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Making sense of scents

Peonies smell nice.
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New research is helping scientists understand how our brains are able to tell the difference between the scent of a rose and the stink of a sweat sock.

Virtually every smell we encounter is produced by a combination of many different types of odor molecules. Inside the nose, each odor molecule locks into the tip of a neuron that's specially outfitted to recognize just that type of odor.

The neuron reaches all the way to a special part of the brain called the "olfactory bulb," which is made up of structures called "glomeruli." When a mouse, human or other mammal is born, the neurons are all mixed up among the glomeruli.

As the mammal develops, however, the neurons for each type of odor cluster together in their own glomerulus. This helps the brain to process the odor-related information so we know what we're smelling.

Two research teams studied growing mice to investigate this neuron-clustering process. Dong-Jing Zou of Columbia University and colleagues experimented with blocking the mice's sense of smell as they developed. The scientists found that experiencing smells early in life is necessary for the neurons in the olfactory bulb to become organized correctly.

In a second study, G. Barnea of Howard Hughes Medical Institute and Columbia University and his colleagues found that the same proteins that help the neurons lock on to certain odor molecules in the nose also exist in the brain. There, they help guide the neurons to their correct glomerulus in the olfactory bulb. The two studies appear in the 04 June 2004 issue of the journal Science.


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