Cortico-tectal and intertectal modulation of visual responses in the rat's superior colliculus

Summary In rats under urethane anesthesia, electrolytic destruction of one superior colliculus resulted in an increase in the amplitude of the light-evoked potential recorded in the remaining contralateral superior colliculus. In another group of rats, unilateral ablation of visual cortex produced a depression of the light-evoked potential recorded in the ipsilateral superior colliculus. However, in these same animals, subsequent destruction of the contralateral superior colliculus resulted in an increase in the amplitude of the tectal response to near normal levels. These findings suggest that the activity of the colliculus of the rat is subject to two opposing and tonic influences: 1. cortico-tectal facilitation, and 2. tectotectal inhibition.This study was supported by a grant from the National Research Council of Canada to Dr. A. Monjan. I would like to thank Dr. Monjan for his guidance and assistance in this work.