Ibotenic acid lesions of the lateral substantia nigra restore visual orientation behavior in the hemianopic cat

Transaction of non‐tectotectal fibers in the caudal one‐half of the commissure of the superior colliculus restores visual orienting to a cat previously rendered hemianopic by a large unilateral visual cortical lesion. Other observations related to this recovery phenomenon (i.e., the Sprague effect) have suggested that the caudal commissural fibers whose destruction produces the recovery (1) are contralateral afferents to the superior colliculus on the side of the cortical lesion, and (2) profoundly influence visuo‐motor processing in this superior colliculus. We performed anatomical and behavioral experiments to determine which of the more than 40 contralateral collicular afferents are directly involved in the Sprague effect.