Waking experiences are replayed in multiple parts of the brain in a coordinated fashion during sleep, reports a paper in the January issue of Nature Neuroscience.
Matt Wilson and colleagues recorded neural activity in the hippocampus and visual cortex of rats during a part of the sleep cycle called slow wave sleep and during intervening sessions of awake activity, which included time spent running back and forth on a track. Previous research by the same group had shown that hippocampal activity during slow wave sleep often recapitulates sequences of activity produced when the rat traverses a path during waking. The function of such replay remains unclear, but it has been suggested to be important for learning and memory, perhaps by solidifying memories of events experienced during waking.
The authors now report that similar replay activity is also observed in the visual cortex, and that replays in the hippocampus and visual cortex tend to occur at the same time. The results suggest that memory representations of the same event are reactivated during sleep across multiple brain areas. This study did not test the function of coordinated replay activity, but the authors suggest that it may be involved in the transfer of information from the temporary storage space provided by the hippocampus to more permanent representations in the neocortex.
Matthew Wilson (Massachusetts Institute of Technology, Cambridge, MA, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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