[Neuronal populations: sources of the corticothalamic projections to the partially deafferented ventrolateral thalamic nucleus].

The features of distribution and morphological structure of the motor cortex neuronal populations projecting to the cerebellar-recipient ventrolateral nucleus of the thalamus after its partial deafferentation were studied in adult cats. The partial deafferentation of the ventrolateral nucleus was evoked by preliminary (three months) electrolytic destruction of the contralateral interpositus nucleus of the cerebellum. The method of retrograde axonal transport with local introductions of the marker was used. All labeled neurons were presented by populations of non-pyramidal neurons and small and medium-sized pyramids, which were distributed in the deep cortical layers: in a lower layer division of V and mostly in layer VI. The labeled neurons were observed in cortical fields 4γ and field 6αß. The data obtained showed no structural reorganization of cortical projections to the deafferented ventrolateral nucleus of the thalamus. It is assumed that this is due to the high degree of specialization of the studied system, triggering the motor program. Neuroplastic changes manifested in the abnormal transformation of proximal portions of dendrites and presence of a large number of "paired" pyramidal neurons compared to intact animals.

[Primary motor and primary sensory cortex are two local cortical centers of sensorimotor body representation].

The ipsilateral cortical associative connections of different areas of primary somatic sensory (S1) and motor (M1) cortex were studied in 25 cats after local coagulation and infusion of horseradish peroxidase. It was shown, that the distribution of the associative fiber in M1 and S1 areas corresponded to the borders of somatotopic representation of different body parts. The fields within M1 (4y, 6ab) and S1 (1,2, 3a, 3b) with different morpho-functional organization were not connected by the system of association fibers crossing the cytoarchitectonic borders of the above mentioned areas. Primary somatosensory (S1) and motor (M1) cortex had no reciprocal connections. Single fibers connected neighboring areas of M1 and S1.

[Can the thalamic projections of medulla oblongata nucleus Z be reorganized following partial deafferentation of the ventral lateral thalamic nucleus?].

Following partial deafferentation of ventral lateral thalamic nucleus by means of HRP retrograde labeling, possible plastic reorganization of projections of the brain stem relay Z nucleus was studied in cats. The partial deafferentation of ventral lateral thalamic nucleus was evoked by preliminary (3 months before) destroying of contralateral cerebellar nucleus interpositus or Deiters' lateral vestibular nucleus. The local intensive labeling of neurons in the Z nucleus and a little group of neurons in the cellular group x of the vestibular complex projecting to ventral lateral thalamic nucleus and overlapping with those projecting from cerebellum was observed. It was shown that, following destruction of the cerebellar nucleus interpositus or Deiters' nucleus, the ipsilateral projections in the nucleus monosynaptic link are not forming. The absence of Z nucleus-ventral lateral thalamic nucleus projections reorganization similar to the formation ofipsilateral projections possibly depends on its belonging to the somatosensory relay nucleus which provides switching and transmission of specific proprioceptuve modality.

[Reorganization of the vestibular-thalamic projections following injury of the cerebellar interpositus and deiters vestibuar nuclei].

Plastic reorganization of the vestibular-thalamic system was studied in adult cats. It was shown, that preliminary (3 months before) injury of the cerebellar contralateral nucleus interpositus or lateral vestibular nucleus of Deiters leads to reorganization of vestibular-thalamic projections. Ipsilateral projections to the ventrolateral nucleus of thalamus arised from vestibular nuclear complex since the pattern of normal representations to mentioned thalamic nucleus were changed. The peculiarities of distribution and morphological structure of vestibular neurons forming new projections to the ventrolateral thalamic nucleus were studied as well.

[Plastic reorganisation in the cerebellothalamic system after partial deafferentation of the thalamic ventrolateral nucleus]. / Plasticheskaia reorganizatsiia v mozzhechkovo-talamicheskoi sisteme posle chastichnoi deafferentatsii ventrolateral'nogo iadra talamusa.

Using the method of retrograde axonal transport of horseradish peroxidase the formation of new ipsilateral thalamic projections from all three cerebellar nuclei and from the nuclei of vestibular complex was demonstrated 3 months after the lesion of contralateral intermediate cerebellar nucleus or lateral vestibular nucleus of Deiters of adult cats.

[Sources of thalamocortical afferentation of the area of forelimb representation in the first somatosensory zone of the cerebral cortex in the cat]. / Istochniki talamo-korkovoi afferentatsii oblasti predstavitel'stva perednei lapy v pervoi somatosensornoi zone kory mozga koshki.

Retrogradely labelled thalamic neurons--the sources of afferentation in the focus of maximal activity evoked by stimulation of n. radialis--were studied in adult cats by means of microiontophoretic injections of horseradish peroxidase into the first somatosensory zone of the cerebral cortex. The labelled cells were predominantly found in the thalamic nucleus ventralis posterolateralis; some cells (a minor part) were also found in the nucleus ventralis posteromedialis. The labelled neurons in these nuclei were distributed in groups whose composition according to many morphological characteristics was heterogeneous.