Amputees can feel
relief from phantom limb pain just by watching someone else rub
their hands together, a study says.
The treatment appears to fool the brain that it is their missing
hand being massaged, California researchers say.
New Scientist magazine reports that it harnesses nerve cells in the
brain which become active when watching someone else carry out an
action.
UK experts said this kind of therapy may help amputees, as long as
they can go along with the illusion.
Mirror neurons in the brain fire up when a person performs an
intentional action, such as waving, and also when they observe
someone else performing the same action.
They are thought to help predict the intentions of others by
simulating the action in the mind.
Similar cells exist for touch, and become active both when a person
is being touched and when they watch someone else being touched.
Researchers at the University of California, San Diego, say the
reason people do not constantly feel what they observe happening to
others is that a person's sensory cells do not give the right
signals, so they know it is not happening to them.
In the study, Vilayanur Ramachandran tested the therapy on
ex-soldiers.
His first test used a device called a mirror box, which he
developed. An amputee puts their remaining limb, in this case their
hand, in front of the mirror and their brain is tricked into
thinking the mirror image is actually another working limb.
Two amputees had their normal hand touched while using the mirror
box, and felt the sensation of being touched on their missing hand.
In a second experiment, when amputees watched a volunteer's hand
being stroked, they also began to experience a stroking sensation
arising from their missing limb.
One even said their pain disappeared for between 10 and 15 minutes.
Dr Ramachandran suggested the amputees "felt" the actions of others
because their missing limb provided no feedback to prevent their
mirror neurons being stimulated, and therefore not telling them they
were not "literally" being touched.
He said: "If an amputee experiences pain in their missing limb, they
could watch a friend or partner rub their hand to get rid of it."
But Dr Ramachandran said there could be other uses for the therapy,
including helping people who have had strokes.
"If performed early enough, it may also be used to help stroke
patients regain movements by watching others perform their lost
actions."
Kate McIver, of the Pain Research Institute at Liverpool University,
said work done there on helping amputees create mental images of
pain-free limbs - which operated on the same basic principle as the
US research - had also proved effective.
She said watching massage could help, but added: "With something
external like this, the patient has to accept that the illusion is
real for it to work."
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