Corticostriatal connections of the superior temporal region in rhesus monkeys.

Corticostriatal connections of auditory areas within the supratemporal plane and in rostral and caudal portions of the superior temporal gyrus were studied by the autoradiographic anterograde tracing technique. The results show that the primary auditory cortex has limited projections to the caudoventral putamen and to the tail of the caudate nucleus. In contrast, the second auditory area within the circular sulcus has connections to the rostral and the caudal putamen and to the body of the caudate nucleus and the tail. The association areas of the superior temporal gyrus collectively have widespread corticostriatal projections characterized by differential topographic distributions. The rostral part of the gyrus projects to ventral portions of the head of the caudate nucleus and of the body and to the tail. In addition, there are connections to rostroventral and caudoventral portions of the putamen. The mid-portion of the gyrus projects to similar striatal regions, but the connections to the head of the caudate nucleus are less extensive. Compared with the rostral and middle parts of the superior temporal gyrus, the caudal portion has little connectivity to the tail of the caudate nucleus. It projects more dorsally within the head and the body and also more dorsally within the caudal putamen. These differential patterns of corticostriatal connectivity are consistent with functional specialization at the cortical level.