Abstract
The purpose of the present study was to examine the contributions made by the superior colliculus to the learning and recall of form discriminations. Six cats were trained to learn and recall a battery of four different classes of form discriminations: simple two-dimensional patterns, complex two-dimensional patterns, three-dimensional junk objects three-dimensional black objects. Following training, three of the animals had one pair of cryoloops bilaterally implanted over the dorsal surface of the superior colliculus and the other three animals served as controls. Bilateral deactivation of the superficial layers of the superior colliculus impaired the learning of both the simple and complex patterns, with the complex pattern learning being profoundly retarded. Bilateral collicular deactivation had a minor effect on the learning of black three-dimensional objects, and no effect on the learning of three-dimensional junk object pairs. Deactivation of the superior colliculus did not have any effect on the ability to recall any of the form discriminations. Therefore, we conclude that bilateral cooling of superior colliculus disrupts the tecto-extrageniculate pathway to extrastriate visual cortex and impairs the learning of two-dimensional patterns. These observations have significant bearing on our understanding of contributions that non-geniculate pathways to extrastriate cortex make to visual processing in cat, monkey and human cortices.