In the cerebral cortex, all stimuli that come from the surrounding external and internal environment are analyzed. The largest number of afferent impulses reaches the cells of the 3rd and 4th layers of the cerebral cortex. The cerebral cortex contains centers that regulate the performance of certain functions. I. P. Pavlov considered the cerebral cortex as a set of cortical ends of analyzers. The term “analyzer” refers to a complex complex of anatomical structures, which consists of a peripheral receptor (perceiving) apparatus, conductors of nerve impulses and a center. In the process of evolution, functions are localized in the cerebral cortex. The cortical end of the analyzers is not any strictly defined zone. In the cerebral cortex, a “core” of the sensory system and “scattered elements” are distinguished. The nucleus is the area where the largest number of cortical neurons are located, in which all the structures of the peripheral receptor are accurately projected. Scattered elements are located near the nucleus and at varying distances from it. If higher analysis and synthesis are carried out in the nucleus, then simpler ones are carried out in scattered elements. At the same time, the zones of “scattered elements” of various analyzers do not have clear boundaries and overlap each other.

Functional characteristics of the cortical zones of the frontal lobe. In the area of ​​the precentral gyrus of the frontal lobe there is the cortical nucleus of the motor analyzer. This area is also called the sensorimotor cortex. Some of the afferent fibers from the thalamus come here, carrying proprioceptive information from the muscles and joints of the body (Fig. 8.7). Descending pathways to the brain stem and spinal cord also begin here, providing the possibility of conscious regulation of movements (pyramidal tracts). Damage to this area of ​​the cortex leads to paralysis of the opposite half of the body.

Rice. 8.7. Somatotopic distribution in the precentral gyrus

The center of writing lies in the posterior third of the middle frontal gyrus. This zone of the cortex gives projections to the nuclei of the oculomotor cranial nerves, and also, through cortico-cortical connections, communicates with the center of vision in the occipital lobe and the control center for the muscles of the arms and neck in the precentral gyrus. Damage to this center leads to impaired writing skills under visual control (agraphia).

The speech motor center (Broca's center) is located in the area of ​​the inferior frontal gyrus. It has pronounced functional asymmetry. When it is destroyed in the right hemisphere, the ability to regulate timbre and intonation is lost, speech becomes monotonous. When the speech motor center on the left is destroyed, speech articulation is irreversibly impaired, up to the loss of the ability to articulate speech (aphasia) and singing (amusia). With partial violations, agrammatism may be observed - the inability to form phrases correctly.

In the area of ​​the anterior and middle third of the upper, middle and partially inferior frontal gyri there is a vast anterior associative zone of the cortex, which programs complex forms of behavior (planning various forms of activity, decision-making, analysis of the results obtained, volitional reinforcement of activity, correction of the motivational hierarchy).

The area of ​​the frontal pole and medial frontal gyrus is associated with the regulation of the activity of emotiogenic areas of the brain included in the limbic system, and is related to the control of psycho-emotional states. Disturbances in this area of ​​the brain can lead to changes in what is commonly called “personality structure” and affect a person’s character, his value orientations, and intellectual activity.

The orbital region contains the centers of the olfactory analyzer and is closely connected anatomically and functionally with the limbic system of the brain.

Functional characteristics of the cortical zones of the parietal lobe. In the postcentral gyrus and superior parietal lobule there is the cortical center of the analyzer of general sensitivity (pain, temperature and tactile), or somatosensory cortex. The representation of various parts of the body in it, as in the precentral gyrus, is built according to the somatotopic principle. This principle assumes that body parts are projected onto the surface of the groove in the topographic relationships that they have in the human body. However, the representation of different parts of the body in the cerebral cortex varies significantly. The greatest representation is in those areas (hand, head, especially tongue and lips) that are associated with complex movements such as writing, speech, etc. Cortical disorders in this area lead to partial or complete anesthesia (loss of sensitivity).

Lesions of the cortex in the area of ​​the superior parietal lobule lead to a decrease in pain sensitivity and impairment of stereognosis - recognition of objects by touch without the aid of vision.

In the inferior parietal lobule, in the region of the supramarginal gyrus, there is a center of praxia, which regulates the ability to carry out complexly coordinated actions that form the basis of labor processes, which require special training. A significant number of descending fibers that follow as part of the pathways that control conscious movements (pyramidal pathways) also originate from here. This area of ​​the parietal cortex, through cortico-cortical connections, closely interacts with the frontal cortex and with all sensory areas of the posterior half of the brain.

The visual (optical) speech center is located in the angular gyrus of the parietal lobe. Its damage leads to the inability to understand readable text (alexia).

Functional characteristics of the cortical zones of the occipital lobe. In the area of ​​the calcarine sulcus is the cortical center of the visual analyzer. Its damage leads to blindness. If there are disturbances in the areas of the cortex adjacent to the calcarine sulcus in the region of the occipital pole on the medial and lateral surfaces of the lobe, loss of visual memory, the ability to navigate in an unfamiliar environment may occur, functions associated with binocular vision are disrupted (the ability to use vision to evaluate the shape of objects, the distance to them , correctly proportion movements in space under visual control, etc.).

Functional characteristics of the cortical zones of the temporal lobe. In the area of ​​the superior temporal gyrus, deep in the lateral sulcus, there is the cortical center of the auditory analyzer. Its damage leads to deafness.

The auditory speech center (Wernicke's center) lies in the posterior third of the superior temporal gyrus. Injuries in this area lead to the inability to understand spoken language: it is perceived as noise (sensory aphasia).

In the area of ​​the middle and inferior temporal gyri there is a cortical representation of the vestibular analyzer. Damage to this area leads to imbalance when standing and decreased sensitivity of the vestibular apparatus.

Functional characteristics of the cortical zones of the insula.

Information regarding the functions of the insula is contradictory and insufficient. There is evidence that the cortex of the anterior part of the insula is related to the analysis of olfactory and taste sensations, and the posterior part is related to the processing of somatosensory information and auditory perception of speech.

Functional characteristics of the limbic system. Limbic system– a set of a number of brain structures, including the cingulate gyrus, isthmus, dentate and parahippocampal gyri, etc. Participates in the regulation of the functions of internal organs, smell, instinctive behavior, emotions, memory, sleep, wakefulness, etc.

The cingulate and parahippocampal gyri are directly related to the limbic system of the brain (Fig. 8.8 and 8.9). It controls a complex of vegetative and behavioral psycho-emotional reactions to external environmental influences. The cortical representation of the gustatory and olfactory analyzers is located in the parahippocampal gyrus and uncus. At the same time, the hippocampus plays an important role in learning: the mechanisms of short-term and long-term memory are associated with it.

Rice. 8.8. Medial surface of the brain

Basal (subcortical central) nuclei – accumulations of gray matter that form separately lying nuclei that lie closer to the base of the brain. These include the striatum, which constitutes the predominant mass of the hemispheres in lower vertebrates; fence and amygdala (Fig. 8.10).

Rice. 8.9. Limbic system

Rice. 8.10. Basal ganglia

The striatum consists of the caudate and lenticular nuclei. The gray matter of the caudate and lenticular nuclei alternates with layers of white matter, which led to the common name of this group of subcortical nuclei - the striatum.

The caudate nucleus is located lateral and superior to the thalamus, being separated from it by the stria terminalis. The caudate nucleus has a head, body and tail. The lenticular nucleus is located lateral to the caudate. A layer of white matter, the internal capsule, separates the lenticular nucleus from the caudate and from the thalamus. In the lenticular nucleus, the globus pallidus (medially) and the putamen (laterally) are distinguished. The outer capsule (a narrow strip of white matter) separates the shell from the enclosure.

The caudate nucleus, putamen and globus pallidus control complexly coordinated automated movements of the body, control and maintain the tone of skeletal muscles, and are also the highest center for the regulation of such autonomic functions as heat production and carbohydrate metabolism in the muscles of the body. If the putamen and globus pallidus are damaged, slow, stereotypical movements (athetosis) may be observed.

The nuclei of the striatum belong to the extrapyramidal system, which is involved in the control of movements and the regulation of muscle tone.

The fence is a vertical plate of gray matter, the lower part of which continues into the substance of the anterior perforated plate at the base of the brain. The fence is located in the white matter of the hemisphere lateral to the lenticular nucleus and has numerous connections with the cerebral cortex.

The amygdala lies in the white matter of the temporal lobe of the hemisphere, 1.5–2 cm posterior to its temporal pole, through its nuclei it has connections with the cerebral cortex, with the structures of the olfactory system, with the hypothalamus and the nuclei of the brain stem that control the autonomic functions of the body. Its destruction leads to aggressive behavior or an apathetic, lethargic state. Through its connections with the hypothalamus, the amygdala influences the endocrine system as well as reproductive behavior.

The white matter of the hemisphere includes the internal capsule and fibers passing through the cerebral commissures (corpus callosum, anterior commissure, fornix commissure) and heading to the cortex and basal ganglia, fornix, as well as systems of fibers connecting areas of the cortex and subcortical centers within one half of the brain (hemispheres).

I and II lateral ventricles. The cavities of the cerebral hemispheres are the lateral ventricles (I and II), located in the thickness of the white matter under the corpus callosum. Each ventricle consists of four parts: the anterior horn lies in the frontal, the central part - in the parietal, the posterior horn - in the occipital and the inferior horn - in the temporal lobe (Fig. 8.11).

The anterior horns of both ventricles are separated from each other by two plates of a transparent septum. The central part of the lateral ventricle bends from above around the thalamus, forms an arc and passes posteriorly - into the posterior horn, downwards into the inferior horn. The choroid plexus protrudes into the central part and lower horn of the lateral ventricle, which connects to the choroid plexus of the third ventricle through the interventricular foramen.

Rice. 8.11. Ventricles of the brain:

1 - left hemisphere of the brain, 2 - lateral ventricles, 3 - third ventricle, 4 - midbrain aqueduct, 5 - fourth ventricle, 6 - cerebellum, 7 - entrance to the central canal of the spinal cord, 8 - spinal cord

The ventricular system includes paired C-shaped cavities - the lateral ventricles with their anterior, inferior and posterior horns, extending respectively into the frontal lobes, temporal lobes and occipital lobes of the cerebral hemispheres. About 70% of all cerebrospinal fluid is secreted by the choroid plexus of the walls of the lateral ventricles.

From the lateral ventricles, fluid passes through the interventricular foramina into the slit-like cavity of the third ventricle, located in the sagittal plane of the brain and dividing the thalamus and hypothalamus into two symmetrical halves. The cavity of the third ventricle is connected by a narrow canal - the aqueduct of the midbrain (aqueduct of Sylvius) with the cavity of the fourth ventricle. The fourth ventricle communicates through several channels (apertures) with the subarachnoid spaces of the brain and spinal cord.

Diencephalon

The diencephalon is located under the corpus callosum and consists of the thalamus, epithalamus, metathalamus and hypothalamus (Fig. 8.12, see Fig. 7.2).

Thalamus(visual tubercle) – paired, ovoid, formed mainly by gray matter. The thalamus is the subcortical center of all types of sensitivity. The medial surface of the right and left thalami, facing each other, form the lateral walls of the cavity of the diencephalon - the third ventricle; they are connected to each other by an interthalamic fusion. The thalamus contains gray matter, which consists of clusters of neurons that form the thalamic nuclei. The nuclei are separated by thin layers of white matter. About 40 nuclei of the thalamus were studied. The main nuclei are anterior, medial, posterior.

Rice. 8.12. Brain parts

Epithalamus includes the pineal gland, leashes and leash triangles. The pineal body, or pineal gland, which is an endocrine gland, is suspended, as it were, on two leashes, interconnected by a commissure and connected to the thalamus through triangles of leashes. The leash triangles contain nuclei related to the olfactory analyzer. In an adult, the average length of the epiphysis is ~0.64 cm and the mass is ~0.1 g. Metathalamus formed by paired medial and lateral geniculate bodies lying behind each thalamus. The medial geniculate body is located behind the thalamic cushion; it is, along with the lower colliculi of the midbrain roof plate (quadrigeminal), the subcortical center of the auditory analyzer. Lateral - located downward from the pillow, it, together with the upper colliculi of the roof plate, is the subcortical center of the visual analyzer. The nuclei of the geniculate bodies are connected with the cortical centers of the visual and auditory analyzers.

Hypothalamus, representing the ventral part of the diencephalon, is located anterior to the cerebral peduncles and includes a number of structures that have different origins - the anteriorly located visual part is formed from the telencephalon (optic chiasm, optic tract, gray tubercle, infundibulum, neurohypophysis); from the intermediate - the olfactory part (mammillary bodies and the subthalamic region itself - the hypothalamus) (Fig. 8.13).

Figure 8.13. Basal ganglia and diencephalon

The hypothalamus is the center for the regulation of endocrine functions; it combines nervous and endocrine regulatory mechanisms into a common neuroendocrine system, coordinates nervous and hormonal mechanisms for regulating the functions of internal organs. The hypothalamus contains neurons of the usual type and neurosecretory cells. The hypothalamus and the pituitary gland form a single functional complex, in which the former plays a regulatory and the latter an effector role.

The hypothalamus has more than 30 pairs of nuclei. Large neurosecretory cells of the supraoptic and paraventricular nuclei of the anterior hypothalamic region produce neurosecretes of a peptide nature.

The medial hypothalamus contains neurons that perceive all changes occurring in the blood and cerebrospinal fluid (temperature, composition, hormone content, etc.). The medial hypothalamus is also connected to the lateral hypothalamus. The latter does not have nuclei, but has bilateral connections with the overlying and underlying parts of the brain. The medial hypothalamus is a link between the nervous and endocrine systems. In recent years, enkephalins and endorphins (peptides), which have a morphine-like effect, have been isolated from the hypothalamus. They are believed to be involved in the regulation of behavior and vegetative processes.

Anterior to the posterior perforated substance lie two small spherical mastoid bodies, formed by gray matter covered with a thin layer of white. The nuclei of the mammillary bodies are the subcortical centers of the olfactory analyzer. Anterior to the mastoid bodies is a gray tubercle, which is limited in front by the optic chiasm and the optic tract; it is a thin plate of gray matter at the bottom of the third ventricle, which is extended downward and anteriorly and forms a funnel. The end of it goes into pituitary – an endocrine gland located in the pituitary fossa of the sella turcica. The nuclei of the autonomic nervous system lie in the gray mound. They also influence a person's emotional reactions.

The part of the diencephalon, located below the thalamus and separated from it by the hypothalamic groove, constitutes the hypothalamus itself. The coverings of the cerebral peduncles continue here, the red nuclei and the black substance of the midbrain end here.

III ventricle. Cavity of the diencephalon - III ventricle It is a narrow slit-like space located in the sagittal plane, bounded laterally by the medial surfaces of the thalamus, below by the hypothalamus, in front by the columns of the fornix, the anterior commissure and the terminal plate, behind by the epithalamic (posterior) commissure, above by the fornix, above which the corpus callosum is located. The upper wall itself is formed by the vascular base of the third ventricle, in which its choroid plexus lies.

The cavity of the third ventricle passes posteriorly into the midbrain aqueduct, and in front on the sides through the interventricular foramina communicates with the lateral ventricles.

Midbrain

Midbrain – the smallest part of the brain, lying between the diencephalon and the pons (Fig. 8.14 and 8.15). The area above the aqueduct is called the roof of the midbrain, and on it there are four convexities - the quadrigeminal plate with the superior and inferior colliculi. This is where the visual and auditory reflex pathways go to the spinal cord.

The cerebral peduncles are white round cords that emerge from the pons and move forward to the cerebral hemispheres. The oculomotor nerve (III pair of cranial nerves) emerges from the groove on the medial surface of each peduncle. Each leg consists of a tire and a base, the border between them is a black substance. The color depends on the abundance of melanin in its nerve cells. The substantia nigra belongs to the extrapyramidal system, which is involved in maintaining muscle tone and automatically regulates muscle function. The base of the pedicle is formed by nerve fibers running from the cerebral cortex to the spinal and medulla oblongata and the pons. The tegmentum of the cerebral peduncles contains mainly ascending fibers heading to the thalamus, among which the nuclei lie. The largest are the red nuclei, from which the motor red nucleus-spinal tract begins. In addition, the reticular formation and the nucleus of the dorsal longitudinal fasciculus (intermediate nucleus) are located in the tegmentum.

hindbrain

The hindbrain includes the ventrally located pons and the cerebellum lying behind the pons.

Rice. 8.14. Schematic representation of a longitudinal section of the brain

Rice. 8.15. Transverse section through the midbrain at the level of the superior colliculus (the plane of the section is shown in Fig. 8.14)

Bridge looks like a lying transversely thickened ridge, from the lateral side of which the middle cerebellar peduncles extend to the right and left. The posterior surface of the pons, covered by the cerebellum, participates in the formation of the rhomboid fossa, the anterior surface (adjacent to the base of the skull) borders the medulla oblongata below and the cerebral peduncles above (see Fig. 8.15). It is transversely striated due to the transverse direction of the fibers that go from the pontine nuclei to the middle cerebellar peduncles. On the anterior surface of the bridge along the midline there is a basilar groove located longitudinally, in which the artery of the same name passes.

The bridge consists of many nerve fibers that form pathways, among which are cellular clusters - nuclei. The anterior pathways connect the cerebral cortex with the spinal cord and the cerebellar cortex. In the posterior part of the bridge (tegmentum) there are ascending pathways and partially descending ones, the reticular formation, the nuclei of the V, VI, VII, VIII pairs of cranial nerves are located. On the border between both parts of the bridge lies a trapezoidal body formed by the nuclei and transversely running fibers of the conductive path of the auditory analyzer.

Cerebellum plays a major role in maintaining body balance and coordination of movements. The cerebellum reaches its greatest development in humans in connection with upright posture and the adaptation of the hand to work. In this regard, humans have highly developed hemispheres (new part) of the cerebellum.

In the cerebellum, there are two hemispheres and an unpaired middle phylogenetically old part - the vermis (Fig. 8.16).

Rice. 8.16. Cerebellum: top and bottom views

The surfaces of the hemispheres and the vermis are separated by transverse parallel grooves, between which there are narrow long leaves of the cerebellum. The cerebellum is divided into anterior, posterior and floculonodular lobes, separated by deeper fissures.

The cerebellum consists of gray and white matter. The white matter, penetrating between the gray matter, seems to branch, forming on the median section the figure of a branching tree - the “tree of life” of the cerebellum.

The cerebellar cortex consists of gray matter 1–2.5 mm thick. In addition, in the thickness of the white matter there are accumulations of gray - paired nuclei: dentate nucleus, cork-shaped, spherical and tent nucleus. Afferent and efferent fibers connecting the cerebellum with other parts form three pairs of cerebellar peduncles: the lower ones go to the medulla oblongata, the middle ones to the pons, the upper ones to the quadrigemulus.

By the time of birth, the cerebellum is less developed than the telencephalon (especially the hemisphere), but in the first year of life it develops faster than other parts of the brain. A pronounced enlargement of the cerebellum is observed between the 5th and 11th months of life, when the child learns to sit and walk.

Medulla is a direct continuation of the spinal cord. Its lower boundary is considered to be the place of exit of the roots of the 1st cervical spinal nerve or the decussation of the pyramids, the upper is the posterior edge of the bridge, its length is about 25 mm, its shape approaches a truncated cone, with the base facing upward.

The anterior surface is divided by the anterior median fissure, on the sides of which there are pyramids formed by pyramidal pathways that partially intersect (pyramid decussation) in the depth of the described fissure at the border with the spinal cord. Fibers of the pyramidal tracts connect the cerebral cortex with the nuclei of the cranial nerves and the anterior horns of the spinal cord. On each side of the pyramid there is an olive, separated from the pyramid by the anterior lateral groove.

The posterior surface of the medulla oblongata is divided by the posterior median sulcus; on either side of it there are continuations of the posterior cords of the spinal cord, which diverge upward, passing into the inferior cerebellar peduncles.

The medulla oblongata is built of white and gray matter, the latter is represented by the nuclei of the IX–XII pairs of cranial nerves, olives, centers of respiration and circulation, and the reticular formation. White matter is formed by long and short fibers that make up the corresponding pathways.

Reticular formation is a collection of cells, cell clusters and nerve fibers located in the brain stem (medulla oblongata, pons and midbrain) and forming a network. The reticular formation is connected to all sense organs, motor and sensory areas of the cerebral cortex, the thalamus and hypothalamus, and the spinal cord. It regulates the level of excitability and tone of various parts of the central nervous system, including the cerebral cortex, and is involved in the regulation of the level of consciousness, emotions, sleep and wakefulness, autonomic functions, and purposeful movements.

IV ventricle- This is the cavity of the rhomboid brain; downward it continues into the central canal of the spinal cord. The bottom of the IV ventricle, due to its shape, is called a rhomboid fossa (Fig. 8.17). It is formed by the posterior surfaces of the medulla oblongata and the pons, the upper sides of the fossa are the upper, and the lower are the inferior cerebellar peduncles.

Rice. 8.17. Brainstem; back view. The cerebellum is removed, the rhomboid fossa is open

The median groove divides the bottom of the fossa into two symmetrical halves; on both sides of the groove, medial elevations are visible, expanding in the middle of the fossa into the right and left facial tubercles, where they lie: the nucleus of the VI pair of cranial nerves (abducens nerve), deeper and more lateral – the nucleus of the VII pair ( facial nerve), and downwards the medial eminence passes into the triangle of the hypoglossal nerve, lateral to which is the triangle of the vagus nerve. In the triangles, in the thickness of the brain substance, lie the nuclei of the nerves of the same name. The superior angle of the rhomboid fossa communicates with the midbrain aqueduct. The lateral sections of the rhomboid fossa are called the vestibular fields, where the auditory and vestibular nuclei of the vestibulocochlear nerve (VIII pair of cranial nerves) lie. From the auditory nuclei, transverse medullary stripes extend to the median sulcus, located on the border between the medulla oblongata and the pons and are the fibers of the conductive path of the auditory analyzer. In the thickness of the rhomboid fossa lie the nuclei of the V, VI, VII, VIII, IX, X, XI and XII pairs of cranial nerves.

Blood supply to the brain

Blood enters the brain through two paired arteries: the internal carotid and the vertebral. In the cranial cavity, both vertebral arteries merge, together forming the main (basal) artery. At the base of the brain, the basilar artery merges with the two carotid arteries, forming a single arterial ring (Fig. 8.18). This cascade mechanism of blood supply to the brain ensures sufficient blood flow if any of the arteries fails.

Rice. 8.19. Arteries at the base of the brain and circle of Willis (right cerebellar hemisphere and right temporal lobe removed); The circle of Willis is shown with a dotted line

Three vessels depart from the arterial ring: the anterior, posterior and middle cerebral arteries, which supply the cerebral hemispheres. These arteries run along the surface of the brain, and from them, blood is delivered deep into the brain by smaller arteries.

The carotid artery system is called the carotid system, which provides 2/3 of the brain's arterial blood needs and supplies the anterior and middle parts of the brain.

The “vertebral-basal” artery system is called the vertebrobasilar system, which provides 1/3 of the needs of the brain and delivers blood to the posterior sections.

The outflow of venous blood occurs mainly through the superficial and deep cerebral veins and venous sinuses (Fig. 8.19). The blood ultimately flows into the internal jugular vein, which exits the skull through the jugular foramen, located at the base of the skull lateral to the foramen magnum.

Meninges

The membranes of the brain protect it from mechanical damage and from the penetration of infections and toxic substances (Fig. 8.20).

Rice. 8.19. Veins and venous sinuses of the brain

Fig.8.20. Coronal section through the skull shell and brain

The first membrane that protects the brain is called the pia mater. It is closely adjacent to the brain, extends into all the grooves and cavities (ventricles) present in the thickness of the brain itself. The ventricles of the brain are filled with a fluid called cerebrospinal fluid or cerebrospinal fluid. The dura mater is directly adjacent to the bones of the skull. Between the soft and hard membranes is the arachnoid (arachnoid) membrane. Between the arachnoid and soft membranes there is a space (subarachnoid or subarachnoid space) filled with cerebrospinal fluid. The arachnoid membrane spreads over the grooves of the brain, forming a bridge, and the soft one merges with them. Due to this, cavities called cisterns are formed between the two shells. The cisterns contain cerebrospinal fluid. These tanks protect the brain from mechanical injuries, acting as “airbags.”

Nerve cells and blood vessels are surrounded by neuroglia - special cellular formations that perform protective, support and metabolic functions, providing the reactive properties of nervous tissue and participating in the formation of scars, inflammatory reactions, etc.

When the brain is damaged, the plasticity mechanism is activated, when the remaining brain structures take over the functions of the affected areas.

The limbic system is a functional union of brain structures that provides complex forms of behavior.

The limbic system includes structures of the ancient cortex, old cortex, mesocortex and some subcortical formations. A feature of the limbic system is that the connections between its structures form many closed circles, and this creates conditions for long-term circulation of excitation in the system. The main circles with functional specificity are described. This is a large circle of Papes, which includes: hippocampus - fornix - mamillary bodies - mamillary-thalamic fasciculus Vic-d, Azira - anterior nuclei of the thalamus - cingulate cortex - parahippocampal gyrus - hippocampus.

A very important multifunctional structure in the large circle is the hippocampus. Its damage in humans disrupts memory for events that preceded the damage, memorization, processing of new information, discrimination of spatial signals are impaired, emotionality and initiative decrease, and the speed of basic nervous processes slows down.

The small circle of Nauta is formed by: amygdala - stria terminalis - hypothalamus - septum - amygdala.

An important structure of the small circle is the amygdala. Its functions are associated with ensuring defensive behavior, autonomic, motor, emotional reactions, and motivation of conditioned reflex behavior. Numerous autonomic effects of the amygdala are due to connections with the hypothalamus.

In general, the limbic system provides:

• 1. Organization of vegetative-somatic components of emotions.
• 2. Organization of short-term and long-term memory.
• 3. Participates in the formation of orientation-research activities (Klüver-Bucy syndrome).
• 4. Organizes the simplest motivational and informational communication (speech).
• 5. Participates in sleep mechanisms.
• 6. The center of the olfactory sensory system is located here.

According to McLean (1970), from a functional point of view, the limbic is divided into: 1) the lower section - the amygdala and hippocampus, which are centers of emotions and behavior for survival and self-preservation; 2) the upper section - the cingulate gyrus and temporal cortex, they represent the centers of sociability and sexuality; 3) middle section - hypothalamus and cingulate gyrus - centers of biosocial instincts.

The hemispheres of the brain consist of white matter, which is covered on the outside by gray matter or cortex. The cortex is the youngest and most complex part of the brain, where sensory information is processed, motor commands are formed, and complex forms of behavior are integrated. In addition to neurons, there is a huge number of glial cells that perform ion-regulatory and trophic functions.

The cerebral cortex has morphofunctional features: 1) multi-layered arrangement of neurons; 2) modular principle of organization; 3) somatotopic localization of receptor systems; 4) screenability - distribution of external reception on the plane of the neuronal field of the cortical end of the analyzer; 5) dependence of the level of activity on the influence of subcortical structures and reticular formation; 6) presence of representation of all functions of the underlying structures of the central nervous system; 7) cytoarchitectonic distribution into fields; 8) the presence in specific projection sensory and motor systems of the cortex of secondary and tertiary fields with a predominance of associative functions; 9) the presence of specialized associative areas of the cortex; 10) dynamic localization of functions, which is expressed in the possibility of compensating for the functions of lost cortical structures; 11) overlap in the cortex of zones of neighboring peripheral receptive fields; 12) the possibility of long-term preservation of traces of irritation; 13) reciprocal functional relationship between excitatory and inhibitory states of the cortex; 14) ability to irradiate the state; 15) the presence of specific electrical activity.

The bark consists of 6 layers:

• 1. The outer molecular layer is represented by a plexus of nerve fibers that lie parallel to the surface of the cortical convolutions and are mainly dendrites of pyramidal cells. Afferent thalamocortical fibers from the nonspecific nuclei of the thalamus come here; they regulate the level of excitability of cortical neurons.
• 2. The outer granular layer is formed by small stellate cells, which determine the duration of circulation of excitation in the cortex and are related to memory.
• 3. The outer pyramidal layer is formed by medium-sized pyramidal cells.

Functionally, the 2nd and 3rd layers carry out cortico-cortical associative connections.

• 4. Afferent thalamocortical fibers from specific (projection) nuclei of the thalamus come to the internal granular layer.
• 5. The inner pyramidal layer is formed by giant pyramidal cells of Betz. The axons of these cells form the corticospinal and corticobulbar tracts, which are involved in the coordination of goal-directed movements and posture.
• 6. Polymorphic or spindle cell layer. This is where the corticothalamic pathways are formed.

All analyzers are characterized by the somatotopic principle of organizing the projection of peripheral receptor systems onto the cortex. For example, in the sensory cortex of the second central gyrus there are areas of representation of each point on the skin surface, in the motor cortex each muscle has its own topic, its own place, in the auditory cortex there is a topical localization of certain tones.

A feature of cortical fields is the screen principle of functioning, which lies in the fact that the receptor projects its signal not onto one cortical neuron, but onto their field, which is formed by collaterals and connections of neurons. In this case, the signal is focused not point to point, but on many neurons, which ensures its complete analysis and the possibility, if necessary, of transmission to other structures.

In the vertical direction, the input and output fibers together with the stellate cells form “columns”, which are the functional units of the cortex. And when the microelectrode is immersed perpendicularly into the cortex, along the entire path it encounters neurons that respond to one type of stimulation, while if the microelectrode goes horizontally along the cortex, then it encounters neurons that respond to different types of stimuli.

The presence of structurally different fields also implies their different functional purposes.

The most important motor area of ​​the cortex is located in the precentral gyrus. In 30 last century, Penfield established the presence of a correct spatial projection of somatic muscles of various parts of the body to the motor area of ​​the cortex. The most extensive and with the lowest threshold are the zones that control the movements of the hands and facial muscles. A secondary motor area was found on the medial surface next to the primary one. But these areas, in addition to the motor output from the cortex, have independent sensory inputs from skin and muscle receptors, so they were called the primary and secondary motosensory cortex.

The postcentral gyrus contains the first somatosensory area, which receives afferent signals from specific nuclei of the thalamus. They carry information from skin receptors and the motor system. And here the somatotopic organization is noted.

The second somatosensory area is located in the Sylvian fissure, and since. The first and second somatosensory zones, in addition to afferent inputs, also have motor outputs; it is more correct to call them primary and secondary sensorimotor zones.

The primary visual area is located in the occipital region.

In the temporal lobe is the auditory region.

In each lobe of the cerebral cortex, next to the projection zones, there are fields that are not associated with the performance of a specific function - this is the associative cortex, the neurons of which respond to stimulation of various modalities and participate in the integration of sensory information, and also provide communication between the sensitive and motor areas of the cortex. This is the physiological basis of higher mental functions.

The frontal lobes have extensive bilateral connections with the limbic system of the brain and are involved in the control of innate behavioral acts with the help of accumulated experience, ensure the coordination of external and internal motivations for behavior, the development of behavioral strategies and action programs, and the mental characteristics of the individual.

There is no complete symmetry in the activity of the hemispheres. So, in 9 out of 10 people, the left hemisphere dominates for motor acts (right-handed) and speech. For most left-handers, the center of speech is also on the left. Those. There is no absolute dominance. Hemispheric asymmetry is especially noticeable when one hemisphere is separated from the other (commissurotomy). The left hemisphere contains the center of written language, stereognosis. In the left hemisphere, verbal, easily distinguishable, and familiar stimuli are better recognized. The left hemisphere is better at performing tasks involving temporal relationships, establishing similarities, and identifying stimuli by name. The left hemisphere carries out analytical and sequential perception, generalized recognition.

In the right hemisphere, stereognosis for the left hand, understanding of elementary speech, non-verbal thinking (i.e., thinking in images) is carried out; non-verbal, difficult-to-distinguish, and unfamiliar stimuli are better recognized. Tasks on spatial relationships, establishing differences, and identity of stimuli based on physical properties are performed better. In the right hemisphere, holistic, simultaneous perception and specific recognition take place.

The right hemisphere of 9 out of 10 people is slightly inhibited, the alpha rhythm dominates, which in turn somewhat slows down the left hemisphere and prevents it from becoming overexcited. When the right hemisphere is turned off, a person talks a lot and continuously (logorrhea), promises a lot, but does not keep his promises (chatterbox).

With the left hemisphere put to sleep, on the contrary, the person is silent and sad.

The right hemisphere is responsible for nonverbal (subconscious) thinking. The left hemisphere is responsible for understanding what the right hemisphere subconsciously sends to it.

The functional state of brain structures is studied by methods of recording electrical potentials. If the recording electrode is located in a subcortical structure, then the recorded activity is called a subcorticogram, if in the cerebral cortex - a corticogram, if the electrode is located on the surface of the scalp, then the total activity is recorded through it, in which there is a contribution from both the cortex and subcortical structures - this is a manifestation activity is called an electroencephalogram (EEG).

The EEG is a wave-like curve, the nature of which depends on the state of the cortex. So, at rest, a slow alpha rhythm (8-12 Hz, amplitude = 50 μV) predominates on the EEG in a person. During the transition to activity, the alpha rhythm changes to a fast beta rhythm (14 - 30 Hz, amplitude 25 μV). The process of falling asleep is accompanied by a slower theta rhythm (4 - 7 Hz) or delta rhythm (0.5 - 3.5 Hz, amplitude 100 - 300 µV). When, against the background of rest or another state of the human brain, an irritation is presented, for example, light, sound, electric current, then with the help of microelectrodes implanted into certain structures of the cortex, so-called evoked potentials are recorded, the latency period and amplitude of which depend on the intensity of irritation, and the components , the number and nature of oscillations depend on the adequacy of the stimulus.

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 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 localization of functions 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 involved in providing various forms of activity, while realizing the main, genetically inherent function (O.S. Adrianov). The degree of multifunctionality of various cortical structures varies. In the fields of the associative cortex it is higher. 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, for example, the nonspecific nuclei of the thalamus, the basal ganglia on cortical functions, the interaction of cortical-subcortical and intercortical pathways of excitation. Using microelectrode technology, it was possible to register in various areas of the cerebral cortex the activity of specific neurons responding to stimuli of only one type of stimulus (only light, only sound, etc.), i.e. there is multiple representation of functions in the cerebral cortex .

Currently, the division of the cortex into sensory, motor and associative (nonspecific) 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 (nuclei of analyzers according to I.P. Pavlov). They consist of monomodal 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.

The 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 portion of these neurons have the highest specificity. For example, neurons in 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 individual cortical areas also include neurons of a multimodal type that respond to several types of stimuli. In addition, there are neurons whose reaction reflects the influence of nonspecific (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 multimodal.

Localization of sensory zones. The most important sensory area is parietal lobe postcentral gyrus and the corresponding part of the paracentral lobule on the medial surface of the hemispheres. This zone is designated as somatosensory areaI. 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, tendon receptors (Fig. 2).

Rice. 2. Diagram of sensory and motor homunculi

(according to W. Penfield, T. Rasmussen). 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

In addition to somatosensory area I, there are somatosensory area II of smaller size, located at the border of the intersection of the central groove with the upper edge temporal lobe, in the depth of the lateral groove. The accuracy of localization of body parts is less pronounced here. A well-studied primary projection zone is auditory cortex(fields 41, 42), which is located in the depth of the lateral sulcus (cortex of Heschl’s transverse temporal gyri). 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 lingual lobule, area 17). Here there is a topical representation of retinal receptors. Each point of the retina corresponds to its own section of the visual cortex, while the macula zone has a relatively 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. Near field 17 there is a bark 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. In this visual area, a synthesis of different types of sensitivity occurs, more complex visual images and their recognition 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 internal environment of the body, received in the sensory cortex, is transferred for further processing to the associative cortex, after which it is initiated (if necessary) behavioral reaction with the obligatory participation of the motor cortex.

Motor cortex areas. There are primary and secondary motor zones.

IN primary motor zone (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 (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. 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). When this cortical zone is damaged, the ability to make 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 (supplementary motor area). In functional terms, the secondary motor cortex has a dominant role in relation to the primary motor cortex, carrying out higher motor functions associated with planning and coordination of voluntary movements. Here the slowly increasing negative is recorded to the greatest extent. readiness potential, occurring approximately 1 s before the start of movement. The cortex of area 6 receives the bulk of impulses from the basal ganglia and cerebellum and is involved in the recoding of information about the plan of complex movements.

Irritation of the cortex of area 6 causes complex coordinated movements, for example, turning the head, eyes and torso in the opposite direction, cooperative contractions of the flexors or extensors 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 motor speech center in the posterior part of the inferior frontal gyrus (field 44), providing speech praxis, as well as musical motor center (field 45), providing the tonality of speech and the ability to sing. Neurons of the motor cortex receive afferent inputs through the thalamus from muscle, joint and skin receptors, from the basal ganglia and 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, motor and sensory areas of higher order (second, third, etc.) and the associative (nonspecific) cortex

Association cortical areas(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, therefore they cannot be attributed predominantly sensory or motor functions; the neurons of these zones have large learning abilities. The boundaries of these areas are not clearly defined. The association cortex is phylogenetically the youngest part 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 term “associative cortex” arose in connection with the existing idea that these zones, due to cortico-cortical connections passing through them, connect motor areas and at the same time serve as a substrate for higher mental functions. Main association areas of the cortex are: parieto-temporo-occipital, prefrontal cortex of the frontal lobes and limbic association zone.

Neurons of the associative cortex are polysensory (polymodal): they respond, as a rule, not to one (like neurons of the primary sensory zones), but to several stimuli, i.e. the same neuron can be excited by stimulation of auditory, visual, skin and other receptors. The polysensory nature of the neurons of the associative cortex is created by cortico-cortical connections with different projection zones, connections with the associative nuclei of the thalamus. As a result of this, 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 cellular 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 as a condition for synaptic modification the coincidence of presynaptic activity with the discharge of a postsynaptic neuron, since not all synaptic activity leads to excitation of the postsynaptic neuron. Based on 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 cellular ensembles that distinguish “sub-patterns”, 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 device that acts as a regulator of the level of wakefulness, as well as selectively modulating and updating 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 brain systems with activating and inactivating structures. Among the activating formations, the reticular formation of the midbrain, the posterior hypothalamus, and the locus coeruleus in the lower parts of the brain stem are primarily distinguished. Inactivating structures include the preoptic area of ​​the hypothalamus, the raphe nuclei in the brain stem, and the frontal cortex.

Currently, based on thalamocortical projections, it is proposed to distinguish three main associative systems of the brain: thalamoparietal, thalamofrontal And thalamotemporal.

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. 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 and praxis. Under gnosis understand the function of various types of recognition: shape, size, meaning 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 there is a center of stereognosis, which provides the ability to recognize objects by touch. A variant of the gnostic function is 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 supracortical gyrus of the left hemisphere; it ensures the storage and implementation of a program of motor automated acts.

Thalamobic system 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 basic systemic mechanisms for the formation of functional systems of purposeful behavioral acts (P.K. Anokhin). The prefrontal region plays a major role in developing behavioral strategies. The disruption of this function is especially noticeable when it is necessary to quickly change the action and when some time passes between the formulation of the problem and the beginning of its solution, i.e. Stimuli have time to accumulate and require proper inclusion in a holistic behavioral response.

Thalamotemporal system. 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 of the left hemisphere. This center provides speech gnosis: recognition and storage of oral speech, both one’s own and that of others. 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 there is a reading center that provides recognition and storage of images.

A significant role in the formation of behavioral acts is played by the biological quality of the unconditional reaction, namely its significance for the preservation of life. In the process of evolution, this meaning was fixed in two opposite emotional states - positive and negative, which in humans 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 during the action of the stimulus. During behavioral reactions of a negative nature, the tension of the autonomic 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).

This part of the book examines the main general issues of the analytical and synthetic activity of the brain, which will allow us to move on in subsequent chapters to the presentation of specific issues of the physiology of sensory systems and higher nervous activity.

• 1) at the beginning of the 19th century. F. Gall suggested that the substrate of various mental “abilities” (honesty, frugality, love, etc.))) are small areas of n. tk. KBPs that grow with the development of these abilities. Gall believed that various abilities have a clear localization in the GM and that they can be determined by the protrusions on the skull, where the brain corresponding to this ability supposedly grows. tk. and begins to bulge, forming a tubercle on the skull.
• 2) In the 40s of the XIX century. Gall is opposed by Flourens, who, based on experiments in the extirpation (removal) of parts of the GM, puts forward the position of equipotentiality (from the Latin equus - “equal”) of the functions of the CBP. In his opinion, the GM is a homogeneous mass that functions as a single integral organ.
• 3) The basis of the modern doctrine of the localization of functions in the CBP was laid by the French scientist P. Broca, who identified the motor center of speech in 1861. Subsequently, the German psychiatrist K. Wernicke in 1873 discovered the center of word deafness (impaired speech understanding).

Since the 70s. The study of clinical observations showed that damage to limited areas of the KBP leads to a predominant loss of well-defined mental functions. This gave rise to the identification of separate areas in the CBP, which began to be considered as nerve centers responsible for certain mental functions.

Having summarized 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 KBP. But the approach of direct localization of complex mental functions in certain areas of the CBP is untenable. An analysis of clinical observations showed that disturbances in such complex mental processes as speech, writing, reading, and counting can occur with lesions of the KBP that are completely different in location. Damage to limited areas of the cerebral cortex, as a rule, leads to disruption of a whole group of mental processes.

4) a new direction has emerged that considers mental processes as a function of the entire GM as a whole (“anti-localizationism”), but it is untenable.

Through 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 KBP, it led to a radical revision of the concept of “function” - it began to be considered as a set of complex temporary connections. The foundations were laid for new ideas about the dynamic localization of functions in the KBP.

To summarize, 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 areas of the brain that are sufficiently distant from each other and, if necessary, replace each other;
• - when a certain area of ​​the brain is damaged, a “primary” defect occurs - a violation of a certain physiological principle of operation characteristic of a given brain structure;
• - as a result of damage to a 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 explaining the relationship between the psyche and the brain.

Histological and physiological studies have shown that the KBP is a highly differentiated apparatus. Different areas of the cerebral cortex have different structures. Cortical neurons often turn out to be so specialized that from among them one can distinguish those that respond only to very special stimuli or to very special signs. There are a number of sensory centers located in the cerebral cortex.

Localization in the so-called “projection” zones - cortical fields directly connected by their paths with the underlying sections of the NS and the periphery is firmly established. The functions of the KBP are more complex, phylogenetically younger, and cannot be narrowly localized; Very large 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 CBP there are areas whose damage causes varying degrees, for example, speech disorders, disorders of gnosis and praxia, the topodiagnostic value of which is also significant.

Instead of the idea of ​​the KBP as, to a certain extent, an isolated superstructure above other floors of the NS with narrowly localized areas connected along the surface (association) and with the periphery (projection), I.P. Pavlov created the doctrine of the functional unity of neurons belonging to various parts of the nervous system - from receptors in 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 connected to certain areas of the cerebral cortex

3) The doctrine of the localization of functions in the cerebral cortex developed in the interaction of two opposing concepts - anti-localizationism, or equipontentialism (Flourens, Lashley), which denied the localization of functions in the cortex, and narrow localization psychomorphology, 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 Hitzig 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 disruption of complex mental processes in focal brain lesions. 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 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 individual 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 cortical representation is not limited to the projection zone of the corresponding conductors, going far beyond its limits, and that the cortical zones of various analyzers overlap each other. The result of Pavlov's research was the doctrine of 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 distant points of the nervous system, united in common work in accordance with the nature of the required final result. The doctrine of dynamic localization of functions received its further development 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 specific function. The functional system includes each time in different combinations various central and peripheral structures: cortical and deep nerve centers, pathways, peripheral nerves, executive organs. The same structures can be included in many functional systems, which expresses the dynamism of the localization of functions. I.P. Pavlov believed that individual areas of the cortex have different functional significance. However, there are no strictly defined boundaries between these areas. Cells from one area move into neighboring areas. In the center of these areas there are clusters of the most specialized cells - the so-called analyzer nuclei, and at the periphery there are less specialized cells. It is not strictly defined points that take part in the regulation of body functions, 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 significantly larger areas of the cortex. According to Pavlov, the center is the brain end of the so-called analyzer. An analyzer is a nervous mechanism, the function of which is to decompose the known complexity of the external and internal world into separate elements, that is, to carry out analysis. At the same time, thanks to broad connections with other analyzers, there is also a synthesis of analyzers with each other and with different activities of the body.

This question is extremely important theoretically and especially practically. Hippocrates already knew that brain injuries lead to paralysis and convulsions on the opposite half of the body, and are sometimes accompanied by loss of speech.

In 1861, the French anatomist and surgeon Broca, in an autopsy of the corpses of several patients suffering from a speech disorder in the form of motor aphasia, discovered profound changes in the pars opercularis of the third frontal gyrus of the left hemisphere or in the white matter under this area of ​​the cortex. Based on his observations, Broca established a motor speech center in the cerebral cortex, which was later named after him.

The English neurologist Jackson (1864) also spoke in favor of the functional specialization of individual areas of the hemispheres on the basis of clinical data. Somewhat later (1870), German researchers Fritsch and Hitzig proved the existence of special areas in the dog’s cerebral cortex, irritation of which by a weak electric current is accompanied by a contraction of individual muscle groups. This discovery led to a large number of experiments, mainly confirming the existence of certain motor and sensory areas in the cerebral cortex of higher animals and humans.

On the issue of localization (representation) of function in the cerebral cortex, two diametrically opposed points of view competed with each other: localizationists and antilocalizationists (equipotentialists).

Localizationists were supporters of narrow localization of various functions, both simple and complex.

Anti-localizationists took a completely different view. They denied any localization of functions in the brain. All the bark was equal and homogeneous for them. All its structures, they believed, have the same capabilities for performing various functions (equipotential).

The problem of localization can receive a correct resolution only with a dialectical approach to it, taking into account both the integral activity of the entire brain and the different physiological significance of its individual parts. This is exactly how IP Pavlov approached the problem of localization. Numerous experiments by I.P. Pavlov and his colleagues with the extirpation of certain areas of the brain convincingly support the localization of functions in the cortex. Resection of a dog's occipital lobes of the cerebral hemispheres (vision centers) causes enormous damage to the conditioned reflexes it has developed to visual signals and leaves all conditioned reflexes to sound, tactile, olfactory and other stimuli intact. On the contrary, resection of the temporal lobes (hearing centers) leads to the disappearance of conditioned reflexes to sound signals and does not affect reflexes associated with optical signals, etc. The latest electroencephalography data also speaks against equipotentialism and in favor of the representation of the function in certain areas of the cerebral hemispheres . Irritation of a certain area of ​​the body leads to the appearance of reactive (evoked) potentials in the cortex in the “center” of this area.

I.P. Pavlov was a convinced supporter of localization of functions in the cerebral cortex, but only relative and dynamic localization. The relativity of localization is manifested in the fact that each part of the cerebral cortex, being the bearer of a certain special function, the “center” of this function, responsible for it, also participates in many other functions of the cortex, but no longer as the main link, not as the “center” ”, but on a par with many other areas.

The functional plasticity of the cortex, its ability to restore lost function by establishing new combinations speak not only of the relativity of the localization of functions, but also of its dynamism.

The basis of any more or less complex function is the coordinated activity of many areas of the cerebral cortex, but each of these areas participates in this function in its own way.

The basis of modern ideas about “systemic localization of functions” is the teaching of I. P. Pavlov about the dynamic stereotype. Thus, higher mental functions (speech, writing, reading, counting, gnosis, praxis) have a complex organization. They are never carried out by any isolated centers, but are always processes “located along a complex system of zones of the cerebral cortex” (A. R. Luria, 1969). These “functional systems” are mobile; in other words, the system of means by which this or that task can be solved changes, which, of course, does not reduce the importance for them of the well-studied “fixed” cortical areas of Broca, Wernicke, and others.

The centers of the human cerebral cortex are divided into symmetrical, represented in both hemispheres, and asymmetrical, present in only one hemisphere. The latter include centers of speech and functions associated with the act of speech (writing, reading, etc.), existing only in one hemisphere: in the left - for right-handers, in the right - for left-handers.

Modern ideas about the structural and functional organization of the cerebral cortex come from the classical Pavlovian concept of analyzers, refined and supplemented by subsequent research. There are three types of cortical fields (G.I. Polyakov, 1969). Primary fields (nuclei of analyzers) correspond to the architectural zones of the cortex, in which sensory pathways (projection zones) end. Secondary fields (peripheral sections of the analyzer nuclei) are located around the primary fields. These zones are indirectly connected to the receptors; more detailed processing of incoming signals occurs in them. Tertiary, or associative, fields are located in areas of mutual overlap of the cortical systems of the analyzers and occupy more than half of the total surface of the cortex in humans. In these zones, inter-analyzer connections are established, providing a generalized form of generalized action (V. M. Smirnov, 1972). Damage to these zones is accompanied by disturbances in gnosis, praxis, speech, and goal-directed behavior.