The US Department of Defense has a good reason to fund research in advanced bionic limbs—in fact, it has a couple thousand good reasons. In the last thirteen years, 2,000 men and women have lost a limb in military service. And of course, military amputees are hardly the only amputees. Far from it.
Advanced prosthetic research in clinical settings is providing a ray of hope for all these folks—military or civilian—as participants in DARPA’s Reliable Neural-Interface Technology (RE-NET) program continue to make progress in the realm of brain-interfacing prosthetic devices.
Two recently released DARPA videos demonstrate just how far researchers have come. In the first video (below) a man manipulates a prosthetic arm using targeted muscle re-innervation (TMR) developed by Rehabilitation Institute of Chicago. TMR allows direct manipulation of the prosthetic with thoughts alone.
How does it work? After a limb is amputated the nerves still fire as they once did—they just don’t lead anywhere anymore. So, soon after the amputation doctors surgically reattach severed nerve endings to different muscles in the arm.
The patient thinks of moving his hand, elbow, or wrist and the old nerve groups fire as normal. Now, however, they contract these new muscles. A computer learns to recognize various muscle contraction patterns as commands for particular movements of the prosthetic—‘turn wrist’, ‘close hand’, or ‘bend elbow’.
The technique has been used successfully in both leg and arm amputees. We wrote about another TMR patient last year, Zac Vawter, who climbed 2,100 stairs to the top of Chicago’s Willis Tower on a TMR-controlled prosthetic leg.
The cool thing about the latest TMR demonstration is the complexity of motions the subject is able to employ. As he snatches a piece of cloth out of the air, he’s simultaneously bending his prosthetic elbow and closing his hand.
A second demonstration shows off a flat interface nerve electrode (FINE), developed by researchers at Case Western Reserve University. FINE gives rudimentary sensory input back to an amputee. The technique is similar to TMR, but instead of sending a signal from the brain to the prosthetic, the prosthetic stimulates nerve endings to send a signal to the brain. The brain learns to interpret the stimulation as touch.
Being able to feel the roughness of a surface or sensing pressure can help the patient decide how hard to grip and removes the need to always be looking at an object as it’s manipulated. Perhaps the best thing about FINE (and TMR) is the procedures are minimally invasive—no cortical implant required.
For now, TMR and FINE are being tested separately with select patients. But in the future, one can imagine a combination of the two in a single prosthetic device—restoring touch and natural movement to those who’ve lost an arm or leg, and maybe beyond restoration, giving these future cyborgs powers they didn’t have before.
