The term area 13 (macaque) refers to a portion of the orbital gyri defined on the basis of internal structure in the macaque. It is one of six subdivisions of the orbitomedial prefrontal cortex, where it is also referred to as 'central orbital cortex'. It is subdivided into four areas: area 13l (macaque), area 13m (macaque), Area 13a (macaque), and area 13b (macaque). ( Carmichael-1994 ). Its human equivalent is area 13 ( Ongur-2003 ). All of its subdivisions except Area 13a (macaque) are granular cortex and have no equivalent in the rat. Area 13a, the most caudal of the subdivisions, is agranular ( Wallis-2012 ). For related areas in the rat and mouse, see orbital areas (rodent).