Frontal lobe connections of the superior temporal sulcus in the rhesus monkey.

The frontal lobe connections of different architectonic areas of the superior temporal sulcus (STS) in the rhesus monkey were investigated with the aid of both anterograde and retrograde tracing techniques. The proisocortical area in the rostralmost STS connects with proisocortical regions on the ventral and medial surfaces of the frontal lobe. The frontal lobe projections of polymodal cortex (area TPO) in the upper bank of the STS are organized according to the rostral-to-caudal topography of the sulcus. Rostral TPO interconnects with ventral (areas 13, 12, 11, and 14), medial (areas 24, 32, 14, and 9), and lateral (areas 10, 12, and 46) sectors of the frontal lobe. The mid-portion of polymodal cortex projects to, and receives fibers from, rostral subdivisions of lateral prefrontal cortex, viz. dorsal area 46, areas 9 and 10, whereas the caudal segment of TPO has reciprocal connections with caudal subdivisions (areas 46, 8, and 6) of the lateral frontal lobe. Visual-related zones (areas TEa and TEm) in the rostral lower bank of the STS have connectional relationships with orbitofrontal areas 11 and 12 and lateral frontal areas 46 and 8. A presumed somatic sensory-related area in the rostral depth of the STS (area IPa) projects to orbital (areas 11 and 14) and lateral (areas 46, 10, and 12) sectors of the frontal lobe.