[Conditioned trace reactions of hypothalamic neurons following exposure to vibration]

Trace reactions were studied in 112 hypothalamic units in rabbits during motor defensive conditioning to time after vibration action of two intensities. A later formation of conditioned trace reactions was observed as compared to the control. Vibration of lesser intensity improved the course of trace processes and slightly increased the number of neurones responding to the conditioned stimulus (45% as against 43% in the control); after a stronger vibration action, conditioned reactions to time were recorded only in 29% of the hypothalamic cells eith a simultaneous diminution of the trace response. It has been assumed that the observed transformations result from changes of the significance of the reinforcing factor in the formation of a motor defensive conditioned reflex after the action of vibration.