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F V Kopytova

Publications and source records attributed to F V Kopytova.

42 records · Page 3Linked to original sources
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[Interrelation between signal and reinforcing stimuli at the cellular level during extinction of motor conditioned reflexes].

Comparative analysis of extinction of neuronal activation conditioned reactions in the motor cortex, the ventromedial and perifornical hypothalamic nuclei attest that the connection between the signal and reinforcing components of pairings in these structures of alert rabbits is more stable in defensive conditioned reflexes than in conditioned reflexes to time. A more stable connection between two components is established during conditioning in neurones of the motor cortex and the perifornical nucleus, and a less stable one at the level of the hypothalamic ventromedial nucleus and the medial geniculate body. In conditioned reflex to time a more stable connection has been detected in neurones of the motor cortex, the medial geniculate body and the perifornical nucleus, a less stable connection in the neurones of the hypothalamic ventromedial nucleus.

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[Activity of hypothalamic neurons during elaboration of a defensive conditioned reflex].

During elaboration of conditioned defensive reflex to combinations of acoustic and electro-cutaneous stimuli in alert rabbits 44% out of 86 neurones in the ventromedial nucleus and 42% out of 40 cells in the perifornical nucleus of the hypothalamus elaborated conditioned responses. 71% of ventromedial neurones and 53% of perifornical cells (out of those that were conditioned) showed inhibitory responses while the rest demonstrated an activation. In half of the neurones that showed conditioned responses it was possible to elaborate differentiation and extinctive inhibition. Significant conditioned responses appeared following 20-30 pairings of sound and electro-cutaneous stimulation. Their extinction took place after 10-20 non-reinforcements. A correlation was found between conditioned activity of neurones in the ventromedial nucleus groups and changes in heart-rate. Different roles of lateral and medial nuclear groups of the hypothalamus in conditioning were shown. This may point to their participation, along with other brain structures, in the formation of respectively vegetative and motor components of the integrative behaviour.

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[Conditioned responses of striopallidal system neurons to time].

The study was concerned with conditioned responses to time, elaborated in alert rabbits through pairing of sound stimuli with electro-cutaneous reinforcement, applied each 30 s. Conditioned responses to time were observed in 60% of neurones of the caudate nucleus, in 55% of neurones of the putamen and 59% of cells of the pale globe. Trace conditioned responses occured first in neurones of the putamen and of the pale globe and then of the caudate nucleus. No significant correlation between initial unit reactivity to the stimuli of paired modalities and their ability for elaboration of temporary connections was revealed. Conditioned responses to time were also found in 42-61% of the initially areactive units. Individual characteristics of formation and reproduction of trace activity in each of the studied brain structures are due to its structural-functional organization.

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PubMedDate not supplied

[The functional and morphochemical characteristics of the hippocampal neurons during the formation of trace processes in old rabbits].

Trace rhythmic activity of dorsal hippocampal neurons were studied after the long-lasting (10-20 min) rhythmic (0.5-2 Hz) electrocutaneous stimulation of the forelimb in alert young (5-7 months), middle-aged (54-65 months), and very old (66-84 months) rabbits. During aging the number of spontaneously active neurons was shown to be significantly decreased, the proportion of slowly firing neurons to be increased, the interspike intervals and intervals between spike groups to lengthen, and the number of spikes per a group to be reduced. Spectral analysis of neuronal firing rate revealed that ability to reproduce the rhythm of the previous stimulation declined with age. No appropriate rhythms were found in hippocampal neurons of the old animals. Morphological and cytochemical analysis of the hippocampal neurons revealed changes in nuclear-cytoplasmic relations and also a fall of protein synthesis in the neurons of the old animals. The observed deteriorations may explain the impairment of trace rhythmic activity in hippocampal cells with age.

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[Conditioned reactions of the neurons of the dorsal region of the hippocampus to a combination of sound and extracellular polarization].

Neuronal responses were recorded in the dorsal part of the rabbit hippocampus to a, aperiodical (45 units) and b, periodical (25 units) presentations of combinations of a sound and a DC pulse (anode, 0,1-2,0 na) acting through the recording microelectrode. In the group (a) identified conditioned responses to a former indifferent acoustic stimulus were elaborated in 22% of the neurones. More than a half of them produced differentiation and extinction. Differences were revealed between conditioned reactions and responses in pseudoconditioning tests. In the group (b) 30% of units elaborated a conditioned reaction to time. Activation type reactions were predominant. They appeared when the stimuli were omitted, and sometimes they emerged in 12 or more successive omissions.

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