Current Biology
Volume 26, Issue 3, 8 February 2016, Pages 396-403
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Local Slow Waves in Superficial Layers of Primary Cortical Areas during REM Sleep

https://doi.org/10.1016/j.cub.2015.11.062Get rights and content
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Highlights

  • Slow waves with neuronal OFF periods, typical of NREM sleep, occur in REM sleep

  • REM slow waves mainly occur in layers 3 and 4 of primary sensory and motor cortex

  • REM slow waves may partly account for sensory disconnection during REM sleep

Summary

Sleep is traditionally constituted of two global behavioral states, non-rapid eye movement (NREM) and rapid eye movement (REM), characterized by quiescence and reduced responsiveness to sensory stimuli [1]. NREM sleep is distinguished by slow waves and spindles throughout the cerebral cortex and REM sleep by an “activated,” low-voltage fast electroencephalogram (EEG) paradoxically similar to that of wake, accompanied by rapid eye movements and muscle atonia. However, recent evidence has shown that cortical activity patterns during wake and NREM sleep are not as global as previously thought. Local slow waves can appear in various cortical regions in both awake humans [2] and rodents [3, 4, 5]. Intracranial recordings in humans [6] and rodents [4, 7] have shown that NREM sleep slow waves most often involve only a subset of brain regions that varies from wave to wave rather than occurring near synchronously across all cortical areas. Moreover, some cortical areas can transiently “wake up” [8] in an otherwise sleeping brain. Yet until now, cortical activity during REM sleep was thought to be homogenously wake-like. We show here, using local laminar recordings in freely moving mice, that slow waves occur regularly during REM sleep, but only in primary sensory and motor areas and mostly in layer 4, the main target of relay thalamic inputs, and layer 3. This finding may help explain why, during REM sleep, we remain disconnected from the environment even though the bulk of the cortex shows wake-like, paradoxical activation.

Keywords

REM sleep
local sleep
cortical layers
laminar recordings

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