In my view when a brain is on the way out, you can get all kinds of odd experiences, hallucinations, etc. … some of which may seem to show that the mind can separate from the brain. I don’t think that is really the case, however.
Greyson raises some interesting points, nevertheless. How many brain cells are actually needed to have your particular consciousness?
It would be interesting if we could turn groups of brain cells on and off to see what happened.