The term caudal 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 larger cells. In that regard, it is equivalent to the lateral zone of the pregeniculate nucleus in the rodent ( Franklin-2008 ). Functionally the pregeniculate nucleus belongs to the reticular formation (functional) of the brainstem motor system ( Swanson-2004 ).