I was reading an aricle that described some research regarding our old standby technique of the pain dial. Luckily Wendi Friesen on her website at wendi.com had the whole article from "The New Scientist" from August 2005.
A fMRI experiment has shown that the hypnotised mind is consciously able to manipulate pain perception. In a study to be published later this year, a team led by Stuart Derbyshire of the University of Pittsburgh in Pennsylvania hypnotised patients with fibromyalgia, a rheumatic condition that causes chronic pain in the extremities. Then he asked the patients to imagine a dial representing their pain. When they turned this imaginary dial down, the patient reported feeling less pain, and fMRI images confirmed that there was less activity in the brain areas responsible for pain. "There was a direct correlation between the subjective pain and the amount of activity in those pain areas," says team member David Oakley of University College London.
The whole article can be found at http://www.wendi.com/html/article001.html.