The term area PGa of Seltzer refers to the innermost of three narrow, parallel cortical areas that line the upper bank of the superior temporal sulcus of the macaque. The others are area TAa of Seltzer and area TPO of Seltzer. Defined on the basis of cytomyeloarchitecture area PGa is narrower anteriorly and wider posteriorly. It is relatively thin with a broad external granular layer (II); the other layers are not prominent, and the cells of the multiform layer (VI) cluster in a characteristic manner. "These cellular features of area PGa contrast sharply with those of the adjacent [area PG of Bonin] of the inferior parietal lobule." The two zones also differ in that PGa is better myelinated both with respect to the bands of Baillarger and vertical fibers, particularly in the more anterior portion ( Seltzer-1978 ).