Memory processing during human sleep as assessed by functional neuroimaging

Sleep is believed to participate in memory consolidation, possibly through off-line processing of recent memory traces. In this paper, we summarize functional neuroimaging data testing this hypothesis. First, sleep deprivation disrupts the processing of recent memory traces and hampers the changes in functional segregation and connectivity which underpin the gain in performance usually observed in subjects allowed to sleep on the first post-training night. Second, experience-dependent changes in regional brain activity occur during post-training sleep. These changes are shown to be related to the processing of high-level material and to be modulated by the amount of learning achieved during the training session. These changes do not involve isolated brain areas but entire macroscopic cerebral networks. These data suggest a role for sleep in the processing of recent memory traces.