Projection of visual field on superior colliculus of ground squirrel ( Citellus tridecemlineatus)

Abstract

The relations of the visual field to the superior colliculus in the ground squirrel ( Citellus tridecemlineatus) were determined electrophysiologically by mapping with a perimeter the receptive fields for 114 collicular sites distributed over the dorsolateral, the medial and the caudal surfaces of the colliculus in five animals. The entire visual field of the contralateral eye is represented on the colliculus and no evidence for an ipsilateral input was secured. The horizontal meridian of the eye projects upon the dorsolateral and tentorial aspects of the colliculus in a near horizontal position dividing the colliculus into approximately equal dorsomedial and ventrolateral halves. The vertical meridian passes vertically in an anteromedial direction over the caudal part of the dorsolateral surface from a position on the lower tentorial surface of the colliculus to reach the mesial surface somewhat behind the center of the dorsomedial edge and then passes downward and forward on the medial surface to a point somewhat forward of the center of the inner margin of the colliculus. Collicular representation of the nasal half of the visual field is somewhat greater than for the temporal half. The upper visual field is represented dorsomedially and the ventral field ventrolaterally