( chanical stimuli both resulted in the s...)Penn study on olfactory nerve cells shows why we smell better when we sniff

Although this study was conducted on a mouse model, the researchers tested two different parts of the nose, one that humans have and one that humans do not. The first, the septal organ, is a patch of smell-sensitive tissue on the septal wall of the nasal cavity. The second, the main olfactory epithelium, is a smell-sensitive tissue inside the nasal cavity.

Synchronized Breathing

The septal organ is only about 1 percent the size of the main olfactory epithelium and isn't shared by all mammals. Mice, for example, have a septal organ. Humans do not. But in this study, Ma's group found that 50 percent of the cells in the main olfactory epithelium are sensitive to physical stimuli, suggesting that mechanosensitivity of the olfactory sensory neurons exists in all mammals, even those like humans, without the septal organ.

The mechanosensitivity of our olfactory neurons has two possible functions, suggest the investigators. The first is that it increases our ability to smell, enhancing the detection of odorous molecules in the air. The second is a peripheral drive in the brain to synchronize rhythmic activity, which is the concurrent firing of neurons in the olfactory bulb with breathing.

"The mechanosensitivity may increase the sensitivity of our nose, especially when stimulated by weak odors," says Ma. "It helps the brain make better sense out of odor responses when it integrates airflow information. We still don't know how it happens, but sniffing is essential for odor perception."