The US government has successfully built a prosthetic arm which lets its wearer actually feel things.
An unnamed 28-year-old patient paralysed by a spinal cord injury over a decade ago was given the prosthetic limb controlled directly by his brain. What was particularly significant was Darpa claimed he was the first ever human who was also able to feel the prosthetic fingers being pressed.
"We've completed the circuit," said Justin Sanchez, manager of the program at blue-sky military research arm Defense Advanced Research Project Agency (Darpa). "By wiring a sense of touch from a mechanical hand directly into the brain, this work shows the potential for seamless bio-technological restoration of near-natural function."
According to Darpa, the blindfolded volunteer was able to report with nearly 100 per cent accuracy which mechanical finger was being touched. The feeling, he reported, was as if his own hand were being touched.
The only other group who has created a prosthetic that can feel was Dr Silvestro Micera and a team at the Swiss Federal Institute of Technology, Lausanne along with the The Sant'Anna School of Advanced Studies in Italy.
While wearing this artificial hand, Dennis Aabo Sorensen, a 36-year-old amputee from Denmark, was able to distinguish between hard, soft, round and square objects even while blindfolded and wearing earplugs. The arm wasn't controlled by his mind, though.
Here's how Darpa's brain-prosthesis system works: a 1mm silicon chip containing several electrodes is embedded in the person's motor cortex - the part of their brain that controls their arm and hand movements.
A similar chip is also placed in the paralyzed volunteer's sensory cortex- the area responsible for identifying tactile sensations such as pressure.
The robotic arm, which contains pressure sensors on its surface, is connected to both chips by wires.
This allows the wearer to control the motion of the robot arm, and also send electrical signals to the the sensory cortex which gives the wearer the sensation that they are touching something.
"At one point, instead of pressing one finger, the team decided to press two without telling him," said Sanchez. "He responded in jest asking whether somebody was trying to play a trick on him."
The advance is part of Darpa's Revolutionising Prosthetics program, launched in 2006 and headed by neurologist and retired army colonel, Sanchez.
The team has been working to restore movement to quadriplegics, amputees and anyone in need of a functional limb - particularly the hundreds of soldiers injured while on duty.
This announcement came on the heels of Darpa's July announcement that they had given a former US serviceman Glen Lehman a mind-controlled prosthetic limb, without the need for implanting a brain chip.
Other research groups testing out a brain-controlled prosthesis in paralysed volunteers include the BrainGate team at Brown University, the California Institute of Technology and the University of Pittsburgh, which is funded by Darpa.
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