The truncated abstract from the article by deCharms et al. in PNAS follows:
"If an individual can learn to directly control activation of localized regions within the brain, ...this... could potentially provide a different route for treating disease. ... Here, we found that by using real-time functional MRI (rtfMRI) to guide training, subjects were able to learn to control activation in the rostral anterior cingulate cortex (rACC), a region putatively involved in pain perception and regulation. When subjects deliberately induced increases or decreases in rACC fMRI activation, there was a corresponding change in the perception of pain caused by an applied noxious thermal stimulus. ..... Chronic pain patients were also trained to control activation in rACC and reported decreases in the ongoing level of chronic pain after training. "
See also "Believe in Your Placebo" which reviews experiments showing how rACC and other brain areas are altered during the placebo effect.