CLASSICAL-CONDITIONING WITH ELECTRICAL-STIMULATION OF CEREBELLUM AS BOTH CONDITIONED AND UNCONDITIONED STIMULUS

Stimulating electrodes were implanted in rabbit cerebellum, providing an electrical conditioned stimulus (CS) activating cortical parallel f ibers and thence Purkinje and other cells, and an electrical unconditi oned stimulus (US) activating underlying white matter and eliciting un conditioned responses. Paired CS-US presentations led to the developme nt of conditioned responses, which showed extinction following CS-alon e trials and reacquisition with significant savings on reinstatement o f paired trials. Increased local excitability as a result of paired tr aining (but not following unpaired stimulus presentations) was observe d in cerebellar cortex, as manifested in substantial decreases in CS t hreshold for response elicitation in all subjects. This preparation of fers a model for the study of plastic neuronal interactions within cer ebellar networks critically involved in associative learning.