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Marian Sauter, Heinrich Liesefeld, Hermann Müller; Learning to shield visual search from salient distractors: Evidence from the N2pc component. Journal of Vision 2017;17(10):1137. doi: https://doi.org/10.1167/17.10.1137.
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In visual singleton search, interference by salient distractors can be more efficiently shielded in locations where they appear more frequently (Goschy et al, 2014). In a previous study, we found that this probability cueing effect originates from spatial suppression, which is heavily modulated by the dimensional relationship between distractor and search target (Sauter et al., submitted). In the present study, we aimed to reveal a neural correlate of this suppression using electroencephalography. Fifteen subjects searched for a slightly left or right tilted target bar among 59 vertically oriented bars. In half of the trials, one of the non-targets was a horizontal 'distractor' bar. Crucially, when a (same-dimensional) distractor appeared, it appeared 90% of the time in either the top or bottom half of the search display (counterbalanced across participants). On distractor-present trials, either the distractor or the search target was displayed on the vertical midline. We analyzed the N2pc, an event-related potential that appears strongest at the parietal-occipital electrode sites PO7/8 contralateral to the attended stimulus and is thought to reflect attentional selection by mechanisms of distractor suppression. The results show that for distractor-present trials (1) reaction times are lower when a distractor appears in the frequent distractor area and (2) the N2pc yields a higher amplitude for distractors that appear in the frequent as compared to the rare distractor area; for distractor-absent trials (3) reaction times are lower when a target appears in the frequent distractor area and (4) the N2pc also yields a higher amplitude for targets that appear in the frequent as compared to the rare distractor area. This is indicative of the higher degree to which distractor suppression is recruited in the frequent distractor area due to learned shielding and supported by the role of the N2pc in top-down attentional mechanisms.
Meeting abstract presented at VSS 2017
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