Bitter flavors such as black coffee may become more appealing through a learning process that links taste with the nutritional benefits that follow. A study published in Nature identifies a dopamine pathway that carries information from the digestive system to the brain over several minutes, helping animals associate flavors with calories.
Researchers led by scientists at the University of California, San Francisco, studied how nutrients affect dopamine activity after food reaches the gut. In mice, sugar and fat delivered directly into the stomach prompted a sustained dopamine increase in a small region of the anterior basolateral amygdala (BLA). The signal developed more slowly than dopamine responses to immediate sensory cues such as seeing or tasting food.
The team tested the pathway’s role in flavor learning. When dopamine signaling in the BLA was disrupted, mice could still eat normally but could not learn to connect a new flavor with nutritional value. Conversely, stimulating dopamine terminals in the region while presenting a calorie-free flavor led the mice to develop a preference for it.
The researchers also found that the nutrient-triggered response was stronger in the left BLA than in the right in mice. Analyses of human PET data and fMRI scans from 38 adults likewise indicated greater left-sided activity after nutrients entered the digestive system.
The study identifies a neural mechanism for learning about food’s nutritional content, but it did not test GLP-1 medicines. The researchers suggested that future work could investigate whether these drugs affect the gut-driven dopamine signal and, in turn, food preferences.
Sources: Neuroscience News.