People spend approximately half of their waking hours in a so- called offline state — daydreaming, mind wandering or otherwise inattentive to their surroundings. These activities are often viewed as a waste of time, perhaps as moments of lost productivity.
However, periods of offline waking rest can facilitate the consolidation of newly formed memories. Even a few minutes of rest with closed eyes can improve memory, perhaps to the same degree as a full night of sleep. These findings have profound implications for understanding the memory consolidation process, its time course and its underlying mechanisms.
This Review, describes evidence that offline waking rest retroactively facilitates memory. Similar to the beneficial effect of sleep, the effect of rest might be driven by neural- level reactivation of newly formed memory traces. As both rest and sleep seem to support consolidation, the review next considesr whether these two states support the same or dissociable stages of consolidation. Then evidence is reviewed that seconds- long bouts of offline rest occur throughout the day and that even these ultrashort offline periods might benefit memory. Finally, the review concludes by describing future directions for research into the underlying processes of sleep and wake states.
a | Either offline wakefulness or sleep lead to the creation of an enduring, long-term memory trace.
b | Initially, offline wakefulness acts to temporarily stabilize newly encoded memory. After this, sleep acts to promote a more enduring, long-term memory. In this scenario, sleep consolidation depends on the prior waking stabilization, with disruption of stabilization during offline wakefulness preventing subsequent sleep consolidation from occurring.
c | Wakefulness acts to temporarily stabilize memory and sleep acts to promote a more enduring, long-term memory, as in part b. However, sleep and wake consolidation occur in parallel, rather than serially. Disruption of initial stabilization during offline wakefulness would have no effect on the efficacy of subsequent sleep-dependent processing, potentially leading to the impression that sleep ‘rescues’ memory that had been forgotten.
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