Correlation of overt escape behavior, multiunit thalamic activity, and midbrain lemniscal stimulation in rats.

An acute and a chronic experiment were conducted in order to assess the extent to which ventral thalamic multiunit activity could account for the specific form of bar-pressing escape behavior in rats stimulated by trains of midbrain medial lemniscal pulse pairs. A paradigm used by Kestenbaum, Deutsch, and Coons was utilized in which the intra-pair interval of the train was varied. Results in anesthetized and freely moving animals indicated that midbrain lemniscal stimulation produces both an excitatory short-latency thalamic response showing the property of temporal facilitation and a long-lasting inhibitory process consistent with results of studies using anesthetized cats. The overall electrophysiological response, however, correlated significantly with the behavioral response function.