ELICITATION, MODIFICATION, AND CONDITIONING OF THE RABBIT NICTITATING-MEMBRANE RESPONSE BY ELECTRICAL-STIMULATION IN THE SPINAL TRIGEMINAL NUCLEUS, INFERIOR OLIVE, INTERPOSITUS NUCLEUS, AND RED NUCLEUS

Elicitation of responses by electrical brain stimulation (EBS) was rel ated to the synaptic distance of the target nucleus from the accessory abducens. Specifically, responses to EBS in the spinal trigeminal nuc leus (TRIG) and red nucleus (RN) increased as a positive function of s timulation parameters. Responding to EBS in the interpositus nucleus ( IP) was lower, and responding to EBS in the inferior olive (IO) was ne gligible. EBS in the TRIG, LP, and RN nuclei was then paired with a to ne conditioned stimulus (CS). The CS modified responses for EBS in RN and TRIG but not IF. CS-EBS pairings yielded conditioned response (CR) acquisition, in which Groups TRIG, IF, and RN reached asymptotes of 9 0%, 70%, and 43% CRs, respectively. Thus, contrary to previous finding s, EBS in the efferent pathway can support CR acquisition. The results are discussed with respect to the role of projections from the RN to the cerebellar cortex and the TRIG nucleus.