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Kyle Killebrew, Candace Peacock, Gennadiy Gurariy, Marian Berryhill, Gideon Caplovitz; Frequency domain analyses of EEG reveal neural correlates of visual working memory capacity limitations observed during encoding using a full report paradigm.. Journal of Vision 2017;17(10):123. doi: 10.1167/17.10.123.
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© ARVO (1962-2015); The Authors (2016-present)
Visual working memory (VWM) is capacity limited. In an attempt to better understand the role of encoding-related processes in this capacity limitation, we combined a full report VWM paradigm with an EEG frequency tagging technique to measure neural correlates of encoding related processes. This paradigm allows behavioral and neural responses for all items in a memory array to be measured independently. Specifically, observers performed a full report VWM task in which they were presented with a four-item memory array and asked to recall as many items as possible after a brief delay. The memory arrays contained visual shape stimuli, each flickering at different rates. Each of these was 'tagged' using that particular flicker frequency. While performing the task, neural activity was recorded using high-density electroencephalography (hdEEG) and the steady-state visual evoked potential (SSVEP) was measured during the WM encoding period in response to the frequency tagged stimuli. During retrieval, observers either recalled the location and identity of each item in the order they chose or in an order explicitly demanded by the paradigm. Our results demonstrate that the frequency tag amplitudes for correctly recalled items were larger than for forgotten items for both recall types on electrodes broadly distributed across the scalp. A secondary induced-power analysis found increased power in the theta (5-8Hz), alpha (9-12Hz) and beta (13-31Hz) bands on trails in which 3 or 4 items were correctly recalled compared to 1 or 2 items. However this effect was only observed in the sequential-recall conditions. Building on our previous work using a recognition paradigm, the current results further demonstrate the important role of encoding-related processes in the overall capacity limitation of VWM.
Meeting abstract presented at VSS 2017
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