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Harriet A. Allen, Glyn W. Humphreys; The preview benefit is active ignoring. Journal of Vision 2006;6(6):445. doi: 10.1167/6.6.445.
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In visual search experiments, when some distractors are previewed before the remainder, participants discount these distractors from search. Behavioral data suggests active inhibition underlies this Preview Benefit. In an fMRI study, we localized and then measured BOLD activation in areas responsive to previewed, ignored and passively viewed stimuli. Participants performed a visual search task. Each trial consisted of 2 displays. The target, always in the second display, was defined by a conjunction of form (house/face) and color (red/blue). Experiment 1: Passive condition - the first display contained irrelevant distractors. Preview condition- the first display contained face distractors which remained on screen throughout both displays. Experiment 2: Replicated Passive and Preview conditions (except that the target could be either a face or house) and added an Ignore Category condition where the target was always the opposite category to items in the first display, and these items were repositioned in the second display. Search for the target was slowest in the Passive condition, faster in the Ignore Category condition and fastest in the Preview Search condition. In face- and house-specific brain areas, earlier and higher activations were associated with this preview benefit. This pattern of activations was different to that found for ignored items in the Ignore Category condition. The data are consistent with the preview benefit being an active process, involving different brain states to those correlated with simply ignoring a stimulus. Active ignoring of a preview is mediated by preactivation of the ignored items.
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