Researchers at Aalborg University have devised a test using virtual reality to trick the brain into thinking it is still in control of a missing limb. They suggest this may help ease phantom limb pain.
“The tactile representation of different body parts are arranged in the brain in a sort of map,” explains Bo Geng, Postdoc at the Faculty of Medicine at Aalborg University in Denmark
“If the brain no longer receives feedback from an area, it tries to reprogram its signal reception map. That is the most common conception of how phantom limb pain occurs,” she says, in a media release from Aalborg University.
The foundation of the test is to place a mirror at an angle in front of the chest, to create the visual illusion that the body is symmetrical. If one then pretends to do the same movements simultaneously with both hands, the brain in many cases can be convinced that it is in contact with an amputated hand, for example.
Geng developed the test in collaboration with Dr Martin Kraus and Master’s students Bartal Henriksen and Ronni Nedergaard Nielsen from Medialogy at Aalborg University.
“The mirror therapy has some limitations because you have to physically sit down in front of a mirror, do the same movement in a confined space with both hands at the same time and keep your eyes on the mirror. The illusion can easily be broken,” Geng explains, in the release. “With virtual reality there is a much better chance of creating a convincing alternative reality.”
In the new method, the patients put on VR goggles and a glove. At the same time, small electrodes are placed on the residual limb. Then, by stimulating the stump with tiny electrical impulses, the sensation of the phantom hand can be recreated.
The amputee then plays a number of different VR games that involve doing the same thing with both hands, such as grabbing a pole that has to be twisted into different shapes or pushing different virtual buttons.
“Even though a person who has had a hand amputated can no longer see it, in many cases he or she can still feel it. This sensory conflict may be interpreted by the brain as pain. With this new method we try to overcome that conflict by providing an artificial visual and tactile feedback and in that way suppress the pain,” Geng adds, in the release.
The researchers note that their virtual reality test only works with upper body amputees, but students at Aalborg University are developing a version for people who have had a foot or leg amputated.
[Source(s): Aalborg University, Science Daily]