Researchers have been exploring the link between memories and sleep for a long period of time. During a recent study, they found that the two activities in the brain, slow oscillations and sleep spindles, help keep the memories strong.While we sleep, the brain produces particular activation patterns. When two of these patterns gear into each other, previous experiences are reactivated. The stronger the reactivation, the clearer will be our recall of past events, a new study reveals. Scientists have long known that slow oscillations (SOs) and sleep spindles – sudden half-second to two-second bursts of oscillatory brain activity – play an important role in the formation and retention of new memories.But experts in the UK and Germany have discovered that the precise combination of SOs and sleep spindles is vital for opening windows during which memories are reactivated; helping to form and cement memories in the human brain.Researchers at the University of Birmingham and Ludwig-Maximilians-University Munich today published their findings in Nature Communications.