Brain Interprets Certain Aromas as Taste

Researchers at Karolinska Institutet in Sweden have shown how the brain interprets certain aromas as if they were actual tastes, helping explain why flavored drinks without sugar can still be experienced as sweet. The study, published in Nature Communications, demonstrates that aromas and tastes are integrated earlier in brain processing than previously thought.

When people eat or drink, they experience flavor as a combination of both taste and smell. Smell molecules reach the nose through the oral cavity in a process known as retronasal odor. The researchers found that the brain integrates taste and smell signals in the insula, a region called the taste cortex, rather than only later in the frontal cortex, which regulates emotion and behavior. “We saw that the taste cortex reacts to taste-associated aromas as if they were real tastes,” explains lead author Putu Agus Khorisantono. According to the researchers, this helps explain why some odors, such as those in flavored water, can trigger taste sensations and may play a role in food enjoyment, cravings, and overeating.

The study included 25 healthy adults who first learned to associate sweet and savory tastes with particular smells. The participants then underwent two rounds of functional magnetic resonance imaging (fMRI). During the scans, they were exposed to either a tasteless aroma or a taste without smell. Meanwhile, an algorithm was trained to identify brain activity patterns linked to sweet and savory tastes, and researchers tested if the same patterns appeared with aromas alone.

The results showed that sweet- or savory-related aromas activated the taste cortex in a manner similar to real tastes. Overlapping brain activity was especially clear in regions connected to integrating sensory inputs. “This shows that the brain does not process taste and smell separately, but rather creates a joint representation of the flavor experience in the taste cortex,” says Janina Seubert, senior author of the study. These findings suggest that the integration of smell and taste strongly influences taste perception, shaping preferences and dietary habits.

Looking ahead, the team plans to study whether this mechanism also applies to external smells, or orthonasal odors, such as scents encountered in daily environments. As Khorisantono notes, “We want to find out whether the activation pattern in the brain’s taste cortex changes from salty to sweet when we walk from the cheese aisle to the pastries in the supermarket.”