Topographical linkage of tecto-thalamo-anterior ectosylvian sulcal cortex in the cat: an 125I-WGA autoradiographic study.

Following injection of 125I-WGA into various parts of the caudal thalamus in the cat, the distribution of orthograde and retrograde labels in the cortex around the anterior ectosylvian sulcus (AESS) and the superior colliculus (SC) was examined autoradiographically. When 125I-WGA injections involved the medial part of nucleus lateralis posterior (Lp) of the thalamus, both orthograde and retrograde labels consistently appeared in the cortex around AESS, and retrograde labels in the SC. The topographical organization of the cortical connections with the medial part of Lp can be well correlated with that of the tecto-thalamic projections, in such a way that the dorsal portion of the medial part of Lp which receives fibers from the rostromedial part of SC is connected reciprocally with the lateral lip of AESS and the crown of the anterior sylvian gyrus; whereas, the most ventral portion of the medial part of Lp which receives tectal afferents from the caudolateral part of SC is connected with the dorsal bank and fundus of AESS. These results suggest the existence of retinotopically ordered linkage between the tecto-Lp and the Lp-AESS connections in the cat.