Brain and Behavior of Visual Expectations

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DESCRIPTION (provided by applicant): Foreknowledge about what will happen, when it will happen, and where it will happen, can help an organism find food and avoid predators. Preparatory responses use this foreknowledge to ready sensory and motor systems. Recent findings from neurophysiology and neuroimaging suggest that portions of the posterior parietal cortex (PPC) may function as a preparatory region. For instance, neurons in the monkey PPC region respond as though signaling the re-emergence of a briefly occluded moving target. Other studies have shown that cells in the PPC begin to fire seconds before a monkey looks a certain direction or reaches a certain direction. However, the functionality of the PPC is disputed because many studies have reported that various other tasks - attention, working memory, shape processing - also depend on the PPC. In this grant we advance the hypothesis that the PPC is importantly involved in linking sensory and motor signals in preparation to act. In Aim 1 we address the relationship of preparatory responses to working memory. In Aim 2 the relationship of sensory expectations to motor expectations is examined to gain some understanding of both the generality and specificity of preparatory processing. Last of all, in Aim 3 we do a finer grained analysis of preparatory processing by asking whether activity in the IPS is sensitive to the value of a preparatory cue. These questions will be addressed through functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and behavioral experimentation.