Anninva,

I cannot answer your questions because I do not know the answers. I am taking 4 drugs and every one of them warns of hallucinations as a side effect, in addition to the disease itself. It is such a chemical soup I don't know what causes what. I know that the elderly with dementia can slip deeply into an unreal world.

It is a frightening thing to face. One way to make it less frightening is to see it. Dr. Sacks is not talking about near-death hallucinations; he is talking about people who live with hallucinations in their every day life. This does not help in dealing with the disease, but I find it helps in humanizing it, to reduce the fear of it.
Dr. Sacks latest:
http://www.oliversacks.com/books/hallucinations/