Thalamic connections of the cortex of the superior temporal sulcus in the rhesus monkey.

The thalamocortical connections of the superior temporal sulcus (STS) were studied by means of the WGA-HRP retrograde tracing technique. The results indicate that the distribution of thalamic projections varies along the rostral-caudal dimension of the STS. Thus the rostral portion of the upper bank receives input primarily from the medialmost portion of the medial pulvinar (PM) nucleus. The middle region of the upper bank receives projections from medial and central portions of the PM nucleus, and also from the oral pulvinar, limitans, suprageniculate, medial geniculate, and dorsomedial nuclei. The cortex of the caudal portion of the upper bank has basically similar thalamic input; however, the projections from the PM nucleus originate in central and lateral portions. Additionally, there are projections from the lateral pulvinar (PL), ventroposterolateral, central lateral, parafascicular, and paracentral nuclei. In contrast to the dorsal bank, the cortex of the ventral bank of the STS receives somewhat different and less extensive thalamic input. The rostral portion of the lower bank receives projections only from the ventromedial sector of the PM nucleus, whereas the middle portion of the lower bank receives projections from the PL and the inferior pulvinar nuclei as well as from the PM nucleus. The upper bank of the STS, on the basis of physiological and anatomical studies (Jones and Powell, '70; Seltzer and Pandya, '78; Gross et al., '81; Baylis et al., '87), has been shown to contain multimodal areas. The present data indicate that the multimodal region of the STS has a preferential relationship with the central sector of the PM nucleus.