The mind seems to be profoundly affected by changes to the brain. Studies into patients that suffer from various kinds of brain damage have shown some of the most bizzare types of behavior, changes in personality, and interpretations of reality. For example, a condition called anosognosia means "unawareness of illness". One can suffer a severe disabling injury yet be unaware that there is a problem. There is a case of a patient who was unaware that he was blind. A condition known as somatoparaphrenia could cause someone with a paralized arm to claim that it is their brother's arm. There's the story of the man who mistook his wife for a hat. These people can be completely rational in all other respects.
From these examples, and many others, it would appear that our mind is subject to the flaws in the physical brain. It also seems that our personalities are very much dependent on our brains. So, if the soul does survive death, it must be very different from who you consider yourself to be.
An excellent article that goes into these matters in detail can be found
here. An excellent book that goes into these stories and more can be found at
"Phantoms in the Brain". It was certainly an eye opener for me.
Regards,
--Robert