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Nick Berggren, Martin Eimer; Event-related contralateral delay activity: A measure of working memory maintenance or the allocation of spatial attention?. Journal of Vision 2016;16(12):707. doi: 10.1167/16.12.707.
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© ARVO (1962-2015); The Authors (2016-present)
Retaining visual information in working memory (WM) results in a sustained event-related potential over occipital regions, contralateral to the side of space where memorised information is located, known as contralateral delay activity (CDA). Given its relationship to memory load and individual differences in memory performance, the CDA component is often interpreted as a neural marker of active WM maintenance/storage. However, the CDA could also reflect the allocation of spatial attention to task-relevant locations within WM. To assess this, we conducted a sequential load task where participants memorised four items that were presented in two successive displays (M1 and M2; e.g., two item at M1, then a further two items at M2). In Experiment 1, CDA components were elicited contralateral to to-be-memorised items at M1. Critically, CDA components switched polarity after M2 was presented on trials where relevant stimuli appeared in opposite hemifields. CDA components to M1 stimuli were also significantly reduced after M2 stimuli were presented non-laterally (Experiment 2). This suggests that the CDA is primarily driven by the current focus of attention rather than WM maintenance per se. However, there were also small increases of CDA amplitude after M2 presentation when M1 and M2 stimuli appeared at the same location, and also when M1 and M2 stimuli appeared at different locations in the same hemifield (Experiment 3). Overall, our results suggest that the CDA component is predominantly a reflection of the focus of spatial attention during WM maintenance. However, the CDA amplitude increase observed when additional stimuli are maintained within the same hemifield may indeed signify WM storage.
Meeting abstract presented at VSS 2016
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