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Joram van Driel, Eren Gunseli, Martijn Meeter, Christian Olivers; Local and interregional alpha oscillatory dynamics are sensitive to different levels of working memory-guided visual search. Journal of Vision 2016;16(12):709. doi: 10.1167/16.12.709.
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© 2017 Association for Research in Vision and Ophthalmology.
Attention during visual search is thought to be guided by an active visual working memory (VWM) representation of the search target. However, it is unclear if and how neural mechanisms that support VWM dissociate between different levels of anticipated search difficulty. We tested the hypothesis that posterior alpha band (8–14 Hz) oscillatory dynamics during VWM encoding and maintenance of the search target, are sensitive to the anticipated level of competing information present during search. To this end, we analyzed an existing EEG dataset from 20 human subjects while they performed three different VWM tasks. Each task started with a lateralized cue as to which target to look for in a subsequent search display that was presented after a one second delay. In one task subjects had to recognize the target without distractors. In the other two tasks, recognition after the delay was compromised by competing distractors in a pop-out (distinct), or serial (non-distinct) search display. Behavioral performance decreased with increasing search difficulty. During the delay period, parieto-occipital sites contralateral to the WM cue exhibited robust alpha power suppression, as well as reduced alpha phase synchronization with mid-parietal sites. This oscillatory signature of VWM maintenance, importantly, was strongest prior to non-distinct search and weakest prior to simple recognition. Functional connectivity analyses further showed that, before WM cue-onset, alpha phase synchrony between prefrontal sites and mid-parietal sites was strongest in the non-distinct search task, possibly reflecting anticipatory control of VWM encoding. Directional connectivity analyses confirmed this effect to be in an anterior-to-posterior direction. Together, these results provide evidence for frontally mediated top-down control of VWM in preparation of visual search.
Meeting abstract presented at VSS 2016
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