The term area TPO of Seltzer refers to one 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 PGa of Seltzer. Defined on the basis of cytomyeloarchitecture area TPO lies "medial to area TAa [area TEa of Seltzer] and occupying the crest of a small secondary gyrus." LIke area TAa it begins near the anterior tip of the central sulcus and runs posteriorly. The external pyramidal layer (III) is broad with a distinct sublayer IIIc. The internal granular layer (IV) is well developed, though "non-columnar". The cells of the internal pyramidal layer (V) are less prominent and those of the multiform layer are fewer giving the impression of a wider space between layers V and VI. The inner band of Baillarger is "scarcely visible", but vertical myelinated fibers are well developed ( Seltzer-1978 ).