Abstract
Attention enhances attended targets and suppresses ignored distractors. In this study, we examined the time courses of neural representations of simultaneously presented and spatially overlapping target and distractor stimuli. We hypothesized that the strength of the cortical representation of task-irrelevant visual information would match that of the task-relevant information in the period shortly after stimulus onset, reflecting that early visual stimulus processing is deployed uniformly over incoming visual stimulation, but then fade as cognitive mechanisms selectively prioritize target information for task performance. To test this hypothesis, we recorded EEG data from 20 human participants performing a cued object-based attention task in which participants were cued to attend one of three object categories on each trial: faces, scenes, or tools. Stimuli were overlaid images from two categories, and each image could be either blurry or clear. Participants were instructed to identify whether the cued object image was blurry or clear on each trial and ignore the other object image. We used a support vector machine classification algorithm to decode clear versus blurry targets and clear versus blurry distractors at each time point in the stimulus period. In agreement with our hypothesis, our decoding results indicated that visual information about both target stimuli and distractor stimuli is highly decodable shortly after stimulus presentation, but the decodability of distractor stimuli rapidly declined whereas that of target stimuli remained high for an extended period of time. These data yield novel insights into the time course of distractor information processing by revealing that although distracting visual information is represented in cortical activity at the time of its presentation, its representation quickly diminishes, whereas task-relevant visual information is maintained.