Psychologists widely recognise the existence of the Rubber Hand Illusion – where the brain is tricked into feeling pain on a dummy hand – but new research by the University of Hull shows for the first time that the mind can also be tricked into experiencing pain relief on the fake limb too.
It is the first known demonstration that a placebo (false) analgesic effect can be induced through the application of a treatment to an artificial limb. The results could help with the treatment of a number of pain-related conditions such as phantom limb pain.
During the Rubber Hand Illusion, one hand is obscured from view with a partition and substituted with a fake hand. As the brain works to pull together the sensory information it is presented with, it is confused into believing that the external object is part of the body. The brain believes the rubber hand is the body’s actual hand to such an extent that when a pain stimulus is introduced, people feel the physical sensation of that pain as if it were being administered to a real limb.
Progressing the Rubber Hand Illusion to its next stage, Dr Matthew Coleshill, Professor Giuliana Mazzoni, and Dr David George at the University of Hull have demonstrated that it is possible to trick the mind into reducing that pain sensation too – when a placebo treatment is used.
Having replicated the Rubber Hand Illusion, with participants experiencing a pain sensation on the rubber arm, researchers introduced a placebo ‘treatment’ cream as a powerful analgesic called ‘Lidocaine’. The application of the cream to the rubber arm significantly decreased the severity of the reported pain – despite the treatment being applied to a fake limb and containing no analgesic properties at all. The placebo contained only moisturiser with an addition of the treatment containing no analgesic properties at all. The placebo contained only moisturiser with an addition of an alcohol sanitiser to imitate a medical smell.
The groundbreaking study has implications for the treatment of a range of conditions where sufferers experience chronic pain including phantom limb pain (where amputees still sense pain in a limb post-amputation), Fibromyalgia and Complex Regional Pain Syndrome.