ERP Correlates of Visuospatial Attention
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At almost every given moment, the visual system in our brain is constantly bombarded by visual stimuli. Unfortunately, our brain does not have an infinite amount of neurons to process every visual stimulus in the environment so it must select some at the expense of others. That is, objects compete for representation in the limited capacity visual system. Studies have shown that stimuli presented in close proximity exhibit greater competition than stimuli that are farther apart. Attention is also biased towards more salient objects through top-down mechanisms meaning that a task relevant object will be selected over another object. Previous work has also identified possible neural correlates for both spatial and saliency mediated competition. The N2pc component of the event-related potential (ERP) may be related to spatially-mediated competition, while the subsequent Ptc component may be related to the operation of a top-down biasing mechanism. In this study, a colored target and decoy are displayed at various spatial separations to participants while their ERPs are recorded. The participant will not be told the color of the target in advance so that both target and decoy must be attended. The participant is expected to bias processing towards the target and away from the decoy based on top-down factors. A positive correlation between the amplitude of the N2pc and Ptc components of the ERP and the amount of spatial and top-down mediated competition will provide converging evidence that those two components map to their respective biasing mechanism.