Effect on the Superior Colliculus of Cortical Removal in Visually Deprived Cats

Abstract

ONE of the principal goals of analyses of the processing of sensory information has been an understanding of the receptive field properties of central neurones in terms of the convergence of afferents from more peripheral levels. Although it is well known that most cell groups receiving peripheral input also receive inputs descending from higher centres, there have been relatively few studies of descending effects on the organization of the receptive field¹. We are concerned here with the superficial layers of the superior colliculus which receive optic nerve fibres, chiefly from the contralateral retina, and descending input from the ipsilateral visual cortex². Most collicular cells in the normal cat are binocularly driven by slits, bars or edges and are directiorially selective, that is they respond much better to movement of a visual stimulus in one direction than to movement in the opposite direction³. After the visual cortex is removed, collicular cells respond to the same types of visual stimuli, but most cells are driven only by the contralateral eye. The cells also lose their directional selectivity and respond equally well to all directions of stimulus movement⁴. It therefore seems clear that some features of collicular cells depend on the cortex. The work described here with visually deprived animals demonstrates in another way the influence of the cortex on collicular cells.