Ah, ganzfeld. It reminds me of Altered States, a movie about sensory deprivation that went horribly wrong. I was fascinated by this movie when I was a kid.

http://en.wikipedia.org/wiki/Altered_States

http://www.youtube.com/watch?v=MbYT3UclhNY (trailer)

http://www.youtube.com/watch?v=LTqFXfn3kdo (few scary scenes)