The term posterior orbital gyrus ORGp) refers to one of four orbital gyri (ORG) on the ventral surface of the frontal lobe (FLB) in the human and the macaque.. Identified in the human by dissection and histology, it is located between the medial orbital sulcus (mos) and the lateral orbital sulcus (los). It is separated from the anterior orbital gyrus (ORGa) by the, transverse orbital sulcus (tos) ( Mai-1997 ). Together, the ORGa and ORGp constitute the intermediate orbital gyrus (ORGi). Histologically it is area 13l in the human ( Ongur-2003 ), The topological equivalent in the macaque is the caudal part of the ORGi, and the histological equivalent is largely area13m ( Carmichael-1994 ), dysgranular cortex ( Mesulam-1985 ). Thus, while the macaque has no tos separating it topologically from the ORGp ( Martin-2000 it differs in histology similarly to the human ( Carmichae-1994 Ongur 2003 ). Equivalent features are not found in the smooth cerebral cortex (CTX) of the rat or mouse ( Preuss-2022 ). Updated 5 Sep 2024.