Nose Learns Danger's Subtle Scent

March 27, 2008 -- Fear may heighten people's sense of smell, changing the way people respond to scent, a new study shows.

The findings may hold clues for new anxiety disorder treatments, according to the researchers.

For the study, 12 healthy young adults took smell tests while getting their brains scanned using functional magnetic resonance imaging.

First, participants sniffed scents from two bottles. The scents were almost identical, with one subtle chemical variation. Participants couldn't tell the two scents apart.

But when they smelled one of the scents while getting an uncomfortable, but bearable, electric shock to their leg, they quickly learned to distinguish that scent from its virtual twin.

The brain scans showed different patterns in brain activity when the "danger" scent wafted through the air than brain activity when the "no danger" scent was used.

"It's evolutionary," researcher Wen Li, PhD, of Northwestern University's Feinberg School of Medicine, says in a news release. "This helps us to have a very sensitive ability to detect something that is important to our survival from an ocean of environmental information. It warns us that it's dangerous and we have to pay attention to it."

Li's team suggests that a breakdown in the ability to distinguish between important and unimportant cues "may underlie the emergence of anxiety disorders characterized by exaggerated sensory sensitivity and hypervigilance."

If so, that could lead to a new approach to anxiety disorder therapies, the researchers note in Science.