When it comes to taste, the nose knows

Anyone whose enjoyment of food has been blunted by a bad cold knows that a good part of taste involves the sense of smell. Our taste buds distinguish five elemental sensations—sweet, sour, salty, savory and bitter—but food’s flavor arises from pleasant odors that enter our nasal passages through the back of the mouth.

In new research published in the August 18 issue of Neuron, Dana Small, Ph.D., assistant professor of surgery, and colleagues at Yale, the John B. Pierce Laboratory and the University of Dresden Medical School in Germany inserted tubes that pumped odors, such as chocolate and lavender, into study subjects’ noses, either to the front of the nostrils (yellow arrow) or “retronasally,” to a region at the back of the nasal cavity (blue arrow).

Using functional magnetic resonance imaging, the team found that a single odor could activate different brain regions depending on which nasal route it traveled. Odors presented retronasally activated brain areas devoted to the mouth, which Small says is “evidence of the existence of distinct olfactory subsystems,” one specialized for sensing objects at a distance, the other for sensing objects in the mouth.