific sensory nuclei of the thalamus (ventral, posterior lateral and medial). The sensory cortex has well-defined layers II and IV and is called granular .

Areas of the sensory cortex, irritation or destruction of which causes clear and permanent changes in the sensitivity of the body, are called primary sensory areas . They consist predominantly of unimodal neurons and form sensations of the same quality. In the primary sensory zones there is usually a clear spatial (topographic) representation of body parts and their receptor fields. Around the primary sensory areas are less localized secondary sensory areas , whose multimodal neurons respond to the action of several stimuli.

╠ The most important sensory area is the parietal cortex of the postcentral gyrus and the corresponding part of the paracentral lobule on the medial surface of the hemispheres (fields 1-3), which is designated as the primary somatosensory area (S I). Here there is a projection of skin sensitivity on the opposite side of the body from tactile, pain, temperature receptors, interoceptive sensitivity and sensitivity of the musculoskeletal system from muscle, joint and tendon receptors. The projection of parts of the body in this area is characterized by the fact that the projection of the head and upper parts of the body is located in the inferolateral areas of the postcentral gyrus, the projection of the lower half of the body and legs is in the superomedial zones of the gyrus, the projection of the lower part of the lower leg and feet is in the cortex of the paracentral lobule on the medial surface of the hemispheres . Moreover, the projection of the most sensitive areas (tongue, lips, larynx, fingers) has relatively large areas compared to other parts of the body (see Fig. 2). It is assumed that the projection of taste sensitivity is located in the area of ​​tactile sensitivity of the tongue.

In addition to S I, a smaller secondary somatosensory area (S II) is distinguished. It is located on the upper wall of the lateral sulcus, at the border of its intersection with the central sulcus. The functions of S II are poorly understood. It is known that the localization of the body surface in it is less clear; impulses come here both from the opposite side of the body and from “its own” side, suggesting its participation in the sensory and motor coordination of the two sides of the body.

╠ Another primary sensory area is the auditory cortex (fields 41, 42), which is located deep in the lateral sulcus (cortex of Heschl’s transverse temporal gyri). In this zone, in response to irritation of the auditory receptors of the organ of Corti, sound sensations are formed that change in volume, tone and other qualities. There is a clear topical projection here: different areas of the cortex represent different parts of the organ of Corti. The projection cortex of the temporal lobe also includes the center of the vestibular analyzer in the superior and middle temporal gyri (fields 20 and 21). The processed sensory information is used to form a “body schema” and regulate the functions of the cerebellum (temporo-pontine tract).

Fig.2. Diagram of sensory and motor homunculi. Section of the hemispheres in the frontal plane: a – projection of general sensitivity in the cortex of the postcentral gyrus; b – projection of the motor system in the cortex of the precentral gyrus.

╠ Another primary projection area of ​​the new cortex is located in the occipital cortex - the primary visual area (cortex of part of the sphenoid gyrus and lingual lobule, area 17). Here there is a topical representation of the retinal receptors, and each point of the retina corresponds to its own section of the visual cortex, while the area of ​​the macula has a large area of ​​representation. Due to the incomplete decussation of the visual pathways, the same halves of the retina are projected into the visual area of ​​each hemisphere. The presence of a retinal projection in both eyes in each hemisphere is the basis of binocular vision. Irritation of the 17th field cortex leads to the appearance of light sensations. Near field 17 is the cortex of the secondary visual area (fields 18 and 19). The neurons of these zones are multimodal and respond not only to light, but also to tactile and auditory stimuli. Synthesis occurs in this visual area various types sensitivity and more complex visual images and their recognition arise. Irritation of these fields causes visual hallucinations, obsessive sensations, and eye movements.

The main part of the information about the environment and the internal environment of the body, received in the sensory cortex, is transferred for further processing to the associative cortex.

Association cortical areas. Association cortical areas include areas of the neocortex that are located adjacent to sensory and motor areas, but do not directly perform sensory and motor functions. The boundaries of these areas are not clearly defined; the uncertainty is mainly associated with secondary projection zones, the functional properties of which are transitional between the properties of the primary projection and associative zones. In humans, the association cortex makes up 70% of the neocortex.

The main physiological feature of the neurons of the associative cortex is multimodality: they respond to several stimuli with almost the same strength. Polymodality (polysensory) of the neurons of the associative cortex is created due to, firstly, the presence of corticocortical connections with different projection zones, and secondly, due to the main afferent input from the associative nuclei of the thalamus, in which complex processing of information from various sensitive pathways has already occurred. As a result of this, the associative cortex is a powerful apparatus for the convergence of various sensory excitations, allowing for complex processing of information about external and internal environment body and use it to carry out higher psychophysiological functions. In the associative cortex, three associative brain systems are distinguished: thalamoparietal, thalamofrontal and thalamotemporal.

╠ Thalamotparietal system represented by associative zones of the parietal cortex (fields 5, 7, 40), receiving the main afferent inputs from the posterior group of associative nuclei of the thalamus (lateral posterior nucleus and pillow). The parietal associative cortex has efferent outputs to the nuclei of the thalamus and hypothalamus, the motor cortex and the nuclei of the extrapyramidal system. The main functions of the thalamoparietal system are gnosis, the formation of a “body schema” and praxis. Under gnosis understand the function of various types of recognition: shape, size, meaning of objects, understanding of speech, knowledge of processes, patterns. Gnostic functions include the assessment of spatial relationships. In the parietal cortex, there is a center of stereognosis, located behind the middle sections of the postcentral gyrus (fields 7, 40, partially 39) and providing the ability to recognize objects by touch. A variant of the gnostic function is the formation in consciousness of a three-dimensional model of the body (“body diagram”), the center of which is located in field 7 of the parietal cortex. Under praxis understand purposeful action, its center is located in the supramarginal gyrus (fields 39 and 40 of the dominant hemisphere). This center ensures the storage and implementation of a program of motor automated acts.

╠ Thalamobic system represented by associative zones of the frontal cortex (fields 9-14), which have the main afferent input from the associative mediodorsal nucleus of the thalamus. Main function The frontal associative cortex is the formation of programs of goal-directed behavior, especially in a new environment for a person. The implementation of this general function is based on other functions of the thalamic system: 1) the formation of a dominant motivation that provides the direction of human behavior. This function is based on the close bilateral connections of the cortex with the limbic system and the role of the latter in the regulation of higher human emotions associated with his social activities and creativity.; 2) providing probabilistic forecasting, which is expressed by a change in behavior in response to changes in the environmental situation and dominant motivation; 3) self-control of actions through constant comparison of the result of the action with the original intentions, which is associated with the creation of a foresight apparatus (acceptor of the result of the action).

When the prefrontal frontal cortex, where the connections between the frontal lobe and the thalamus intersect, is damaged, a person becomes rude, tactless, unreliable, and has a tendency to repeat any motor acts, although the situation has already changed and other actions need to be performed.

╠ Thalamotemporal system not studied enough. But if we talk about the temporal cortex, then it should be noted that some associative centers, for example, stereognosis and praxis, also include areas of the temporal cortex (field 39). In the temporal cortex there is Wernicke's auditory speech center, located in the posterior parts of the superior temporal gyrus (fields 22, 37, 42 of the left dominant hemisphere). This center provides speech gnosis - recognition and storage oral speech, both your own and someone else's. In the middle part of the superior temporal gyrus (area 22) there is a center for recognizing musical sounds and their combinations. At the border of the temporal, parietal and occipital lobes (area 39) there is a center for reading written speech, which ensures the recognition and storage of images of written speech.

Motor cortex areas. The motor cortex is divided into primary and secondary motor areas.

╠ In the primary motor cortex(precentral gyrus, field 4) there are neurons innervating the motor neurons of the muscles of the face, trunk and limbs. It has a clear topographic projection of the muscles of the body. In this case, the projections of the muscles of the lower extremities and trunk are located in the upper parts of the precentral gyrus and occupy a relatively small area, and the projections of the muscles of the upper extremities, face and tongue are located in the lower parts of the gyrus and occupy a large area (see Fig. 2). The main pattern of topographic representation is that the regulation of the activity of muscles that provide the most accurate and varied movements (speech, writing, facial expressions) requires the participation of large areas of the motor cortex. Motor reactions to stimulation of the primary motor cortex are carried out with a minimum threshold (high excitability), and are represented by elementary contractions of the muscles of the opposite side of the body (for the muscles of the head, the contraction can be bilateral). When this area of ​​the cortex is damaged, the ability to make fine coordinated movements of the hands, especially the fingers, is lost.

╠ Secondary motor cortex(field 6) is located on the lateral surface of the hemispheres, in front of the precentral gyrus (premotor cortex). It carries out higher motor functions associated with planning and coordination of voluntary movements. The cortex of area 6 receives the bulk of the efferent impulses from the basal ganglia and cerebellum and is involved in the recoding of information about the program of complex movements. Irritation of the cortex of area 6 causes more complex coordinated movements, for example, turning the head, eyes and torso in the opposite side, friendly contractions of the flexor or extensor muscles on the opposite side. In the premotor cortex there are motor centers associated with human social functions: the center of written speech in the posterior part of the middle frontal gyrus (field 6), the Broca's motor leakage center in the posterior part of the inferior frontal gyrus (field 44), which provides speech praxis, as well as musical motor center (field 45), which determines the tone of speech and the ability to sing.

▓ Afferent and efferent connections of the motor cortex. In the motor cortex, the layer containing Betz's giant pyramidal cells is better expressed than in other areas of the cortex. Neurons of the motor cortex receive afferent inputs through the thalamus from muscle, joint and skin receptors, as well as from the basal ganglia and cerebellum. The main efferent output of the motor cortex to the stem and spinal motor centers is formed by the pyramidal cells of layer V. Pyramidal neurons and their associated interneurons are located vertically relative to the surface of the cortex and form neuronal motor columns. Pyramidal neurons of the motor column can excite or inhibit motor neurons of the brainstem and spinal centers. Adjacent columns functionally overlap, and pyramidal neurons that regulate the activity of one muscle are usually located not in one, but in several columns.

The main efferent connections of the motor cortex are carried out through the pyramidal and extrapyramidal tracts, which begin from giant pyramidal cells of Betz and smaller pyramidal cells of the V layer of the cortex of the precentral gyrus (60% of fibers), premotor cortex (20% of fibers) and postcentral gyrus (20% of fibers) . Large pyramidal cells have fast-conducting axons and background impulse activity of about 5 Hz, which increases to 20-30 Hz with movement. These cells innervate large (high-threshold) ά-motoneurons in the motor centers of the brainstem and spinal cord, which regulate physical movements. Thin, slow-conducting myelin axons extend from small pyramidal cells. These cells have a background activity of about 15 Hz, which increases or decreases during movement. They innervate small (low-threshold) ά-motoneurons in the brainstem and spinal motor centers, which regulate muscle tone.

Pyramid paths consist of 1 million fibers of the corticospinal tract, which begin from the cortex of the upper and middle third of the precentral gyrus, and 20 million fibers of the corticobulbar tract, which begins from the cortex of the lower third of the precentral gyrus. The fibers of the pyramidal tract end on the ά-motoneurons of the motor nuclei III - VII and IX - XII cranial nerves (corticobulbar tract) or on the spinal motor centers (corticospinal tract). Through the motor cortex and pyramidal tracts, voluntary simple movements and complex goal-directed motor programs are carried out, for example, professional skills, the formation of which begins in the basal ganglia and cerebellum and ends in the secondary motor cortex. Most of the fibers of the pyramidal tracts cross, but a small part of the fibers remain uncrossed, which helps compensate for impaired movement functions in unilateral lesions. The premotor cortex also carries out its functions through the pyramidal tracts: motor skills of writing, turning the head, eyes and torso in the opposite direction, as well as speech (Broca’s speech motor center, area 44). In the regulation of writing and especially oral speech, there is a pronounced asymmetry of the cerebral hemispheres: in 95% of right-handers and 70% of left-handers, oral speech is controlled by the left hemisphere.

To the cortical extrapyramidal pathways include corticorubral and corticoreticular tracts, starting approximately from those zones that give rise to the pyramidal tracts. The fibers of the corticorubral tract end on the neurons of the red nuclei of the midbrain, from which the rubrospinal tracts further extend. The fibers of the corticoreticular tracts end on the neurons of the medial nuclei of the reticular formation of the pons (the medial reticulospinal tracts extend from them) and on the neurons of the reticular giant cell nuclei of the medulla oblongata, from which the lateral reticulospinal tracts begin. Through these pathways, tone and posture are regulated, which provide precise, targeted movements. Cortical extrapyramidal tracts are a component of the extrapyramidal system of the brain, which includes the cerebellum, basal ganglia, and motor centers of the brainstem. The extrapyramidal system regulates tone, balance posture, and the performance of learned motor acts such as walking, running, speaking, and writing. Since the corticopyramidal pathways give off their numerous collateral structures to the extrapyramidal system, both systems work in functional unity.

Assessing in general the role of various structures of the brain and spinal cord in the regulation of complex directed movements, it can be noted that the urge (motivation) to move is created in the limbic system, the intention of movement - in the associative cortex of the cerebral hemispheres, movement programs - in the basal ganglia, cerebellum and premotor cortex, and the execution of complex movements occurs through the motor cortex, motor centers of the brainstem and spinal cord.

Interhemispheric relationships. Interhemispheric relationships in humans manifest themselves in two forms - functional asymmetry of the cerebral hemispheres and their joint activity.

╠ Functional asymmetry hemispheres is the most important psychophysiological property of the human brain. There are mental, sensory and motor interhemispheric functional asymmetries of the brain. In a study of psychophysiological functions, it was shown that in speech the verbal information channel is controlled by the left hemisphere, and the non-verbal channel (voice, intonation) by the right. Abstract thinking and consciousness are associated primarily with the left hemisphere. When developing a conditioned reflex, the right hemisphere dominates in the initial phase, and during the strengthening of the reflex, the left hemisphere dominates. The right hemisphere processes information simultaneously, synthetically, according to the principle of deduction; spatial and relative features of an object are better perceived. The left hemisphere processes information sequentially, analytically, according to the principle of induction, and better perceives the absolute characteristics of an object and temporal relationships. IN emotional sphere the right hemisphere causes predominantly negative emotions, controls the manifestations of strong emotions, and is generally more “emotional.” The left hemisphere causes mainly positive emotions and controls the manifestation of weaker emotions.

In the sensory sphere, the role of the right and left hemispheres is best demonstrated in visual perception. The right hemisphere perceives the visual image holistically, in all details at once, it more easily solves the problem of distinguishing objects and recognizing visual images of objects, which is difficult to describe in words, creating the prerequisites for concrete sensory thinking. The left hemisphere evaluates the visual image in a dissected, analytical way, with each feature analyzed separately. Familiar objects are easier to recognize and problems of object similarity are solved; visual images are devoid of specific details and have a high degree of abstraction; the prerequisites for logical thinking are created.

Motor asymmetry is expressed primarily in right-left-handedness, which is controlled by the motor cortex of the opposite hemisphere. The asymmetry of other muscle groups is individual, not specific.

Fig.3. Asymmetry of the cerebral hemispheres.

╠ Pairing in the activity of the cerebral hemispheres is ensured by the presence of the commissural system (corpus callosum, anterior and posterior, hippocampal and habenular commissures, interthalamic fusion), which anatomically connect the two hemispheres of the brain. In other words, both hemispheres are connected not only by horizontal connections, but also by vertical ones. Basic facts obtained using electrophysiological techniques have shown that excitation from the site of stimulation of one hemisphere is transmitted through the commissural system not only to the symmetrical region of the other hemisphere, but also to asymmetrical areas of the cortex. A study of the method of conditioned reflexes showed that in the process of developing a reflex, a “transfer” of the temporary connection to the other hemisphere occurs. Elementary forms of interaction between the two hemispheres can be carried out through the quadrigeminal region and the reticular formation of the trunk.

Brain based the latest anatomical... influences bark large hemispheres on bark cerebellum. Lower reflex centers of the spinal brain and stem parts head brain ...

G. A. Petrov physiology with basic anatomy

Document

... BARK BIG HEMISPHERE HEAD BRAIN Module 3. HUMAN SENSORY SYSTEMS 3.1. General physiology ... new ... 14 . vital Part respiratory center is located in the spinal brain rear brain average brain intermediate brain bark large hemispheres ...

N. P. Rebrova Physiology of sensory systems

Educational and methodological manual

Included composite part in natural science disciplines “Anatomy and physiology person", " Physiology sensory systems... in head brain. These pathways begin in the spinal cord brain, switch in the thalamus and then go to bark large hemispheres. ...

Anastasia Novykh “Sensei. Primordial Shambhala" (2)

Document

Average brain, subcortical departments bark large hemispheres and the cerebellum... one of the most mysterious parts head brain and a man on... a tram. 14 We left... in the beginning new shower, creation new"larvae... historian, orientalist, physiologist. But simple...

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

Limbic system

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

History of origin

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

• Dominance is a manifestation of superiority in a variety of parameters.
• Food – subject's nutrition
• Reproduction - transferring one's genome to the next generation

Because man has animal roots, the human brain has a limbic system. Initially, Homo sapiens possessed only affects that influenced the physiological state of the body. Over time, communication developed using the type of scream (vocalization). Individuals who were able to convey their state through emotions survived. Over time, the emotional perception of reality was increasingly formed. This evolutionary layering allowed people to unite into groups, groups into tribes, tribes into settlements, and the latter into entire nations. The limbic system was first discovered by 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 subcortical structures (caudate nucleus, amygdala, globus pallidus). The listed names of the various types of bark indicate their formation at the indicated time of evolution.

Weight specialists in the field of neurobiology, they studied 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 anatomy of the limbic complex is based on the gradual layering of one part onto another. So, the cingulate gyrus lies on top, and then descending:

• corpus callosum;
• vault;
• 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 of closed circles, which creates conditions for prolonged circulation of excitation in the limbus.

Functionality of the limbic system

The visceral brain actively receives and processes information from the surrounding 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 environmental conditions.

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 environmental phenomena.
• Memory. This function is carried out by the hippocampus, located in the structure of the limbic system. Mnestic processes are ensured by reverberation processes - a circular movement of excitation in the closed neural circuits of the seahorse.
• Selecting and correcting a model of appropriate behavior.
• Training, retraining, fear and aggression;
• Development of spatial skills.
• Defensive and foraging behavior.
• Expressiveness of speech.
• Acquisition and maintenance of various phobias.
• Function of the olfactory system.
• Reaction of caution, preparation for action.
• Regulation of sexual and social behavior. There is a concept emotional intelligence– the ability to recognize the emotions of others.

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

Perhaps there is a question among women about how to turn on the limbic system in men. However answer simple: no way. In all men, the limbus works fully (with the exception of 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 achieve the development of limbus at the level of women.

The development of the limbic system in an infant largely depends on the type of upbringing and the general attitude towards it. A stern look and a cold smile do not contribute to the development of the limbic complex, unlike a tight hug and a sincere smile.

Interaction with the neocortex

The neocortex and limbic system are tightly connected through many pathways. Thanks to this unification, these two structures form one whole of the human mental sphere: they connect the mental component with the emotional one. The neocortex acts as a regulator of animal instincts: before committing any action spontaneously caused by emotions, human thought, as a rule, undergoes a series of cultural and moral inspections. In addition to controlling emotions, the neocortex has an auxiliary effect. The feeling of hunger arises in the depths of the limbic system, and the higher cortical centers that regulate behavior search for food.

The father of psychoanalysis, Sigmund Freud, did not ignore 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 no data on the limbus, but the great scientist guessed about similar brain devices. Thus, the more cultural and moral layers (super ego - neocortex) an individual had, the more his primary animal instincts (id - limbic system) are suppressed.

Violations and their consequences

Based on the fact that the limbic system is responsible for many functions, this very many can be susceptible to various damages. The limbus, like other structures of the brain, can be subject to injury and other harmful factors, which include tumors with hemorrhages.

Syndromes of damage to the limbic system are rich in number, the main ones are:

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 hippocampus.

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

Pathological anxiety and phobias. Disturbance in the activity of the amygdala leads to a mediator imbalance, which, in turn, is accompanied by a disorder of emotions, which includes anxiety. A phobia is an irrational fear of a harmless object. In addition, an imbalance of neurotransmitters provokes depression and mania.

Autism. At its core, autism is a deep and serious maladjustment in society. The inability of the limbic system to recognize the emotions of other people leads to serious 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 damage human brain is subject to various disorders of loss of consciousness, including absence and syncope.

Neocortex

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

History of origin

IN this moment neocortex is the highest stage of human evolution. Scientists were able to study the first manifestations of the neobark in representatives of reptiles. The last animals in the chain of development that did not have a new cortex were birds. And only a person is developed.

Evolution is a complex and long process. Every species of creature goes through a harsh evolutionary process. If an animal species was unable to adapt to a changing external environment, the species lost its existence. Why does a person was able to adapt and survive to this day?

Being in favorable living conditions (warm climate and protein foods), human descendants (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 critical mass over a short period of time (several million years). By the way, the brain mass in those days was 20% greater than that of a modern person.

However, all good things come to an end sooner or later. With a change in climate, descendants needed to change their place of residence, and with it, start looking for food. Having a huge brain, descendants began to use it to find food, and then for social involvement, because. It turned out that by uniting into groups according to certain behavioral criteria, it was easier to survive. For example, in a group where everyone shared food with other members of the group, there was a greater chance of survival (Someone was good at picking berries, someone was good at hunting, etc.).

From this moment it began separate evolution in the brain, separate from the evolution of the whole body. Since those times, a person’s appearance has not changed much, but the composition of the brain is radically different.

What does it consist of?

The new cerebral cortex is a collection of nerve cells that form a complex. Anatomically, there are 4 types of cortex, depending on its location - , occipital, . Histologically, the cortex consists of six balls of cells:

• Molecular ball;
• external granular;
• pyramidal neurons;
• internal granular;
• ganglion layer;
• multiform cells.

What functions does it perform?

The human neocortex is classified into three functional areas:

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

Conclusion

To summarize, we can highlight the following:

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