Yes, AFAIK the brain is electrically the most similar to being awake when it is in REM. I’ve seen deep sleep used synonymously with “deep NREM” (non-REM). The

Yes, AFAIK the brain is electrically the most similar to being awake when it is in REM. I’ve seen deep sleep used synonymously with “deep NREM” (non-REM). They are indeed different, but both support cognitive function in different ways.