Classical conditioning of the rabbit eyelid response with a mossy-fiber stimulation CS: II. Lateral reticular nucleus stimulation.

Stimulation of mossy fibers arising from the pontine nuclei can be used as a conditioned stimulus (CS) during classical conditioning of the eyelid/nictitating membrane response (NM). In the present experiment we stimulated another source of mossy fibers, the lateral reticular nucleus (LRN), as a CS for NM conditioning. LRN stimulation was an effective CS, resulting in learning, and the conditioned response to LRN stimulation showed normal extinction. Unpaired presentation of CS and UCS did not result in pseudo-conditioning. Lesions of the cerebellar dentate-interpositus region abolished the conditioned response but left the unconditioned reflex response intact. We suggest that mossy fibers may normally carry CS information to the cerebellum.