Reactivating ordinal position information from auditory sequence memory in human brains

Abstract

Retaining a sequence of events in their order is a core ability of many cognitive functions, such as speech recognition, movement control, and episodic memory. Although content representations have been widely studied in working memory (WM), little is known about how ordinal position information of an auditory sequence is retained in the human brain as well as its coding characteristics. In fact, there is still a lack of an efficient approach to directly access the stored ordinal position code, since the neural activities enter a relatively activity-silent WM state during WM retention. Here participants performed an auditory sequence WM task with their brain activities recorded using electroencephalography (EEG). We developed new triggering events that could successfully reactivate neural representations of ordinal position from the activity-silent retention stage. Importantly, the rank reactivation is further related to recognition behavior, confirming its indexing of WM storage. Furthermore, the ordinal position code displays an intriguing stable-dynamic format, i.e., undergoing the same dynamic neutral trajectory during both encoding and retention (whenever reactivated). Overall, our results provide an effective approach to access the behaviorally-relevant ordinal position information in auditory sequence WM and reveal its new temporal characteristics.