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Rinat Hilo, Marisa Carrasco, Shlomit Yuval-Greenberg; Task performance in covert, but not overt, attention correlates with early ERP laterality. Journal of Vision 2017;17(10):387. doi: https://doi.org/10.1167/17.10.387.
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Background. Visual performance decreases with target eccentricity. To compensate for such decrements, we move our eyes to target locations (overt attention) or attend to these locations without accompanying eye-movements (covert attention). Both overt and covert attention enhance perceptual performance, but it is undetermined whether they do so to the same extent. Here we compared overt and covert attentional enhancements using electrophysiological and behavioral measurements. Methods. ERP and eye-tracking were measured in 16 participants. On each trial, a central directional cue (100% valid) pointed to the left or right. In most (80%) trials a task-irrelevant probe appeared bilaterally 300-500ms post cue. Only trials with probes were analyzed and the ERP signal was examined relative to probe-onset at time zero, to reveal ongoing attentional enhancement while observers attended to the cued location. In half the trials, a target Gabor-patch was presented 300-500ms after the probe in the cued location. To indicate target detection, observers responded either by pressing a button (covert condition) or by shifting the eyes (overt condition). Results. Mean visual sensitivity was significantly higher for the covert than the overt condition, resulting from same hit rate and lower false alarm. Laterality of the ERP responses (difference between contralateral and ipsilateral channels relative to the cue) was found for both overt and covert attention shifts, around the P1 component (90-135ms) and the N2 component (185-300ms). ERP laterality in the P1 time-range was positively correlated across participants with task performance on the covert, but not the overt, task. Conclusion. Covert attention can be more effective than overt attention. Overt attention is a natural dual-task requiring both shifting of attention and performing a target-directed action. Covert attention requires only shifting of attention without a goal-directed action, and therefore can be easier to perform and is more correlated with early attentional ERP components.
Meeting abstract presented at VSS 2017
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