March 27, 2008 -- Know how a whiff of certain odors can take you back in time, either to a great memory or bad one?

It turns out emotion plays an even bigger role with the nose, and that your sense of smell actually can sharpen when something bad happens.

Northwestern University researchers proved the surprising connection by giving volunteers electric shocks while they sniffed novel odors.

The discovery, reported in Friday's edition of the journal Science, helps explain how our senses can steer us clear of danger. More intriguing, it could shed light on disorders such as post-traumatic stress syndrome.

"This is an incredibly unique study," said Dr. David Zald, a Vanderbilt University neuroscientist who studies how the brain handles sensory and emotional learning. "We're talking about a change in our perceptual abilities based on emotional learning."