Why Rubbing an Owwie Works

New findings show that the way the mind pictures the body plays a role in our perception of sharp pains. And so touching our own body may help the brain get a clearer picture of what's happening in the body and may lessen pain.

A mental representation of the body was thought to be a factor in only chronic pain sufferers. For example, studies of amputees who experience phantom limb pain have shown their pain may be caused by a mental picture of the body that isn't up-to-date, so to speak. A mirror can be used to fool the brain into thinking the limb is still present, and can often alleviate the pain.

A new study published online today (Sept. 22) in the journal Current Biology shows that mental pictures are also important in the experience of acute pain.

Using a method called the thermal grill illusion, a team of researchers, led by Marjolein Kammers of the University College London, asked participants to place their index and ring fingers of both their left and right hands in water warmed to about 109 degrees Fahrenheit (43 degrees Celsius). At the same time, the participants submerged their middle fingers in water cooled to 57 degrees Fahrenheit (14 degrees Celsius).

The difference in the temperatures creates the illusion that the middle fingers are in extremely hot water and causes pain — the brain has been tricked into thinking the fingers have been scalded when they haven't. The pain is caused by the way the brain integrates the differing signals coming from the fingers.

The participants were next instructed to touch the fingers of one hand to the other, and they reported a 64-percent reduction in the pain they felt in their middle fingers.

"Interestingly, this significant drop in heat was only reported when the subject's own hands experienced the illusion and both hands were pressed together," Kammers said.

The team concluded that touching the hands together was not only providing the brain with feedback about the fingers' real temperature, it also allowed the brain to create a more coherent picture of the body.

"In other words, self-touch affects how the brain represents the current state of the body," Kammers said, “and that can influence the way we experience pain.”

Self-touch has the potential to become a part of the pain doctor’s toolkit, but there is still much to learn about how it modulates pain. Also needed is a better understanding of where the brain stores knowledge about the present state of the body.

If Kammers and other scientists can answer these questions, it could lead to more effective methods of treating individuals who suffer from acute and chronic pain, she said.

"It's challenging but also exciting to do these kinds of studies," Kammers told MyHealthNewsDaily.

She plans to next study the underlying brain processes behind the interaction of self-touch and pain experience.

This article was provided by MyHealthNewsDaily, a sister site to LiveScience.