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Antonio Fernandez, Hsin-Hung Li, Marisa Carrasco; How exogenous spatial attention affects visual representation. Journal of Vision 2019;19(10):100b. doi: https://doi.org/10.1167/19.10.100b.
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Purpose: Orienting covert spatial attention to a target location enhances visual sensitivity and benefits performance in many visual tasks. Attention alters the representation of low-level visual features by modulating gain, tuning width, or both. Endogenous spatial attention only boosts the gain of the orientation tuning corresponding to the attended stimulus. Pre-saccadic attention, the deployment of attention to the saccade target prior to the saccade onset, both enhances orientation gain and narrows tuning width, and increases sensitivity to high spatial frequencies. It is unknown whether exogenous spatial attention alters representations similarly to endogenous and/or pre-saccadic attention. Here we investigate how exogenous spatial attention affects the representation of orientation and spatial frequency using reverse correlation. Methods: Fifteen observers detected a vertical target grating embedded in noise. Following a valid, invalid or neutral pre-cue, stimuli were simultaneously presented at each of four peripheral locations (10° eccentricity). Whether a target was embedded in the noise was independently randomized for each location. A response cue determined the test stimulus observers had to detect. The feature content of the noise was correlated with behavioral responses (Reverse Correlation) to derive perceptual tuning curves for each of the three cue conditions for both the orientation and spatial frequency domains. Results: Exogenous attention enhanced the gain of the target orientation without affecting its tuning width. Moreover, exogenous attention did not affect spatial frequency tuning. Conclusions: The effects of exogenous attention were similar to those of endogenous attention but differed from those of presaccadic attention. We conclude that covert spatial attention modulates orientation information strictly by boosting gain.
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