Sleep-wake state and memory function.

Facility of memory formation and retrieval is affected by sleep-wake state. This paper discusses memory function while individuals are awake, but sleepy, at the transitions in state (i.e., wake to sleep and sleep to wake), and in REM and NREM sleep. The basal state of arousal at the time of memory function seems to be critical and the sleepy state, state transitions, and NREM sleep seem to define a continuum of arousal with respect to memory function. While different memory systems have been described, the effect of sleep-wake state on memory systems appears to be non-specific. Finally there is a shift in neurobiology from the NREM to REM state and memory function also appears to change in REM sleep.