What separates the soul from the brain, or are they both the same thing?

If a brain of an older person was to be transplanted into an entirely new body (granted science is not yet capable of doing so), my expectation would be that the older person would continue to exist but in a younger body.

So basically, a person can receive a transplant of any organ and continue being that same person, unless the organ in question is the brain. So if a young person takes a brain transplant they effectively would cease to be. Or would their soul still exist within the body (as opposed the brain) and drive the new brain?

So what separates the soul from the brain? We all have brains but they all behave very differently. Is it our brain and our experiences that determines our path and the decisions we make, or is this driven by the soul? Does a persons true self stem from the brain or the soul?

Is it experiences that make one person good and another bad? Is badness a dysfunctioning of the brain?