Ah... for the most part, yes? I have not done much work with altered states of consciousness, and most of the books I can think of offhand aren't available on this planet for some reason.

[ What, were you expecting all of the best books on human psychology to have been written by humans? Pshhhhh. ]

Ah, but mutations - definitely that one. In fact, some of my early work--

[ ... Uh. Definitely did not involve human test subjects, move along. ]

... had a lot to do with that. Specifically ones that affected the structure and function of the central nervous system.