A Clue to Interaction between the Visual Areas and Pain Perception

in News
February 25th, 2011

You know how getting an injection is painful? Next time, try looking at your arm for a change.

Researchers at University College London and University of Milan-Bicocca have found that more pain can be tolerated if one looks at the afflicted body part. For instance, in the case of receiving an injection and anticipating pain, one should try looking at the arm to help reduce the pain perceived.

In one experiment, the researchers heated their participant’s hands using a heat probe, and increased the temperature in increments. As soon as participants felt pain, the heat was stopped and their pain threshold and the active brain pathways were noted. Next, they used mirrors to change participation’s perception. They found that the participants could tolerate more pain when shown their own hands in the mirror and tolerated less pain when their hand was blocked from view. Using the pain threshold already noted, researchers found out that on average the participants could tolerate an increase of 3 degrees in temperature when they could see their hand.

Dr. Haggard, a professor of cognitive neuroscience at the University College London, notes that, “You always advise children not to look when they are having an injection or a blood sample taken, but we have found that looking at the body is analgesic-just looking at the body reduces pain levels”. He also adds, “So my advice would be to look at your arm, but try to avoid seeing the needle- if that’s possible”.

Another part of the experiment manipulated the size of the body part that the participants perceived. Researchers used convex mirrors to enlarge the participant’s hands, and found that when a larger hand was shown, the participants tolerated more pain that they did when looking at a normal-sized hand. When the participant’s hands were shown smaller than normal size; their pain tolerance decreased.

This research paves the way for new analysis of pain from within the brain itself. Much is known about pain signal transduction to the brain, but manipulation of signals once they are inside the brain is not well understood. Dr. Paul Nandi, one of the researchers at the UCL hospital notes that “Increasingly there is an interest in what the brain does to the pain signals”. This research also shows the interactions between the visual areas and the areas involved in pain perception, and scientists hope that it will aide in finding a cure for chronic pain. So next time you are getting a flu shot, arm yourself with a magnifying glass and make sure to look at your arm.

Pain reduced by changing what you look at – Rebecca Morelle, BBC News