Induction of cortical ON/OFF periods in awake mice fulfills sleep functions.

Can animals obtain core benefits of sleep while remaining awake? In mammals, slow-wave sleep is characterized by synchronized neuronal activity alternating between ON and OFF periods. Slow-wave activity and synchrony reflect sleep need, are correlated with synaptic strength in cortical circuits, and promote synaptic down-selection and memory consolidation. To address the above question, we locally induced alternating ON/OFF periods during wakefulness using optogenetics in mice. This led to a local, ipsilateral reduction of slow-wave activity and synchrony during subsequent sleep and to reduced markers of synaptic strength. Moreover, bilateral induction of OFF periods over sensorimotor cortex during sleep deprivation restored memory consolidation. Thus, inducing ON/OFF activity during wakefulness is sufficient to reduce local sleep need and fulfills core functions of sleep.