Where is the visual tubercle of the brain located. Visual tubercles

The continuation of the brain stem anteriorly are the visual tubercles located on the sides III ventricle.

The visual hillock is a powerful accumulation of gray matter in which a number of nuclear formations can be distinguished.

There is a division of the thalamus proper into the thalamus, hupothalamus, metathalamus and epithalamus.

Thalamus- the main mass of the thalamus - consists of the anterior, external, internal, ventral and posterior nuclei.

Hypothalamus has a number of nuclei located in the walls of the third ventricle and its funnel (infundibulum). The latter is very closely related to the pituitary gland, both anatomically and functionally. This also includes the nipple bodies (corpora mamillaria). Metathalamus includes external and internal geniculate bodies (corpora geniculata laterale et mediale).

Epithalamus includes the epiphysis, or pineal gland (glandula pinealis), and the posterior commissure (comissura posterior).

The optic thalamus is an important stage on the way to the conduction of sensitivity. The following sensitive conductors are suitable for it (on the opposite side).

I. The medial loop with its bulbo-thalamic fibers (touch, joint-muscular sense, vibration sense, etc.) and the spinothalamic pathway (pain and temperature sensation).

II. Lemniscus trigemini - from the sensitive nucleus trigeminal nerve(sensitivity of the face) and fibers from the nuclei of the glossopharyngeal and vagus nerves (sensitivity of the pharynx, larynx, etc., as well as internal organs).

III. Visual tracts ending in the pulvinar thalamus and in the corpus geniculatum laterale (optic tracts).

IV. Lateral loop ending in the corpus geniculatum mediale (auditory tract).

Olfactory pathways and fibers from the cerebellum (from the red nuclei) also end in the visual tubercle.

Thus, impulses of exteroceptive sensitivity flow to the visual tubercle, perceiving stimuli from the outside (pain, temperature, touch, light, etc.), proprioceptive (joint-muscular feeling, sense of position and movement) and interoceptive (from internal organs).

Such a concentration of all types of sensitivity in the thalamus opticus will become clear if we take into account that at certain stages of the evolution of the nervous system, the thalamus was the main and final sensitive center that determines the general motor reactions of the organism of a reflex order by transmitting irritation to the centrifugal motor apparatus.

"Topical diagnosis of diseases of the nervous system", A.V. Triumfov

The internal capsule (capsula interna) is a strip of white matter located between the subcortical ganglia of the base. It is divided into three main sections: anterior thigh, posterior thigh and knee (genu capsulae internae). The anterior thigh is located between the nucleus caudatus and the nucleus lenticularis, the posterior thigh is between the thalamus opticus and the nucleus lenticularis. The internal capsule is a very important formation, where on a relatively ...

Lesions in the area of ​​​​the internal capsule, interrupting the paths passing here, cause motor and sensory disorders on the opposite side of the body (sensory conductors are crossed in the spinal cord and medulla oblongata, pyramidal - on their border). For foci in the region of the internal capsule, a half type of disorder is characteristic, since the location of the fibers here, as already mentioned above, is very close. At…

Between the ganglia of the base with their internal capsule and the cerebral cortex in the hemispheres there is a continuous mass of white matter (centrum semiovale), in which fibers of various directions are located. They can be divided into two main groups - projection and association. Projection fibers connect the cerebral cortex with the underlying parts of the central nervous system and are located in relation to ...

diencephalon

The diencephalon forms the walls of the third ventricle. Its main structures are the visual tubercles (thalamus) and the hypothalamic region (hypothalamus), as well as the suprathalamic region (epithalamus) (Fig. 30 A, B).

Rice. 30 A. 1 - thalamus (visual tubercle) - the subcortical center of all types of sensitivity, the "sensory" of the brain; 2 - epithalamus (supratuberous region); 3 - metathalamus (foreign region).

Rice. 30 B. Schemes of the visual brain (thalamencephalon): a - top view b - rear and bottom view.

Thalamus (thalamus) 1 - anterior burf of the thalamus, 2 - pillow 3 - intertubercular fusion 4 - brain strip of the thalamus

Epithalamus (supratuberous region) 5 - triangle of the leash, 6 - leash, 7 - commissure of the leash, 8 - pineal body (pineal gland)

Metathalamus (foreign region) 9 - lateral geniculate body, 10 - medial geniculate body, 11 - III ventricle, 12 - roof of the midbrain

Rice. 30. Visual Brain

In the depths of the brain tissue of the diencephalon are the nuclei of the external and internal geniculate bodies. The outer border is formed by white matter separating the diencephalon from the final.

Thalamus (optical tubercles)

The neurons of the thalamus form 40 nuclei. Topographically, the nuclei of the thalamus are divided into anterior, median and posterior. Functionally, these nuclei can be divided into two groups: specific and nonspecific.

Specific nuclei are part of specific pathways. These are ascending pathways that transmit information from the receptors of the sense organs to the projection zones of the cerebral cortex.

The most important of the specific nuclei are the lateral geniculate body, which is involved in the transmission of signals from photoreceptors, and the medial geniculate body, which transmits signals from auditory receptors.

Nonspecific thalamic ridges are referred to as the reticular formation. They play the role of integrative centers and have a predominantly activating ascending effect on the cortex of the cerebral hemispheres (Fig. 31 A, B)

1 - front group (olfactory); 2 - rear group (visual); 3 - lateral group (general sensitivity); 4 - medial group (extrapyramidal system; 5 - central group (reticular formation).

Rice. 31B. Frontal section of the brain at the level of the middle of the thalamus. 1a - anterior nucleus of the thalamus. 16 - medial nucleus of the thalamus, 1c - lateral nucleus of the thalamus, 2 - lateral ventricle, 3 - fornix, 4 - caudate nucleus, 5 - internal capsule, 6 - external capsule, 7 - external capsule (capsula extrema), 8 - ventral nucleus of the thalamus, 9 - subthalamic nucleus, 10 - third ventricle, 11 - brain stem. 12 - bridge, 13 - interpeduncular fossa, 14 - hippocampal stalk, 15 - lower horn of the lateral ventricle. 16 - black substance, 17 - island. 18 - pale ball, 19 - shell, 20 - Trout H fields; and b. 21 - interthalamic fusion, 22 - corpus callosum, 23 - tail of the caudate nucleus.

Fig 31. Scheme of groups of nuclei of the thalamus

Activation of neurons of nonspecific nuclei of the thalamus is especially effectively caused by pain signals (thalamus - highest center pain sensitivity).

Damage to the nonspecific nuclei of the thalamus also leads to a violation of consciousness: the loss of the body's active connection with the environment.

diencephalon in the process of embryogenesis develops from the anterior cerebral bladder. It forms the walls of the third cerebral ventricle. The diencephalon is located under the corpus callosum and consists of the thalamus, epithalamus, metathalamus, and hypothalamus.

Thalamus (optical tubercles) They are an ovoid-shaped collection of gray matter. The thalamus is a large subcortical formation through which a variety of afferent pathways pass into the cerebral cortex. Its nerve cells are grouped into a large number of nuclei (up to 40). Topographically, the latter are divided into anterior, posterior, median, medial and lateral groups. By function, the thalamic nuclei can be differentiated into specific, nonspecific, associative and motor.

From specific nuclei, information about the nature of sensory stimuli enters strictly defined areas of 3-4 layers of the cortex. The functional basic unit of specific thalamic nuclei are "relay" neurons, which have few dendrites, a long axon, and perform a switching function. Here, the pathways leading to the cortex from skin, muscle and other types of sensitivity are switched. Violation of the function of specific nuclei leads to the loss of specific types of sensitivity.

Nonspecific nuclei of the thalamus are associated with many parts of the cortex and take part in the activation of its activity, they are referred to as the reticular formation.

The associative nuclei are formed by multipolar, bipolar neurons, the axons of which go to the 1st and 2nd layers of the associative and partially projection areas, giving off to the 4th and 5th layers of the cortex along the way, forming associative contacts with pyramidal neurons. Associative nuclei are associated with the nuclei of the cerebral hemispheres, the hypothalamus, the midbrain and the medulla oblongata. Associative nuclei are involved in higher integrative processes, but their functions have not yet been studied enough.

The motor nuclei of the thalamus include the ventral nucleus, which has an input from the cerebellum and basal ganglia, and at the same time gives projections into the motor zone of the cerebral cortex. This core is included in the movement regulation system.

The thalamus is a structure in which the processing and integration of almost all signals going to the cerebral cortex from the neurons of the spinal cord, midbrain, and cerebellum take place. The ability to obtain information about the state of many body systems allows it to participate in the regulation and determine the functional state of the body as a whole. This is confirmed by the fact that there are about 120 differently functional nuclei in the thalamus.

The functional significance of the thalamic nuclei is determined not only by their projection onto other brain structures, but also by what structures send their information to it. Signals come to the thalamus from the visual, auditory, gustatory, skin, muscular systems, from the nuclei of the cranial nerves, brainstem, cerebellum, medulla oblongata and spinal cord. In this regard, the thalamus is actually a subcortical sensory center. The processes of thalamic neurons are directed partly to the nuclei of the striatum of the telencephalon (in this regard, the thalamus is considered as a sensitive center of the extrapyramidal system), partly to the cerebral cortex, forming thalamocortical pathways.

Thus, the thalamus is the subcortical center of all types of sensitivity, except for the olfactory one. Ascending (afferent) pathways are approached and switched to it, along which information is transmitted from various receptors. Nerve fibers go from the thalamus to the cerebral cortex, making up the thalamocortical bundles.

Hypothalamus- phylogenetic old part of the diencephalon, which plays an important role in maintaining the constancy of the internal environment and ensuring the integration of the functions of the autonomic, endocrine and somatic systems. The hypothalamus is involved in the formation of the bottom of the third ventricle. The hypothalamus includes the optic chiasm, the optic tract, the gray tubercle with a funnel, and the mastoid body. The structures of the hypothalamus have a different origin. The visual part (optic chiasm, optic tract, gray tubercle with a funnel, neurohypophysis) is formed from the telencephalon, and the olfactory part (mastoid body and hypothalamus) is formed from the intermediate brain.

The optic chiasm has the form of a transversely lying roller, formed by the fibers of the optic nerves (II pair), partially passing to the opposite side. This roller on each side laterally and posteriorly continues into the optic tract, which runs behind the anterior perforated substance, goes around the brain stem from the lateral side and ends with two roots in the subcortical centers of vision. The larger lateral root approaches the lateral geniculate body, and the thinner medial root goes to the superior hillock of the midbrain roof.

To the anterior surface of the optic chiasm, the terminal (boundary, or terminal) plate, which belongs to the telencephalon, is adjacent and fuses with it. It closes the anterior part of the longitudinal fissure of the cerebrum and consists of a thin layer of gray matter, which in the lateral parts of the plate continues into the substance frontal lobes hemispheres.

Visual decussation (chiasm) - place in the brain where they meet and partially cross over optic nerves coming from the right and left eyes.

Behind the optic chiasm is a gray tubercle, behind which lie the mastoid bodies, and on the sides are the optic tracts. From top to bottom, the gray tubercle passes into a funnel, which connects to the pituitary gland. The walls of the gray tubercle are formed by a thin plate of gray matter containing gray-tuberous nuclei. From the side of the cavity of the third ventricle, into the region of the gray tubercle and further into the funnel, a narrowing down, blindly ending deepening of the funnel protrudes.

The mastoid bodies are located between the gray tubercle in front and the posterior perforated substance in the back. They look like two small, about 0.5 cm in diameter each, white spherical formations. White matter is located only outside the mastoid body. Inside is a gray matter in which the medial and lateral nuclei of the mastoid body are isolated. In the mastoid bodies, the pillars of the arch end. According to their function, the mastoid bodies belong to the subcortical olfactory centers.

Cytoarchitectonically, there are three areas of accumulation of nuclei in the hypothalamus: anterior, middle (medial), and posterior.

In the front The hypothalamus contains the supraoptic nucleus and paraventricular nuclei. The processes of the cells of these nuclei form the hypothalamic-pituitary bundle, ending in the posterior lobe of the pituitary gland. The neurosecretory cells of these nuclei produce vasopressin and oxytocin, which enter the posterior pituitary gland.

In the middle the areas are arcuate, gray-tuberous and other fields, where releasing factors, liberins and statins are produced, which regulate the activity of the adenohypophysis.

To the cores posteriorly th area includes scattered large cells, among which there are clusters of small cells, as well as the nuclei of the mastoid body. The latter are subcortical centers of olfactory analyzers.

The pituitary gland contains 32 pairs of nuclei, which are links of the extrapyramidal system, as well as nuclei related to the subcortical structures of the limbic system.

Under the third ventricle are the mastoid bodies, which belong to the subcortical olfactory centers, the gray tubercle and the optic chiasm formed by the optic chiasm. At the end of the infundibulum is the pituitary gland. The nuclei of the autonomic nervous system lie in the gray hillock.

The pituitary gland has extensive connections both with all parts of the central nervous system and with peripheral endocrine glands. Thanks to these extensive multifunctional connections, the hypothalamus acts as a higher subcortical regulator of metabolism, body temperature, urination, and the function of the endocrine glands.

Through nerve impulses, the medial region of the hypothalamus (mediobasal nucleus) controls the activity of the posterior pituitary gland, and through hormonal mechanisms (releasing factors) - the anterior pituitary gland. Under the influence of various afferent impulses entering the medial hypothalamus, the latter begin to synthesize releasing hormones, which through the blood system (median eminence) enter the adenohypophysis. They regulate the production of various tropic hormones in the anterior pituitary gland. Each liberin is responsible for the synthesis and release of a strictly defined tropic hormone in the pituitary gland. Tropic hormone from the anterior pituitary enters the bloodstream and regulates the synthesis and entry into the blood of hormones from the peripheral endocrine glands. Hence, it follows that each tropic hormone corresponds to a strictly defined peripheral gland. The only somatotropic hormone (GH) does not have a peripheral gland; it is a protein hormone that acts directly on body tissues, forming a hormone-receptor complex on the surface of cell membranes. Hormonal regulation lies in the fact that with a decrease in the content of hormones of peripheral endocrine glands in the blood plasma or under the action of some kind of stressor, during physical exertion, the medial pituitary gland increases the release of liberins into the blood. The latter act on the adenohypophysis and stimulate the production of tropic hormones. If, on the contrary, the content of hormones of the peripheral endocrine glands is increased, then the formation and corresponding release of inhibitory hormones (statins) in the medial hypothalamus increase, which inhibit the secretion of tropic hormones and reduce their content in the blood plasma. This mechanism of regulation is called regulation by the principle of negative feedback.

The hypothalamus and behavior.

The hypothalamus performs the following functions:

participates in the regulation of digestion, a behavior that is closely related to a decrease in blood glucose;

provides thermoregulation of the body;

participates in the regulation of osmotic pressure;

participates in the regulation of the activity of the sex glands;

participates in the formation of defensive reactions - defensive behavior and flight.

Eating behavior is accompanied by a search for food. At the same time, the autonomic reaction is somewhat different - salivation increases, intestinal motility and blood supply increase, muscle blood flow decreases, as the activity of the parasympathetic nervous system increases.

In the hypothalamus, there are areas responsible for certain behavioral responses that overlap. Morphologically, areas are identified that clearly correspond to strictly defined behavioral responses. In violation of the lateral (lateral) areas of the hypothalamus, where the nuclei of hunger and satiety are located, aphagia (refusal to eat) and hyperphagia (excessive food intake) occur.

The hypothalamus produces a large number of mediators: adrenaline, nordadrenaline - excitatory mediators, glycine, -aminobutyric acid - inhibitory mediators.

Thus, the hypothalamus occupies a leading place in the regulation of many functions of the body and, above all, homeostasis. Under its control are the functions of the autonomic nervous system and endocrine glands.

Epithalamus. The epithalamic region is located dorsally in relation to the caudal parts of the thalamus and occupies a relatively small volume. It includes a triangle of leashes, formed as an extension of the caudal part of the thalamic brain strips and the leash nuclei located at its base. The triangles are connected by a commissure of the leashes, in the depth of which the posterior commissure passes. On leashes - paired strands starting from a triangle, an unpaired pineal body, or epiphysis, is suspended - a conical formation about 6 mm long. In the anterior part, it is connected with both commissures and lying in back wall III ventricle is a subcommissural organ.

The nuclei of the leashes are formed by two cell groups - medial and lateral nuclei. The afferents of the medial nucleus are the fibers of the brain strips, which conduct impulses from the limbic formations of the telencephalon (the area of ​​​​the partitions, the hippocampus, the amygdala), as well as from the medial nucleus, the pale ball and the hypothalamus. The lateral nucleus receives inputs from the lateral preoptic region, the internal segment of the globus pallidus, and the medial nucleus. The efferents of the medial nucleus, addressed to the interpeduncular nucleus of the midbrain, form an unfolded bundle. The efferents of the lateral nucleus of the leashes follow the same path, pass the interpeduncular nucleus without switching and are addressed to the compact part of the substantia nigra, the central gray matter of the midbrain and the reticular nuclei of the midbrain.

The pineal gland is located in the middle under the thickened posterior part of the corpus callosum and is located in a shallow groove that separates the upper mounds of the roof of the midbrain from each other. Outside, the epiphysis is covered with a connective tissue capsule containing a large number of blood vessels. From the capsule, connective tissue trabeculae penetrate into the organ, subdividing the parenchyma of the epiphysis into lobules.

The pineal gland is an endocrine gland (pineal gland) and consists of glial elements and special cells of pinealocytes. It is innervated by the nuclei of the leashes, fibers of the brain strips of the posterior commissure and projections of the superior cervical sympathetic ganglion also approach it. Axons entering the gland branch among pinealocytes, providing regulation of their activity. Among the biologically active substances produced by the pineal gland are melatonin and substances that play an important role in the regulation of developmental processes, in particular, puberty and adrenal activity.

In the pineal body in adults, especially in old age, there are often bizarre deposits that give the epiphysis a certain resemblance to a spruce cone, which explains its name.

Metathalamus represented by lateral and medial cranked bodies - paired formations. They have an oblong-oval shape and are connected to the mounds of the roof of the midbrain with the help of handles of the upper and lower mounds. The lateral geniculate body is located near the inferolateral surface of the thalamus, on the side of its pillow. It can be easily detected by following the course of the optic tract, the fibers of which are directed to the lateral geniculate body.

Somewhat medially and behind the lateral geniculate body, under the pillow, is the medial geniculate body, on the cells of the nucleus of which the fibers of the lateral (auditory) loop end.

The metathalamus is composed of gray matter.

The lateral geniculate body, right and left, is the subcortical, primary center of vision. Nerve fibers of the visual tract (from the retina of the eye) approach the neurons of its nucleus. The axons of these neurons go to the visual cortex. The medial geniculate bodies are the subcortical primary hearing centers.

IIIventricle is a narrow vertical slit that serves as a continuation of the aqueduct forward to the region of the diencephalon. On the sides of its anterior part, the third ventricle communicates with the right and left interventricular foramina with the lateral ventricles lying inside the hemispheres. In front, the III ventricle is bounded by a thin plate of gray matter - the final plate, which is the most anterior part of the original brain wall, remaining in the middle between the two strongly grown hemispheres. Connecting both hemispheres of the telencephalon, this plate itself belongs to it. Directly above it is a connecting bundle of fibers extending from one hemisphere to another in the transverse direction; these fibers connect the areas of the hemispheres related to the olfactory nerves. This is the anterior commissure. Below the end plate, the cavity of the third ventricle is limited by the optic chiasm.

The lateral walls of the third ventricle are formed by the medial sides of the optic tubercles. On these walls there is a longitudinal depression - the hypotuberous furrow. It leads back to the aqueduct of Sylvius, forward to the interventricular foramen. The bottom of the third ventricle is built from the following formations (from front to back): optic chiasm, funnel, gray tubercle, mastoid bodies and posterior perforated space. The roof is formed by the ependema, which is part of the choroid plexuses III and the lateral ventricles. Above it is the vault and the corpus callosum.

THALAMUS [thalamus(PNA, JNA, BNA); syn. thalamus] - a paired formation of the diencephalon, which is the main collector of somatosensory information going through the brain stem to the cerebral cortex. T. of the right hemisphere is separated from T. of the left hemisphere by the third ventricle throughout, except for the place of interthalamic fusion (adhesio interthalamica, massa intermedia), in which unpaired nuclei of the so-called are located. middle line.

Based on embryos. studies V. Gis (1904) for the first time identified the main structural formations of the diencephalon: epithalamus (see. Diencephalon), dorsal (posterior) thalamus, ventral (anterior) thalamus and hypothalamus (see). In BNA also the metathalamus was allocated, to-rogo are a part of medial and lateral geniculate bodies. Further phylontogenetic studies of the structure and connections of the diencephalon showed that the dorsal part of the nucleus of the lateral geniculate body belongs to the dorsal T., and the ventral nucleus of the lateral geniculate body and the ventral large cell part of the medial geniculate body belong to the ventral T.

Comparative anatomy

Comparative anatomical and embryological studies have revealed a very complex nature of the development of T. and its individual complexes, determined both by the general patterns of evolution of the brain of chordates, and environmental factors formation sensory systems in various representatives of this type.

The formations of the ventral T., especially the most ancient ventral part of the lateral geniculate body, differentiate already in selachia, that is, much earlier than the structures of the dorsal T., the division of which into separate formations is detected only in reptiles. In birds and reptiles, the most developed structure of the dorsal T. is the round nucleus, which has no direct homologues in the dorsal T. of mammals. The structures of the dorsal T. are most difficult to differentiate in mammals. The most ancient formations of the dorsal T., the posterior and pretectal nuclei, are well developed in lower mammals and are reduced in higher mammals. A similar process occurs with intralaminar (intralamellar, T.) nuclei, as well as with the ventral part of the nucleus of the lateral geniculate body, which belongs to the ventral T.

The complication of the differentiation of the structures of the dorsal T. is associated with an even greater complication of the structure of the new cortex (neo-cortex) of the mammalian brain, where the patterns of divergent (multidirectional) development are manifested in the relative progression of the newest and relative regression of the phylogenetically ancient zones of the cortex of the cerebral hemispheres. This process is explained by the fact that as the evolutionary complication of the brain in cortical-subcortical relations, cortical-thalamic connections become decisive, and in them, in turn, associative connections become predominant (compared to projection, relay). Thus, in monkeys, the projection zones occupy an even larger area of ​​the cerebral cortex compared to the associative zones; e.g., occipital only projection zone is approx. 20% of the area of ​​the entire bark. In humans, the ratios are reversed - the associative zones are dominant, and the occipital projection zone makes up only 12% of the area of ​​the new cortex. Therefore, in the thalamic complexes of the human brain, associative nuclei are most developed.

Anatomy and microscopic structure

T. is accurately delimited from surrounding structures. The hypothalamic groove, which runs along the wall of the third ventricle from the interventricular foramen to the opening of the Sylvian aqueduct (aqueduct of the brain, T.), limits T. from the ventrally located hypothalamus. On the dorsal surface of T., the so-called. an attached plate that forms the central part of the bottom of the lateral ventricle of the brain; in the dorsolateral direction, T. is separated by a border strip from the structures of the caudate nucleus; laterally, the internal capsule separates T. from the lenticular nucleus and the head of the caudate nucleus (see Basal nuclei). The rostral end of T. is represented by the anterior tubercle, and the caudal end forms a pillow, under the posterior end the lateral geniculate body is located, and medially from it is the medial geniculate body, which are part of the thalamic complex.

Morfol. The classifications of nuclear formations in T. are based on the topographic principle and distinguish the anterior, posterior, outer, and inner groups of nuclei. Development of modern complex morpho-fiziol. research methods led to the possibility of identifying and structural and functional differentiation of the thalamic nuclei, which are divided into: 1) specific sensory (relay, switching) nuclei, each of which receives predominantly one main type of sensory afferentation from the periphery; 2) non-specific nuclei that receive and process impulses that come primarily from the reticular formations of the brain stem and hypothalamus; 3) associative nuclei related to the further processing and integration of various sensory impulses. The identification of an associative group of nuclei is associated with new data on the integrating (and not just relay) functions of thalamic structures.

The anterior group of nuclei, located in the anterior tubercle of T., includes the anterodorsal and anteroventral nuclei, which belong to specific relay formations, and the anteromedial nucleus, which belongs to nonspecific structures (Fig., a). Relay nuclei receive impulses along the mastoid-thalamic bundle and transmit them to the pre- and post-subicular fields of the old cortex, but Ch. arr. - in the fields of the limbic region of the new cortex. These formations are part of the limbic system (see). The posterior group of nuclei is enclosed in the posterior pole of the T. (cushion) and is the associative nucleus most developed in primates, and especially in humans. Structurally and functionally, the posterior group is related not only to visual (to a greater extent), but also to somatosensory and auditory (to a lesser extent) projections onto the cerebral cortex.

The outer complex of nuclei (ventrolateral nuclei, T.) includes the lateral anterior (ventral) nucleus and the ventral group of nuclei, in which the anterior and posterior ventral nuclei are isolated. The lateral anterior nucleus is the phylogenetically most ancient formation of the complex, located posterior to the anterior group of nuclei and clearly delimited from the surrounding structures; has direct connections with the fornix of the brain, which allows the nucleus to be attributed to the relay formations of the limbic system (Fig., b). The posterior lateral nucleus belongs to the associative nuclei of T., however, it is assumed that this nucleus is also related to specific sensory systems.

The main relay nucleus of T., which transmits somatic afferentation to the cerebral cortex, is the posteromedial ventral, or posteromedial nucleus, the medial loop, the spinal-thalamic pathway, the cerebellar-rubro-thalamic pathway, and the axons of cells of the spinal nucleus are suitable for Krom. trigeminal nerve pathways.

The inner group of nuclei (medial nuclei, T.) of the thalamus is located outside the central gray matter surrounding the walls of the third ventricle (see. Cerebral ventricles). The most developed in primates and humans is the dorsal medial nucleus, which belongs to the associative nuclei and has direct connections with the structures of the frontal region of the neocortex. Inside the plate surrounding this nucleus, there are intralaminar (intralamellar) nuclei. The parafascicular complex of nuclei also belongs to this group, outward from which the median center of Lewis (centrum medianum Luysi) or the central median nucleus is located, the question of direct connections to-rogo with the cerebral cortex to the present time is not well understood. The medial ventral nucleus, located under the dorsal medial one, is phylogenetically more ancient and can be classified as nonspecific structures in the same way as the midline nuclei located inside the central gray matter.

The pretectal and posterior nuclei belong to the more ancient structures of T.

The lateral geniculate body, belonging to the thalamic complex, consists of a phylogenetically newer dorsal part of the nucleus (dorsal nucleus) and an older ventral part (ventral nucleus). The dorsal nucleus is a classic relay formation that transmits visual afferentation to the cortex (see Visual Analyzer). Terminals from the retina are also found in the ventral part of the nucleus of the lateral geniculate body, and fibers from the occipital region of the cortex are distributed both in the ventral and dorsal parts of the nucleus of the lateral geniculate body.

The medial geniculate body, especially its outer small cell part, is the main relay formation auditory analyzer(see), receiving information along the fibers of the lateral loop and transmitting it to the structures of the temporal region of the new cortex.

Blood supply to T. - see Cerebral circulation.

Physiology

A study of the structure and function of thalamic formations using modern complex methods revealed an extremely complex nature of the relationship of T. both with the higher located parts of the forebrain and with the lower structures of the brain stem, cerebellum and spinal cord. The close integration of somatic, visceral, motivational influences, carried out at the level of thalamic complexes, determines the leading role of these diencephalic formations in the formation of not only cortical-subcortical relations, but also in the formation and development of integral behavioral acts in animals and humans.

The study of the functions of T. is carried out by electrical stimulation or destruction in combination with an analysis of the dynamics of various behavioral reactions, EEG registration, evoked potentials, or electrical activity single neurons in response to various peripheral irritations in experiments on animals and in to lay down. purposes - in humans.

It is established that in the relay nuclei of T. impulses of tactile, kinesthetic, temperature, pain (localized pain), taste and visceral sensitivity are switched (see). Each nucleus receives impulses from the opposite side of the body, only the face area has a bilateral representation in the posterior ventral nucleus of T. Parts of the body that perform the most intense sensory-motor functions (face, tongue, distal extremities) have a more extensive representation. In the medial part of the posterior ventral nucleus, the somatotopic organization of which is well studied, afferentation comes from the rostral parts of the body and impulses from the taste buds, in the lateral part - from the receptors of the trunk and extremities. Projections of tactile and visceral sensitivity have a wide overlap in T., which can cause the phenomenon of irradiation of visceral pain (see) on the surface of the body. General projections in T. also have tactile and deep (pro-prioceptive) sensitivity. Finely differentiated afferent impulses from thermo- and nocireceptors pass predominantly along the spinothalamic pathway to the posterior ventral nucleus, while the coarser forms of these types of sensitivity (diffuse pain, differentiation of large temperature ranges) are associated mainly with nonspecific intralaminar nuclei of T. (parafascicular complex), as well as possibly with back nuclei. Electrical stimulation of the posterior ventral nucleus in humans during stereotaxic operations (see C. Tereotactic Neurosurgery, Stereotaxic Method) causes paresthesias, less often violation of the body map (see Body map).

Non-sensory relay formations include the anterior group of nuclei, which transmit impulses from the mastoid bodies to the limbic region of the cortex, as well as two nuclei of the ventral group of T. - the anterior ventral and lateral ventral, which transmit the bulk of excitations from the cerebellum and the globus pallidus to the motor sections of the cerebral cortex, which determines their role in the regulation of involuntary motor activity and muscle tone. These connections of the lateral ventral nucleus substantiate the expediency of its destruction in patients with parkinsonism and with various hyperkinesis.

The group of associative nuclei of T. has relay and partly non-specific structures of T. and the hypothalamus as the main source of afferentation. AT recent times it has been shown that some of the sensory projections (somatosensory, auditory, visual, visceral) can end in these nuclei. The interaction of various afferent impulses on the neurons of the associative nuclei of T., their complex intrathalamic and interthalamic connections explain the important role of this group of formations in the integrative activity of the brain. There are thalamoparietal and thalamofrontal associative systems. The first is predominantly related to the formation of complexes of afferent influences necessary to assess the signal significance complex types stimuli that underlie the gnostic function, especially visual and auditory perception, as well as sensory control of voluntary movements. The medial dorsal nucleus belongs to the thalamofrontal associative system, which is primarily involved in affective-emotional and programming activities. Stimulation of the medial dorsal nucleus of T. in patients causes a variety of positive and negative emotional reactions; destruction of this kernel in to lay down. purposes, as well as in animal experiments, reduces the feeling of fear, anxiety and tension, but at the same time there are mild symptoms of the so-called. frontal syndrome - a decrease in initiative and intellectual abilities against the background of a persistent decrease in emotional reactivity. At distribution patol. process on medial departments of T. observe the development of dementia (see).

The group of nonspecific nuclei of T. receives afferentation primarily from the reticular formations of the brain stem, however, there is evidence of the possibility of ending in hYix fibers that go as part of specific ascending systems. Although the nuclei of this group are projected onto the cortex more diffusely than the first two groups, some of them are characterized by a more or less local nature of connections with the cortex and the striatum (striopallidum). This group includes intralamellar (intralaminar) nuclei (parafascicular nucleus, lateral central and paracentral nuclei), the reticular nucleus of the thalamus, the nuclei of the midline T. The discovery of nonspecific nuclei T. is associated with the work of Dempsey and Morison (E. W. Dempsey, R. S. Morison , 1943), who showed that when these nuclei are irritated, a widespread involvement reaction occurs in the cerebral cortex. Later, S. P. Narikashvili, E. S. Moniava, V. I. Guselnikov and A. Ya. Supin (1968) and others found that in the genesis of this reaction, as well as the enhancement reaction, interaction of non-specific nuclei of T. with its specific formations.

Data on the functional significance of the nuclei of this group are contradictory: on the one hand, it has been established that the destruction of the complex parafascicular nucleus - the central median nucleus (median center) affects the positive and negative learning of rats; on the other hand, the effect of damage to this complex largely depends on the previous emotional background; the important role of the afferentation of this complex in the activity of the neurons of the caudate nucleus is also shown (see Basal nuclei). The idea of ​​non-specificity of this group of nuclei is relative. On the basis of data on their structure, connections, and function, one can speak of the existence in T. of complex complexes formed by relay and nonspecific nuclei. The study of the functions of the midline nuclei is hampered by their closest proximity to the associative and relay nuclei of T. The destruction of the medial departments of T. may be accompanied by impaired conditioned reflexes (see), memory (see), sleep (see).

In the group of nonspecific nuclei, a special place is occupied by the reticular nucleus of T. The latter adjoins from the outside to various relay nuclei of the dorsal T. and partially has a common projection onto the cortex with them. It is assumed that this nucleus is a mediator both in the activity of other T. nuclei and in the thalamo-cortical interaction of its specific and nonspecific formations. In a crust, time, the important role of T. is obvious in the implementation of the complex functions of perception and processing of various signals that go further to the cerebral cortex and basal ganglia, in maintaining the level of wakefulness and emotional state, in the normal provision of simple and more complex forms of behavior and memory. Complete bilateral removal of T. in dogs and cats reveals a sharp deficit in adaptive reactions, impaired sensitivity, and alternations of the wakefulness-sleep cycle. Operational isolation of the cortex and basal nuclei from T. and the brain stem (the so-called thalamic animal) leads to massive retrograde degeneration of T. neurons and is accompanied by sharp and irreversible changes in adaptive behavior, up to the impossibility of self-feeding.

Recently, in connection with the accumulation of data on interhemispheric asymmetry, indications have appeared of the functional unequalness of the right and left T. in humans. Thus, the use of verbalized material in tests for short term memory, apparently, is carried out with the participation of predominantly left T., non-verbalized material - with the participation of right T.; the most significant syndrome of left-sided lesion of the thalamus is the inconsistency of speech.

In the 70s. a number of new principles of thalamocortical interaction were formulated that are relevant to the understanding of integration nervous processes at the level of the forebrain: the principles of "nuclear" and "scattered" types of thalamocortical projections, the interlayering of these various projections among themselves, their different distribution in the projection and associative areas of the neocortex, mono- and oligo-gosynaptic transmission of excitations from the T. to the cortex , as well as topographic correspondence (mainly for relay and associative structures) and inconsistencies (Ch. arr. for nonspecific structures of T.) of thalamocortical and cortico-thalamic influences. In neuro-rofisiol. Studies have found dynamic integration of specific and non-specific influences at the diencephalic and cortical levels; It is found out that neurofiziol. the basis of the rhythmic activity of the brain are the mechanisms of recurrent inhibition (see) p excitation (see), played out at the thalamic and cortical levels. New ways of relationships between associative and projection thalamocortical systems have been identified and studied, and a position has been formulated on complexly functioning thalamocortico-thalamic associative systems. The problem of cortical regulation of the activity of the thalamic nuclei received new coverage: it is shown that the regulation of the relay thalamic nuclei is carried out by Ch. arr. direct cortico-thalamic pathways, and nonspecific nuclei - mainly with the participation of the reticular formation of the brain stem. It has been established that the reticular systems of the brain are able to differentiate afferent signals and direct them to the corresponding brain structures under the influence of corticofugal modulation.

Pathology

Focal defeats of T. can develop at various patol. processes, but most often - in case of violations cerebral circulation(ischemia, hemorrhage due to atherosclerosis and hypertension). The most common circulatory disorders in the zone of deep branches of the posterior cerebral artery. With a stroke in this pool, the ventrolateral nuclei of T. or its dorsal medial nucleus are mainly damaged. In T., both ischemic heart attacks and hemorrhages are possible with ruptured arteries, vasculitis, hypertensive crises with high blood pressure, and with arteriovenous aneurysms. Much less often, thalamic complexes are damaged in infectious, tumor, dystrophic and other diseases.

Inflammatory lesions of T. occasionally occur in tuberculosis, syphilis, sepsis, and encephalitis (viral, bacterial). Degenerative processes in the structures of T. occur with genetic defects in metabolism or with intoxications (exogenous, endogenous), as well as in the residual stage of an infectious or traumatic brain injury. Primary tumors of T. are rather rare, more often T. is involved in patol. process with infiltrative tumor growth from neighboring parts of the brain (with gliomas, astrocytomas, etc.).

Wedge, symptoms at defeat of T. are diverse and depend on functional role damaged structures. The thalamic syndrome was for the first time described in detail by Zh. Dezherin and G. Roussy in 1906 at T.'s softening owing to blockage of a back cerebral artery and its branches. When turning off a. thalamoge-niculata on the side opposite to the lesion in T., the following symptoms develop: 1) hemihypesthesia or hemianesthesia with pronounced violation deep sensitivity is more on the limbs, sometimes without a disorder of sensitivity on the face; 2) hyperpathy or dysesthesia (see Sensitivity, Disorders), paroxysms or persistent severe pains that spread to the entire half of the body (thalamic pain syndrome); 3) loss of vibration sensitivity; 4) transient hemiparesis without severe muscle spasticity and patol. Babinski's reflex; 5) atrophy of the muscles of the affected half of the body; 6) choreic and athetoid movements in the fingers; 7) hemiataxia; 8) sometimes homonymous hemianopsia; 9) notnagel's mimic paresis; 10) attention disorders.

At partial lesion T. Separate groups of these symptoms can prevail. At destruction of medial part of T. (pool a. tha-lamoperforata) the dentato-rubrothalamic way is damaged, on Krom in T. impulses from a cerebellum arrive, at the same time there is a hyperkinesia (athetoid, choreic) and a hemiataxia on the side opposite to the center. At defeat of forward departments of T. reveal contralateral mimic paresis of facial muscles. With diffuse lesions of T., thalamic syndrome is often combined with autonomic disorders (cyanosis, atrophy of the skin and nails, pastosity, coldness of the skin on the affected side of the body), more pronounced in the arm. In this case, the hand acquires a characteristic position: the forearm is bent and penetrated, the hand is bent at the wrist joint, the proximal phalanges of the fingers are bent, while the middle and distal phalanges are unbent (the so-called thalamic hand). Sometimes on the side of the focus there is a syndrome of Bernard - Horner (see Bernard - Horner syndrome).

Diagnosis of thalamic syndrome is based on the identification of a complex of its constituent symptoms. Wedge, diagnostic methods consist in determining superficial and deep sensitivity, determining visual fields (see), muscle strength of the limbs, coordination of movements (see), etc. The diagnosis is helped by Ferster's symptom: irritation of various receptors (visual, auditory, gustatory) causes pain and an unpleasant sensation in the affected half of the body.

The differential diagnosis of the thalamic Dejerine-Roussy syndrome should be carried out with the Ged-Holmes syndrome - unilateral affective dysesthesia, which is characterized by unilateral dysesthesia, exaggerated external manifestations of affective reactions (grimacing), sharp protective movements in response to minor physical irritation (eg. , a slight prick with a pin), unilateral disorder of taste and smell. This symptom complex develops in violation of the cortical-thalamic and cortical-hypothalamic connections. Besides, the thalamic syndrome should be differentiated from a syndrome of defeat of the internal capsule, at Krom along with a hemianesthesia (sometimes in combination with a hemianopsia) the spastic hemiplegia is observed. T.'s defeat can be revealed at a cerebral angiography (see), a computer tomography (see. Computer tomography ).

Treatment of thalamic syndrome is pathogenetic. Considerable difficulties arise at a thalamic hemialgia, at a cut usual analgesics are a little effective. It is recommended to use seduxen, chlorpromazine, finlepsin, tegretol, etc. pain syndromes apply stereotaxic operations on T.'s nuclei (see Stereotactic neurosurgery).

The forecast of a thalamic syndrome depends on character of the main patol. process.

Bibliography: Adrianov O. S. On the principles of organizing the integrative activity of the brain, M., 1976; Batuev A. S. Higher integrative systems of the brain, D., 1981, bibliogr.; GuselnikovV. I. Electrophysiology of the brain, M., 1976; Durinyan R. A. Central structure of afferent systems, L., 1965; he, Cortical control of nonspecific systems of a brain, M., 1975; Kesarev V. S. Quantitative architectonics of the human brain, Vestn. USSR Academy of Medical Sciences, No. 12, p. 29, 1978; Clinical neurophysiology, ed. N. P. Bekhtereva, p. 49, L., 1972; Krol M. B. and Fedorova E. A. Main neuropathological syndromes, M., 1966; Kurepina M. M. The brain of animals, M., 1981; General and private physiology of the nervous system, ed. P. G. Kostyuk, p. 313, L., 1969; Serkov F. N. and Kazakov V. N. Neurophysiology of the thalamus, Kyiv, 1980, bibliogr.; Vascular diseases of the nervous system, ed. E. V. Schmidt, p. 56, 330, Moscow, 1975; Experimental Psychology, ed. S. S. Stevens, trans. from English, p. 174, Moscow, 1960; In a r r a q u e r-V o g- d a s L. a. about. Thalamic hemorrhage, Stroke, v. 12, p. 524, 1981; Brow n J. W. Thalamic mechanisms in language, Handb. behavioral neurobiol., ed. by F. A. King, v. 2, p. 215, N. Y, -L., 1979; DantzerR. et Dela-c o u r J. Modification d'un phenomene de suppression conditionnee par une leson thalamique, Physiol. Behav., t. 8, p. 997, 1972; Dejerine J.a. Roussy G. Le syndrome thalamique, Rev. neurol. (Paris), t. 14, p. 521, 1906; Einfiihrung in die stereotaktischen Operationen mit einem Atlas des menschlichen Gehirns, hrsg. v. G. Schaltenbrand a. P. Bailey, Bd 1, S. 230, 1959, Bibliogr.; Graeber R. C. a. Ebbesson S.O. Retinal projections in the lemon shark (Negaprion previrostris), Brain Behav. Evolut., v. 5, p. 461, 1972; G r a y b i e 1 A. M. Some fiber pathways related to the posterior thalamic region in the cat, ibid., v. 6, p. 363, 1972; Henderson V. W., Alexander M. P. a. N a e s e g M. A. Right thalamic injury, impaired visuospatial perception, and alexia, Neurology, v. 32, p. 235, 1982, bibliogr.; K w a k R., K a d o u a S. a. Suzuki T. Factors affecting the prognosis in thalamic hemorrhage, Stroke, v. 14, p. 493, 1983; Lapresle J.a. Ha-g and e n a and M. Anatomico-chemical correlation in focal thalamic lesions, Z. Neurol., v. 205, p. 29, 1973; L e j e u n e H. Lesions thalamiques medianes et effets differentiels dans les apprentissages operants, Physiol, a. Behav., t. 18, p. 349, 1977; Van B u-r e n J. M. a. In o r k e R. C. Variations and connections of the human thalamus, pt 1 - 2, N. Y.a. o., 1972; V e 1 a s c o F. a. Velasco M. A reticulothalamic system mediating proprioceptive attention and tremor in man, Neurosurgery, v. 4, p. 30, 1979; Villablanca J.a. Sali-nas-Zeballos M. E. Sleep-wakeful-ness, EEG and behavioral studies of chronic cats without the thalamus, Arch. ital. Biol., v. 110, p. 383, 1972.

D. K. Bogorodinsky, A. A. Skoromets; O. S. Adrianov (phys.), V. S. Kesarev (an., comparative anatomy).

The thalamus is a structure of the brain, which in fetal development is formed from the diencephalon, making up its bulk in an adult. It is through this formation that all information from the periphery is transmitted to the cortex. The second name of the thalamus is visual tubercles. More about it later in the article.

Location

• specific;
• associative;
• non-specific.

Specific nuclei

The specific nuclei of the optic tubercle have a number of distinctive features. All formations of this group receive sensory information from the second neurons ( nerve cells) sensitive pathways. The second neuron, in turn, can be located in the spinal cord or in one of the structures of the brain stem: the medulla oblongata, the bridge, the midbrain.

Each of the signals coming from below is processed in the thalamus and then goes to the corresponding area of ​​the cortex. Which region a nerve impulse enters depends on what information it carries. So, information about sounds enters the auditory cortex, about the objects seen - into the visual cortex, and so on.

In addition to impulses from the second neurons of the pathways, specific nuclei are responsible for the perception of information coming from the cortex, the reticular formation, and the nuclei of the brain stem.

The nuclei, which are located in the anterior part of the thalamus, ensure the conduction of impulses from the limbic cortex of the brain through the hippocampus and hypothalamus. After processing the information, it again enters the limbic cortex. Thus, it circulates in a certain circle.

Associative nuclei

Associative nuclei are located closer to the posterior-medial part of the thalamus, as well as in the pillow area. The peculiarity of these structures is that they do not participate in the perception of information that comes from the underlying formations of the central nervous system. These nuclei are necessary to receive already processed signals in other nuclei of the thalamus or in the overlying brain structures.

The essence of the "associativity" of these nuclei is that any signals are suitable for them, and neurons are able to adequately perceive them. Signals from these structures arrive in cortical areas with the corresponding name - associative zones. They are located in the temporal, frontal and parietal parts of the cortex. Thanks to the receipt of these signals, a person is able to:

• recognize objects;
• associate speech with movements and objects seen;
• be aware of the position of your body in space;
• perceive space as three-dimensional and so on.

Non-specific nuclei

This group of nuclei is called non-specific because it receives information from almost all structures of the central nervous system:

• reticular formation;
• nuclei of the extrapyramidal system;
• other nuclei of the thalamus;
• stem structures of the brain;
• formations of the limbic system.

The impulse from nonspecific nuclei also goes to all areas of the cerebral cortex. Such selectivity, as in the case of associative and specific nuclei, is absent here.

Since it is this group of nuclei that has the largest number of connections, it is believed that thanks to it, the coordinated work of all parts of the brain is ensured.

Metathalamus

Separately, a group of nuclei of the optic tubercle called the metathalamus is isolated. This structure consists of the medial and lateral geniculate bodies.

The medial geniculate body receives information about hearing. From the underlying parts of the brain, information enters through the upper humps of the midbrain, and from above the structure receives an impulse from the auditory cortex.

The lateral geniculate body belongs to visual system. Sensitive information to the nuclei of this group comes from the retina through the optic nerves and the optic tract. Information processed in the thalamus then goes to the occipital region of the cortex, where the primary center of vision is located.

Functions of the thalamus

How is the processing of sensitive information coming from the periphery, which is then transmitted to the forebrain cortex? This is the main role of the visual tubercle.

Thanks to this function, when the cortex is damaged, it is possible to restore sensitivity through the thalamus. Thus, the reparation of pain, temperature sensations, as well as coarse touch is possible.

Another important function of the thalamus is the coordination of movements and sensitivity, that is, sensory and motor information. This is due to the fact that not only sensory impulses enter the thalamus. It also receives impulses from the cerebellum, ganglia of the extrapyramidal system, and the cerebral cortex. And these structures, as you know, take part in the implementation of movements.

Also, the visual tubercle is involved in maintaining conscious activity, regulating sleep and wakefulness. This function is carried out due to the presence of connections with the blue spot of the brain stem and the hypothalamus.

Damage symptoms

Since almost all signals from other structures of the nervous system pass through the thalamus, damage to the visual tubercle can be manifested by a host of symptoms. Extensive damage to the thalamus can be diagnosed by the following clinical signs:

• violation of sensitivity, first of all - deep;
• burning, sharp pains that first appear when touched, and then spontaneously;
• motor disorders, among which there is the so-called thalamic hand, manifested by excessive flexion of the fingers in the metacarpophalangeal and extension in the interphalangeal joints;
• visual disturbances - hemianopsia on the opposite side of the lesion).

Thus, the thalamus is an important structure of the brain, which ensures the integration of all processes in the body.