The mammalian superior colliculus (SC) is a subcortical structure that integrates visual and other sensory information and controls eye and head movements to orient the animal towards novel sensory stimuli. The SC is divided into superficial and deep layers corresponding to a sensory representation of the external environment and a motor representation responsible for the control of orienting responses within that environment. A great deal of attention has been devoted to development of the sensory representation in the superficial layers which contains an orderly topographic map of visual space. In contrast, development of the motor map in the deep layers has not been studied. In fact, little is known about the development of motor representations anywhere in the central nervous system. In this study, we will test the hypothesis that the development of the SC motor map is patterned after the overlying sensory map. The experiments we propose will provide the first systematic mapping of the deep layers of the mouse SC. This will be followed by examination of the motor representations in mutant mice shown to have disrupted visual maps in the superficial layers. Our hypothesis predicts that the organization of the motor map in these mice will closely parallel the disrupted visual map in these mice.
Jianhua Cang, Ph.D.