Subcortical parts of the brain (subcortex)

The subcortical areas of the brain include the visual hillock, the basal nuclei at the base of the brain (caudate nucleus, lenticular nucleus consisting of a shell, lateral and medial pallid spheres); white matter of the brain (semi-oval center) and inner capsule, as well as the hypothalamus. Pathological processes (hemorrhage, ischemia, tumors, etc.) often develop simultaneously in several listed formations, but it is also possible to involve only one of them (complete or partial).

The thalamus (visual hillock). An important subcortical afferent system; the conductive paths of all kinds of sensitivity are interrupted in it. The cortical parts of all analyzers also have feedbacks to the thalamus. Afferent and efferent systems provide interaction with the cortex of the cerebral hemispheres. The thalamus consists of numerous nuclei (there are about 150 of them), which are grouped in groups of different structures and functions (anterior, medial, ventral and posterior groups of nuclei).

Thus, in the thalamus, three main functional groups of nuclei can be distinguished.

1. A complex of specific, or relay thalamic nuclei, through which afferent impulses of a certain modality are carried out. These nuclei include an anterior-dorsal and antero-ventral nucleus, a group of ventral nuclei, a lateral and medial geniculate body, and a bridle.
2. Nonspecific thalamic nuclei are not associated with the conduct of afferent impulses of any particular modality. The neuronal connections of nuclei are projected in the cerebral cortex more diffusely than the bonds of specific nuclei. Nonspecific nuclei include: nuclei of the middle line and adjacent structures (medial, submedial and medial central nucleus); the medial part of the ventral nucleus, the medial part of the anterior nucleus, the inner-plate nuclei (paracentral, lateral central, parafascicular and central median nucleus); nuclei lying in the paralaminar part (dorsal medial nucleus, anterior ventral nucleus), as well as the mesh complex of the thalamus,
3. The associative nuclei of the thalamus are those nuclei that receive stimulation from other thalamus nuclei and transmit these effects to the associative regions of the cerebral cortex. These dolamus formations include the dorsal medial nucleus, the lateral group of nuclei, the thalamus pillow.

The thalamus has numerous connections to other parts of the brain. Cortico-thalamic connections form the so-called thalamus legs. The anterior thalamus leg is formed by fibers connecting the thalamus with the bark of the frontal region. Through the upper or middle leg to the thalamus, there are paths from the frontal-parietal region. The back leg of the thalamus is formed from fibers coming from the cushion and the external geniculate body to the field 17, as well as the temporal-thalamic bundle connecting the pillow to the bark of the temporal-occipital region. The lower-inner leg consists of fibers connecting the cortex of the temporal region to the thalamus. The podbugornoe nucleus (lyisovuyu body) refers to the subtal region of the intermediate brain. It consists of the same type of multipolar cells. The trout and the indeterminate zone (zona incetta) also belong to the subthalamic region. The trout field H ¹ is located under the thalamus and includes fibers connecting the hypothalamus with the striatum body - fasciculis thalami. Under the field H ^{1 of the} Trout there is an indeterminate zone, which passes into the periventricular zone of the ventricle. Under an undefined zone is the field H ² Trout, or fasciculus lenticularis, connecting the pale sphere with the pancreatic nucleus and periventricular nuclei of the hypothalamus.

The hypothalamus (a podbugorju) includes a leash with a soldering, an epithalamic adhesion and an epiphysis. In trigonum habenulae there is gangl, habenulae, in which two nuclei are distinguished: internal, consisting of small cells, and external, in which large cells predominate.

The defeat of the visual hillock causes, above all, violations of cutaneous and deep sensitivity. There is a hemianesia (or hypesthesia) of all kinds of sensitivity: pain, thermal, joint-muscle and tactile, more in the distal parts of the limbs. Hemigipesthesias are often combined with hyperpathy. Defeats of the thalamus (especially its medial parts) can be accompanied by intense pain - hemialgia (painful sensations of the pack, burning sensation) and various vegetative-skin disorders.

A gross violation of the joint-muscular sense, as well as a disorder of the cerebellar-thalamic connections cause the appearance of ataxia, which usually has a mixed character (sensitive and cerebellar).

The consequence of the defeat of the subcortical areas of the visual analyzer (lateral geniculate bodies, the cushion of the thalamus) explains the appearance of hemianopsia - the fall of the opposite halves of the fields of vision.

In the defeat of the thalamus, disruption of its connections to the striopallidal system and extrapyramidal cortical fields (mainly the frontal lobes) can cause the appearance of motor disorders, in particular of complex hyperkinesis - the choreic athetosis. A peculiar extrapyramidal disorder is the position in which the hand is located; it is bent in the radiocarpal joint, brought to the ulnar side, and the fingers are unbent and pressed against each other (thalamic arm, or "obstetrician's hand"). The functions of the thalamus are closely related to the emotional sphere, so when it is defeated, violent laughter, crying and other emotional disorders may occur. Often, with half of the lesions, you can observe the paresis of the facial muscles on the opposite side to the side, which is revealed when moving on the task (mimic paresis of the facial musculature). The most constant thalamic hemisyndromes include hemianesthesia with hyperpathy, hemianopsia, hemiataxia.

Tapion syndrome Dejerine-Russi: hemianesthesia, sensitive hemi-ataxia, homonymous hemianopsia, hemialgia, "thalamic arm", vegetative-trophic disturbances on the opposite side, violent laughter and crying.

[1], [2], [3], [4]