Parsing the role of sleep in memory processing

•The full extent of post-encoding memory 'evolution' is yet to be determined.•Sleep's role depends on the type of memory and type of processing.•Sleep can stabilize, enhance, integrate, generalize, or abstract memories.•Offline processing during wake tags memories for sleep-dependent processing.

It would be nice if we could talk about sleep and memory as if there were only one type of memory and one type of sleep. But this is far from the case. Sleep and memory each comes in many forms, and furthermore, memories can go through multiple forms of post-encoding processing that must be individually addressed. Finally, sleep stages per se do not affect memories. Rather, the neuromodulatory and electrophysiological events that characterize these sleep stages must mediate sleep-dependent memory processing. In this review, we attempt to parse out the relative contributions and interactions of these often frustratingly complex systems.