[claylimo]

Being aware while asleep is something that can happen to advanced meditators. The more aware you are the more you are there is no difference between being awake or asleep. I haven’t heard it brought up in any other contexts except maybe for lucid dream practitioners. I’ve also read accounts from those who have done dark room retreats where perception of being awake and asleep blur and the perception of what you are experiencing has a lot of mind generated in experiences that can seem very real, dream-like, or using Buddhist language, empty.

[mikelevins]

I went to school at Naropa University, where a lot of meditation was part of the required curriculum (at least, when I was there; I have no idea what it's like now). I never experience the awake/asleep thing in connection with meditation, either at Naropa or in meditation practice outside the school, but I doubt that I could be in any way considered an advanced meditator.

[claylimo]

Should be clear: not every advanced meditator experiences this and is not a prerequisite to be “advanced”. It would just not be unusual if it did happen.