You know on such a topic it would be relevant to bring up the matter of training. A study was done here in Australia on our Special Force elements, namely the Special Air Service Regiment and 2Commando Regiment. I believe the study was done on these members during black role, as they trained for home or close-to counter-terrorist incidents under the esteemed Tactical Assault Group (
http://www.youtube.com/watch?v=XJdreNh1nxE).
The 'overstimulation' of certain parts of the brain caused operators to 'overdevelop' and make more use of these areas due to the unrelentless degree of high intensity training on a daily basis over a intermediate to relatively long period of time.
I have no reference as it was on the news for a short period of time, then vanished and I cannot find it published.
But, to cause more interactions of the body and advances within neural developments or stimulation, this could probably be true to some degree. Of course they are secreting more hormones than the average human, and their workload is a lot more mentally and physically demanding - as they say, it sharpens the mind.
Their body 'norms' and degree of sensitivity to stimulation, or specific stimulants, would be at a different level and boundary limit to others. Just a thought...