Ian Burkhart drapes his hand over a beige tube, squeezes his fingers, and lifts it into the air. For most, this movement would be no big deal: You think "grab that tube," and your spinal cord whisks the command down to your hand, which does the deed before you even realize it. But for Ian, who lost the use of his arms below the elbow eight years ago, the process plays out differently. When he thinks "grab," a bead-sized device in his brain picks up the resulting electric blips, a desktop computer interprets them, and a zippered sleeve jolts his forearm with electric current, moving his hand. Over the last five years Ian, who never expected to control his hand again, has learned to pour from a bottle, stir with a straw, and even play Guitar Hero.