Sleep aids us in original ways to consolidate our memories. Being deprived of it during the night which follows day-time learning activities significantly diminishes our memory's performance.

Why do we sleep? And what roles do the different sleep components play, such as rapid eye movement sleep (REM) and slow wave sleep (non REM)? The answers are far from being cut and dried and several points of view are disputing a terrain on which there exist as many doubts as certainties.

The relationships between sleep and memory are at the heart of numerous studies. Should one believe the Nobel Prize for medicine winner Francis Crick when he argues that REM sleep, which is a great generator of dreams, performs the principal task of eliminating 'excesses of memory', or irrelevant memories? Or should one, alternatively, follow close on the heels of those who attribute to this sleep phase the mission of stabilizing mnesic traces, those phenomena which remain very mysterious but enable us to reconstruct our memories?

In fact, although the elimination and stabilisation of such ‘imprints’ are judged complementary by the majority of neurobiologists, Crick's theory has yet to be corroborated by the data of a single authoritative experiment. By contrast, the thesis that what has been learned is consolidated during sleep is no longer to be treated with suspicion. Sleep, sleep, and tomorrow you will perform better! Not only will you have recovered better but, moreover, the brain will have made use of the night to ‘impregnate itself’ with all the data it has been force fed in the preceding hours. Four researchers at the Cyclotron Research Centre (CRC), Pierre Maquet, Steven Laureys, Philippe Peigneux, now a professor at the Free University of Brussels (ULB), and Pierre Orban have contributed significantly to advances in the knowledge of this particular field.