Neural mechanisms of distractor filtering in the parietal cortex

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DESCRIPTION (provided by applicant): How does the brain filter distracting visual information? It is well known that salient visual stimuli can elicit transient saccadic or attentional capture. This phenomenon is ecologically useful if the goal is to rapidly orient to a potential predator in the periphery, but highly detrimental if it distracts from a different goal such as monitoring elusive prey. Therefore, neural mechanisms for filtering distracting, irrelevant visual information are crucial for preventing wasteful saccadic or attentional shifts. This filtering may emerge as a direct consequence of lateral suppressive interactions between competing neural representations of visual stimuli, though the details underlying these processes are not well understood. The lateral intraparietal area (LIP) of the monkey encodes the relative priority of spatial locations, and activity in this brain area can reliably predict the locus of attention or the target of an upcoming saccade. Within LIP's "salience map," spatial locations compete using their activity for attentional and saccadic priority. Previous studies have explored how "top-down" excitatory processes such as motivation or attention can enhance the activity associated with behaviorally relevant stimuli in LIP, thus increasing their relative priority on this map. However, preliminary evidence suggests that lateral suppressive interactions in LIP operate in tandem with these excitatory processes and may be crucial for filtering distracting information and resolving competition between stimuli, though this has not yet been explored. In this proposal, my goal is to systematically explore the role of lateral suppressive interactions in LIP in filtering distracting visual information, and determine how this is related to saccadic behavior in the awake behaving monkey. We will use a combination of psychophysics and physiological recordings in LIP to investigate the following 3 aims: 1) Characterize the spatiotemporal properties of lateral suppression in LIP and how they are modulated by expected reward 2) Determine how these processes are related to saccadic behavior, and 3) Explore the mechanism of distractor filtering by using paired electrode recordings to directly compare the responses of competing stimuli. This research will hopefully give us insight into the general neural mechanisms that underlie the processes of spatial attention and saccadic decision making. This proposal offers significant health benefits to parietal patients, who exhibit extreme deficits in perception and oculomotor behavior. The first two aims would directly characterize unexplored areas of normal functioning, and the third aim could potentially lead to the identification of cellular populations for future drug targeting.