Retired Army Sgt. 1st Class Ramon Padilla, who lost his left arm while serving in Afghanistan in 2007, is the second person in the United States to have a prosthetic arm that uses implanted sensors to stimulate movement.
They implanted electrodes inside my muscles. So the same muscles you use to move to close your hand - left to right, thumb - it's the same ones I use to power this prosthesis. It's slow-- of course it's not going to be as fast as your hand, but as soon as i do it happens. So whatever your processes - from your brain, to your muscles, to your nerves and everything - however that works, it works.