Michael Egnor has a fascinating post on neurosurgeon Wilder Penfield’s evidence-based conversion from materialism to dualism:
Penfield began his career as a materialist, convinced that the mind was wholly a product of the brain. He finished his career as an emphatic dualist.
During surgery, Penfield observed that patients had a variable but limited response to brain stimulation. Sometimes the stimulation would cause a seizure or evoke a sensation, a perception, movement of muscles, a memory, or even a vivid emotion. Yet Penfield noticed that brain stimulation never evoked abstract thought….
Penfield noted that intellectual function – abstract thought – could only be switched off by brain stimulation or a seizure, but it could never be switched on in like manner. The brain was necessary for abstract thought, normally, but it was not sufficient for it. Abstract thought was something other than merely a process of the brain….
Furthermore, Penfield noted that patients were always aware that the sensation, memory, etc., evoked by brain stimulation was done to them, but not by them. Penfield found that patients retained a “third person” perspective on mental events evoked by brain stimulation. There was always a “mind” that was independent of cortical stimulation.
It’s worth reading the rest of the post to see the relevant quotes from Penfield himself.