An anonymous reader writes "A number of amputees are now using a prosthetic arm that moves intuitively, when they think about moving their missing limb. Todd Kuiken and colleagues at the Rehabilitation Institute of Chicago surgically rearrange the nerves that normally connect to the lost limb and embed them in muscles in the chest. The muscles are then connected to sensors that translate muscle movements into movement in a robotic arm. The researchers first reported the technique in a single patient in 2007, and have now tested it in several more. The patients could all successfully move the arm in space, mimic hand motions, and pick up a variety of objects, including a water glass, a delicate cracker, and a checker rolling across a table. (Three patients are shown using the arm in the related video.) The findings are reported today in Journal of the American Medical Association."