I usually don't remember my dreams (and if I do, memories are usually very vague). However, I still have a sense of time passing when I sleep - ie: I wake up in

I usually don't remember my dreams (and if I do, memories are usually very vague). However, I still have a sense of time passing when I sleep - ie: I wake up in the morning and I feel like some number of hours have passed since I went to sleep, even if I can't remember what happened during those hours. I've been under general anaesthesia once, and there was no sense of time passing. One instant I was in the OR, the next I was in the PACU. If you'd asked me, I'd have had no way of telling you if I'd been out for 20 minutes or 8 hours (I was out for about three).