Recruitment of a Long-term-memory Supporting System During Repeated Maintenance of an Abstract Visual Image in Working Memory: An EEG Study

Humans can flexibly transfer information between different memory systems. Information in visual working memory (VWM) can for instance be stored in long-term memory (LTM) when a scene is repeatedly memorized. Conversely, information can be retrieved from LTM and temporarily held in WM when needed. It has previously been suggested that a neural transition from parietal- to midfrontal activity reflects transfer of information from WM to LTM during repeated visual search for the same single item. However, whether these observed neural changes truly represent consolidation and are also observed when memorizing and (explicitly) recollecting a rich visual scene (rather than a single target), remains unclear. The current EEG study investigates whether such a gradual shift in memory-correlates is also observed when an abstract colour-array is repeatedly memorized and explicitly recollected in a WM paradigm. Importantly, we tested the functional significance of a neural shift for longer-term consolidation in a subsequent recognition task. Our results provide supporting evidence for recruitment of an LTM-supporting storage system during WM, which facilitates visual WM maintenance and is indexed by (sustained) modulation of a midfrontal component. Enhanced explicit memory recollection during WM is associated with- and possibly facilitated by an emerging late contralateral parietal activity.