The US military agency DARPA says it has successfully restored a test subject's sense of touch using a prosthetic hand connected directly to the brain. The research was carried out on an anonymous 28-year-old man, who was paralyzed after suffering a spinal cord injury more than a decade ago. An array of electrodes was placed in the volunteer's sensory cortex (part of the brain that identifies touch) and connected to pressure sensors on a prosthetic hand, with electrical signals sent from the hand to the brain. When blindfolded, the subject was able to tell "with almost 100 percent accuracy" which of the mechanical fingers on the hand were being touched.

"The feelings he was perceiving ... were near-natural."

"At one point, instead of pressing one finger, the team decided to press two without telling him," said Justin Sanchez, head of DARPA's Revolutionizing Prosthetics program, which has been developing new upper-limb prosthetics since 2006. "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." DARPA previously released footage of their prosthetics work in February this year, showing a volunteer rock-climbing using a robot arm:

DARPA claims its research represents a first in the world of prosthetics, but the full extent of their work is not yet clear. It's not the first time that prosthetic limbs have been used to restore a sense of touch, but previous research has run up against limitations such as short-lived or imprecise sensations. But even if technology can never restore the full (and staggering) accuracy of our sense of touch, even a vague approximation can be incredibly helpful, making it easier for amputees to interact with objects and in some cases even eliminating the phantom pain associated with lost limbs.

DARPA's research is awaiting peer review

The work by DARPA is currently awaiting peer review and acceptance for publication in a scientific journal, reports the agency. However, its researchers are confident that they've taken a big step forward toward the "seamless bio-technological restoration of near-natural function" in prosthetic limbs. "Prosthetic limbs that can be controlled by thoughts are showing great promise, but without feedback from signals traveling back to the brain, it can be difficult to achieve the level of control needed to perform precise movements," said Sanchez. "We’ve completed the circuit."

Verge Video: Competing at the DARPA Robotics Challenge