Le travail de la mémoire pendant le sommeil

The beneficial role of sleep in processes of learning and memory is a commonly accepted view. This review is intended to clarify this role, taking as an example the consolidation, one of the best studied aspects of memory. Consolidation is a dynamic process that protects learning from interference and facilitates performance after a variable period from a few hours to several days. Several teams have shown that sleep improves the consolidation of declarative and procedural memory. It also appears that the respective roles of slow-wave sleep (SWS) and paradoxical sleep (PS or REM sleep) are quite different. Memory consolidation of learning tasks that involve the hippocampus (declarative memory) is facilitated by slow-wave sleep. Paradoxical sleep, in turn, increases performance memory for procedural learning tasks where the hippocampus is not involved. Interdisciplinary approaches in humans and animals led us to suggest hypotheses about the mechanisms of memory regulated by SWS and PS. SWS could be a privileged period without plastic changes, which protects learning from interferences and allows the transfer of information between hippocampus and neocortex. By contrast, during PS, the dialogue between cortical areas seems limited but longterm synaptic reorganizations could provide basis for memory consolidation.