Taste and smell—the nose knows

Although our taste buds distinguish sweet, sour, salty, savory and bitter, flavor arises from a combination of tastes with odors that enter our nasal passages through the back of the mouth. These “retronasal” odors get special treatment from the brain, according to a new study led by Dana Small, M.Sc., Ph.D., assistant professor of surgery (otolaryngology) and psychology at Yale and an assistant fellow at the John B. Pierce Laboratory.

In a report published in Neuron in August, Small and colleagues at Yale and in Germany inserted tubes that pumped odors such as chocolate into subjects’ noses, either to the front of the nostrils or to the back of the nasal cavity. They found that a single odor could activate different brain regions, depending on the route it traveled. Odors presented retronasally activated brain areas devoted to the mouth, which Small said 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.