With brain implants, this paralyzed man rediscovered his sense of touch

Breakthrough research delivering the sense of touch from a robotic arm directly to the human brain could dramatically change how prosthetics wearers interact with the world in the coming years. The trial, run by researchers at the University of Pittsburgh and University of Pittsburgh Medical Center (UPMC), demonstrated that brain implants could restore the absent sense to a quadriplegic man paralyzed from the upper chest down. Although still in early stages, it could have huge implications for future robotics.

Brain-controlled prosthetics, such as robotic arms, have long been a topic of research and development. However, what's been less frequently explored is information flowing in the opposite direction. That is to say, feedback from the robotic limb passed back to the user.

That feedback is vital in human limbs. Our fingertips recognize how much pressure we're placing on delicate objects, for instance, or the degree of grip we have on a carried item. It also allows us to differentiate between different substances and textures.

The Pitt-UPMC set out to restore that missing sense to a 28-year-old subject, who had been left paralyzed for a decade after a car accident. Their theory was that, through microstimulation of the sensory cortex, data picked up from artifical sensors in a robot gripper could be interpreted in just the same way that flesh and blood would be recognized.

First, using brain imaging techniques, the group tracked which regions of subject participant Nathan Copeland's cortex responded to feelings in each of his fingers and palm. Based on that personalized map, four tiny microelectrode arrays were implanted. Each is approximately half the size of a shirt button, the Pitt-UPMC team says.

The result is a system by which Copeland can now feel when the robotic hand is applying pressure and, "to some extent", the degree of that pressure. However it's still a long way off what the typical human hand could register. Temperature is out of its scope, for instance.

"I can feel just about every finger — it's a really weird sensation," Copeland described of the sensation after roughly a month of using the system. "Sometimes it feels electrical and sometimes its pressure, but for the most part, I can tell most of the fingers with definite precision. It feels like my fingers are getting touched or pushed."

Even though the group of researchers warns that it's still very early days for the technology, they're nonetheless confident in its potential. It builds on previous research into understanding control of movement, which led to a brain-controlled prosthetic four years ago.

"The most important result in this study is that microstimulation of sensory cortex can elicit natural sensation instead of tingling," study co-author Andrew B. Schwartz, Ph.D. said of the technology. "This stimulation is safe, and the evoked sensations are stable over months."

Efforts to create more and more lifelike and responsive prosthetics are underway in numerous research facilities and private companies. DEKA's Luke arm, for instance, developed by the company established by Segway creator Dean Kamen, was given FDA approval earlier this year.