The term area OAa of Seltzer refers to an area of cerebral cortex in the macaque that is defined on the basis of cytomyeloarchitecture. It is located in the lateral wall and floor of the superior temporal sulcus internal to area OA of Bonin and lateral to area PGa of Seltzer. It differs from area OA in that it has a thinner internal granular layer (IV), a more prominent multiform layer (VI) and its external pyramidal layer (III) is considerably larger than its internal pyramidal layer (V). The part of the OAa located in the floor of the sulcus has a columnar appearance that is different from that in the lower bank of the sulcus. The inner band of Baillarger is better developed than in area OA and the outer band of Baillarger is less compact than in OA ( Seltzer-1978 ).