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Reshanne Reeder, Christian Olivers, Stefan Pollmann; Cortical evidence for negative search templates. Journal of Vision 2017;17(10):928. doi: 10.1167/17.10.928.
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Predefined targets of visual search are thought to be actively represented in a "target template", but little is known about the representation of impending distractors. Knowing what to ignore prior to search should improve distractor inhibition and benefit target detection; thus it would be beneficial to set up a "negative template" specifying distractor features. The question is whether preparing for targets or preparing for distractors involve different preparatory representations. Is a negative template the same as a target template? Is it something completely different? Or does it simply not exist (i.e. distractor information is simply ignored)? In the current study, we compared the representations of different types of information prior to search, using fMRI. Specifically, we compared prior distractor information to prior target information, or task-irrelevant information. Subjects were required to search for a letter T among slightly different distractors enclosed in differently colored circles. Prior to search, a color cue appeared with one of three symbols: "+" (positive cue: the target will appear in the same color); "—" (negative cue: only distractors will appear in the same color); or "o" (neutral cue: this color will not appear in the search display). fMRI results showed increased activation in large parts of visual cortex following the positive cue compared to the negative cue. The negative cue showed deactivation as compared to the neutral cue in largely the same regions. The neutral cue, compared to the task-relevant cues, showed increased BOLD signal in superior parietal lobule bordering precuneus, a region previously found to be involved in actively ignoring irrelevant spatial stimuli. These results reveal that negative templates have a distinct neurophysiological signature compared to either target templates or completely irrelevant stimuli.
Meeting abstract presented at VSS 2017
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