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Elizabeth Rislove, Dennis Levi; Variations in stimulus onset asynchrony affect attentive processing in amblyopia. Journal of Vision 2009;9(8):1034. doi: 10.1167/9.8.1034.
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Crowding is a phenomenon generally characterized by decreased ability to identify a target among nonoverlapping distractors in the normal periphery and central visual field of observers with amblyopia (a condition of degraded spatial vision generally caused by early monocular form deprivation). Recent experimental results have suggested that amblyopes experience disrupted attentive processing (Popple and Levi, 2008) as well as a different timecourse for temporal integration (Song and Levi, 2008) when compared with normally sighted observers. Our aim in this experiment was to assess the extent to which varying the stimulus onset asynchrony (SOA) between an attentional cue and a crowded stimulus affected the ability of attention to reduce crowding. We measured this in terms of performance improvement for a task in which observers were asked to identify the central target among an array of distractors under one of two conditions: (1) no cue, and (2) the target was cued with a colored, size-appropriate spatial cue of the same mean luminance as the background presented at one of five durations of stimulus onset asynchrony. Our stimuli consisted of vertically and horizontally oriented black and white bars as well as probable conjunctions of two bars (one horizontal and one vertical) presented on an otherwise homogenous gray field of mean luminance. All experiments were conducted monocularly; both amblyopic and fellow eyes of participants with amblyopia were tested along with non-dominant eyes of normally-sighted control participants. We found that for normally sighted observers, an accurate attentional precue improved performance relative to the uncued condition with the greatest improvements being at a 120 ms SOA, while for amblyopic observers, improvements were smaller on the whole with the largest improvements being at a 40 ms SOA.
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