Once science figures out better ways to attach artificial limbs, prosthetics themselves need to become smarter, able to act on signals sent directly from the brain. Consider the case of Jesse Sullivan, a power lineman from Dayton, Tennessee, who lost both arms at the shoulder after being electrocuted on the job in 2001. A year later, doctors transferred four nerves (which were no longer infusing muscle) that had controlled his left arm out of his shoulder area and into his pectoral muscles. Six months after that, Todd Kuiken, director of the Rehabilitation Institute of Chicago´s Neural Engineering Center for Artificial Limbs, detected signals in the nerves. Kuiken´s team studded the surface of Sullivan´s chest with electrodes and joined them with wires to a multi-jointed prosthetic. The goal was to connect brain to artificial arm by redirecting signals from Sullivan's severed nerves. It worked. When doctors asked Sullivan to think about opening his hand, the device, almost instinctively, sprung open. "It was the greatest feeling I'd had since I'd been hurt," Sullivan says. He can now eat, mow the lawn, and do his laundry, but his arm fulfills only a small fraction of the nerves´ potential power. The nerve for hand closing controls at least 20 muscles, Kuiken says, "and I'm using it for just two different signals. If we tease it out, we might get better and better control." Kuiken is now developing sensors that will allow Sullivan to feel what he is touching.