Such 'highly damaged' brain is still 90 percent or more structured the same as a normal human brain. See it as a brain that runs in debug mode.

It is known that the narrative part of the brain is separate from the decision taking brain. If someone asks you, in a very convincing, persuasive way, why you did something a year ago and you can't clearly remember you did, it can happen that you become positive that you did so anyway. And then the mind just hallucinates a reason. That's a trait of brains.