CORTICOTECTAL CIRCUITS IN VISUAL PROCESSING

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In mammals, virtually all areas of visual cortex send a massive projection to the superior colliculus, a structure associated with selective attention and the initiation of eye and head movements. Although the physiology and anatomy of this corticotectal pathway have been studied extensively, its contribution to selective attention and visuomotor behavior are virtually unknown because most studies have used the paralyzed, anaesthetized animal. We propose to study the activity of antidromically-activated corticotectal neurons in areas 17, 18, 7, posteromedial lateral suprasylvian cortex (PMLS) and the frontal eye fields of alert cats trained in visuomotor tasks. We will evaluate the activity of corticotectal cells prior to and during saccadic eye movements using the magnetic search coil technique to monitor eye position. We will relate the pre-saccadic activity of corticotectal cells to spatially directed attention. We will also examine activity during the saccade to elucidate the possible role of corticotectal cells in such phenomena as saccadic suppression, distinguishing real from apparent movement, and updating relations between retinal and spatial coordinates. Examining response properties of corticotectal cells in different areas of cortex will provide insight into the contribution of multiple visual areas to collicular function. Finally, in prior work in area 17 of the paralyzed, anaesthetized cat we found two types of corticotectal cells that participate in two different intracortical circuits. We will look for differences in their activity during saccades to gain insight into the functional significance of these two intracortical circuits. The long-range goal of this project is to determine the contribution of visual cortex to selective attention and control of gaze.