The term area 13l (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 13a (macaque), and area 13b (macaque). Identifying features of area 13l are: 1) a dense horizontal bundle of fibers stain for myelin in the internal granular layer (IV); 2) bands of cells in the external pyramidal layer (III) and the internal pyramidal layer (V) stain darkly for neurofilament protein by SMI-32, and 3) dense bands of fibers and cells in the external pyramidal layer (III) and internal granular layer (IV) stain for parvalbumin. Another feature that distinguishes area 13l from some adjacent areas is the presence of large pyramidal cells deep in the external pyramidal layer (III) ( Carmichael-1994 ). Its human equivalent is area 13l ( Ongur-2003 ). As granular prefrontal cortex, it has no equivalent in the rat ( Wallis-2012 ).