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David Sutterer, Geoffrey Woodman; Alpha-band activity selectively tracks targets but not distractors following spatial cues.. Journal of Vision 2020;20(11):1228. doi: https://doi.org/10.1167/jov.20.11.1228.
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Recent work finds that the location of remembered stimuli can be reconstructed from patterns of EEG alpha-band activity (Foster, Sutterer, Serences, Vogel, & Awh, 2016) and that online spatial representations are maintained even when the location of stimuli are task irrelevant (Foster, Bsales, Jaffe, & Awh, 2017). Interestingly, power increases in this same frequency band of activity (8 – 12 Hz) have been hypothesized to reflect the filtering of irrelevant visual input (Jensen & Mazaheri, 2010), and a well-known characteristic of alpha-band activity is that power decreases contralateral to a cued hemifield and increases ipsilateral to the un-cued hemifield. Previous work reconstructing the location of remembered stimuli has always relied on stimuli presented across hemifields. Thus, an open question is whether alpha-band activity spontaneously tracks the location of distractors presented in an irrelevant hemifield or if a spatial pre-cue is sufficient to allow filtering of distractors.
To answer this question, we used a lateralized spatial estimation task. On each trial, observers were centrally cued to remember the location of dots (1 or 2) presented to the left or right of fixation while ignoring the location of distractor dots presented on the un-cued side of the screen. Dots in both hemifields were presented on a circle (radius of 4 degrees of visual angle) that was centered 6 degrees of visual angle from fixation. By applying an inverted encoding model (IEM) to the topography of alpha-band activity on the scalp, we found that we were able to successfully estimate remembered locations for target items on both one- and two-item trials. Critically, we were unable to reconstruct the location of distractor items. Together these results suggest that alpha-band activity tracks the location of targets but not distractors and that spatial cues are an effective means of filtering distractors.
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