Paralyzed man feels physical sensation through a prosthetic hand

The feeling, he reported, was as if his own hand were being touched.

"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. That is when we knew that the feelings he was perceiving through the robotic hand were near-natural," he said.

The advance, made possible by sophisticated neural technologies developed under US Defence Advanced Research Projects Agency (DARPA)'s Revolutionising Prosthetics points to a future in which people living with paralysed or missing limbs will not only be able to manipulate objects by sending signals from their brain to robotic devices, but also be able to sense precisely what those devices are touching.

"We've completed the circuit" said DARPA programme manager Justin Sanchez.

"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," said Sanchez.

The clinical work involved the placement of electrode arrays onto the paralysed volunteer's sensory cortex - the brain region responsible for identifying tactile sensations such as pressure.

In addition, the team placed arrays on the volunteer's motor cortex, the part of the brain that directs body movements.

Wires were run from the arrays on the motor cortex to a mechanical hand developed by the Applied Physics Laboratory (APL) at Johns Hopkins University.

That gave the volunteer - whose identity is being withheld to protect his privacy - the capacity to control the hand's movements with his thoughts.

Then, breaking new neurotechnological ground, the researchers went on to provide the volunteer a sense of touch.

The APL hand contains sophisticated torque sensors that can detect when pressure is being applied to any of its fingers, and can convert those physical "sensations" into electrical signals.