Sleep: off-line memory reprocessing.

Behavioral studies of memory and learning in both humans and animals support a role for sleep in the consolidation and integration of memories. Physiological studies of hippocampal and cortical activity as well as of brainstem neuromodulatory systems demonstrate the state-dependence of communication both between and within the neocortex and hippocampus. These findings are consonant with observed cognition during sleep and immediately following awakening.