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Hrag Pailian, Viola Störmer, George Alvarez; Neurophysiological Marker of Visual Working Memory Manipulation. Journal of Vision 2017;17(10):1116. doi: 10.1167/17.10.1116.
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© ARVO (1962-2015); The Authors (2016-present)
Previous research has discovered the neural correlates of visual working memory storage capacity (e.g., Vogel & Machizawa, 2004), but not the neural correlates of the defining feature of working memory – the manipulation of stored information. To this end, we recorded neural activity using electroencephalography (EEG) while observers completed a working memory (WM) manipulation task. Observers were cued to remember 3 colored circles on one side of the display (ignoring a perceptually matched display on the other side), followed by a maintenance period where the colors disappeared leaving behind placeholders. These events were succeeded by a placeholder-motion period, in which a pair of placeholders underwent smooth motion to swap locations. Observers were instructed to either update the spatial-featural bindings, keeping the features aligned with the moving placeholders (storage and manipulation) or to ignore the movement altogether and remember the features at their original locations (storage only). Observers subsequently identified the color of a cued item. We observed a sustained contralateral delay activity (CDA) at posterior electrode sites for both conditions during the initial maintenance prior to placeholder motion (representing the initial storage of information). This lateralized activity persevered into the placeholder-motion period, and remained active throughout this time window. The magnitude of the CDA did not differ between Update and Ignore conditions during either the initial maintenance period, F(1,11)=2.31, p=.16, or the placeholder-motion period, F(1,11)=3.69, p=.08. However, we observed a sustained nonlateralized negativity for Update trials, but not Ignore trials, at frontal-central electrode sites during the placeholder-motion period, F(1,11)=7.13, p=.02, but not during the initial maintenance period before movement, F(1,11)=1.46, p=.25. This negativity showed a bilateral anterior scalp distribution, focusing over frontal-central electrode sites. These results present the "Frontal-Central Negativity" as a candidate neurophysiological marker of visual WM manipulation, and suggest that storage and manipulation are separable cognitive and neural mechanisms.
Meeting abstract presented at VSS 2017
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