Deep brain stimulation is becoming very precise. This technique allows surgeons to place electrodes in almost any area of the brain, and turn them up or down — like a radio dial or thermostat — to correct dysfunction. Andres Lozano offers a dramatic look at emerging techniques, in which a woman with Parkinson's instantly stops shaking and brain areas eroded by Alzheimer's are brought back to life. (Filmed at TEDxCaltech.)