In the deep recesses of the nose are millions of sensory neurons that, along with our eyes and ears, help conjure the world around us. When stimulated by a chemical with a smell, or an odorant, they send nerve impulses to thousands of clusters of neurons in the glomeruli, which make up the olfactory bulb, the brain’s smell center.
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The authors of the new study sought to identify distinguishing features involved in forming the representation of odors in the brain. To do so, they used a technique called optogenetics to activate glomeruli in mice. Optogenetics uses light to stimulate specific neurons in the brain. And it can help determine the function of particular brain regions.
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They found that the sequence of glomerular activation was crucial to odor perception. When they changed which glomerulus was activated first, the mice demonstrated a 30 percent drop in the ability to sense the correct odor.
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[Neuroscientist Dmitry] Rinberg likens smell perception to the melody of a song: The notes—in this case, representing activated glomeruli—are important. But without the right timing, the song, or the perceptual experience, falls apart. Changing the seventh note of a melody might be unnoticeable. Swapping the first two might result in a new tune altogether. When we smell, it is not only about which glomeruli are activated but also what time sequence they follow.
