Dorsal accessory inferior olive activity diminishes during acquisition of the rabbit classically conditioned eyelid...

Eight rabbits were implanted with chronic recording electrodes in the rostromedial region of the dorsal accessory inferior olive (DAO). Multiple-unit DAO activity was recorded during 5 training sessions consisting of paired tone conditioned stimulus (CS) and air puff unconditioned stimulus (US) trials. Initially, the air puff US produced a large somatosensory-evoked response in the DAO during the paired CS-US presentations. As percent CRs increased across sessions, however, the DAO activity on paired trials decreased dramatically. In contrast, there were no significant decreases in DAO activity on US-alone trials presented at the end of each paired conditioning session. These results suggest that an associative process suppresses DAO activity during classical eyelid conditioning. Possible mechanisms of DAO inhibition and its involvement as part of the US 'reinforcement' pathway are discussed.