Alvaro Pascual-Leone holds a figure-eight-shaped paddle to his head and flips a switch. His left arm begins to twitch. He turns off the device-quelling its pulsing magnetic field, which was inducing an electrical current inside his brain-and his arm relaxes. But Pascual-Leone, a neuroscientist at Boston's Beth Israel Deaconess Medical Center, is interested in more than muscle twitches; he believes that magnetic stimulation provides the last, best hope for treating patients with severe depression. This fall, researchers will begin large-scale human trials of the technology to see if he is right.

Select from the choices above to read the entire article.