News
3/26/08 - Sniffing Out Danger
CHICAGO -- Each human nose encounters hundreds of thousands of
scents in its daily travels perched front and center on our face. Some of
these smells are nearly identical, so how do we learn to tell the critical
ones apart?
Something bad has to happen. Then the nose becomes a very quick
learner.
New research from Northwestern University's Feinberg School of
Medicine shows a single negative experience linked to an odor rapidly teaches
us to identify that odor and discriminate it from similar ones.
"It's evolutionary," said Wen Li, lead author of the study and a postdoctoral
fellow at the Cognitive
Neurology and Alzheimer's Disease Center at the Feinberg School. "This
helps us have a very sensitive ability to detect something that is important
to our survival from an ocean of environmental information. It warns us it's
dangerous and we have to pay attention to it."
The study will be published March 28 in the journal Science.
In the study, subjects were exposed to a pair of grassy smells
which were nearly identical in their chemical makeup and perceptually indistinguishable.
The subjects received an electrical shock when they were exposed to one scent,
but not when they were exposed to the other similar one.
After being shocked, the subjects learned to discriminate between
the two similar smells. This illustrates the tremendous power of the human
sense of smell to learn from emotional experience. Odors that once were impossible
to tell apart became easy to identify when followed by an aversive event.
Li and her colleagues also found specific changes in how odor
information is stored in "primitive" olfactory regions of the brain, enhancing
perceptual sensitivity for smells that have a high biological relevance.
Li's collaborators include Jay Gottfried, senior author and assistant
professor of neurology, Todd Parrish, associate professor of radiology, and
James Howard, technologist.
The research was funded by a grant from the National Institute
for Deafness and Other Communication Disorders.
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