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David Sutterer, Edward Awh; Evidence for concurrent activation of sequentially encoded spatial locations. Journal of Vision 2018;18(10):109. doi: 10.1167/18.10.109.
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A robust body of work has demonstrated speeded reaction times to the last item encoded in a Sternberg task (Vergauwe et al., 2016, Oztekin, Davachi, & McElree 2010). A key debate is whether this RT benefit reflects a narrow focus of attention on the most recently presented item, in line with suggestions that working memory capacity may be limited to a single item or encoding episode. Here, we tested this hypothesis by using alpha band activity to track the time course and content of representations maintained in spatial working memory (Foster et al., 2016). This method allowed us to observe whether or not sequentially encoded items are concurrently represented during the delay period of a working memory task. On each trial, observers memorized the location of two sequentially presented colored dots while EEG was recorded. After a 1s delay period, participants were cued to report the location of one of the dots. We trained an inverted encoding model (IEM) to assess alpha selectivity for the location of each item and found robust representations of both to-be-remembered locations during the 1s delay interval consistent with the interpretation that both items are simultaneously maintained in an active state. These findings disconfirm the hypothesis that only the final item in a sequence is actively represented during the delay period. Thus, although faster RT for the final item in a sequence may reflect a higher priority or familiarity for the most recently encoded item, multiple items in a sequence can be simultaneously stored in visual working memory.
Meeting abstract presented at VSS 2018
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