THALAMUS [thalamus (PNA, JNA, BNA); synonym visual hillock] — the pair formation of a diencephalon which is the main collector of the somatosensory information going through a brain trunk to bark of cerebral hemispheres. T. the right hemisphere it is separated from T. the left hemisphere throughout, except for the place of an interthalamic union (adhesio interthalamica, massa intermedia), in Krom unpaired kernels of the so-called centerline are located with the third ventricle.
On the basis embriol. researches V. Gis (1904) for the first time allocated the main textural features of a diencephalon: an epithalamus (see the Diencephalon), a dorsal (back) thalamus, a ventral (front) thalamus and a hypothalamus (see). In BNA it was allocated as well a metathalamus, medial and lateral cranked bodies are a part to-rogo. Further phyloontogenetic researches of a structure and bonds of a diencephalon showed accessory of a dorsal part of a kernel of a lateral cranked body to dorsal to T., and a ventral kernel of a lateral cranked body and a ventral macrocellular part of a medial cranked body — to ventral T.
A comparative anatomy
Comparative and anatomic and embryological researches revealed very difficult developmental character of T. and its separate complexes, determined both by the general patterns of evolution of a brain of chordates, and ecological factors of formation of touch systems at various representatives of this type.
Educations ventral T., especially the most ancient ventral part of a lateral cranked body, T are differentiated already at selakhiya, i.e. much earlier structures dorsal., the division to-rogo on separate educations comes to light only at reptiles. At birds and reptiles the most developed structure dorsal T. the round kernel which does not have direct homologs in dorsal T is. mammals. Structures dorsal are most difficult differentiated by T. at mammals. The most ancient educations dorsal T. — the back and pretektalny kernels which are well developed at the lowest mammals, at the highest — are reduced. Similar process happens also with intralaminarny (vnutriplastincha-ty, T.) kernels, and also with a ventral part of a kernel of a lateral cranked body, to the T relating to ventral.
Complication of a differentiation of structures dorsal T. it is connected with even big complication of a structure of new bark (neocortex) of a brain of mammals where patterns of divergent (multidirectional) development are shown in relative progressing of the latest and relative regressing phylogenetic of the most ancient zones of bark of cerebral hemispheres. This process is explained by the fact that in process of evolutionary complication of a brain in the corticosubcortical relations corticothalamic bonds become defining, and in them, in turn, prevailing (in comparison with projective, relay) there are associative bonds. So, projective zones occupy monkeys still considerably the big territory of a cerebral cortex in comparison with associative zones; e.g., only the occipital projective zone makes apprx. 20% of the area of all bark. The person has return ratios — associative zones are dominating, and the occipital projective zone makes only 12% of the area of new bark. Therefore and in thalamic complexes of a brain of the person associative kernels are most developed.
Anatomy and microscopic structure
T. it is accurately delimited from surrounding structures. The hypothalamic furrow going along a wall of the third ventricle from an interventricular foramen to an opening of a silviyev of a water supply system (a water supply system of a brain, T.), limits T. from ventrally the located hypothalamus. On a dorsal surface of T. the so-called attached plate forming the central part of a bottom of a side cerebral cavity is located; in the dorsolateral direction T. it is separated by a terminal stria from structures of a kernel having a tail; lateralno the internal capsule separates T. from a lenticular kernel and a head of a kernel having a tail (see. Basal kernels). Rostral end of T. it is presented by a front hillock, and caudal forms a pillow, under the back end a cut a lateral cranked body, and knutr from it — a medial cranked body, entering a thalamic complex are located.
Morfol. classifications of nuclear formations of T. have the topographical principle in a basis and allocate front, back, outside and internal groups of kernels. Development modern complex morfo-fiziol. methods of a research caused a possibility of identification and a structurally functional differentiation of thalamic kernels, to-rye subdivide on: 1) specific touch (relay, switching) kernels, any one main type of a touch afferentation comes to each of to-rykh from the periphery preferential; 2) the nonspecific kernels accepting and processing the impulses arriving first of all from reticular formations of a brain trunk and hypothalamus; 3) the associative kernels concerning further processing and integration of various touch impulses. Allocation of associative group of kernels is connected with new data about integrating (and not just about relay) functions of thalamic structures.
The front group of kernels which is in a front hillock of T., includes the perednedorsalny and peredneventralny kernels relating to specific relay educations and the anteromedial kernel relating to nonspecific structures (fig., a). Relay kernels receive impulses on mastoidal thalamically bunch and transfer them in pre-and postsubikulyarny fields of old bark, but hl. obr. - to fields of limbic area of new bark. These educations are a part of limbic system (see). The back group of kernels is imprisoned in a back pole of T. (pillow) is also the associative kernel which is the most developed at primacies, and especially at the person. Structurally and functionally back group is related not only to visual (to a large extent), but also to somatosensory and acoustical (in a smaller measure) to projections to bark of cerebral hemispheres.
In an outside complex of kernels (vent-rolateralny kernels, T.) the lateral front (ventral) kernel and ventral group of kernels enter, in a cut lobbies and back ventral kernels allocate. The lateral front kernel — phylogenetic the most ancient formation of a complex, is located kzad from front group of kernels and accurately delimited from surrounding structures; has feedforwards with the arch of a brain that allows to carry a kernel to relay formations of limbic system (fig., b). The back lateral kernel belongs to associative kernels of T., however it is supposed that this kernel is related also to specific touch systems.
Main relay kernel of T. the zadnemedialny ventral, or posteromedialny kernel is transferring a somatic afferen-tation to a cerebral cortex, the medial loop, a back and thalamic way, a cerebellar and rubrothalamic way and axons of cells of a kernel of a spinal way of a trifacial approaches Krom.
Internal group of kernels (medial kernels, T.) a thalamus is located outside from the central gray matter surrounding walls of the third ventricle (see Ventricles of a brain). The dorsal medial kernel relating to associative kernels and having feedforwards with structures of frontal area of new bark is the most developed at primacies and the person. In the plate surrounding this kernel intralaminar-ny (intra lamellar) kernels are located. Carry to the same group also a parafascicular complex of kernels, knaruzh from to-rogo the median center of Lyuis (centrum medianum Luysi) or the central median kernel, a question of feedforwards to-rogo with bark of cerebral hemispheres to a crust is located, time it is insufficiently studied. The medial ventral kernel located under dorsal medial is phylogenetic more ancient education and can be carried to nonspecific structures as well as the kernels of the centerline located in the central gray matter.
To more ancient structures of T. pretektalny and back kernels belong.
The lateral cranked body relating to a thalamic complex consists of phylogenetic newer dorsal part of a kernel (a dorsal kernel) and older ventral part (a ventral kernel). The dorsal kernel is the classical relay education transferring a visual af-ferentation to bark (see. Visual analyzer). Bombways from a retina of eyes find also in a ventral part of a kernel of a lateral cranked body, and fibers from occipital area of bark are distributed both in ventral, and in dorsal parts of a kernel of a lateral cranked body.
The medial cranked body, especially its outside small-celled part, is the main relay formation of the acoustic analyzer (see) accepting information on fibers of a lateral loop and transferring her to structures of temporal area of new bark.
Blood supply of T. — cm. Cerebral circulation.
the Research of structure and function of thalamic educations by means of modern complex methods revealed extremely slozhnsh character of the relations of T. both with above the located departments of a neoncephalon, and with the structures of a brain trunk, a cerebellum and spinal cord which are below. The close integration of somatic, visceral, motivational influences which is carried out at the level of thalamic complexes defines the leading role of these formations of a diencephalon in formation not only the korkovopodkorkovy relations, but also in formation and development of complete behavioural acts of animals and the person.
Studying of functions T. carry out by his electric irritation or destruction in combination with the analysis of dynamics of various behavioural reactions, registration of EEG, evoked potentials or electric activity of single neurons in response to various peripheral irritations in experiments on animals and in to lay down. the purposes — at the person.
It is established that in relay kernels of T. impulses tactile, kinaesthetic, temperature, painful (the localized pain), flavoring and visceral sensitivity switch (see). Impulses from the opposite side of a body come to each kernel, only the area of the person has in a back ventral kernel of T. bilateral representation. The parts of a body performing the most intensive touch and motive functions (the person, language, distal departments of extremities) have more extensive representation. In medial department of a back ventral kernel, the somato-topical organization to-rogo is well studied, the afferenta-tion from rostral parts of a body and impulses from flavoring receptors, comes to lateral department — from receptors of a trunk and extremities. Projections of tactile and visceral sensitivity have in T. broad overlapping that can cause a phenomenon of irradiation of visceral pain (see) on a body surface. The general projections in T. have also tactile and deep (proprioceptive) sensitivity. The Tonkodifferentsirovanny afferent impulsation from thermo - and notsiretseptor passes preferential on a spinotalamichesky way to a back ventral kernel whereas more gross forms of these types of sensitivity (diffusion pain, a differentiation of big temperature ranges) are connected preferential with nonspecific intralaminarny kernels of T. (a parafascicular complex), and also, perhaps, with back kernels. Electrostimulation of a back ventral kernel at the person in the course of stereotaxic operations (see. With tereotaksichesky neurosurgery, the Stereotaxic method) causes paresthesias, disturbance of a body scheme is more rare (see the Body scheme).
Carry the front group of kernels giving an impulsation from mastoidal bodies to limbic area of bark and also two kernels of ventral group T to not touch relay educations. — front ventral and lateral ventral, transferring the ground mass of vozbuzhdeniye from a cerebellum and a pale sphere to motor departments of a cerebral cortex, as defines their role in regulation of an involuntary physical activity and muscle tone. The specified bonds of a lateral ventral kernel prove expediency of its destruction at patients with parkinsonism and with various hyperkinesias.
Group of associative kernels of T. has the main source of an affe-rentation relay and partly nonspecific structures of T. and hypothalamus. Recently it is shown that in these kernels a part of touch projections can come to an end (somatosensory, acoustical, visual, visceral). Interaction of various afferent impulses on neurons of associative kernels of T., their difficult intra those-lamichesky and interthalamic bonds explain an important role of this group of educations in integrative activity of a brain. Distinguish talamopariyetalny and talamofron-talny associative systems. The first has preferential relation to formation of complexes of the afferent influences necessary for assessment of the alarm importance of difficult types of irritants which is the cornerstone of Gnostic function, especially visual and acoustical perception, and also touch ensuring management of autokinesias. The medial dorsal kernel belongs to the talamofrontalny associative system participating first of all in affective and emotional and programming activity. Stimulation of a medial dorsal kernel of T. causes various positive and negative emotional reactions in patients; destruction of this kernel in to lay down. the purposes, and also in experiments on animals weakens sensation of fear, alarms and tensions, but at the same time there are unsharply expressed symptoms of a so-called frontal syndrome — decrease in an initiative and mental abilities against the background of permanent reduction of emotional reactivity. At distribution patol. process on medial departments of T. observe development of weak-mindedness (see).
Group of nonspecific kernels of T. receives an afferentation first of all from reticular formations of a brain trunk, however there are data on a possibility of the termination in hYix of the fibers going as a part of the specific ascending systems. Though kernels of this group are projected on bark more diffuzno, than the first two groups, a nek-eye of them svoystven more or less local nature of bonds with bark and a striate body (extrapyramidal system). Carry intra lamellar (intralaminarny) kernels (a parafascicular kernel, lateral central and paracentral kernels), a reticular kernel of a thalamus, a kernel of the centerline of T to this group. Opening of nespetsi-fitsesky kernels of T. it is connected with the works Dempsey and Morrison (E. W. Dempsey, R. S. Morison, 1943) which showed that at irritation of these kernels in a cerebral cortex there is a widespread reaction of involvement. Is later S. P. Narikashvili, E. S. Monia-va, V. I. Guselnikov and A. Ya. Supin (1968), etc. found out that in genesis of this reaction as well as reactions of strengthening, the leading role is played by interaction of nesiyetsifichesky kernels of T. with its specific educations.
Data on functional value of kernels of this group are contradictory: on the one hand, it is established that destruction of a complex a parafascicular kernel — the central median kernel (the median center) influences positive and negative training of rats; on the other hand, the effect of damage of this complex substantially depends on the previous emotional background; also important role of an afferentation of this complex in activity of neurons of a kernel having a tail is shown (see. Basal kernels ). Idea of not specificity of this group of kernels is relative. On the basis of data on their structure, bonds and function it is possible to speak about existence in T. the difficult complexes formed by relay and nonspecific kernels. Studying of functions of kernels of the centerline is complicated by their closest proximity to associative and relay kernels of T. Destruction of medial departments of T. can be followed by disturbances of conditioned reflexes (see), memories (see), dream (see).
In group of nonspecific kernels a specific place is held by a reticular kernel T. Posledney the T adjoins outside various relay kernels dorsal. and partially has the general with them a projection to bark. Assume that this kernel is an intermediary as in activity of other kernels of T., and in talamo-cortical interaction of its specific and nonspecific educations. In a crust, time the important role of T is obvious. in implementation of difficult functions of perception and processing of various signals coming further to a cerebral cortex and basal kernels in maintenance of level of wakefulness and an emotional state, in normal ensuring simple and more irregular shapes of behavior and memory. Full bilateral removal of T. finds in dogs and cats sharp deficit of adaptive reactions, disturbances of sensitivity and alternations of a cycle wakefulness — a dream. Operational isolation of bark and basal kernels from T. and a brain trunk (a so-called thalamic animal) leads to massive retrograde degeneration of neurons of T. also is followed by sharp and irreversible changes of adaptive behavior, up to impossibility of independent food.
Recently in connection with accumulation of data about an intersemicircle - ache asymmetries instructions on functional inadequacy right and left T appeared. at the person. So, use of verbalizuyemy material in tests for a short-term memory, probably, is carried out with participation preferential left in T., neverbalizuyemy material — with participation right T.; the most essential syndrome of left-side damage of a thalamus is not pithiness of the speech.
In the 70th a number of the new principles of talamokortikal-ny interaction concerning understanding of integration of nervous processes at the level of a neoncephalon was formulated: the principles of «nuclear» and «scattered» types of talamokorti-kalny projections, interlayerings of these various projections among themselves, their various distribution in projective and associative areas of new bark, mono - and oli-gosinaptichesky transfer of vozbuzhdeniye from T. in bark, and also topographical compliance (it is preferential for relay and associative structures) and discrepancy (hl. obr. for nonspecific structures of T.) talamokortikalny and box-Tiko-thalamic influences. In it-rofiziol. researches dynamic integration of specific and nespetsnfichesky influences at diencephalic and cortical levels is found, it is established that rhythmic activity of a cerebral cortex is caused by activity of thalamic kernels that formation of an a-rhythm in bark happens with participation of both thalamic, and cortical structures. It is revealed that neyrofiziol. a basis of rhythmic activity of a brain are mechanisms of returnable braking (see) p excitement (see), played at the thalamic and cortical levels. New ways of relationship of associative and projective talamokortikalny systems are allocated and studied and the provision on difficult functioning talamokortiko-thalamic associative systems is formulated. The problem of cortical regulation of activity of thalamic kernels received new lighting: it is shown that regulation of relay thalamic kernels is carried out by hl. obr. direct kortiko-talamiche-skimi in the ways, and nonspecific kernels — it is preferential with participation of a reticular formation of a brain trunk. It is established that reticular systems of a brain are capable to differentiate afferent signals and to send them to the relevant structures of a brain under the influence of corticofugal modulation.
Focal defeats of T. can develop at various patol. processes, however most often — at disturbances of cerebral circulation (ischemia, hemorrhage because of atherosclerosis and a hypertension). Disturbances of blood circulation in a zone of deep branches of a back brain artery are most frequent. At a stroke in this pool are generally damaged veins-trolateralnye of a kernel of T. or its dorsal medial kernel. V T. both ischemic heart attacks, and hemorrhages at ruptures of arteries, vasculites, hypertensive crises with the high ABP are possible, at arteriovenous aneurisms. Much less often thalamic complexes are damaged at infectious, tumoral, dystrophic and other diseases.
Inflammatory defeats of T. occasionally meet at tuberculosis, syphilis, sepsis, at encephalitis (virus, bacterial). Degenerative processes in structures of T. arise at genetic defects of a metabolism or at intoxications (exogenous, endogenous), and also in a residual stage of infectious or traumatic damage of a brain. Primary tumors of T. are rather rare, the T is more often. it is involved in patol. process with an infiltrative growth of a tumor of the next departments of a brain (at gliomas, astrocytomas, etc.).
Wedge, symptoms at defeat of T. are diverse and depend on a functional role of the damaged structures. The thalamic syndrome is for the first time in detail described by Zh. Dezhe-rin and G. of Russia in 1906 at a softening of T. owing to obstruction of a back brain artery and its branches. At switching off of a. thalamoge-niculata on the party opposite to the center of defeat in T., the following symptoms develop: 1) the ge-migipesteziya or a hemianaesthesia with the expressed disturbance of deep sensitivity is more on extremities, sometimes without disorder of sensitivity on a face; 2) a hyperpathia or dizesteziya (see Sensitivity, frustration), a paroxysm of l no the arising or constant cruel pains extending to all half of a body (a thalamic pain syndrome); 3) pallesthesia; 4) a passing hemiparesis without the expressed spasticity and patol. Babinski's reflex; 5) atrophy of muscles of an affected half of a body; 6) the choreic and atetoid-ny movements in fingers of a hand; 7) hemiataxia; 8) sometimes gomonimny hemianopsia; 9) notnagelevsky mimic paresis; 10) disorders of attention.
At partial defeat of T. separate groups of these symptoms can prevail. At destruction of medial part T. (the pool of a. tha-lamoperforata) the dentato-rubrotalamichesky way, on Krom in T is damaged. impulses from a cerebellum arrive, at the same time there is a hyperkinesia (atetoidny, choreic) and a hemiataxia on the party opposite to the center. At defeat of front departments of T. reveal contralateral mimic paresis of facial muscles. At diffusion defeat of T. the thalamic syndrome is quite often combined with the vegetative disturbances (cyanosis, an atrophy of skin and nails, pastosity, a cold snap of skin on the struck side of a body) which were more expressed in a hand. At the same time the hand acquires the characteristic provision: the forearm is bent and proni-rovano, the brush is bent in a radiocarpal joint, proximal phalanxes of fingers are bent while average and distal phalanxes are unbent (a so-called thalamic arm). Sometimes on the party of the center there is Bernard's syndrome — Horner (see Bernard — Horner a syndrome).
Diagnosis of a thalamic syndrome is based on identification of a complex of the symptoms making it. Wedge, diagnostic methods consist in definition of superficial and deep sensitivity, definition of fields of vision (see), forces of muscles of extremities, coordination of movements (see) etc. Diagnosis is helped by Ferster's symptom: the irritation of various receptors (visual, acoustical, flavoring) causes pain and an unpleasant feeling in an affected half of a body.
The differential diagnosis of a thalamic syndrome of Dezherin — Russia should carry out with Ged's syndrome — Holmes — a unilateral affective dizesteziya, for to-rogo the unilateral dizeste-ziya, the exaggerated external manifestations of affective reactions (grimacing), the sharp protective movements in response to insignificant physical irritation (e.g., an easy prick a pin), unilateral disorder of taste and sense of smell are characteristic. This symptom complex develops at disturbance of corticothalamic and cortical and hypothalamic bonds. Besides, the thalamic syndrome should be differentiated with a syndrome of defeat of the internal capsule, at Krom along with a hemianaesthesia (sometimes in combination with a hemianopsia) the spastic hemiplegia is observed. Defeat of T. it is possible to reveal at a cerebral angiography (see), a computer tomography (see the Tomography computer).
Treatment of a thalamic syndrome pathogenetic. Considerable difficulties arise at a thalamic hemialgia, at a cut usual analgetics are a little effective. Recommend to apply Seduxenum, aminazine, Finlepsinum, Tegretolum, etc. At hyperkinesias and unremovable pain syndromes apply stereotaxic operations on kernels of T. (see. Stereotaxic neurosurgery).
The forecast of a thalamic syndrome depends on character of the basic patol. process.
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D. K. Bogorodinsky, A. A. Skoromets; O. S. Adrianov (physical.), V. S. Kesarev (An., comparative anatomy).