The Role of the Cerebellar Interpositus Nucleus in Short and Long Term Memory for Trace Eyeblink Conditioning

摘要

In previous studies the cerebellar interpositus nucleus, but not the hippocampus, was shown to be necessary both for initial learning and retention and for long-term retention of the standard delay eyeblink conditioned response (CR). However, in the trace eyeblink CR procedure, the hippocampus is also necessary for initial learning and retention, but not for long-term retention. Here we evaluate the role of the interpositus nucleus in both initial learning and retention, and in long-term retention of the trace eyeblink CR, using muscimol infusion to reversibly inactivate the interpositus nucleus. For the short-term study, there were 2 subgroups, the first sequentially passed through acquisition, inactivation, and reacquisition phases, whereas the second subgroup went through inactivation, acquisition, and inactivation phases. For the long-term study, the rabbits acquired the conditioned response (CR) and then rested for a month. Next, they were distributed into 2 subgroups: with or without retention training, and finally went through inactivation and reacquisition phases. The results showed that the pre-learning IP nucleus inactivation prevented the acquisition of the trace CR, whereas the post-learning inactivation reversibly abolished the expression of both the short- and long-term CR.