Figure 1: Model of the neurophysiological basis of sleep’s function on memory and cognition. Brain states cycle throughout the night between nREM and REM sleep stages. Early in the night (a), SWS predominates with interleaving bouts of REM sleep. The evolution of the memory varies across these cycles (b). At the beginning of the night (A), recent memories (represented by various shapes) are active. In early SWS, overlapping recent memories (illustrated as circles and squares) are integrated. During interleaving REM (B), similar existing memories (circles and squares) and new memories with future relevance are tagged for integration in subsequent SWS bouts (C).