National Geographic : 2010 Jan
"bionic arm." He knew that nerves in an amputee's stump could still carry signals from the brain. And he knew that a computer in a prosthesis could direct electric motors to move the limb. e problem was making the connection. Nerves conduct electricity, but they can't be spliced together with a computer cable. (Nerve bers and metal wires don't get along well. And an open wound where a wire enters the body would be a dangerous avenue for infections.) Kuiken needed an ampli er to boost the sig- nals from the nerves, avoiding the need for a direct splice. He found one in muscles. When muscles contract, they give off an electrical burst strong enough to be detected by an elec- trode placed on the skin. He developed a tech- nique to reroute severed nerves from their old, damaged spots to other muscles that could give their signals the proper boost. In October 2006 Kuiken set about rewir- ing Amanda Kitts. e rst step was to salvage major nerves that once went all the way down her arm. " ese are the same nerves that work the arm and hand, but we had to create four dif- ferent muscle areas to lead them to," Kuiken says. e nerves started in Kitts's brain, in the motor cortex, which holds a rough map of the body, but they stopped at the end of her stump---the disconnected telephone wires. In an intricate op- eration, a surgeon rerouted those nerves to dif- ferent regions of Kitts's upper-arm muscles. For BIONIC WOMAN Kitts imagines a hand movement, and muscle activity in her residual arm---decoded by a computer on her back---causes the actual motion. When she straps on the experimental Johns Hopkins--developed arm at the Rehabilita- tion Institute of Chicago, she says, "often it feels like I'm not missing anything."