Well, if mind is indeed an epiphenomenon of brain, then the fact that we can change our mind’s structure already told us we could change our brain structure. It’s just that the brain changes are undetectable with current technology.

If it isn’t, then the original question is of marginal interest.

Of course, there’s always another way for the mind to change the brain. Suppose I fall into a deep, suicidal depression and resolve to take my life. Being of a gruesome temperament, I take an icepick and… ummm details omitted for propriety… but fail to complete the job. Unfortunately, I do manage to inflict serious brain injury on myself and proceed through life with much altered intellectual capacities.

So in this case, something in my mind — the depression — led to a change in the brain — the injury.

I realize there are differences between that and the changes in the taxi driver’s brain form doing a lot of geolocating. But when you get down to it, both kinds of changes are mediated by physical processes: the former by signals to the muscles to pick up an ice pick and proceed with the deed; the latter, presumably by some yet undiscovered neurological/biochemical process in the body. But is there a fundamental difference from a philosophic standpoint?

–David.