Effects of superior colliculus lesion upon a black-white discrimination learning in the albino rat with one eye removed at birth.

It has previously been shown that, following original training of a black-white discrimination task, rats with one eye removed at birth (OEB) relearned the task faster than rats monocularly enucleated at three months of age (OET) when relearning was conducted after extirpation of the visual cortex contralateral to the remaining eye. The aim of the present study was to examine the role of the crossed and uncrossed retina-superior colliculus-lateral posterior nucleus of the thalamus-visual cortex pathway in mediation of original learning and relearning of OEBs in comparison with OETs. For this purpose the superior colliculus was destroyed bilaterally either before or after original learning. It was found that SC lesions did not affect original learning nor its retention in both OEBs and OETs, and there was no difference in the learning rate between the two. In relearning, it was also found that only when SC lesions were made before original learning, did OEBs fail to show faster relearning. Based on these findings it was suggested that enhanced functioning of the uncrossed retina-superior colliculus-lateral posterior nucleus of the thalamus-visual cortex pathway in original learning plays an indispensable role in enabling OEBs to relearn the discrimination task faster than OETs.