How REM and non-REM sleep may work together to help us solve problems -- ScienceDaily
Suppose I give you a creativity puzzle where you have all the information you need to solve it, but you can't, because you're stuck," says first author Penny Lewis, a professor at the Cardiff University School of Psychology. "You could think of that as you've got all the memories that you need already, but you need to restructure them -- make links between memories that you weren't linking, integrate things that you weren't integrating."
Studies show that this kind of restructuring often happens while we are asleep, so Lewis and her co-authors drew on that literature, as well as physiological and behavioral data, to create a model of what might be happening during each stage. Their model proposes that non-REM sleep helps us organize information into useful categories, whereas REM helps us see beyond those categories to discover unexpected connections.