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 identified 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 relate the pre-saccadic activity of corticotectal cells to spatially directed attention. We will 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. We will determine to what extent the excitability of the neuron is dependent on angle of gaze. Neurons sensitive to eye position provide a mechanism for encoding visual space in a head-centered frame of reference. Examining response properties of corticotectal cells in different areas of cortex will provide insight into the contribution of multiple visual areas to collicular function. The long-range goal of this project is to determine the contribution of visual cortex to selective attention and control of gaze.