Competitive learning modulates memory consolidation during sleep

Competition between memories can cause weakening of those memories. Here we investigated memory competition during sleep by presenting auditory cues that had been linked to two distinct picture-location pairs during wake. We manipulated competition during learning by requiring subjects to rehearse item pairs associated with the same sound either competitively (choosing to rehearse one over the other, leading to greater competition) or separately; we hypothesized that greater competition during learning would lead to greater competition when memories were cued during sleep. With separate-pair learning, we found that cueing benefited spatial retention. With competitive-pair learning, no benefit of cueing was observed on retention, but cueing impaired retention of well-learned pairs (where we expected strong competition). During sleep, post-cue beta power (16-30 Hz) indexed competition-based weakening and forgetting, whereas sigma power (11-16 Hz) indexed memory strengthening. These findings show that memory consolidation during sleep fundamentally engages competition and selective memory weakening.