Phantom sensations have been a mysterious symptom that amputees often experience in their missing limbs. This phenomenon has fascinated clinicians and the public in general, and now researchers from Karolinska Institutet in Sweden have developed a simple way to recreate the sensation, without losing an arm and a leg. The technique involves caressing a hand that’s hidden from the subject using a paint brush while doing the very same to an empty space that the person can see. When a knife is surprisingly introduced and is used to swipe at the free space, the subject reacts as though there’s fear of being injured.
The researchers, beside noting the behavioral reaction, confirmed the findings using functional MRI that showed brain regions mapping to the “missing limb” are activated when the knife makes its appearance.
From the announcement:
“Taken together, our results show that the sight of a physical hand is remarkably unimportant to the brain for creating the experience of one’s physical self,” says [study lead] Arvid Guterstam.
The researchers hope that the results of their study will offer insight into future research on phantom pain in amputees.”This illusion suggests that the experience of phantom limbs is not unique to amputated individuals, but can easily be created in non-amputees,” says the principal investigator, Dr Henrik Ehrsson, Docent at the Department of Neuroscience. “These results add to our understanding of how phantom sensations are produced by the brain, which can contribute to future research on alleviating phantom pain in amputees.”
Here’s one of the study authors talking about and demonstrating the experiment you can actually try at home:
Study abstract in Journal of Cognitive Neuroscience: The Invisible Hand Illusion: Multisensory Integration Leads to the Embodiment of a Discrete Volume of Empty Space
More from Karolinska Institutet: Scientists create phantom sensations in non-amputees