Conditioning of Switch-off Behavior Induced by Midbrain Central Gray Stimulation in Cats

Abstract

Cats, who had displayed escape or “fear”-like behavior by electrical stimulation of the midbrain central gray, were trained to interrupt the delivery of electrical stimulation of the midbrain central gray by plate pushing (switch-off behavior). After cats successfully learned to perform this switch-off behavior, they were further subjected avoidance conditioning trials in which neutral stimulus such as bell sound served as conditioned stimulus (CS), and electrical midbrain central gray stimulation as unconditioned stimulus (UCS). After cats reached the criterion of the avoidance learning, that is, appearance of the conditioned avoidance responses (CR) above 80%, then they were subjected extinction trials until they showed no CR. After that, they were given re-conditioning trials and extinction trials.
Results are following :
1. Four cats out of seven succeeded in avoidance learning. Their stimulation sites were in the mid-paramedian position of the periaquedual gray matter (see Figs. 1 and 2).
2. Two cats showed CR a little. One cat completely failed to show CR. Their stimulation points were in the basic and medial position of the midbrain central gray (see Figs. 1, 3, 4 and 5).
These findings suggest differences between learning induced by intracranial stimulation and that induced by peripheral stimulation, and also differences between avoidance learning based on switch-off behavior induced by midbrain stimulation and that induced by hypothalamic stimulation.