The term periolivary region refers to neurons that surround the superior olive. Identified by Nissl substance they together with the superior olive and the trapezoid nucleus constitute the superior olivary complex ( Carpenter-1983 ). The grouping of cells identified in different species varies by author. In humans the dorsomedial periolivary nucleus is most clearly identified; less consistently identified are the medial periolivary nucleus, ventral periolivary nucleus, and rostral periolivary region ( Amunts-2012 ). In the macaque the groups include the dorsal periolivary region, medioventral periolivary nucleus, lateroventral periolivary nucleus, and superior paraolivary nucleus ( Paxinos-2009a ). Some authors distinguish the same subdivisions in the rat ( Paxinos-2009b ) and the mouse ( Franklin-2008 ). Others report that in the rat ( Swanson-2004 ) and the mouse ( Hof-2000 ) the neurons are not sufficiently organized to be reliably subgrouped. Functionally the periolivary region is part of the subcortical auditory system ( Swanson-2004 ).