New Robotic Arm Takes Cues From Brain

Artificial limbs have come a long way from the wooden legs and plastic arms of old: Today's prosthetics take messages directly from the brain. Their performance far exceeds that of the previous generation of devices, which required concentrated effort to make ungainly motions. "You think, and then your muscles move," a woman who has one of the newer artificial arms tells the New York Times.

The new arms are complicated and expensive, and implementation requires preserving nerves from the amputated limb. Those nerves are then attached to chest muscles, where tiny electrodes watch for the body's natural nerve signals and radio them to the arm. With the new technology, amputees can manipulate small objects like balls and shoelaces without having to concentrate more than any other person.
(More artificial limb stories.)