There is a discussion of this in Kelly McGonigal's talk here: http://www.buddhistgeeks.com/2012/02/bg ... -practice/
She first discusses how in some studies meditators are able to be mindful of the pain without getting caught up in thinking about it:
So this is the front of the brain. And what you see here, the blue parts, those are the areas of the brain that are more active in non-meditators. OK. And you’re seeing, this is essentially looking like that default network that I showed you earlier. Meditators on the other hand, what you see is the only area of the brain that is more active are the areas that are listening to pain. The areas of the brain like the insula or the thalamus that are just waiting to feel the pain that is happening, that are giving you perfect information about what is happening in your body.
And yet, meditators were able to tolerate much more pain, even as they carefully attended to it. And I think those of you who have a strong practice will immediately recognize this is how we dissociate pain from suffering that when we attend directly to the experience and turn off that inner chatter, suddenly the experience of suffering that seems to arise from pain starts to dissolve.
And within the meditator’s group, the greater the decoupling, the functional decoupling between these two brain systems, paying attention to the feeling of pain and making a commentary about it, the greater they were dissociated, the higher the meditator’s pain tolerance was.
Then she goes on to this study of less-experienced meditators:
OK now, it is really important I think as a teacher of meditation to notice that this is what happens in experienced meditators.
This is the study lead by researchers at Wake Forest University that took brand new meditators. They’d only been meditating for four days. Mindfulness meditation. And when they were brought into the laboratory and given the exact same pain test, the heat stimulations to the leg, turns out that the successful meditators, those who could tolerate greater levels of pain or found the pain less unpleasant, that they were doing exactly the opposite in their brain than what experienced practitioners too.
They were inhibiting sensory information that somehow they were shifting their attention to ignore what was happening in the present moment. And that was giving rise to less suffering, inhibiting awareness rather than carefully attending to. And I think those of you who teach recognize this as something that often happens when we start to practice. We accidentally end up doing exactly the opposite of what the practice is asking of us. And sometimes we experience what seems to be pretty good results. And I think studies like this can really give teachers insight into how that process is happening in the mind and in the brain so that we can better guide people thru and beyond that.