Sniffing Out the Secrets of Smell

Studies discover the details of how odors are detected

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THURSDAY, June 3, 2004 (HealthDayNews) -- New information about how the brain separates the sweet fragrance of a rose from the horrid stench of a hockey equipment bag is offered in two studies in the June 3 issue of Science.

A combination of many types of odor molecules are responsible for each smell people detect. As the odor molecules enter the nose, each kind attaches to the tip of a neuron specifically designed to recognize that particular molecule.

Each of the neurons, in turn, is connected to an area of the brain called the olfactory bulb. This olfactory bulb is made up of structures called glomeruli.

When humans and other mammals are born, the neurons that detect odor molecules are scattered among the glomeruli. Then, as people grow and develop, the neurons for each specific odor gather together in their own glomerulus.

These two studies examined this neuron-clustering process in mice.

In the first, Columbia University scientists blocked the sense of smell in mice as they developed and found that experiencing smells early in life is necessary for the neurons in the olfactory bulb to organize correctly.

The second study, by researchers at Columbia University and Howard Hughes Medical Institute, revealed the same proteins that help the neurons link up with specific odor molecules in the nose are also present in the brain.

These proteins in the brain help direct neurons to their correct glomerulus in the olfactory bulb.

More information

The Nemours Foundation has more about smell.

SOURCE: Science, news release, June 3, 2004

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