The cognitive activity of sleep.
D003071:Cognition / Q000502:physiology*; D006801:Humans; D007858:Learning / Q000502:physiology; D008568:Memory / Q000502:physiology; D008960:Models, Psychological; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation; D012895:Sleep, REM / Q000502:physiology