The organization of connections between the pulvinar and visual area MT in the macaque monkey.

Injections of horseradish peroxidase were placed in visual area MT which is located in the superior temporal sulcus of the macaque monkey occipital cortex. Overlapping retrogradely filled cells and anterogradely transported terminal grains were found to be located only within a crescent shaped region which traverses the brachium of the superior colliculus to include the inferior pulvinar and dorsal overlying lateral pulvinar. The connections between MT and the pulvinar crescent are reciprocal and topographically organized, with the lower visual field represented dorsally and the upper visual field represented ventrally. There is an expanded representation of central vision located caudally within the crescent while peripheral vision is represented rostrally. These findings indicate that any functional properties derived from the visual thalamus must arise from this crescent shaped region of the pulvinar.