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David Sutterer, David Anderson, John Serences, Edward Vogel, Edward Awh; Theta Oscillations Track the Content of Representations Retrieved from Long Term Memory. Journal of Vision 2015;15(12):1113. doi: 10.1167/15.12.1113.
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© ARVO (1962-2015); The Authors (2016-present)
Recent work has demonstrated that it is possible to reconstruct orientation selective channel tuning functions (CTFs) during the encoding and delay period of a working memory (WM) task using a forward encoding model and electroencephalography (EEG). Specifically these CTFs can be derived from the distribution of alpha-band (8-12hz) activity across the scalp (Anderson et al. 2014), providing a high temporal resolution measure of the content and quality of WM representations. The goal of the present work was to determine whether we could employ a similar approach to track the content of representations retrieved from long term memory (LTM). Subjects (n = 24) learned randomly assigned colors for a collection of 120 unique shapes, with the color selected from a continuous 360 degree space. Twenty four hours after the initial learning session, subjects were presented with shape cues and asked to retrieve the associated color while EEG was recorded. We found that robust color-selective CTFs could be obtained from the distribution of evoked theta-band (4-7 hz) activity during the first 400 ms following the onset of the shape cue. We replicated this pattern of results with a spatial LTM task identical to the color task save that subjects learned and reported the position of 120 unique shapes from 360 degrees of space around a circle (n = 26). Together these results reveal that the content of representations retrieved from LTM is tracked by phasic activity in the theta-frequency band, and that this pattern of results generalizes across visual features. These findings dovetail with the longstanding consensus that low frequency activity in the theta band is integral to LTM function, and they provide a powerful new method for measuring the temporal dynamics of LTM retrieval.
Meeting abstract presented at VSS 2015
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