BEIJING, March 29 -- 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 yesterday's edition of the journal Science, helps explain how our senses can steer us clear of danger. More intriguingly, 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."

    Scientists long have known of a strong link between the sense of smell and emotion. A certain perfume or scent of baking pie, for instance, can raise memories of a long-dead loved one. Conversely, a whiff of diesel fuel might trigger a flashback for a soldier suffering PTSD.

    Could an emotionally charged situation make that initial cue be perceived more strongly in the first place?

    The research team recruited 12 healthy young adults to find out.

    Volunteers repeatedly smelled sets of laboratory chemicals with odors distinctly different from ones in everyday life. An "oily grassy" smell is the best description that lead researcher Wen Li, a Northwestern postdoctoral fellow in neuroscience, could give.

    Two of the bottles in a set contained the same substance and the third had a mirror image of it, meaning its odor normally would be indistinguishable.

    Then Li gave the volunteers mild electric shocks while they smelled just the odd chemical. In later smell tests, they could correctly pick out the odd odor 70 percent of the time.

    MRI scans showed the improvement was more than coincidence.

    There were changes in how the brain's main olfactory region stored the odor information.

    In other words, the brain seems to have a mechanism to sniff out threats.     

    (Source: Shanghai Daily/Agencies)