The research paper I have linked to below is refered to in one of Dr Schubiners blogs. I have managed to find the whole text and have added it to the wiki if anyone is interested, I found it fascinating.
The authors have discovered that the pathways in the brain that are activated by emotional distress (in this case, a game where the person is excluded; i.e. social exclusion) are the same pathways that are activated by physical pain. This is great research and supports TMS.
On a number of occasions I have needed to research the brain and pain processing because of part of my career is in this area. Its been many years since I looked at the literature, but I do well recall the relationship between pain and emotional processing.
The interesting thing is that the actual physical sensation of pain is separate from the emotional response to pain. They run in separate nervous system pathways. It would appear that components of the frontal lobes are needed for the emotional experience of pain -- patients with prefrontal lobotomies do not get nearly as "upset" about pain as people with intact brains. They also may show blunted affect in general.
I recall, but do not remember the exact specifics, that there is a spinothalamic tract and also a tract in the spinal cord called the dorsal column. One projects sensory information and the other projects to areas more involved in the emotional response to pain. In other words, they are parallel but distinct pathways and thus can be separated out. There are probably more divisions but those two I recall the most.
I often thing think that we who have TMS have our "emotional response to pain" pathways cranked up through the way we focus on pain and fear it.
There are probably a few inaccuracies in what I recall above, but the basic idea is the correct one.