Sleep Resolves Competition Between Explicit and Implicit Memory Systems

Sleep supports stabilization of explicit, declarative memory and benefits implicit, procedural memory. In addition, sleep may change the quality of memory representations. Explicit and implicit learning systems, usually linked to the hippocampus and striatum, can compete during learning, but whether they continue to interact during offline periods remains unclear. Here, we investigate for feedback-driven classification learning, whether sleep integrates explicit and implicit aspects of memory. The negative relationship between implicit and explicit memory components was resolved over sleep, but not wakefulness. Additionally, sleep benefitted performance on a task that allows the cooperative use of explicit and implicit memory, and participants who slept showed superior performance in generalizing their knowledge to unseen exemplars. A reinforcement learning model relates this to better transfer of the learned exemplar value representation after sleep. This suggests that sleep integrates information learned by different routes and helps us respond optimally to everyday life contingencies.