In the dark room people would hallucinate because there's nothing to focus attention on.
Now in the absence of information, the human brain carries on working and processing information,
even if there's no information to process.
After a while it starts to create that information itself.
Held in the dark for months, Brian Keenan experienced the most terrible hallucinations.
I can remember one distinctly, because it was dreadfully lucid and clear.
It was about being alone and in a desert and being very, very hot
and then being instantly bone-numbingly cold.
Having the... the winds of the desert stripping away, as if you could feel your flesh falling off you.
And so you were left as a bony hulk shivering in the corner.