Improvement of shuttle-box learning with pre- and post-trial intracranial self-stimulation in rats

Abstract

The effects of intracranial self-stimulation (ICSS) in the lateral hypothalamus upon the acquisition and long-term retention (LTR) of shuttle box avoidance conditioning were studied in Wistar rats. Two groups of subjects learned the avoidance task in 5 daily training sessions and were allowed to self-stimulate either before (Pre-ICSS group), or after (Post-ICSS group) each training session. A control group received training but no ICSS. Ten days following the last training session, LTR of the task was determined in one avoidance session without ICSS. A fourth group was added post-hoc which was allowed to self-stimulate before the training sessions as well as before the LTR test. Both the Post-ICSS and Pre-ICSS groups improved in acquisition of the learned response over the successive training sessions, as compared with Controls. In the LTR test, the animals of the Post-ICSS group maintained the response level achieved in the last acquisition session. In contrast, the subjects of the Pre-ICSS group showed a significant decrease of the same response, unless they were given ICSS treatment prior to the LTR test. This may indicate a ‘state-dependent learning’ effect being responsible for the decrease in the LTR observed in Pre-ICSS group. Because both pre- and post-training ICSS treatments improved the acquisition and the LTR of the learned response, it is suggested that the contingency of the treatment with training (that is, ICSS treatment immediately after the training sessions) is not a necessary condition to facilitate the acquisition and the consolidation of two-way active avoidance learning.