By using virtual reality (VR) it is possible to create a
simulated experience of being present in a 3D world where one can move
around freely and touch and interact with objects. A new test devised by
researchers at Aalborg University (AAU), Denmark, shows that VR
technology can trick a person’s brain into thinking that it is still in
control of a missing limb and thus can ease phantom limb pain.
A subject tests AAU’s VR method to relieve phantom limb pain at the China Rehabilitation Research Center. Photograph courtesy of Geng.
“The
tactile representation of different body parts are arranged in the
brain in a sort of map,” explained Bo Geng, PhD, with the AAU faculty of
medicine. “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.”
Tests have shown that
phantom limb pain can be relieved if the brain is tricked into thinking
that the amputated limb is still attached to the body. A mirror placed
at an angle in front of the chest of a person with an upper-limb
amputation can create the visual illusion that the body is symmetrical.
If the person then pretends to do the same movements simultaneously with
both hands, in many cases the brain can be convinced that it is in
contact with an amputated hand. The method has proven effective in
numerous people with amputations and is the foundation for a new method
that has been developed by Geng in collaboration with Martin Kraus, Dr.
rer. nat. in computer science, and master’s degree students Bartal
Henriksen and Ronni Nedergaard Nielsen from the medialogy program at
Aalborg University.
In the new method, the patient wears VR
goggles and a glove on the intact hand, and small electrodes are placed
on the residual limb. By stimulating the residual limb with tiny
electrical impulses, researchers try to re-create the sensation of the
phantom hand. The patient plays 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 virtual buttons. In VR, the
patient feels as if he or she is using both hands.
“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,” said Geng.
The new approach underwent
its first clinical test at the China Rehabilitation Research Center,
Beijing, last fall. Two of three test subjects reported that they felt
their phantom limb pain ease, and the third subject experienced a
decrease in the frequency of phantom limb pain attacks.
“Of course, we need to do more tests, but the results so far look promising,” Geng said.
Students at AAU are developing a version of the system for people who have lower-limb amputations.
Editor’s note: This story was adapted from materials provided by AAU and ScienceDaily.
