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Biomedical subjects

V L Silakov

Publications and source records attributed to V L Silakov.

At least 55 records · Page 3Linked to original sources
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Long-term changes in the activity of superior colliculus neurons isolated from corticofugal influences.

In acute experiments on nonnarcotized, immobilized cats, spike activity was studied in superior collicular neurons which were isolated from direct, descending cortical influences. Animals were taken for experimentation at various periods (from 3 to 20 months) after the operation which disconnected the cortical connections which projected from one hemisphere. An increase was noted in the regular forms of activity, and there was a decrease in the frequency of group discharges. Evoked activity of the cells was suppressed during the early periods after disconnection of corticocollicular connections. Later (after 9--12 months) its gradual restoration was observed. More than 70% of the neurons again began to respond to adequate stimuli. The sensitivity to moving photic stimuli was restored in only 17% of the neurons studied.

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PubMedDate not supplied

Influence of nembutal on the impulse activity of cells of embryonal nervous tissue transplanted into the rat brain.

The average frequency of the impulse activity of neurons of an allograft of embryonal cortex, in the brain of adult Wistar rats, under nembutal anesthesia was four times lower than in nonanesthetized animals; at the same time the variability of the activity of the cells of the graft, with respect to the frequency and pattern of impulse activity, decreased. As compared with the unanesthetized animals, half as many cells of the graft reacted to tactile stimulation of the contralateral hind extremity; the neuronal reactions to the stimulation of somatic receptors of the ipsilateral side of the body completely disappeared.

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[Intra-analyzer temporary connections in the visual system].

The possibility of setting up intraanalyser temporary connections integrating the activity of various elements within the central part of the visual analyser at a neuronal level was studied in acute experiments on unanaesthetized immobilized cats. In the given model of temporary connection the unit activity in the lateral geniculate bodies (LGB) was investigated. Electrical stimulation of the superior colliculi was used as a conditioned stimulus, and illumination of the receptive fields of the studied LGB neurones, as an unconditioned one. In the process of conditioning, 10 to 11% of learning elements were revealed in LGB. The possibility is discussed of integration of learning elements into a definite microsystem achieving the process of temporary connection closing in the visual analyser in the course of conditioning.

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[The characteristics of the intragroup behavior of rhesus macaques and hamadryas baboons during the realization of food motivation in a competitive situation].

The aim of the present work is to consider the specific interrelations in "family" units of macaques (Macaca mulatta) and baboons (Papio hamadryas) during food-getting reactions in competitive conditions. Detailed analysis of dyadic interactions revealed that competing partners demonstrate more various types of behaviour tactics at the initial stage of learning. At the final one, only males of both investigated species performed instrumental reactions and received the food reward. All females demonstrated much more vocal reactions in comparison with males. Thus the variety of competing interactions between heterosexual partners, learning and possibility to realize its motivation correspond ro novelty of experimental situation and degree of intraspecies social subordination.

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PubMedDate not supplied

[The comparative action of relanium and oxytocin on higher nervous activity in lower monkeys].

Effects of relanium and oxytocin on higher nervous activity was studied in four rhesus monkeys (Macaca mulatta) and two baboons (Papio hamadryas). During observation of the animals in enclosure tranquilizing effect was seen only after relanium administration. Under the same conditions oxytocin practically did not change the general behaviour pattern of monkeys. However, steady behavioural transformations were observed under the conditions of competitive food-procuring behaviour and during the operant goal-directed reaction. Decreasing aggressiveness of dominants oxytocin in contrast to relanium had no negative effect upon their general motor activity and sensory perception. Differences in effects of the tranquilizer and the peptide were seen also at the unit activity level of the neurons. The first drug lowered the unit activity level and the degree of the functional connections in neuronal populations in a number of cortical structures. Administration of the second one led to selective shifts of the unit activity mainly in the frontal cortex of the monkeys.

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[A comparative physiological study of the generalization function in primates].

Fundamental rules of the generalization function formation and development were formulated on the basis of comparative analysis of visual discrimination, summarizing and abstraction in the representatives of various primate subfamilies. It was established that monkeys and apes (Macaca mulatta, Cebus apella, Pan troglodytes) learning to define such abstract characteristic as relative size of visual pictures of natural and geometrical objects were able to use previously remembered rules elaborated under the solving of other visual tasks. Learning processes were realized more affectively, if the pictures of natural objects were represented to the monkeys. The comparison of generalization processes in monkeys and apes revealed multilevel organisation of the processes in apes. The latter showed high level of ability to operate with abstract ideas elaborated previously in the course of the experiments.

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PubMedDate not supplied

[The effect of nembutal on the cellular pulse trains of embryonic nerve tissue transplanted into the brain of the rat].

Under nembutal anaesthesia the mean frequency of single unit discharges recorded from allografts of the rat brain was four times lower than the one measured in unanaesthetized animals. A diminished variability was revealed of firing rates and discharge patterns of the cells within grafts in anaesthetized rat brain. In comparison to unanaesthetized animals the number of graft units reacting to a tactile stimulation of contralateral hindlimb of the operated animals was twice lower. Nembutal anaesthesia provoked a full blockade of reactions to the tactile stimuli applied to the ipsilateral side of the animal body.

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