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Stereo Smell
Introduction
A rose by any other name, still smells as sweet. However, as this Science Update reveals, our nose actually smells that rose two different ways.
Podcast
Stereo Smell
Transcript
Smelling in stereo. I'm Bob Hirshon and this is Science Update.
Our two eyes let us see in three dimensions, our two ears let us hear in stereo; neuroscientist Noam Sobel wanted to know what our two nostrils do for us. His theory was that each nostril would smell things a little differently.
Sobel:
That is, each nostril conveys to the brain a slightly different olfactory image within that one given sniff.
He says researchers had already found that some smells are easiest to detect when they're wafted through the nose quickly, while others get picked up best in slow-moving air. It was also known that at any given moment, we have one nostril with a higher air flow rate than the other.
Sobel:
So that said, we sort of put A and B together and said well, the fact is that we have a high flow rate nostril and a low flow rate nostril, so perhaps indeed the high flow rate nostril is more sensitive to high absorption odorants and the low flow rate nostril is more sensitive to low absorption odorants.
Using a group of twenty volunteers who sniffed a mixture of smells with one nostril and then the other, he found out there really was a difference.
Sobel:
Each nostril here is functioning as sort of a window to the olfactory scenery. So if we have one window we have a certain portion of scenery that we can see through it. But if we have another window that looks at another portion of the scenery, then we just see overall more scenery. So two is better than one, you can say.
For the American Association for the Advancement of Science, I'm Bob Hirshon.
Making Sense of the Research
As you just learned, during each sniff that we take, the olfactory perception in each nostril is slightly different. Researchers have determined that the slight difference in olfactory image occurs because the air flows at a different rate through each nostril. This physiological difference enables each nostril to be better tuned to different odorants.
Consider what happens when we visually take in scenery. What we see with one eye conveys something, while what we see with the other eye conveys something slightly different. Together these perceptions make a more complete picture of that scenery. In the case of smell, the olfactory pictures obtained by each nostril are almost completely overlapping and there's only a small, subtle portion of difference between them. But this difference is important, because it leads scientists to wonder -- does the brain rely on one nostril's olfactory image more than the other's?
The next step for researchers will be to determine how the brain reconciles these disparate olfactory images to create a whole, normal picture.
Going Further
To learn more about olfaction, visit Seeing, Hearing, and Smelling the World from the Howard Hughes Medical Institute.
For more on smell (olfaction), go to the Neuroscience for Kids website. Through a series of activities, you will learn how we experience and get information about the world through our sense of smell.
Visit the Neuroscience for Kids website for an experiment related to olfactory fatigue. In the "CLASS EXPERIMENT," you find that the ability to detect an odor decreases with continued exposure to that odor, a property called olfactory fatigue. You learn basic facts about sensory receptors, nerve connections, and brain centers, and discover what conditions can affect olfactory fatigue.
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