EFFERENT NEURONAL CONTROL OF THE NICTITATING-MEMBRANE RESPONSE IN RABBIT (ORYCTOLAGUS-CUNICULUS) - RE-EXAMINATION

Four Albino rabbits acquired a classically conditioned nictitating membrane response (NMR) to light, tone, and back shock conditioned stimuli using a paraorbital shock applied to the right eye as the unconditioned stimulus. Electrocoagulation lesions were made in the ipsilateral abducens nucleus of the pons in two animals, and the pontine reticular formation in two animals. Reinstitution of conditioning following surgery (retention test) indicated that the lesions failed to eliminate conditioned or unconditioned responses. This result is surprising in light of recent evidence that efferent control of the rabbit NMR derives solely from motoneurons of the ipsilateral abducens nucleus. Alternative hypotheses are considered. © 1979.