NEW ORLEANS--It's an acrophobe's nightmare: being forced to ride a glass elevator to dizzying heights inside the courtyard of a highrise hotel. But a virtual reality game that simulates this experience, when paired with a drug that revs up certain learning circuits in the brain, is helping people overcome their fear of heights in real life, researchers announced here today at the annual meeting of the Society for Neuroscience.
Counterintuitively, many neurobiologists see forgetting fearful experiences as a special kind of learning, and they've found considerable overlap in the neural mechanisms underlying these seemingly different processes. In the mid-1990s, for example, researchers found that a particular receptor for the neurotransmitter glutamate--the so-called NMDA receptor--plays a critical role both in rats' ability to learn that a flash of light signals an impending electrical shock and in their ability to forget their fear of the light after the researchers stop pairing flash with zap. More recently, Michael Davis, a neuroscientist at Emory University in Atlanta, and others have found that drugs that enhance NMDA receptor activity in rats help the animals lose their fearfulness more quickly.
To see if such drugs could help humans with irrational fears, Davis and colleagues gave a drug called D-cycloserine (DCS) to people terrified of heights. Subjects were given either DCS or a sugar pill (neither they nor the experimenters knew which) just before strapping on virtual reality goggles and taking the elevator as far up as they could bear. They could push themselves even further by walking out on a narrow virtual catwalk suspended high above the ground. Although DCS didn't reduce the subjects' self-described level of discomfort immediately, the way an antianxiety drug like Valium might, subjects who took it were markedly bolder in subsequent virtual reality sessions. After just two such sessions, many subjects who got DCS took the elevator all the way to the top floor--control subjects took seven or eight sessions to work up the nerve for this feat. And most importantly, Davis says, those who got DCS were twice as likely to drive over high bridges or use an elevator in real life.
"I think it's great," says Mark Barad, a psychiatrist and neuroscientist at the University of California, Los Angeles. "This is the first example of a new way of doing psychiatry, by using drugs not to treat the illness but as a way of making therapy work."