ABSTRACT
Any detailed understanding of the neural mechanisms underlying the conditioned nictitating membrane (NM) response begins with a characterization of the basic reflex pathway of the UR. Given this foundation one can attempt to link motoneurons to neural systems that subserve the CR. This chapter reviews research on the anatomy and physiology of brain stem systems implicated in the conditioned and unconditioned NM responses. In addition to the reflex pathway of the UR, we consider the evidence that two distinct anatomical entities are essential for the NM CR. One is the supratrigeminal reticular formation and the other is a circuit beginning in the cerebellum that includes red nucleus as an intermediary.
