'Self-Touch' May Reduce Pain, Study Finds

FRIDAY Sept. 24, 2010 -- You burn your hand on a hot stove. You grab that hand with the other, and sometimes the pain goes away. Ever wonder why?

British researchers did, and their unusual study suggests that you can reset your brain's image of your body to help eliminate that pain.

The researchers found that they were able to significantly decrease the levels of pain in the hands of people who thought they were experiencing extreme heat. Their method: they told the participants to touch three fingers on one hand to three fingers on the other.

The effects of the "self-touch" approach sounds more than a little peculiar. But it's a tool that "might create new possibilities for pain treatments," said study co-author Marjolein P.M. Kammers of University College London's Institute of Cognitive Neuroscience in the United Kingdom.

At issue is the brain's "body representation," which is a kind of blueprint of your body parts and where they are in the world. "This sounds simple, but it has been shown that we use different representations depending on what we want to do with our body at a certain moment and that these representations can change over time," Kammers said.

Researchers have directly linked phantom limb pain -- in which amputees feel pain in an arm or leg that is no longer there -- to the body representation system.

"One hypothesis is that phantom limb pain after amputation is due to mismatch between the way that the body really is (without a limb) and the way the brain represents it to be (as it was with all limbs intact)," Kammers said. "Once the body representation is appropriately updated, the phantom limb pain is often reduced."

In the new study, researchers wanted to find out if clutching your hands when they're injured may beneficially disrupt the body representation system. Could it fool the brain?

"Pain is not just a signal from the body reaching the brain," Kammers said. "It is modulated in the brain according to how the brain represents the current state of the body."

The researchers didn't want to actually hurt anyone, so they took advantage of a strange phenomenon: if you put your index and ring fingers in warm water and your middle finger in cool water, you will think your middle finger is burning.

The researchers used the illusion to fool people into thinking their middle fingers were extremely hot and then removed their hands from the water. Some participants touched fingers from one hand to another, while others touched someone else's hand.

Those who touched all three fingers to the same fingers on the other hand felt 64 percent less painful heat, the investigators found.

"Self-touch caused the integration of both hands together into a coherent body representation, which caused a reduction in heat pain," Kammers said.

The study shows that "we can think creatively about how to treat pain by changing what the brain understands to be true," said Beth Darnall, an assistant professor at Oregon Health & Science University who is familiar with the study findings. "We can trick the brain out of pain by making it believe certain things about itself."

Doctors already use an approach called "mirror therapy" to reprogram the brains of amputees who suffer from phantom limb pain.

More widespread use of fooling the brain to treat pain is "a little bit down the road," Darnall said, but she thinks studies like this one are paving the way.

The study findings were published online Sept. 23 in the journal Current Biology.

More information

The U.S. National Library of Medicine has details on phantom limb pain.

Posted: September 2010


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