Cortex. Localization of functions. Defeat syndromes. Localization of functions in the cerebral cortex. Electrical activity of the brain Tasks for independent work
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The cerebral cortex. Localization of functions in the cerebral cortex. limbic system. Eet. Liquor. Physiology vnd. The concept of vnd. Principles of Pavlov's reflex theory. The difference between conditioned reflexes and unconditioned reflexes. The mechanism of formation of conditioned reflexes. The meaning of conditioned reflexes. I and II signal systems. Types of vnd. Memory. Sleep physiology
telencephalon represented by two hemispheres, which include:
· cloak(bark),
· basal nuclei,
· olfactory brain.
In each hemisphere there are
1. 3surfaces:
superolateral,
medial
bottom.
2. 3 the edges:
top,
bottom,
medial.
3. 3 poles:
frontal
occipital,
temporal.
The cerebral cortex forms protrusions - convolutions. Between the convolutions are furrows. Permanent furrows divide each hemisphere into 5 stakes:
frontal - contains motor centers,
parietal - centers of skin, temperature, proprioceptive sensitivity,
occipital - visual centers,
temporal - centers of hearing, taste, smell,
Islet - the highest centers of smell.
Permanent furrows:
central - located vertically, separates the frontal lobe from the parietal;
lateral - separates the temporal from the frontal and parietal lobes, in its depth there is an island, limited by a circular groove;
parieto-occipital - located on the medial surface of the hemisphere, separates the occipital and parietal lobes.
Olfactory brain- contains a number of formations of various origins, which are topographically divided into two sections:
1. Peripheral department(located in the anterior part of the lower surface of the cerebral hemisphere) :
olfactory bulb,
olfactory tract
olfactory triangle,
anterior perforated space.
2. Central department:
vaulted (parahippocampal) gyrus with a hook (anterior part of the vaulted gyrus) - on the lower and medial surface of the cerebral hemispheres,
The hippocampus (gyrus of the sea horse) is located in the lower horn of the lateral ventricle.
cerebral cortex (cloak)- is the highest and youngest department of the central nervous system.
Consists of nerve cells, processes and neuroglia area ~ 0.25 m 2
Most areas of the cerebral cortex are characterized by a six-layer arrangement of neurons. The cerebral cortex consists of 14-17 billion cells.
The cellular structures of the brain are represented by:
Ø pyramidal - predominantly efferent neurons
Ø spindle-shaped - predominantly efferent neurons
Ø stellate - perform an afferent function
The processes of the nerve cells of the cerebral cortex connect its various sections to each other or establish contacts between the cerebral cortex and the underlying sections of the central nervous system.
Form 3 types of connection:
1. Associative - connect different parts of one hemisphere - short and long.
2. Commissural - most often connect identical parts of the two hemispheres.
3. Conductive (centrifugal) - connect the cerebral cortex with other parts of the central nervous system and through them with all organs and tissues of the body.
Neuroglial cells perform the role of:
1. They are a supporting tissue, they are involved in the metabolism of the brain.
2. Regulate blood flow inside the brain.
3. A neurosecret is secreted that regulates the excitability of neurons in the cerebral cortex.
Functions of the cerebral cortex:
1. Carries out the interaction of the organism with the environment due to unconditioned and conditioned reflexes.
2. They are the basis of higher nervous activity (behavior) of a person.
3. The implementation of higher mental functions - thinking, consciousness.
4. Regulates and integrates the work of all internal organs and regulates such intimate processes as metabolism.
HEMISPHERES
gray matter white matter
1. Bark 2. Nuclei
- 1) at the beginning of the XIX century. F. Gall suggested that the substratum of various mental "abilities" (honesty, thrift, love, etc.))) are small areas of n. mk. CBP, which grow with the development of these abilities. Gall believed that various abilities have a clear localization in the GM and that they can be identified by the protrusions on the skull, where the n corresponding to this ability supposedly grows. mk. and begins to bulge, forming a tubercle on the skull.
- 2) In the 40s of the XIX century. Gall is opposed by Flurence, who, on the basis of experiments in the extirpation (removal) of parts of the GM, puts forward a position on the equipotentiality (from the Latin equus - "equal") of the functions of the CBP. In his opinion, the GM is a homogeneous mass, functioning as a single integral organ.
- 3) The basis of the modern theory of the localization of functions in the CBP was laid by the French scientist P. Broca, who in 1861 singled out the motor center of speech. Subsequently, the German psychiatrist K. Wernicke in 1873 discovered the center of verbal deafness (impaired understanding of speech).
Since the 70s. the study of clinical observations showed that the defeat of limited areas of the CBP leads to a predominant loss of well-defined mental functions. This gave grounds to single out separate sections in the CBP, which began to be considered as nerve centers responsible for certain mental functions.
Summarizing the observations made on the wounded with brain damage during the First World War, in 1934 the German psychiatrist K. Kleist compiled the so-called localization map, in which even the most complex mental functions were correlated with limited areas of the CBP. But the approach of direct localization of complex mental functions in certain areas of the CBP is untenable. An analysis of the facts of clinical observations indicated that disturbances in such complex mental processes as speech, writing, reading, and counting can occur with lesions of the CVD that are completely different in location. The defeat of limited areas of the cerebral cortex, as a rule, leads to a violation of a whole group of mental processes.
4) a new direction has arisen that considers mental processes as a function of the entire GM as a whole ("anti-localizationism"), but is untenable.
The works of I. M. Sechenov, and then I. P. Pavlov - the doctrine of the reflex foundations of mental processes and the reflex laws of the work of the CBP, it led to a radical revision of the concept of "function" - began to be considered as a set of complex temporary connections. The foundations of new ideas about the dynamic localization of functions in the CBP were laid.
Summing up, we can highlight the main provisions of the theory of systemic dynamic localization of higher mental functions:
- - each mental function is a complex functional system and is provided by the brain as a whole. At the same time, various brain structures make their specific contribution to the implementation of this function;
- - various elements of the functional system can be located in regions of the brain that are quite remote from each other and, if necessary, replace each other;
- - when a certain part of the brain is damaged, a "primary" defect occurs - a violation of a certain physiological principle of operation inherent in this brain structure;
- - as a result of damage to the common link included in different functional systems, "secondary" defects may occur.
Currently, the theory of systemic dynamic localization of higher mental functions is the main theory that explains the relationship between the psyche and the brain.
Histological and physiological studies have shown that the CBP is a highly differentiated apparatus. Different areas of the cerebral cortex have a different structure. The neurons of the cortex often turn out to be so specialized that it is possible to distinguish among them those that respond only to very special stimuli or to very special signs. There are a number of sensory centers in the cerebral cortex.
Firmly established is the localization in the so-called "projection" zones - cortical fields, directly connected in their ways with the underlying sections of the NS and the periphery. The functions of the CBP are more complex, phylogenetically younger, and cannot be narrowly localized; very extensive areas of the cortex, and even the entire cortex as a whole, are involved in the implementation of complex functions. At the same time, within the CBD there are areas whose damage causes varying degrees, for example, speech disorders, disorders of gnosia and praxia, the topodiagnostic value of which is also significant.
Instead of the idea of the CBP as, to a certain extent, an isolated superstructure over other floors of the NS with narrowly localized areas connected along the surface (associative) and with the periphery (projection) areas, I.P. Pavlov created the doctrine of the functional unity of neurons belonging to various parts of the nervous system - from receptors on the periphery to the cerebral cortex - the doctrine of analyzers. What we call the center is the highest, cortical, section of the analyzer. Each analyzer is associated with certain areas of the cerebral cortex
3) The doctrine of the localization of functions in the cerebral cortex developed in the interaction of two opposite concepts - anti-localizationism, or equipontalism (Flurance, Lashley), which denies the localization of functions in the cortex, and narrow localizational psychomorphologism, which tried in its extreme versions (Gall ) localize in limited areas of the brain even such mental qualities as honesty, secrecy, love for parents. Of great importance was the discovery by Fritsch and Gitzig in 1870 of areas of the cortex, the irritation of which caused a motor effect. Other researchers have also described areas of the cortex associated with skin sensitivity, vision, and hearing. Clinical neurologists and psychiatrists also testify to the violation of complex mental processes in focal lesions of the brain. The foundations of the modern view of the localization of functions in the brain were laid by Pavlov in his doctrine of analyzers and the doctrine of the dynamic localization of functions. According to Pavlov, an analyzer is a complex, functionally unified neural ensemble that serves to decompose (analyze) external or internal stimuli into separate elements. It begins with a receptor in the periphery and ends in the cerebral cortex. Cortical centers are the cortical sections of the analyzers. Pavlov showed that the cortical representation is not limited to the area of projection of the corresponding conductors, going far beyond its limits, and that the cortical areas of different analyzers overlap each other. The result of Pavlov's research was the doctrine of the dynamic localization of functions, suggesting the possibility of the participation of the same nervous structures in providing various functions. Localization of functions means the formation of complex dynamic structures or combinational centers, consisting of a mosaic of excited and inhibited far-distant points of the nervous system, united in a common work in accordance with the nature of the desired end result. The doctrine of dynamic localization of functions was further developed in the works of Anokhin, who created the concept of a functional system as a circle of certain physiological manifestations associated with the performance of a particular function. The functional system includes, each time in different combinations, various central and peripheral structures: cortical and deep nerve centers, pathways, peripheral nerves, and executive organs. The same structures can be included in many functional systems, which expresses the dynamism of the localization of functions. IP Pavlov believed that individual areas of the cortex have different functional significance. However, there are no strictly defined boundaries between these areas. Cells in one region move to neighboring regions. In the center of these areas are clusters of the most specialized cells - the so-called analyzer nuclei, and on the periphery - less specialized cells. In the regulation of body functions, not strictly defined points take part, but many nerve elements of the cortex. Analysis and synthesis of incoming impulses and the formation of a response to them are carried out by much larger areas of the cortex. According to Pavlov, the center is the brain end of the so-called analyzer. The analyzer is a nervous mechanism whose function is to decompose the known complexity of the external and internal world into separate elements, i.e., to perform analysis. At the same time, thanks to extensive connections with other analyzers, there is also a synthesis of analyzers with each other and with various activities of the organism.
Localization of functions in the cerebral cortex
General characteristics. In certain areas of the cerebral cortex, predominantly neurons are concentrated that perceive one type of stimulus: the occipital region - light, the temporal lobe - sound, etc. However, after the removal of the classical projection zones (auditory, visual), conditioned reflexes to the corresponding stimuli are partially preserved. According to the theory of I.P. Pavlov, in the cerebral cortex there is a “core” of the analyzer (cortical end) and “scattered” neurons throughout the cortex. The modern concept of function localization is based on the principle of multifunctionality (but not equivalence) of cortical fields. The property of multifunctionality allows one or another cortical structure to be included in the provision of various forms of activity, while realizing the main, genetically inherent function (O.S. Adrianov). The degree of multifunctionality of different cortical structures varies. In the fields of the associative cortex, it is higher. The multifunctionality is based on the multichannel input of afferent excitation into the cerebral cortex, the overlap of afferent excitations, especially at the thalamic and cortical levels, the modulating effect of various structures, for example, nonspecific thalamic nuclei, basal ganglia, on cortical functions, the interaction of cortical-subcortical and intercortical pathways for conducting excitation. With the help of microelectrode technology, it was possible to register in various areas of the cerebral cortex the activity of specific neurons that respond to stimuli of only one type of stimulus (only to light, only to sound, etc.), i.e. there is a multiple representation of functions in the cerebral cortex .
At present, the division of the cortex into sensory, motor and associative (non-specific) zones (areas) is accepted.
Sensory areas of the cortex. Sensory information enters the projection cortex, the cortical sections of the analyzers (I.P. Pavlov). These zones are located mainly in the parietal, temporal and occipital lobes. The ascending pathways to the sensory cortex come mainly from the relay sensory nuclei of the thalamus.
Primary sensory areas - these are zones of the sensory cortex, irritation or destruction of which causes clear and permanent changes in the sensitivity of the body (the core of the analyzers according to I.P. Pavlov). They consist of monomodal neurons and form sensations of the same quality. Primary sensory areas usually have a clear spatial (topographic) representation of body parts, their receptor fields.
Primary projection zones of the cortex consist mainly of neurons of the 4th afferent layer, which are characterized by a clear topical organization. A significant part of these neurons has the highest specificity. For example, the neurons of the visual areas selectively respond to certain signs of visual stimuli: some - to shades of color, others - to the direction of movement, others - to the nature of the lines (edge, stripe, slope of the line), etc. However, it should be noted that the primary zones of certain areas of the cortex also include multimodal neurons that respond to several types of stimuli. In addition, there are neurons there, the reaction of which reflects the impact of non-specific (limbic-reticular, or modulating) systems.
Secondary sensory areas located around the primary sensory areas, less localized, their neurons respond to the action of several stimuli, i.e. they are polymodal.
Localization of sensory zones. The most important sensory area is parietal lobe postcentral gyrus and its corresponding part of the paracentral lobule on the medial surface of the hemispheres. This zone is referred to as somatosensory areaI. Here there is a projection of skin sensitivity of the opposite side of the body from tactile, pain, temperature receptors, interoceptive sensitivity and sensitivity of the musculoskeletal system - from muscle, articular, tendon receptors (Fig. 2).
Rice. 2. Scheme of sensitive and motor homunculi
(according to W. Penfield, T. Rasmussen). Section of the hemispheres in the frontal plane:
but- projection of general sensitivity in the cortex of the postcentral gyrus; b- projection of the motor system in the cortex of the precentral gyrus
In addition to somatosensory area I, there are somatosensory area II smaller, located on the border of the intersection of the central sulcus with the upper edge temporal lobe, deep in the lateral groove. The accuracy of localization of body parts is expressed to a lesser extent here. A well-studied primary projection zone is auditory cortex(fields 41, 42), which is located in the depth of the lateral sulcus (the cortex of the transverse temporal gyri of Heschl). The projection cortex of the temporal lobe also includes the center of the vestibular analyzer in the superior and middle temporal gyri.
IN occipital lobe located primary visual area(cortex of part of the sphenoid gyrus and lingular lobule, field 17). There is a topical representation of retinal receptors here. Each point of the retina corresponds to its own area of the visual cortex, while the zone of the macula has a relatively large zone of representation. In connection with the incomplete decussation of the visual pathways, the same halves of the retina are projected into the visual region of each hemisphere. The presence in each hemisphere of the projection of the retina of both eyes is the basis of binocular vision. Bark is located near field 17 secondary visual area(fields 18 and 19). The neurons of these zones are polymodal and respond not only to light, but also to tactile and auditory stimuli. In this visual area, a synthesis of various types of sensitivity occurs, more complex visual images and their identification arise.
In the secondary zones, the leading ones are the 2nd and 3rd layers of neurons, for which the main part of the information about the environment and the internal environment of the body, received by the sensory cortex, is transmitted for further processing to the associative cortex, after which it is initiated (if necessary) behavioral response with the obligatory participation of the motor cortex.
motor areas of the cortex. Distinguish between primary and secondary motor areas.
IN primary motor area (precentral gyrus, field 4) there are neurons that innervate the motor neurons of the muscles of the face, trunk and limbs. It has a clear topographic projection of the muscles of the body (see Fig. 2). The main pattern of topographic representation is that the regulation of the activity of muscles that provide the most accurate and diverse movements (speech, writing, facial expressions) requires the participation of large areas of the motor cortex. Irritation of the primary motor cortex causes contraction of the muscles of the opposite side of the body (for the muscles of the head, the contraction can be bilateral). With the defeat of this cortical zone, the ability to fine coordinated movements of the limbs, especially the fingers, is lost.
secondary motor area (field 6) is located both on the lateral surface of the hemispheres, in front of the precentral gyrus (premotor cortex), and on the medial surface corresponding to the cortex of the superior frontal gyrus (additional motor area). In functional terms, the secondary motor cortex is of paramount importance in relation to the primary motor cortex, carrying out higher motor functions associated with planning and coordinating voluntary movements. Here, the slowly increasing negative readiness potential, occurring approximately 1 s before the start of movement. The cortex of field 6 receives the bulk of the impulses from the basal ganglia and the cerebellum, and is involved in recoding information about the plan of complex movements.
Irritation of the cortex of field 6 causes complex coordinated movements, such as turning the head, eyes and torso in the opposite direction, friendly contractions of the flexors or extensors on the opposite side. The premotor cortex contains motor centers associated with human social functions: the center of written speech in the posterior part of the middle frontal gyrus (field 6), the center of Broca's motor speech in the posterior part of the inferior frontal gyrus (field 44), which provide speech praxis, as well as musical motor center (field 45), providing the tone of speech, the ability to sing. Motor cortex neurons receive afferent inputs through the thalamus from muscle, joint, and skin receptors, from the basal ganglia, and the cerebellum. The main efferent output of the motor cortex to the stem and spinal motor centers are the pyramidal cells of layer V. The main lobes of the cerebral cortex are shown in Fig. 3.
Rice. 3. Four main lobes of the cerebral cortex (frontal, temporal, parietal and occipital); side view. They contain the primary motor and sensory areas, higher-order motor and sensory areas (second, third, etc.) and the associative (non-specific) cortex
Association areas of the cortex(nonspecific, intersensory, interanalyzer cortex) include areas of the new cerebral cortex, which are located around the projection zones and next to the motor zones, but do not directly perform sensory or motor functions, so they cannot be attributed primarily to sensory or motor functions, the neurons of these zones have large learning abilities. The boundaries of these areas are not clearly marked. The associative cortex is phylogenetically the youngest part of the neocortex, which has received the greatest development in primates and in humans. In humans, it makes up about 50% of the entire cortex, or 70% of the neocortex. The term "associative cortex" arose in connection with the existing idea that these zones, due to the cortico-cortical connections passing through them, connect the motor zones and at the same time serve as a substrate for higher mental functions. Main association areas of the cortex are: parietal-temporal-occipital, prefrontal cortex of the frontal lobes and limbic association zone.
The neurons of the associative cortex are polysensory (polymodal): they respond, as a rule, not to one (like the neurons of the primary sensory zones), but to several stimuli, i.e., the same neuron can be excited when stimulated by auditory, visual, skin and other receptors. Polysensory neurons of the associative cortex are created by cortico-cortical connections with different projection zones, connections with the associative nuclei of the thalamus. As a result, the associative cortex is a kind of collector of various sensory excitations and is involved in the integration of sensory information and in ensuring the interaction of sensory and motor areas of the cortex.
Associative areas occupy the 2nd and 3rd cell layers of the associative cortex, where powerful unimodal, multimodal, and nonspecific afferent flows meet. The work of these parts of the cerebral cortex is necessary not only for the successful synthesis and differentiation (selective discrimination) of stimuli perceived by a person, but also for the transition to the level of their symbolization, that is, for operating with the meanings of words and using them for abstract thinking, for the synthetic nature of perception.
Since 1949, D. Hebb's hypothesis has become widely known, postulating the coincidence of presynaptic activity with the discharge of a postsynaptic neuron as a condition for synaptic modification, since not all synaptic activity leads to excitation of a postsynaptic neuron. On the basis of D. Hebb's hypothesis, it can be assumed that individual neurons of the associative zones of the cortex are connected in various ways and form cell ensembles that distinguish "subimages", i.e. corresponding to unitary forms of perception. These connections, as noted by D. Hebb, are so well developed that it is enough to activate one neuron, and the entire ensemble is excited.
The apparatus that acts as a regulator of the level of wakefulness, as well as selective modulation and actualization of the priority of a particular function, is the modulating system of the brain, which is often called the limbic-reticular complex, or the ascending activating system. The nervous formations of this apparatus include the limbic and nonspecific systems of the brain with activating and inactivating structures. Among the activating formations, first of all, the reticular formation of the midbrain, the posterior hypothalamus, and the blue spot in the lower parts of the brain stem are distinguished. The inactivating structures include the preoptic area of the hypothalamus, the raphe nucleus in the brainstem, and the frontal cortex.
Currently, according to thalamocortical projections, it is proposed to distinguish three main associative systems of the brain: thalamo-temporal, thalamolobic And thalamic temporal.
thalamotenal system It is represented by associative zones of the parietal cortex, which receive the main afferent inputs from the posterior group of the associative nuclei of the thalamus. The parietal associative cortex has efferent outputs to the nuclei of the thalamus and hypothalamus, to the motor cortex and nuclei of the extrapyramidal system. The main functions of the thalamo-temporal system are gnosis and praxis. Under gnosis understand the function of various types of recognition: shapes, sizes, meanings of objects, understanding of speech, knowledge of processes, patterns, etc. Gnostic functions include the assessment of spatial relationships, for example, the relative position of objects. In the parietal cortex, a center of stereognosis is distinguished, which provides the ability to recognize objects by touch. A variant of the gnostic function is the formation in the mind of a three-dimensional model of the body (“body schema”). Under praxis understand purposeful action. The praxis center is located in the supracortical gyrus of the left hemisphere; it provides storage and implementation of the program of motorized automated acts.
Thalamolobic system It is represented by associative zones of the frontal cortex, which have the main afferent input from the associative mediodorsal nucleus of the thalamus and other subcortical nuclei. The main role of the frontal associative cortex is reduced to the initiation of the basic systemic mechanisms for the formation of functional systems of purposeful behavioral acts (P.K. Anokhin). The prefrontal region plays a major role in the development of a behavioral strategy. The violation of this function is especially noticeable when it is necessary to quickly change the action and when some time elapses between the formulation of the problem and the beginning of its solution, i.e. stimuli that require correct inclusion in a holistic behavioral response have time to accumulate.
The thalamotemporal system. Some associative centers, for example, stereognosis, praxis, also include areas of the temporal cortex. The auditory center of Wernicke's speech is located in the temporal cortex, located in the posterior regions of the superior temporal gyrus of the left hemisphere. This center provides speech gnosis: recognition and storage of oral speech, both one's 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. On the border of the temporal, parietal and occipital lobes there is a reading center that provides recognition and storage of images.
An essential role in the formation of behavioral acts is played by the biological quality of the unconditioned reaction, namely its importance for the preservation of life. In the process of evolution, this meaning was fixed in two opposite emotional states - positive and negative, which in a person form the basis of his subjective experiences - pleasure and displeasure, joy and sadness. In all cases, goal-directed behavior is built in accordance with the emotional state that arose under the action of a stimulus. During behavioral reactions of a negative nature, the tension of the vegetative components, especially the cardiovascular system, in some cases, especially in continuous so-called conflict situations, can reach great strength, which causes a violation of their regulatory mechanisms (vegetative neuroses).
In this part of the book, the main general questions of the analytical and synthetic activity of the brain are considered, which will make it possible to proceed in subsequent chapters to the presentation of particular questions of the physiology of sensory systems and higher nervous activity.
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At present, it is customary to divide the bark into sensory, motor, or motor, And association areas. Such a division was obtained through animal experiments with the removal of various parts of the cortex, observations of patients with a pathological focus in the brain, as well as with the help of direct electrical stimulation of the cortex and peripheral structures by recording electrical activity in the cortex.
The cortical ends of all analyzers are represented in the sensory zones. For visual it is located in the occipital lobe of the brain (fields 17, 18, 19). In field 17, the central visual pathway ends, informing about the presence and intensity of the visual signal. Fields 18 and 19 analyze the color, shape, size and quality of the item. If field 18 is affected, the patient sees, but does not recognize the object and does not distinguish its color (visual agnosia).
Cortical end auditory analyzer localized in the temporal lobe of the cortex (Geshl's gyrus), fields 41, 42, 22. They are involved in the perception and analysis of auditory stimuli, the organization of auditory control of speech. A patient with damage to field 22 loses the ability to understand the meaning of spoken words.
The cortical end is also located in the temporal lobe leadbular analyzer.
Skin analyzer, as well as pain and temperatureChuvvalidity are projected onto the posterior central gyrus, in the upper part of which the lower limbs are represented, in the middle part - the torso, in the lower part - the arms and head.
Paths end in the parietal cortex somatic feelingrelated to speech functions, associated with the assessment of the impact on the skin receptors, the weight and properties of the surface, the shape and size of the object.
The cortical end of the olfactory and gustatory analyzers is located in the hippocampal gyrus. When this area is irritated, olfactory hallucinations occur, and damage to it leads to anosmia(loss of the ability to smell).
motor zones located in the frontal lobes in the region of the anterior central gyrus of the brain, the irritation of which causes a motor reaction. The cortex of the precentral gyrus (field 4) represents the primary motor zone. In the fifth layer of this field are very large pyramidal cells (giant Betz cells). The face is projected onto the lower third of the precentral gyrus, the hand occupies its middle third, the trunk and pelvis - the upper third of the gyrus. The motor cortex for the lower extremities is located on the medial surface of the hemisphere in the region of the anterior part of the paracentral lobule.
The premotor area of the cortex (field 6) is located anterior to the primary motor area. Field 6 is called secondary mothorny area. Her irritation causes rotation of the trunk and eyes with the raising of the contralateral arm. Similar movements are observed in patients during an epileptic attack, if the epileptic focus is localized in this area. Recently, the leading role of field 6 in the implementation of motor functions has been proven. The defeat of field 6 in a person causes a sharp restriction of motor activity, complex sets of movements are difficult to perform, spontaneous speech suffers.
Field 6 is adjacent to field 8 (frontal oculomotor), the irritation of which is accompanied by a turn of the head and eyes in the opposite direction to the irritated one. Stimulation of different parts of the motor cortex causes contraction of the corresponding muscles on the opposite side.
Anterior frontal cortex associated with creative thinking. From a clinical and functional point of view, the region of interest is the inferior frontal gyrus (field 44). In the left hemisphere, it is associated with the organization of the motor mechanisms of speech. Irritation of this area can cause vocalization, but not articulate speech, as well as cessation of speech if the person has spoken. The defeat of this area leads to motor aphasia - the patient understands speech, but he cannot speak.
The association cortex includes the parietal-temporal-occipital, prefrontal, and limbic regions. It occupies about 80% of the entire surface of the cerebral cortex. Its neurons have multisensory functions. In the associative cortex, various sensory information is integrated and a program of purposeful behavior is formed, the associative cortex surrounds each projection zone, providing a relationship, for example, between sensory and motor areas of the cortex. The neurons located in these areas have polysensory, those. the ability to respond to both sensory and motor input.
Parietal association area the cerebral cortex is involved in the formation of a subjective idea of the surrounding space, of our body.
Temporal cortex participates in speech function through auditory control of speech. With the defeat of the auditory center of speech, the patient can speak, correctly express his thoughts, but does not understand someone else's speech (sensory auditory aphasia). This area of the cortex plays a role in the evaluation of space. The defeat of the visual center of speech leads to the loss of the ability to read and write. The function of memory and dreams is associated with the temporal cortex.
Frontal association fields are directly related to the limbic parts of the brain, they take part in the formation of a program of complex behavioral acts in response to the influence of the external environment based on sensory signals of all modalities.
A feature of the associative cortex is the plasticity of neurons capable of restructuring depending on the incoming information. After an operation to remove any area of the cortex in early childhood, the lost functions of this area are completely restored.
The cerebral cortex is capable, in contrast to the underlying structures of the brain, for a long time, throughout life, to preserve traces of incoming information, i.e. participate in the mechanisms of long-term memory.
The cerebral cortex is a regulator of the autonomic functions of the body (“corticolization of functions”). It presents all unconditioned reflexes, as well as internal organs. Without the cortex, it is impossible to develop conditioned reflexes to internal organs. When stimulating interoreceptors by the method of evoked potentials, electrical stimulation and destruction of certain areas of the cortex, its effect on the activity of various organs has been proven. Thus, the destruction of the cingulate gyrus changes the act of breathing, the functions of the cardiovascular system, and the gastrointestinal tract. The bark inhibits emotions - "know how to rule yourself."
In the cerebral cortex, zones are distinguished - Brodmann fields
The 1st zone - motor - is represented by the central gyrus and the frontal zone in front of it - 4, 6, 8, 9 Brodmann's fields. When it is irritated - various motor reactions; when it is destroyed - violations of motor functions: adynamia, paresis, paralysis (respectively - weakening, sharp decrease, disappearance).
In the 1950s, it was established that different muscle groups are represented differently in the motor zone. The muscles of the lower limb - in the upper section of the 1st zone. Muscles of the upper limb and head - in the lower part of the 1st zone. The largest area is occupied by the projection of mimic muscles, muscles of the tongue and small muscles of the hand.
2nd zone - sensitive - areas of the cerebral cortex posterior to the central sulcus (1, 2, 3, 4, 5, 7 Brodmann fields). When this zone is irritated, sensations arise, when it is destroyed, loss of skin, proprio-, interosensitivity occurs. Hypothesia - decreased sensitivity, anesthesia - loss of sensitivity, paresthesia - unusual sensations (goosebumps). The upper sections of the zone - the skin of the lower extremities, genitals is represented. In the lower sections - the skin of the upper limbs, head, mouth.
The 1st and 2nd zones are closely related to each other functionally. There are many afferent neurons in the motor zone that receive impulses from proprioreceptors - these are motosensory zones. In the sensitive area, there are many motor elements - these are sensorimotor zones - are responsible for the occurrence of pain.
3rd zone - visual zone - occipital region of the cerebral cortex (17, 18, 19 Brodmann fields). With the destruction of the 17th field - loss of visual sensations (cortical blindness).
Different parts of the retina are not equally projected into the 17th Brodmann field and have a different location; with a point destruction of the 17th field, the vision of the environment falls out, which is projected onto the corresponding parts of the retina. With the defeat of the 18th field of Brodmann, the functions associated with the recognition of a visual image suffer and the perception of writing is disturbed. With the defeat of the 19th field of Brodmann, various visual hallucinations occur, visual memory and other visual functions suffer.
4th - auditory zone - temporal region of the cerebral cortex (22, 41, 42 Brodmann fields). If 42 fields are damaged, the function of sound recognition is impaired. When the 22nd field is destroyed, auditory hallucinations, impaired auditory orienting reactions, and musical deafness occur. With the destruction of 41 fields - cortical deafness.
The 5th zone - olfactory - is located in the piriform gyrus (11 Brodmann's field).
6th zone - taste - 43 Brodman's field.
The 7th zone - the motor speech zone (according to Jackson - the center of speech) - in most people (right-handed) is located in the left hemisphere.
This zone consists of 3 departments.
Broca's motor speech center - located in the lower part of the frontal gyri - is the motor center of the muscles of the tongue. With the defeat of this area - motor aphasia.
The sensory center of Wernicke - located in the temporal zone - is associated with the perception of oral speech. With a lesion, sensory aphasia occurs - a person does not perceive oral speech, pronunciation suffers, as the perception of one's own speech is disturbed.
The center of perception of written speech - is located in the visual zone of the cerebral cortex - 18 Brodmann's field similar centers, but less developed, are also in the right hemisphere, the degree of their development depends on the blood supply. If the right hemisphere is damaged in a left-handed person, the speech function suffers to a lesser extent. If the left hemisphere is damaged in children, then the right hemisphere takes over its function. In adults, the ability of the right hemisphere to reproduce speech functions is lost.
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