Amputees taught to experience prosthetic hand as their own
7 January 2009
Scientists at the Karolinska Institutet and Lund University in Sweden
have succeeded in inducing people with an amputated arm to experience a
prosthetic rubber hand as belonging to their own body. The results,
published in the latest issue of Brain [1] could lead to the
development of a new type of touch-sensitive prosthetic hand.
The illusion of having a rubber hand was achieved by the scientists
by touching the stump of the amputated arm out of sight of the subject
while simultaneously touching the rubber hand in full view of the same
subject. This created the illusion that the sensory input was coming
from the prosthetic hand rather than from the stump, and that the hand
belonged to the subject’s own body.
The effect was confirmed by the subjects’ own descriptions of the
experience and by their tendency to point to the hand when asked to
localise the point of stimulation. That they experienced the rubber hand
as their own was also substantiated physiologically in that they started
to sweat when the hand was pricked with a needle.
The study, which was carried out at the Red Cross hospital in
Stockholm, opens up new opportunities for developing prosthetic hands
that can be experienced by wearers as belonging to their own bodies,
which would be a great benefit to patients and which is considered an
important objective in applied neuroscience.
“We’ll now be looking into the possibilities of developing a
prosthetic hand that can register touch and stimulate the stump to which
it’s attached,” says Henrik Ehrsson, one of the researchers involved in
the study. “If this makes it possible to make a prosthetic sensitive by
cheating the brain, it can prove an important step towards better and
more practical prosthetic hands than those available today.”
The study is part of the EU’s SmartHand project, which is
administered from Lund University. The objective of the SmartHand
project is to develop a new type of thought-controlled prosthetic hand
with advanced motor and sensory capabilities. Other financiers include
the European Research Council, the Swedish Research Council, and Skåne
County Council.
Reference
1. Henrik Ehrsson, Birgitta Rosén, Anita Stockselius, Christina Ragnö,
Peter Köhler & Göran Lundborg. Upper limb amputees can be induced to
experience a rubber hand as their own. Brain (2008) 131,
3443-3452.
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