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I S Stashkevich

Publications and source records attributed to I S Stashkevich.

At least 19 recordsLinked to original sources
PubMed1981

Correlation analysis of neuronal interaction in the motor cortex of rats during performance of a discrete instrumental reaction.

Unit activity was recorded in 7 rats trained to reach into a narrow feeder for food. Capillary microelectrodes were inserted with a head-mounted microdrive into the motor cortex contralateral to the preferred forepaw. Recordings of pairs of identifiable units were processed with the LINC 8 computer programmed for detection and classification of spikes, compilation of perireach histograms (+/- 512 ms) and construction of auto- (64 ms) and crosscorrelation (+/- 32 ms) histograms. Perireach histograms revealed activity changes (mostly of the excitatory type) in 82% of examined neurons (n = 28). Significant crosscorrelation was found in 8 of 14 pairs of neurons recorded for about 1 h. Most crosscorrelograms showed symmetric inhibitory troughs, lasting for 6 to 15 ms and better expressed in the +/- 512 ms perireach interval than during periods of spontaneous activity. Whereas symmetric crosscorrelograms (n = 6) indicate a shared inhibitory input, asymmetric crosscorrelograms (n = 2) suggest more direct interaction between the recorded neurons. Significant crosscorrelations were found more frequently when both neurons of the pair displayed significant perireach reactions. It is concluded that reaching is accompanied not only by characteristic excitatory and inhibitory reactions of individual neurons but also by modified neural coordination probably due to shared cerebellar and basal ganglia inputs.

Action Potentials↗
PubMedDate not supplied

The formation of lateralized motor habits in rats.

Wistar rats were trained to obtain food from a narrow tube feeder using the forepaw in conditions of free choice of which limb to use. It was found that the presence or absence of limb preference, identified in short preliminary tests, often did not coincide with the nature and degree of lateralization formed during the process of prolonged training. Achievement of the maximum degree of lateralization by the animals finally forming the right-handed group was found to require longer average training periods than was the case for left-handed rats.

Algorithms↗
PubMedDate not supplied

[Formation of lateralized motor skills in rats].

Adult Wistar rats were trained to get food with a forepaw from a narrow tube under conditions of free choice of a limb. It was shown that the presence or absence of limb preference determined by preliminary short-run testing far from always defines the character and extent of lateralization formed in the process of training. It was also found that reaching the maximal extent of lateralization requires, on average, more extended period of training for the animals, which finally constituted the group of right-handers, than for the rats finally classified as left-handers.

Animals↗
PubMedDate not supplied

[Various resistance of motor preference in rats exposed to forced retraining].

Adult Wistar rats were trained to get food from a narrow tube under conditions of free choice of a limb. After reaching a stable level of using the preferred limb, rats (n = 35) were forced to relearn the acquired skill for reaching food with a unpreferred paw. When afterwards the rats returned to the initial conditions of free choice of a limb, 12 animals (34%) did not recover their initial preference, 8 rats (23%) were ambidextrous, and 15 animals (43%) returned to the originally preferred paw. The results demonstrated different resistance of the initial limb preference to forced retraining in different animals. It is suggested that the process of retraining per se is not the only and sufficient condition of the change in "handedness". It also suggested that the different resistance of initial preference to forced retraining reflects individual differences in a degree (intensity) of this preference, which are predetermined by internal, probably by genetic factors.

Animals↗
PubMedDate not supplied

[Nature of functional motor asymmetry in animals: state of the problem].

Handedness in skilled movements of animals is a result of interaction of innate motor preference and learning. The nature of the innate preference is not clear. Breeding of right-handed and left-handed mice revealed that the degree rather than direction of motor preference is an inherited feature. There is, however, a correlation between the direction of preference and a number of morphological, functional, and neurochemical characters. Shifts of a preference direction were found in some strains of mice. Differences between right-handed and left-handed rats were revealed in social behavior, learning, and resistance to forced retraining. Strains of rats with different forms of genetic epilepsy were characterized by the predominance of animals with a certain direction of the motor preference. This evidence suggests some genetic influence on a direction of the motor preference. Perhaps, genetic and environmental factors closely interact in determining motor preference in animals.

Animals↗
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[Reaching behavior of rats during realization of a lateralized motor food skill].

Adult Wistar rats were trained to obtain food pellets from a narrow horizontal tube with a preferred forepaw. The feeder was equipped with five photoelectric sensors with 5-mm spacing. The following parameters were recorded: total number of movements performed for a given task, amplitude (depth) of each movement, number of anticipatory movements performed with different amplitudes, and amplitude of a successful movement. It was shown that in rats with good skill acquisition, a successful food extraction was preceded by a series of differently organized sequence of preliminary movements. In some rats, such a series consisted of initial non-deep attempts followed by movements with high amplitude, whereas in other animals, it was represented, mainly, by deep attempts. Both groups of animals terminated the series by grasping and extracting food from a long distance. It is suggested that the observed organizations of the lateralized food-getting behavior of rats under the given experimental conditions represent fixed (stereotyped) action patterns.

Animals↗
PubMedDate not supplied

[The single administration of ethanol and the amplitude of the action potentials of the neocortical neurons in rats: extracellular studies].

On outbred rats the influence was studied of acute administration of moderate dozes of ethanol (150 mg--1.2 g/kg, intraperitoneally) on the motor cortex neurones. It was shown that ethanol in the range of these dozes led to a change of the amplitude of extracellularly recorded action potentials, which could be directed to an increase or decrease. In the used range minimum as well as maximum dozes in various animals might elicit contrary effects, i.e. no dependence was observed of the direction of reaction of the studied neurones on the administrated doze. Possible mechanisms are discussed which may be the basis of the change of the amplitude of extracellular action potentials. Conclusion is made that use of moderate dozes of ethanol is a useful condition for studies directed to a search of mechanisms of initial reaction to alcohol action.

Action Potentials↗
PubMedDate not supplied

[The reorganization of bimanual movements during formation of a lateralized motor food skill in rats].

After 48 h food deprivation adult Wistar rats were trained to obtain food from a narrow tube feeder using the forepaw under conditions of free choice of limb. At the initial stage of training animals use both paws: the grasping and extraction with one paw can be alternated with food grasping and extraction with another paw, and both paws can be alternately involved in movements preceding this grasping. Character of reorganization of bimanual movements was analyzed during training rats with different motor preference (right-handed and left-handed animals). It was shown that in the process of acquisition of both right- and left-hand skills, bimanual reactions in the anticipating attempts disappeared later than in the final successful movements. The disappearance of bimanual movements in the anticipating attempts is considered as an index of the maximum skill lateralization and acquisition of a novel lateralized movement coordination. The results suggest that left-handed rats more rapidly learn a novel movement coordination than right-handed animals.

Animals↗
PubMedDate not supplied

[Character of functional connections between sensomotor cortex neurons during isolated and combined stimulation of thalamic nuclei].

In experiments on curarized cats pronounced transformations of the "excitatory" component of the "inhibitory-excitatory" dependence of two close neurones in the sensorimotor cortex were found following multiple isolated VPL and VL stimulation. The effects of repetitive stimulation of thalamic nuclei were opposite to each other: VPL stimulation mainly weakened the "excitatory" component of the "inhibitory-excitatory" connection, whereas VL stimulation generally enhanced it. In the course of combined stimulations of both nuclei the character of interneuronal relations, established under the influence of isolated stimuli, showed further changes. Modifications of interneuronal dependence, resulting from thalamic stimulation, could last for several minutes after cessation of all stimulations.

Animals↗
PubMedDate not supplied

[Change in the impulse reactions of sensomotor cortex neurons to combined stimulation of thalamic relay nuclei].

In acute experiments on unanaesthetized cats immobilized with d-tubocurarine, a study was made of the impulse responses of the sensorimotor cortex neurones to stimulation of the thalamic relay nuclei (VPL and VL). Distinct changes of the responses were found as a result of multiple paired stimulations of these thalamic structures. The nature of the changes proved to be different for the responses to the first (VPL) and second (VL) thalamic stimulation: the paired stimulations facilitated the responses to VPL stimulation and suppressed those to the VL stimulation.

Animals↗
PubMedDate not supplied

[Spike responses of sensomotor cortex neurons to isolated and combined stimulation of thalamic nuclei].

Simultaneous records of spike activity of several neighbouring neurones in the cat sensorimotor cortex have shown that isolated single stimulations of the thalamic ventroposterolateral nucleus (VPL) produce in different units of one and the same cortical microarea impulse responses visibly differing by their latencies and general pattern of discharges. These initially different reactions underwent pronounced changes under the action of combined stimulation of the VPL and the ventrolateral thalamic nucleus (VL). Ordinarily such changes were oppositely directed: enhancement of reactions of certain neurones was developing parallel with diminished activity of others of the same cortical microarea.

Animals↗
PubMedDate not supplied

[The effect of moderate doses of ethanol on the evoked neuronal activity of the sensorimotor cortex].

Influence of acute administration of ethanol in moderate doses (170-1200 mg/kg, intraperitoneally) on the evoked activity of sensorimotor cortical neurons in response to electrical stimulation of the contralateral forelimb was studied in outbred rats never earlier exposed to ethanol action. During the first 20-25 min of ethanol action whether augmentation or attenuation in the level of neuronal reactivity could occur as well which in both cases could be accompanied by significant variability of latencies in poststimulus discharges and destabilization of their patterns. Expressed modifications in neuronal patterns at the first stage of ethanol action suggest that ethanol destabilizes evoked reactions of sensorimotor cortical neurons to afferent stimulation. This underlines the need for more complete approach to investigation of primary CNS reactions to ethanol paying more attention to temporal succession of origin and flow of these effects. Possible relations between oppositely directed primary reactions of single cortical neurons and individual characteristics of perception of different animals are discussed.

Animals↗
PubMedDate not supplied

[The effect of moderate doses of ethanol on the nature of the background neuronal impulse activity of the sensorimotor cortex in rats].

The influence of acute administration of moderate doses of ethanol (170-1200 mcg/kg, intraperitoneally) on the spontaneous impulse activity of motor cortex neurons was studied in outbred rats never earlier exposed to alcohol. Initial reactions of the cortical neurons were shown to be characterized by the changes in the frequency of spontaneous activity which could be increased or decreased during the first 20-25 min after the injection. The changes in the mean frequency of spontaneous discharges were accompanied by the changes in their patterns. Both increase and decrease of the mean frequency at the initial stage of ethanol action was accompanied by significant variability of interspike intervals. It is emphasized that examination of the initial reactions of the cortical neurons to ethanol administration demands studying their temporal duration.

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