Abstract
One view of working memory posits that maintaining a series of events requires their sequential and equal mnemonic replay. Another view is that the content of working memory maintenance is prioritized by attention. We decoded the dynamics for retaining a sequence of items using magnetoencephalography (MEG), wherein participants encoded sequences of three stimuli depicting a face, a manufactured object, or a natural item and maintained them in working memory for 5 seconds. Memory for sequence position and stimulus details were probed at the end of the maintenance period. Decoding of brain activity revealed that one of the three stimuli dominated maintenance independent of its sequence position or category; and memory was enhanced for the selectively replayed stimulus. Analysis of event-related responses during the encoding of the sequence showed that the selectively replayed stimuli were determined by the degree of attention at encoding. The selectively replayed stimuli had the weakest initial encoding indexed by weaker visual attention signals at encoding. These findings do not rule out sequential mnemonic replay, but reveal that attention influences the content of working memory maintenance by prioritizing replay of weakly encoded events. We propose that the prioritization of weakly encoded stimuli protects them from interference during the maintenance period whereas the more strongly encoded stimuli can be retrieved from long-term memory at the end of the delay period.
Significance Statement Here we show how information of a sequence of events is prioritized in the working-memory maintenance buffer in humans. Participants retained three consecutive visual stimuli and we decoded the content of working-memory maintenance using multivariate-pattern-classification and magnetoencephalography (MEG). We observed that the least attended events during encoding dominated the content of working-memory during the immediately following offline retention. In essence, the brain selectively and intelligently amplifies the least encoded memory item to maximize recall fidelity, instead of equally rehearsing the whole sequence. Our findings shift the functional role of working-memory from a faculty that “works with memory” to one that “works for memory” by actively selecting which encoded items need to be enhanced to be remembered.
Footnotes
Authors declare no conflict of interest.
Wellcome Trust; McDonnell Foundartion; HHS | NIH | National Institute of Neurological Disorders and Stroke (NINDS) [R3721135].
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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