The term rostral part of the pregeniculate nucleus refers to one of two parts of the pregeniculate nucleus in the macaque ( Olszewski-1952 ). It is distinguished from the other, the caudal part of the pregeniculate nucleus, in that it is composed of smaller cells. In that regard, it is equivalent to the medial zone of the pregeniculate nucleus in the mouse ( Franklin-2008 ). Functionally the pregeniculate nucleus belongs to the reticular formation (functional) of the brainstem motor system ( Swanson-2004 ).