[Role of intralaminar thalamic nuclei in strengthening inhibition induced by stimulation of the caudate nucleus]

Abstract

The influence of preliminary subthreshold activation of thalamic intralaminary nuclei on achievement of instrumental reflex and on inhibitory effects, caused by stimulation of the caudate nucleus head, were studied in chronic experiments on 5 dogs with a model of instrumental defensive conditioned reflexes, providing for maintainance of a given posture. It was shown that the preceding high-frequency electrostimulation of intralaminary nuclei activates motor components of the instrumental response (shortened latency, EMG and mechanogram of the response, increased amplitude of instrumental response) and significantly lowers threshold strength of the current, necessary for obtaining "caudate pause". The greatest increase in inhibitory influences, caused by stimulation of the caudate nucleus head, was observed when thalamic stimulation preceded stimulations, localized in the dorsolateral segment of the caudate nucleus head. The obtained data are discussed in aspect of Buchwald et al. hypothesis on the existence of "caudate loop".