Slow potential changes evoked in nucleus medialis dorsalis of the thalamus by stimulation of the amygdaloid nuclear complex

Abstract

Slow potential changes in the nucleus medialis dorsalis, resulting from stimulation of the amygdaloid nuclear complex, have been recorded with bipolar electrodes in chloralosed cats. The sequence of potential changes was made up of three phases of activity which reached their peaks at 10-15, 40-50 and 100-130 msec after the stimulus artefact. The distribution of these phases of activity was analyzed. Phase I had its optimum amplitude in the caudal half of the medial third of the nucleus. Phase II showed a wider distribution, being the predominant component in the dorsal half of the middle third. Phase III did not show any specific localization. The effects of repetitive stimulation and the recovery cycle of excitability are described. Results are consistent with the suggestion that phase I is due to activity generated through a direct pathway between the amygdala and nucleus medialis dorsalis. Phases II and III represent activity elicited through multisynaptic pathways.