The term area 13b (macaque) refers to a portion of the orbital gyri defined on the basis of internal structure in the macaque. It is one of four components of area 13 (macaque) in the orbitomedial prefrontal cortex. The other components are area 13m (macaque), area 13l (macaque), and area 13a (macaque). A significant feature of area 13b is the presence of radial striations revealed by Nissl stain in the external pyramidal layer (III), the internal granular layer (IV), and the internal pyramidal layer (V). Another feature that distinguishes area 13b from some adjacent areas is the appearance of vertical fiber bundles in the internal pyramidal layer (V) as demonstrated by myelin stain ( Carmichael-1994 ). Its human equivalent is area 13b ( Ongur-2003 ). As granular prefrontal cortex, it has no equivalent in the rat ( Wallis-2012 ).