The term anterior orbital gyrus (ORGa) 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 posterior orbital gyrus (ORGp) by the, transverse orbital sulcus (tos) ( Mai-1997 ). Together, the ORGa and ORGp constitute the intermediate orbital gyrus (ORGi). Histologically it is area 11l in the human ( Ongur-2003 ), The topological equivalent in the macaque is the rostral part of the ORGi ( NeuroNames ), and the histological equivalent ncludes area 11l and area 12m ( Carmichael-1994 ), granular 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 histological features are not found in the smooth cerebral cortex (CTX) of the rat or mouse ( Preuss-2022 ). Updated 5 Sep 2024.