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Biomedical subjects

V L Silakov

Publications and source records attributed to V L Silakov.

At least 37 records · Page 2Linked to original sources
PubMed1982

Free postsynaptic sites in the lateral geniculate nucleus of adult cats following chronic decortication.

Following chronic decortication, free postsynaptic sites were found in the lateral geniculate nucleus of adult cat. Quantitative electron-microscopic analysis of the free postsynaptic sites revealed that they were not identical with the original, vacant postsynaptic sites, but were newly assembled formations. The ability of both relay cells and local interneurons of the adult lateral geniculate nucleus to assemble and/or maintain postsynaptic sites indicates that these nerve cells may be involved in the formation of new synapses.

Afferent Pathways↗
PubMed1981

Myelinated perikarya and dendrites in lateral geniculate nucleus of adult cat following chronic cortical deafferentation.

Chronic (one year) cortical deafferentation resulted in the appearance of myelinated neuronal perikarya and dendritic processes in the lateral geniculate nucleus (LGN) of the cat. Four per cent of all nerve cell bodies, both large and small, were observed to be covered partially or totally by compact myelin sheath. The myelination of the dendrites was confined to the most proximal portion of the processes. A comparison of the fine structural features of the myelinated cell bodies and dendrites with those from intact LGN indicate that both surviving projection neurons and local interneurons may become myelinated. It is suggested that the unorthodox myelination of nerve cell somata and dendrites is caused primarily by the massive deafferentation of the nucleus. This indicates a relationship between synaptic input and the process of myelination of the postsynaptic nerve cells.

Animals↗
PubMed1979

[Convergence of corticofugal impulse projections onto superior colliculus neurons].

In unanesthetized immobilized cats, 82.75% of tectal neurons responded to direct electrical stimulation of different cortical areas. Stimulation of the associative and visual cortex was the most effective. On simultaneous presentation of light and electrical stimuli, facilitation of responses of the collicular neurons was prevalent. The role of striatal and extrastriatal effects of neocortex as well as the regularities of integration of retinotectal and corticofugal afferents upon the neurons of anterior colliculus, are discussed.

Animals↗
PubMed1978

[Spike activity of superior colliculus neurons following blockade of corticofugal regulation].

Changes in background and evoked activity of the superior cooliculus neurons were studied in cats before and after cessation of ipsilateral corticofugal connections. On the operated side of the brain the superior cooliculus neurons slackened their impulsation and most of them were unresponsible to light stimulation (only 7.1% neurons responded to light after operation). It is suggested that afferent inputs to superior colliculus neurons are modulated by corticofugal mechanisms.

Animals↗
PubMed1978

The interactions of central neurons in conditioning and the influence of some limbic structures upon them.

The interactions between the neurons in the cortex and the subcortical visual structures were studied with multimicroelectrode technique. Neurons revealing conditioned reactions were found at various levels of the brain. It is assumed that they are involved, by the conditioning, in a special cellular network: the microsystem, which is considered to be the definite functional level of brain processing mechanisms. The influence of some limbic structures on the formation of the microsystems of conditioning neurons was found. It was concluded that the elaboration or extinction of the temporary connection is performed through formation or destruction of a microsystem which takes part in the conditioning.

Animals↗
PubMed1977

[Characteristics of residual neurons during retrograde degeneration in the lateral geniculate bodies of cats].

The daynamics of functional-structural characteristics of residual neurons was studied in the degenerated lateral geniculate body (LGB) in various periods of time (4-12 months) after neuronal isolation of the neocortex under which all geniculo-cortical connections were cut. Background and evoked spike activity in the degenerated geniculate body were studied as well as the number of persisting cells and their diameters. Neuronal receptive fields were found to undergo destruction along with the prolongation of postoperative period. A gradual diminution in the quantity of light sensitive cells was revealed. Background spike activity was predominantly of a simple type. Progressing decrease in cell number and cell diameters was observed under the morphological examination. Special features inherent in geniculate interneuronal relations are discussed.

Animals↗
PubMed1977

[Long term transformation of neuronal activity in the superior colliculus isolated from corticofugal influences].

Neuronal activity of the superior colliculus isolated from the corticofugal influences was studied in various periods of time (from 3 to 20 months) after unilateral dissection of cortico-subcortical projections. In 16 unanesthetized immobilized cats, after the surgery, spontaneous activity of collicular neurons became more regular and with less complex bursts during the postoperative period. Evoked activity was completely suppressed during early hours of the postoperative period. Only 31.5% of collicular cells were sensitive to light 3 months after the operation. Evoked responses to light of 90.4% cells reappeared in the isolated colliculus not earlier than 10-12 months after the isolation, while directional and movement sensitivity practically did not restore even within 20 months after the surgery. Corticocollicular influences are considered to be a necessary condition for effective visual information processing in the colliculi superiores.

Animals↗
PubMed1976

[Transformation of neuronal activity in the cat lateral geniculate body].

The neuronal activity transformations were studied in the cat LGB under the action of nembutal, light stimulation, and micropolarization of geniculate cells. The transformation of single spike activity into bursts was found to reflect the inhibitory state of the neurons. Their excitation entailed a reverse transformation. Short feed-back connections functioning within the microsystems of LGB neurons are supposed to underlie the transformations.

Animals↗
PubMed1975

[The role of polymodal synaptic influences in the formation of temporary connections in the microsystems of association cortex neurons].

Significance of various sensory convergence of the neuronal activity was investigated in unanaesthetized cats in the process of elaboration of time connections. The elaboration of time connection was realized after studying neuronal responses elicited by the direct electrical or sensory stimulation (light, sound, tactile and proprioceptive stimulation). 42 per cent of all neurons and about 90 per cent of learned cells were found to be polysensory in the investigated cortex. The data obtained are considered from the standpoint position of the hypothesis on the microsystem principle of organization underlying time connection and convergence.

Animals↗
PubMed1975

[Changes in the receptive fields of cat lateral geniculate body neurons following removal of corticofugal influence].

The number of spikes in responses of the lateral geniculate neurons increased after section of ipsilateral corticogeniculate connections. The operation caused a distinct intensification of lateral inhibition effects in the operated side. Zones of complete spatial summation in the receptive fields of neurons in the operated side changed according to the contrast of the used light stimuli. It is suggested that corticogeniculate influences are of inhibitory nature and that receptive fields possessing a changing zone of spatial summation are realized by intrageniculate mechanisms.

Animals↗
PubMed1975

Acquired and inherent trace processes in the neuronally isolated cortex.

Trace processes in the neuronally isolated cerebral cortex of one hemisphere were analysed. EEG and unit activity of the isolated cortex at different times after the operation were investigated. Temporal connections in the isolated cortex were elaborated. Neurons fixing the stimuli traces were revealed. These neurons (23 percent of reactive neurons) form a microsystem of learning neurons.

Animals↗