Decisions about where to look within a typical visual scene are governed by the relative salience of individual stimuli and current behavioral objectives. To date, the majority of studies examining the cognitive control of visual orienting have targeted frontal cortex. However, there is growing evidence to suggest that signals related to working memory and decision-making are critically dependent on interactions between frontal cortex and subcortical structures such as the basal ganglia, cerebellum, and thalamus. Thalamus is unique among these subcortical structures;in addition to providing direct input to cortex, its constituent nuclei mediate the influences of both the basal ganglia and cerebellum on their respective cortical targets. Despite its critical anatomical position, virtually nothing is known about the nature of the information represented in central thalamus. The current experiments seek to fully characterize the central thalamic representations of cognitive factors relevant for producing visually-guided saccadic eye movements. The proposed studies will be the first to examine the potential importance of central thalamic nuclei, and the subcortical-cortical interactions they mediate, to the cognitive control of goal-directed saccadic eye movements. In doing so, these experiments will help to define the essential neural substrates for visuomotor cognition.
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