In one of the most iconic scenes in science-fiction films, Luke Skywalker casually examines his new synthetic forearm and hand. The Star Wars hero is able to move the fingers by extending and contracting pistons shown through an open flap along the wrist. Then he senses the robotic surgeon's pinprick of one of the fingers. Not only can the prosthesis be moved with Skywalker's thoughts, it feels to him like his own hand.
What the audience does not see, however, is the actual connection between man and machine. And yet to neuroscientists like the two of us, it is precisely this hidden interface that should have been at the center the scene. In order for such a linkup to work, it would have to have converted nerve impulses from the brain into electrical signals in the artificial arm, and vice versa. In the world beyond movies, however, no one has yet figured out how to splice together nerves and electrical wires in a way that allows them to control an artificial limb as if it were a natural extension of the body.