The term supraoculomotor cap refers to a group of neurons in the periaqueductal gray about midway in its course from the level of the posterior commissure to the locus ceruleus. The cap is located dorsal to the supraoculomotor nucleus in the human ( Paxinos-2012 ), macaque ( Paxinos-2009a ), rat ( Paxinos-2009b ), and mouse ( Franklin-2008 ). It stains heavily for nitiric oxide synthase (NADPH-diaphorase) compared to the lateral periaqueductal gray dorsal to it ( Carrive-2012 ).