The results of the experiment, which were presented last week at the annual Society for Neuroscience meeting, marked the first time that focused ultrasound was safely and effectively used in a nonhuman primate to alter brain activity rather than destroy tissue. A second study, in sheep, had similar results. “The finding paves the way to noninvasive stimulation of specific brain regions in humans,” says Jan Kubanek, a neural engineer at Stanford University School of Medicine and lead author of the macaque study. The technology might ultimately be used to diagnose or treat neurological diseases and disorders like Parkinson’s disease, epilepsy, addiction and depression. Other scientists are optimistic. “The idea that, with a very carefully designed dose, you could actually deliver [focused ultrasound] and stimulate the brain in the place you want and modulate a circuit rather than damage it, is a really important proof of principle,” said Helen Mayberg, MD, of Emory University School of Medicine, who was not involved with the study.