There was a recent PoE News story about a guy who was in a coma for 23 years who turned out to be conscious, but apparently the "consciousness" was detected via FC, so it's almost certainly the actions of a grieving family, and the guy is a vegetable who should be buried already.
That was an interesting/depressing article, in the sense that it was mostly full of shit, but interesting/horrifying to learn this shit happens.
It's the same desperate need for connection to a lost loved one that leads people to a medium who will channel the spirit of the deceased, except that the person here is "living" and present at the seance.