Reactivating and reorganizing activity-silent working memory: two distinct mechanisms underlying pinging the brain

Abstract

AbstractRecent studies have proposed that visual information can be maintained in an activity-silent state during working memory (WM) and that this activity-silent WM can be reactivated by task-irrelevant high-contrast visual impulses (i.e., “pinging the brain”). Although pinging the brain has become a popular tool for exploring activity-silent WM in recent years, its underlying mechanisms remain unclear. In the current study, we directly compared the neural reactivation effects and behavioral consequences of context-independent and context-dependent pings to distinguish between the noise-reduction and target-interaction hypotheses of pinging the brain. In this electroencephalogram study, our neural decoding results showed that the context-independent pings reactivated activity-silent WM without changing the original representations of memorized items and that reactivation effects were significantly higher in individuals with poorer WM performance. In contrast, the context-dependent pings reactivated activity-silent WM in a more durable and consistent way and further reorganized it by decreasing the variability of items’ neural representations and disturbing the memory structure between items. Notably, reactivation effects were stronger in the trials with larger recall errors. In an additional behavioral study, we optimized our experimental design to minimize expectation and adaptation effects and found that, compared with the baseline condition (no ping), context-dependent pings impaired recall performance, while context-independent pings did not. Together, our results provided clear evidence for two distinct mechanisms underlying pinging the brain, and the ping’s context played a critical role in reactivating and reorganizing activity-silent WM.Significance StatementWorking memory (WM) is the ability to temporarily maintain and manipulate information; notably, it can be maintained in an activity-silent state in which the information cannot be decoded. Such undecodable information can be reactivated by specific visual impulses (i.e., pings), providing direct evidence of activity-silent WM. In this study, we clarified two distinct mechanisms of pinging the brain: pings without contextual information related to the memorized items reactivated WM by reducing noise and did not change the original WM process, while pings with contextual information reactivated and reorganized WM, impairing memory performance. Our findings offer valuable insights for future studies utilizing pings as a research tool and contribute to our understanding of activity-silent WM.