One theory of memory consolidation posits that certain memories initially depend on the hippocampus but then gradually are transferred to the neocortex [37], possibly during slow-wave sleep. In slow-wave sleep, hippocampal neurons that were co-active during wakefulness reactivate together during sharp wave-ripples [38]. Similarly, mPFC neurons that fired together during waking reactivate together during subsequent slow-wave sleep [39]. Reactivation of mPFC neurons may be coordinated by synchronously occurring hippocampal sharp wave-ripples and mPFC spindles because correlations between hippocampal and mPFC firing during slow-wave sleep occur preferentially around the time of sharp wave-ripples (Figure 1c, [40•]), and mPFC spindles tend to occur shortly after sharp wave-ripples are seen in the hippocampus [41].
