Connections between anterior inferotemporal cortex and superior temporal sulcus regions in the macaque monkey

We examined the connections between the anterior inferotemporal cortex and the superior temporal sulcus (STS) in the macaque monkey by injecting Phase olus vulgaris leucoagglutinin (PHA-L) or wheat germ agglutinin conjugated t o horseradish peroxidase (WGA-HRP) into the dorsoanterior and ventroanterio r subdivisions of TE (TEad and TEav, respectively) and observing the labele d terminals and cell bodies in STS. We found a clear dichotomy in the conne ctions of the rostral part of STS: the injections into TEad resulted in a d ense distribution of labeled terminals and cell bodies in the upper bank of rostral STS, whereas labeling was confined to the lower bank and fundus of rostral STS after injections into TEav. The distribution of labeling in th e rostral STS was discontinuous from the distribution of labeling surroundi ng the injection sites: the lower bank of the rostral STS was spared from l abeling in the TEad injection cases, and TEad had only sparse distribution in the TEav injection cases. These results revise the classical view that t he lower bank of rostral STS is connected with TE, whereas the upper bank o f rostral STS is connected with the parietal, prefrontal, and superior temp oral regions (Seltzer and Pandya, 1978, 1991, 1994). The upper bank of the rostral STS is called the superior temporal polysensory area (STP), because it was previously found that neurons there respond to auditory, somatosens ory, and visual stimuli. The present results thus suggest that the polymoda l representation in STP interacts more with information processing in TEad than TEav. It is also suggested that the information processing in the vent ral bank of the rostral STS is distinct from that in TEad, and the former m ore directly interacts with TEav than TEad.