To survive, animals must orient toward important stimuli while ignoring irrelevant ones. Our long-term goal is to understand how the brain selects targets for visual orienting, including saccadic eye movements and shifts of attention without eye movements. Saccade target selection lies at the interface between sensory and motor systems. This project probes the functions of two structures traditionally regarded as motor areas: the superior colliculus (SC), a subcortical region important for saccades, and the frontal eye field (FEF), an anatomically connected cortical region. Activity correlated with target selection has been observed in both areas. However, it is still debatable, particularly for the SC, whether these areas are involved in selecting where to look, or simply receive selection-related activity in preparation for generating a movement. We will test the hypothesis that these areas play functional roles in target selection by temporarily inactivating small regions of either the SC or FEF and testing performance in tasks that distinguish purely sensory or motor deficits from deficits in target selection. Comparisons will reveal how the two structures differ from each other in their contributions to target selection (Aim 1). We will also study the interactions of the SC and the FEF. It is usually assumed that the SC is under the control of cortical regions such as FEF, even though anatomical pathways also lead from the SC back to the FEF. We will test the hypothesis that SC activity influences target selection in the FEF, using single-unit recording and inactivation. This will reveal whether the two areas interact primarily in a feed-forward manner, or whether feedback from the SC influences cortical target selection (Aim 2). Evidence suggests that some of the same brain areas control both eye movements and attention shifts. We will test this hypothesis by investigating the consequences of temporarily disrupting activity in the SC or FEF on tasks requiring shifts of focal attention (Aim 3). These experiments will help to reveal the architecture of the visual orienting system, leading to a better understanding of human neurological syndromes that disrupt eye movements and attention. ? ?
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