Psychologically speaking, what happens to person who is locked up in a penitentiary's isolation unit?

Or I suppose anyone who's in a situation that leaves them isolated for an extended period of time.Psychologically speaking, what happens to person who is locked up in a penitentiary's isolation unit?
They wouldn't be like a normal person. Since they have no one to talk to too, and this depends for how long it lasts, they might start talking to themselves. Maybe imaginary friends, becuase the human race is social to some degree, even the anti-social people need to be in some sort of social situation. Different things will happen to differnt people, going crazy, talking to imaginary people, doing crazy stuff. Being alone for an extended period of time can screw up people. Psychologically speaking, what happens to person who is locked up in a penitentiary's isolation unit?
Depends on their psychological vulnerability. Since man is a social being, isolation becomes a strain and is actually a soft form of torture or punishment. Man loses touch with reality slowly and on the extreme, their minds.
I think this could be the video berea_ky_girl is talking about





http://video.google.com/videoplay?docid=鈥?/a>
They become lonely. They lose track of reality.
The best way to see this upfront is to watch the movie, Cast Away with Tom Hanks..awesome movie..