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REM sleep (random eye movement sleep) is the fourth stage of sleep in which the eyes can be seen to be moving rapidly behind the eyelids. It is associated with increased brain activity and dreaming, but decreased muscle tone.
Neuronal learning activity is reactivated during sleep but the dynamics of this reactivation in humans are still poorly understood. Here the authors show that memory processing occurs during all stages of sleep in humans but that reprocessing of memory content in REM and non-REM sleep has different effects on later memory performance.
Dreaming occurs in REM sleep, yet the neural mechanisms involved in generating it are not understood. Here Cox and colleagues show that glutamatergic neurons in the dorsal pons are activated most during transition to REM sleep while GABAergic neurons are more active during waking state.
Since the discovery of rapid eye movements (REMs), a critical question endures as to whether they represent time points at which visual-like processing is updated. Here the authors demonstrate that cortical activity during sleep REMs shares many properties with that observed during saccades and vision.