A decade ago, Dennis Aabo Sørensen lost his hand in an accident. Now, thanks to an international team of physicians and technicians, he can feel objects once again, this time through the use of a bionic hand that is directly connected to the nerve cells in his arm.
Sørensen is the world's first amputee able to use his bionic hand to experience the sensation of feeling. Because he can feel what he touches, he is able to use his bionic hand with far more agility than other amputees, knowing instantly when he is squeezing something too hard and likely to crush or harm it.
Photo Credit: Sensory feedback enabled prosthesis, close-up. Credit: LifeHand 2/Patrizia Tocci. LINK to Video.
“The sensory feedback was incredible,” reports the 36 year-old amputee from Denmark according to a press release from the Ecole Polytechnique Fédérale de Lausanne. “I could feel things that I hadn’t been able to feel in over nine years.” In a laboratory setting wearing a blindfold and earplugs, Sørensen was able to detect how strongly he was grasping, as well as the shape and consistency of different objects he picked up with his prosthetic. “When I held an object, I could feel if it was soft or hard, round or square.”
The bionic hand, of course, is equipped with touch sensors. But the real key is the bi-directional or two-way connection between the hand's electronics and the brain's neurons. Tiny, cell-size links between electrodes and nerve endings were implanted into Sørensen's arm. Then his new hand was attached and the wires connected.
Over time and with a little practice, he could feel different shapes and degrees of hardness. The sensation was as fast as normal touch. Signals passed from the bionic fingers to the brain and then from the brain to the hand, controlling its movements.
For those in need of bionic hands, this work marks a real milestone. Ordinarily we take two-way processing for granted. But the way things feel helps us use our hands with versatility and skill.
What this means in broader terms is a little less clear. Bionic restoration is a key frontier in today's medicine. But the technologies of healing or restoration can quickly become the technologies of enhancement. Perhaps someday, we will look back at Sørensen's hand as a kind of evolutionary advance, bringing not just the restoration of touch but the extension of power.
The paper, entitled "Restoring NaturalSensory Feedback in Real-Time Bidirectional Hand Prostheses," is the work of an international team largely based in Italy and Switzerland. It appears in the 5 February 2014 issue of Science Translational Medicine.