Working memory undercover
When you follow directions to a new café or keep track of who said what, you rely on working memory. It holds information for seconds to minutes so we can use it right away. Because it supports daily life, understanding it matters for education, aging and mental health.
For decades, the standard idea was that working memory depends on neurons firing continuously. However, this might not be the whole story. The brain can sometimes go quiet between bursts of activity, yet the memory remains available. This led to the idea of “activity-silent” working memory, where short-lived changes in the strength of connections between neurons temporarily store information—like dimming a phone screen to save battery.
In this thesis I examined these states in humans using EEG during wake and after a daytime nap, and in mice using microscopes during sleep deprivation. First, interruptions disrupted both a prioritised item and a deprioritised item similarly: prioritising improved accuracy, but did not uniquely shield memories from distraction. Second, after the nap, participants with longer sleep spindles showed clearer EEG traces of activity-silent memory, suggesting spindles help prepare the system. Third, in mice, the way animals were kept awake mattered: gentle stimulation decreased neural activity, while novel objects increased it.
Overall, working memory seems to be a team effort—brief bursts supported by short-lived connection changes—with sleep helping tune the team for the next day. Next steps are to manipulate spindles and align human and animal tasks directly.