New crust(neocortex) is a layer of gray matter with a total area of 1500-2200 square centimeters, covering the cerebral hemispheres. The neocortex makes up about 72% of the total area of the cortex and about 40% of the mass of the brain. The neocortex contains 14 billion. Neurons, and the number of glial cells is approximately 10 times greater.
In phylogenetic terms, the cerebral cortex is the youngest neural structure. In humans, it carries out the highest regulation of body functions and psychophysiological processes that ensure various shapes behavior.
In the direction from the surface of the new crust inwards, six horizontal layers are distinguished.
Molecular layer. It 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 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 mainly of medium-sized pyramidal cells. The axons of these cells, like granule cells of the 2nd layer, form corticocortical associative connections.
Vgutrenniy granular layer. The nature of the cells (stellate cells) and the arrangement of their fibers is similar to the outer granular layer. In this layer, afferent fibers have synaptic endings coming from neurons of specific nuclei of the thalamus and, therefore, from receptors of sensory systems.
Inner pyramidal layer. Formed by medium and large pyramidal cells. Moreover, Betz's giant pyramidal cells are located in the motor cortex. The axons of these cells form the afferent corticospinal and corticobulbar motor pathways.
Layer of polymorphic cells. It is formed predominantly by spindle-shaped cells, the axons of which form the corticothalamic tracts.
Assessing the afferent and efferent connections of the neocortex in general, it should be noted that in layers 1 and 4 the perception and processing of signals entering the cortex occur. Neurons of layers 2 and 3 carry out corticocortical associative connections. The efferent pathways leaving the cortex are formed mainly in layers 5 and 6.
Histological evidence shows that the elementary neural circuits involved in information processing are located perpendicular to the surface of the cortex. Moreover, they are located in such a way that they cover all layers of the cortex. Such associations of neurons were called by scientists neural columns. Adjacent neural columns can partially overlap and also interact with each other.
Increasing role of the cortex in phylogenesis big brain, analysis and regulation of body functions and subordination of the underlying parts of the central nervous system are defined by scientists as corticalization of functions(Union).
Along with the corticalization of the functions of the neocortex, it is customary to distinguish the localization of its functions. The most commonly used approach to the functional division of the cerebral cortex is to distinguish it into sensory, associative and motor areas.
Sensory cortical areas – zones into which sensory stimuli are projected. 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 (central, posterior lateral and medial). The sensory cortex has well-defined layers 2 and 4 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(nuclear parts of analyzers, as I.P. Pavlov believed). 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 postcentral lobule on the medial surface of the hemispheres (fields 1–3), which is designated as somatosensory area. 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 body parts in this area is characterized by the fact that the projection of the head and upper sections The torso is located in the inferolateral areas of the postcentral gyrus, the projection of the lower half of the torso and legs is in the superomedial zones of the gyrus, and the projection of the lower part of the lower leg and feet is in the cortex of the postcentral lobule on the medial surface of the hemispheres (Fig. 12).
Moreover, the projection of the most sensitive areas (tongue, larynx, fingers, etc.) has relatively large areas compared to other parts of the body.
Rice. 12. Projection of human body parts onto the area of the cortical end of the general sensitivity analyzer
(section of the brain in the frontal plane)
In the depths of the lateral sulcus is located auditory cortex(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: in different areas The cortex represents various parts of the organ of Corti. The projection cortex of the temporal lobe also includes, as scientists suggest, the center of the vestibular analyzer in the superior and middle temporal gyri. The processed sensory information is used to form a “body schema” and regulate the functions of the cerebellum (temporopontine-cerebellar tract).
Another area of the neocortex is located in the occipital cortex. This primary visual area. Here there is a topical representation of retinal receptors. In this case, each point of the retina corresponds to its own section of the visual cortex. 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 cerebral cortex in this area leads to the appearance of light sensations. Located near the primary visual area secondary visual area. Neurons in this area are multimodal and respond not only to light, but also to tactile and auditory stimuli. It is no coincidence that it is in this visual area that synthesis occurs various types sensitivity and more complex visual images and their recognition arise. Irritation of this area of the cortex causes visual hallucinations, obsessive sensations, and eye movements.
The main part of the information about the surrounding world and the internal environment of the body, received in the sensory cortex, is transferred for further processing to the associative cortex.
Association cortical areas (intersensory, interanalyzer), includes areas of the neocortex that are located next to the sensory and motor areas, but do not directly perform sensory or motor functions. The boundaries of these areas are not clearly defined, which is due to secondary projection zones, functional properties which are transitional between the properties of primary projection and associative zones. The association cortex is phylogenetically the youngest area of the neocortex, which has received the greatest development in primates and humans. In humans, it makes up about 50% of the entire cortex or 70% of the neocortex.
The main physiological feature of the neurons of the associative cortex, which distinguishes them from the neurons of the primary zones, is polysensory (polymodality). They respond with almost the same threshold not to one, but to several stimuli - visual, auditory, skin, etc. The polysensory nature of the neurons of the associative cortex is created both by its corticocortical connections with different projection zones, and by its main afferent input from the associative nuclei of the thalamus, in which complex processing of information from various sensory pathways has already occurred. As a result of this, the associative cortex is a powerful apparatus for the convergence of various sensory excitations, allowing complex processing of information about the external and internal environment of the body and using it to carry out higher mental functions.
Based on thalamocortical projections, two associative systems of the brain are distinguished:
thalamoparietal;
Thalomotemporal.
Thalamotparietal system is represented by associative zones of the parietal cortex, 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 afferent 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.
Gnosis- these are various types of recognition: shapes, sizes, meanings of objects, understanding of speech, etc. Gnostic functions include the assessment of spatial relationships, for example, the relative position of objects. The center of stereognosis is located in the parietal cortex (located behind the middle sections of the postcentral gyrus). It provides the ability to recognize objects by touch. A variant of the gnostic function is also the formation in the consciousness of a three-dimensional model of the body (“body diagram”).
Under praxis understand purposeful action. The praxis center is located in the supramarginal gyrus and ensures the storage and implementation of a program of motor automated acts (for example, combing one's hair, shaking hands, etc.).
Thalamobic system. It is represented by associative zones of the frontal cortex, which have the main afferent input from the mediodorsal nucleus of the thalamus. The main function of 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 function is based on other functions of the talomoloby system, such as:
formation dominant motivation providing direction for human behavior. This function is based on the close bilateral connections of the frontal cortex and the limbic system and the role of the latter in the regulation of a person’s higher emotions associated with his social activities and creativity;
ensuring probabilistic forecasting, which is expressed in changes in behavior in response to changes in environmental conditions and dominant motivation;
self-control of actions by constant comparison the result of an action with initial intentions, which is associated with the creation of a foresight apparatus (according to the theory functional system P.K. Anokhin, acceptor of the result of the action).
As a result of a prefrontal lobotomy performed for medical reasons, in which the connections between the frontal lobe and the thalamus intersect, the development of “emotional dullness”, a lack of motivation, strong intentions and plans based on prediction, is observed. Such people become rude, tactless, they have a tendency to repeat certain motor acts, although the changed situation requires the performance of completely different actions.
Along with the thalamoparietal and thalamofrontal systems, some scientists propose to distinguish the thalamotemporal system. However, the concept of the thalamotemporal system has not yet received confirmation and sufficient scientific elaboration. Scientists note a certain role for the temporal cortex. Thus, some associative centers (for example, stereognosis and praxis) also include areas of the temporal cortex. Wernicke's auditory speech center is located in the temporal cortex, located in the posterior parts of the superior temporal gyrus. It is this center that provides speech gnosis - recognition and storage oral speech, both your own and someone else's. In the middle part of the superior temporal gyrus there is a center for recognizing musical sounds and their combinations. At the border of the temporal, parietal and occipital lobes is the reading center writing, providing recognition and storage of written speech images.
It should also be noted that the psychophysiological functions carried out by the associative cortex initiate behavior, the obligatory component of which is voluntary and purposeful movements carried out when mandatory participation motor cortex.
Motor cortex areas . The concept of the motor cortex of the cerebral hemispheres began to form in the 80s of the 19th century, when it was shown that electrical stimulation of certain cortical zones in animals causes movement of the limbs of the opposite side. Based on modern research, it is customary to distinguish two motor areas in the motor cortex: primary and secondary.
IN primary motor cortex(precentral gyrus) there are neurons innervating the motor neurons of the muscles of the face, trunk and limbs. It has a clear topography of the projections of the body muscles. 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. 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 minimum threshold, which indicates her high excitability. They (these motor reactions) are represented by elementary contractions of the opposite side of the body. When this cortical area is damaged, the ability to make fine coordinated movements of the limbs, especially the fingers, is lost.
Secondary motor cortex. 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 premotor cortex receives the bulk of the efferent impulses from the basal ganglia and cerebellum and is involved in recoding information about the plan of complex movements. Irritation of this area of the cortex causes complex coordinated movements (for example, turning the head, eyes and torso in opposite directions). In the premotor cortex there are motor centers associated with human social functions: in the posterior section of the middle frontal gyrus there is a center for written speech, in the posterior section of the inferior frontal gyrus there is a center for motor speech (Broca's center), as well as a musical motor center that determines the tone of speech and ability sing.
The motor cortex is often called the agranular cortex because its granular layers are poorly defined, but the layer containing Betz's giant pyramidal cells is more pronounced. 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 pyramidal cells. Pyramidal neurons and their associated interneurons are located vertically relative to the surface of the cortex. Such nearby neural complexes that perform similar functions are called functional motor speakers. 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 located, as a rule, in several columns.
The main efferent connections of the motor cortex are carried out through the pyramidal and extrapyramidal pathways, starting from the giant pyramidal cells of Betz and the smaller pyramidal cells of the cortex of the precentral gyrus, premotor cortex and postcentral gyrus.
Pyramid Path consists of 1 million fibers of the corticospinal tract, starting from the cortex of the upper and middle third of the percentral gyrus, and 20 million fibers of the corticobulbar tract, starting from the cortex of the lower third of the precentral gyrus. Through the motor cortex and pyramidal tracts, voluntary simple and complex goal-directed motor programs are carried out (for example, professional skills, the formation of which begins in the basal ganglia and ends in the secondary motor cortex). Most of the fibers of the pyramidal tracts cross. But a small part of them remains uncrossed, which helps compensate for impaired movement functions in unilateral lesions. The premotor cortex also carries out its functions through the pyramidal tracts (motor writing skills, turning the head and eyes in the opposite direction, etc.).
To cortical extrapyramidal pathways These include the corticobulbar and corticoreticular tracts, which begin in approximately the same area as the pyramidal tracts. The fibers of the corticobulbar tract end on the neurons of the red nuclei of the midbrain, from which the rubrospinal tracts proceed. 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, providing precise, targeted movements. Cortical extrapyramidal tracts are a component of the extrapyramidal system of the brain, which includes the cerebellum, basal ganglia, motor centers of the trunk. This system regulates tone, posture, coordination and correction of movements.
Assessing the overall role various structures 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 frontal system, the intention of movement is in the associative cortex of the cerebral hemispheres, the movement program is 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 manifest themselves in humans in two main forms:
functional asymmetry cerebral hemispheres:
joint activity of the cerebral hemispheres.
Functional asymmetry of the hemispheres is the most important psychophysiological property of the human brain. The study of functional asymmetry of the hemispheres began in the middle of the 19th century, when French physicians M. Dax and P. Broca showed that human speech impairment occurs when the cortex of the inferior frontal gyrus, usually the left hemisphere, is damaged. Some time later, the German psychiatrist K. Wernicke discovered an auditory speech center in the posterior cortex of the superior temporal gyrus of the left hemisphere, the defeat of which leads to impaired understanding of oral speech. These data and the presence of motor asymmetry (right-handedness) contributed to the formation of the concept according to which a person is characterized by left-hemisphere dominance, which formed evolutionarily as a result of work activity and is a specific property of his brain. In the twentieth century, as a result of the use of various clinical techniques(especially in the study of patients with split brains - transection of the corpus callosum was carried out), it was shown that in a number of psychophysiological functions in humans, not the left, but the right hemisphere dominates. Thus, the concept of partial dominance of the hemispheres arose (its author is R. Sperry).
It is customary to highlight mental, sensory And motor interhemispheric asymmetry of the brain. Again, when studying speech, it was shown that 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 in initial phase The right hemisphere dominates, and during exercises, that is, strengthening the reflex, the left hemisphere dominates. Right hemisphere carries out information processing simultaneously statically, according to the principle of deduction, spatial and relative characteristics of objects are better perceived. Left hemisphere processes information sequentially, analytically, according to the principle of induction, and better perceives the absolute characteristics of objects and temporal relationships. IN emotional sphere the right hemisphere primarily determines older, negative emotions and controls the manifestation of strong emotions. In general, the right hemisphere is “emotional.” The left hemisphere determines 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 that are difficult to describe in words, creating the prerequisites for concrete sensory thinking. The left hemisphere evaluates the visual image as dissected. Familiar objects are easier to recognize and problems of object similarity are solved; visual images are devoid of specific details and have high degree abstractions, the prerequisites for logical thinking are created.
Motor asymmetry is due to the fact that the muscles of the hemispheres, providing a new, higher level of regulation complex functions brain, at the same time increases the requirements for combining the activities of the two hemispheres.
Joint 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.
Clinical studies have shown that in addition to transverse commissural fibers, which provide interconnection between the hemispheres of the brain, also longitudinal and vertical commissural fibers.
Questions for self-control:
General characteristics of the new cortex.
Functions of the neocortex.
The structure of the new cortex.
What are neural columns?
What areas of the cortex are identified by scientists?
Characteristics of the sensory cortex.
What are primary sensory areas? Their characteristics.
What are secondary sensory areas? Their functional purpose.
What is the somatosensory cortex and where is it located?
Characteristics of the auditory cortex.
Primary and secondary visual areas. Their general characteristics.
Characteristics of the associative area of the cortex.
Characteristics of associative systems of the brain.
What is the thalamoparietal system? Its functions.
What is the thalamic system? Its functions.
General characteristics of the motor cortex.
Primary motor cortex; its characteristics.
Secondary motor cortex; its characteristics.
What are functional motor speakers?
Characteristics of cortical pyramidal and extrapyramidal tracts.
Based on its 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, and includes the 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 vegetative functions, plays a role in the formation of sexual, eating, defensive instinctive behavior, and providing emotions.
All other cortical structures belong to the neocortex, which occupies about 96% total area the entire cortex.
Location nerve cells in the cortex is designated by the term “cytoarchitecture.” And the conductive fibers are called “myeloarchitecture”.
The neocortex consists of 6 cell layers that differ in cell composition, nerve connections and functions. In the areas of ancient cortex and old cortex, only 2-3 layers of cells are detected. Neurons in the upper four layers of the neocortex primarily process information from other parts of the 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 functioning of stem structures and the spinal cord.
Layer 1 is the outermost, molecular layer. It contains mainly nerve fibers from deeper neurons. In addition, it does not contain a large number of small cells. The fibers of the molecular layer form bonds between various 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.
Layer 3 - outer pyramidal. It is the widest, contains mainly medium and less often small and large pyramidal neurons. The dendrites of neurons from this layer are directed to the second layer.
4th layer - internal granular. Comprises large number small granular, as well as medium and large stellate cells. They are divided into two sublayers: 4a and 4b.
Layer 5 - ganglion, or internal pyramidal. Characterized by the presence of large pyramidal neurons. Their upwardly directed dendrites reach the molecular layer, and the basal and collateral axons are distributed in the fifth layer.
Layer 6 - polymorphic. It contains, along with cells of other forms, spindle-shaped neurons. The shapes of other cells are very diverse: they have a triangular, pyramidal, oval and polygonal shape.
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 physiological state bodies. 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), the archicortex (old cortex), part of the neocortex (new cortex) and some subcortical structures ( caudate nucleus, amygdala, pale ball). Names listed different types of cortex denotes 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 system reticular formation(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 difficult paths and bilateral relations. Such a branched system of branches forms a complex 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 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 environmental phenomena.
- Memory. This function is carried out by the hippocampus, located in the structure of the limbic system. Mnestic processes are provided by reverberation processes - circular motion excitement in closed neural circuits sea horse
- 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, which manifests itself in the form of: changes 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 mental sphere person: they connect the mental component with the emotional. The neocortex acts as a regulator of animal instincts: before performing 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. The phobia is irrational fear in relation to 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 – highest level 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 kind of creature goes through the rigors 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 conditions residence (warm climate and protein food), 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 group members there was more chances for 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 then appearance the person 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
So, the area of the cerebral cortex of one human hemisphere is about 800 - 2200 square meters. cm, thickness -- 1.5?5 mm. Most of bark (2/3) lies deep in the furrows and is not visible from the outside. Thanks to this organization of the brain in the process of evolution, it was possible to significantly increase the area of the cortex with a limited volume of the skull. The total number of neurons in the cortex can reach 10 - 15 billion.
The cerebral cortex itself is heterogeneous, therefore, in accordance with phylogeny (by origin), ancient cortex (paleocortex), old cortex (archicortex), intermediate (or middle) cortex (mesocortex) and new cortex (neocortex) are distinguished.
Ancient bark
Ancient bark, (or paleocortex)- This is the most simply structured cerebral cortex, which contains 2–3 layers of neurons. According to a number of famous scientists such as H. Fenish, R. D. Sinelnikov and Ya. R. Sinelnikov, indicating that the ancient cortex corresponds to the area of the brain that develops from the piriform lobe, and the components of the ancient cortex are the olfactory tubercle and the surrounding cortex, including area of the anterior perforated substance. The composition of the ancient bark includes the following structural formations such as the prepiriform, periamygdala cortex, diagonal cortex and olfactory medulla, including the olfactory bulbs, olfactory tubercle, septum pellucidum, septum pellucidum nuclei and fornix.
According to M. G. Prives and a number of some scientists, the olfactory brain is topographically divided into two sections, including a number of formations and convolutions.
1. peripheral section (or olfactory lobe), which includes formations lying at the base of the brain:
olfactory bulb;
olfactory tract;
olfactory triangle (within which the olfactory tubercle is located, i.e., the apex of the olfactory triangle);
internal and lateral olfactory gyri;
internal and lateral olfactory stripes (the fibers of the internal stripe end in the subcallosal field of the paraterminal gyrus, the septum pellucidum and the anterior perforated substance, and the fibers of the lateral stripe end in the parahippocampal gyrus);
anterior perforated space or substance;
diagonal stripe, or Broca's stripe.
2. The central section includes three convolutions:
parahippocampal gyrus (hippocampal gyrus, or seahorse gyrus);
dentate gyrus;
cingulate gyrus (including its anterior part - the uncus).
Old and intermediate bark
Old bark (or archicortex)-- this cortex appears later than the ancient cortex and contains only three layers of neurons. It consists of the hippocampus (seahorse or Ammon's horn) with its base, the dentate gyrus and the cingulate gyrus. cortex brain neuron
Intermediate bark (or mesocortex)-- which is a five-layer cortex that separates the new cortex (neocortex) from the ancient cortex (paleocortex) and old cortex (archicortex) and because of this the middle cortex is divided into two zones:
- 1. peripaleocortical;
- 2. periarchiocortical.
According to V. M. Pokrovsky and G. A. Kuraev, the mesocortex includes the ostracic gyrus, as well as the parahippocampal gyrus in the entorhinal region bordering the old cortex and the prebase of the hippocampus.
According to R. D. Sinelnikov and Ya. R. Sinelnikov, the intermediate cortex includes such formations as the lower part of the insular lobe, the parahippocampal gyrus and the lower part of the limbic region of the cortex. But it is necessary to understand that the limbic region is understood as part of the new cortex of the cerebral hemispheres, which occupies the cingulate and parahippocampal gyri. There is also an opinion that the intermediate cortex is an incompletely differentiated zone of the insular cortex (or visceral cortex).
Due to the ambiguity of such an interpretation of structures related to ancient and old bark translated into the expediency of using a unified concept as archiopaleocortex.
The structures of the archiopaleocortex have multiple connections, both among themselves and with other brain structures.
New crust
New bark (or neocortex)- phylogenetically, i.e. in its origin - this is the most recent formation of the brain. Due to later evolutionary emergence And rapid development neocortex in its organization complex shapes higher nervous activity and its highest hierarchical level which is vertically coordinated with the activity of the central nervous system making up the most features of this part of the brain. The features of the neocortex have attracted and continue to hold the attention of many researchers studying the physiology of the cerebral cortex for many years. Currently, old ideas about the exclusive participation of the neocortex in the formation of complex forms of behavior, including conditioned reflexes, came the idea of how top level thalamocortical systems functioning together with the thalamus, limbic and other brain systems. The neocortex is involved in mental experience outside world- his perception and creation of his images, which are preserved for a more or less long time.
A feature of the structure of the neocortex is the screen principle of its organization. The main thing in this principle - the organization of neural systems is the geometric distribution of projections of higher receptor fields on a large surface of the neuronal field of the cortex. Also characteristic of the screen organization is the organization of cells and fibers that run perpendicular to the surface or parallel to it. This orientation of cortical neurons provides opportunities for combining neurons into groups.
As for the cellular composition in the neocortex, it is very diverse, the size of neurons is approximately from 8–9 μm to 150 μm. The vast majority of cells belong to two types: pararamid and stellate. The neocortex also contains spindle-shaped neurons.
In order to better examine the features of the microscopic structure of the cerebral cortex, it is necessary to turn to architectonics. Under the microscopic structure, cytoarchitectonics (cellular structure) and myeloarchitectonics (fibrous structure of the cortex) are distinguished. The beginning of the study of the architectonics of the cerebral cortex dates back to end of the XVIII century, when in 1782 Gennari first discovered the heterogeneity of the structure of the cortex in the occipital lobes of the hemispheres. In 1868, Meynert divided the diameter of the cerebral cortex into layers. In Russia, the first researcher of the bark was V. A. Betz (1874), who discovered large pyramidal neurons in the 5th layer of the cortex in the area of the precentral gyrus, named after him. But there is another division of the cerebral cortex - the so-called Brodmann field map. In 1903, the German anatomist, physiologist, psychologist and psychiatrist K. Brodmann published a description of fifty-two cytoarchitectonic fields, which are areas of the cerebral cortex, different in their cellular structure. Each such field differs in size, shape, location of nerve cells and nerve fibers and of course the various fields are associated with various functions brain. Based on the description of these fields, a map of 52 Brodman fields was compiled
Which are only outlined in lower mammals, but in humans they form the main part of the cortex. The new cortex is located in top layer hemispheres of the brain, has a thickness of 2-4 millimeters and is responsible for higher nerve functions- sensory perception, execution of motor commands, conscious thinking and, in humans, speech.
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. At the beginning of the 20th century, Brodmann showed that in all mammals the neocortex has 6 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 contains memory in time, something like cause-and-effect relationships, hierarchically developing into more and more large objects from smaller ones.
Functions
The neocortex is embryonically derived from the dorsal telencephalon, which is part of the forebrain. The neocortex is divided into regions delimited by cranial sutures, which perform different functions. For example, the occipital lobe contains the primary visual cortex, and the temporal lobe contains the primary auditory cortex. Further subdivisions or areas 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 located 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 important role in the processes of sleep, memory and learning. Semantic memories appear to be stored in the neocortex, specifically in the anterolateral temporal lobe of the neocortex. The neocortex is also responsible for transmitting sensory information to the basal ganglia. The pulsation frequency 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, it was created computer model brain, which modeled the electrochemistry of the neocortex - “Blue Brain project” (Blue Brain Project). The project was created to improve understanding of the processes of perception, learning, memory and to obtain additional knowledge about mental disorders.