EVIDENCE OF PLASTICITY IN THE PONTOCEREBELLAR CONDITIONED-STIMULUS PATHWAY DURING CLASSICAL-CONDITIONING OF THE EYEBLINK RESPONSE IN THE RABBIT

Electrical stimulation thresholds required to elicit eyeblinks with ei ther pontine or cerebellar interpositus stimulation were measured befo re and after classical eyeblink conditioning with paired pontine stimu lation (conditioned stimulus, CS) and corneal airpuff (unconditioned s timulus, US). Pontine stimulation thresholds dropped dramatically afte r training and returned to baseline levels following extinction, where as interpositus thresholds and input-output functions remained stable across training sessions. Learning rate, magnitude of threshold change , and electrode placements were correlated. Pontine projection pattern s to the cerebellum were confirmed with retrograde labeling techniques . These results add to the body of literature suggesting that the pens relays CS information to the cerebellum and provide further evidence of synaptic plasticity in the cerebellar network.