The amputee optical illusion is a trick used by doctors in which the amputee holds a mirror against their healthy limb at a certain angle, and seeing the reflection in the mirror makes it seem as though there’s another limb where the missing one should be. When they see that the limb is moving freely, their brain is tricked into relieving the pain.
So that’s the illusion, but how does the technique work with arthritis pain? In a new study from the lab of Vilayanur S. Ramachandran (a member of Scientific American Mind’s board of advisers) at the University of California, San Diego, cognitive scientist Laura Case, modified the mirror technique to see if it could also improve the wellbeing of people with arthritis.
For her modified version of the mirror technique, Case superimposed a researcher’s healthy hand over a subject’s arthritic hand. The arthritis sufferers’ hands were painfully constricted or contorted, but when they mimicked the slow, purposeful movements of the researcher’s hand with their own unseen hand, Case discovered that the technique produced great results.
According to Case, the results were that the study participants had an increased range of motion in the previously contorted hand, and they reported that their arthritis pain was slightly lower after they had experienced the illusion of their hand moving smoothly. This led Case to surmise that the toxic soup of inflammatory molecules bathing an arthritic joint is not the only source of painful sensations.
When presenting her results at the Society for Neuroscience meeting last November in Washington, D.C., Case explained, ‘The brain has learned to associate movement with pain.’ This means that the brain needs a way to disconnect the sight from the sensation, and Case says that the illusion provides the brain with this. She concluded by saying that the group of researchers will go on to investigate whether this type of mirror therapy might provide more long-term benefits for arthritis sufferers.