Subregions within the rostral anterior cingulated cortex (rACC) are involved in mediating the conscious perception of pain, a team led by Dr. R. Christopher deCharms explains in their report in the Proceedings of the National Academy of Sciences for December 20. They reasoned that subjects can learn to activate the rACC and thereby alter pain perception.
"It is well understood that if you electrically activate brain regions that produce pain you can make pain go away," Dr. deCharms told Reuters Health. "It is also understood that if you use opiates to activate those regions, you can make pain go away, but typically a person cannot consciously control that system."
To test their theories, Dr. deCharms, with Omneuron Inc. in Menlo Park, California, and his associates tested healthy volunteers, using as a pain stimulus a thermode placed on the palm of their hand, with temperature levels selected that would yield the maximally painful stimulus that each subject could tolerate without moving.
"There are two key elements that someone needs to learn how to control brain activation," Dr. deCharms said.
"One is initial guiding instructions to give them strategies to try to control brain region." These include shifting attention away from the pain, and consciously attempting to perceive the stimulus as a neutral sensory experience rather than one that is tissue damaging or frightening.
"Second, they need real-time neuroimaging information, what we're calling neuroimaging therapy, that allows them to watch second by second activation in the brain region that they are trying to control and learn how to control it."
Results for eight healthy volunteers showed that their control over activation in the rACC as seen by rtfMRI increased over three training runs of 13 minutes each.
By the last training run, when they were instructed to increase activation of the brain area, they rated the stimulus as significantly less painful than when they were told to decrease activation.
There was a significant correlation between the induced changes in rACC activation and the corresponding difference in pain intensity ratings (p < 0.0007). The participants showed a 23% enhancement in control over pain intensity (p < 0.001) and a 38% enhancement in control over pain unpleasantness, an affective measure of pain (p < 0.01).
"Control experiments demonstrated that this effect was not observed after similar training conducted without rtfMRI information, or using rtfMRI information derived from a different brain region or sham rtfMRI information derived previously from a different subject," the authors write. Another control group received autonomic biofeedback information rather than rtfMRI, and they, too, failed to control brain activation.
"All of those experiences would be expected to work if this was a placebo effect, and none did," Dr. deCharms said.
The investigators repeated the experiments among eight chronic pain patients who had in the past failed to achieve pain relief from pharmacologic, psychological, and behavioral interventions.
They observed a 64% decrease in McGill pain questionnaire (MPQ) pain rating sums after brain activation training (p < 0.00015) and a 44% decrease in visual analog scale pain ratings (p < 0.0016). There were significant correlations between the extent to which patients learned to control rACC activation and their decrease in pain ratings.
However, Dr. deCharms stressed, this was just a pilot study, and more research testing this training is under way. "This is quite some ways away from being ready for the clinic, so we don't want to create false hopes among chronic pain patients," he added.
By Karla Gale
Last Updated: 2005-12-12 17:00:15 -0400 (Reuters Health)
Proc Natl Acad Sci USA 2005;102:18626-18631.
U.K. science center to probe mysteries of the mind, January 17, 2005
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