Chee is designing an odor wheel that relates individual chemicals to the odors they produce. "Acetone," she uses as an example, "will smell like peach and apple and something sweet at the same time. Based on a huge volume of data, the wheel will serve as guide to the "spectrum" of odors, equating about 1000 smells with associated chemicals.

For hundreds of years people have made odor charts of various kinds. But they were all composed of subjective groupings, Chee says: "People saying, 'Oh, I think apple smells like pear' or, 'Gee, Parmesan cheese smells like Mozzarella'. I don't care if the odors smell alike or not. All I'm concerned about is which ones appear with each other chemically."

Right now her odor chart is like a globe, lacking in more specific structure. In the future, she says, "I'd like to change that. I'd like to be able to say that odor A is close to odor G, or opposite of odor X," just as a color wheel opposes and compares the light spectrum. "I've come up with several candidate structures, she says, adding she won't publish the odor chart until the structure is "pinned down.

The odor wheel could have widespread application when complete, says Chee, "in the perfume industry. Or aroma therapy. Or even in cooking. Much of our sense of taste is mediated by our olfactory sense. So how do chefs come up with these tastes? Perhaps this model could be used to guide the development of new food dishes by combining complimentary scents and flavors."

The next step will be to test whether her model accurately reflects the real world, and if it's a useful tool in helping us understand how the brain processes odor. "The ultimate goal," says Chee, "is seeing whether approaching the problem this way can tell us how the olfactory system works."

The reason Chee wanted a map in the first place is to test objectively what people can smell. "If I can't define the whole of what is people can smell, there's no way for me to know I'm if I'm testing the whole system. In other words, if I'm testing the color system on blues, I may not be getting the reds or yellows. I want to be pretty sure I'm getting the whole thing."

Does the brain contain "topographical maps" of the olfactory system, as it does with auditory and visual stimuli? "It would be hard to say what the topography might be because until now nobody really tried to define what the nose smelled. That's what I'm trying to do with this wheel."

-- Linda Marsa