When we eat, the tongue and nose quickly inform the brain about flavors. But it takes more time for the stomach and intestine to detect what the food actually provides. The brain must then connect this separate information to make us appreciate the most nourishing foods.
This association explains why a flavor that initially seems unusual can become enjoyable after several meals. To understand how it forms, researchers studied the brain's responses to foods and nutrients. Their work, published in Nature, is based mainly on experiments conducted in mice, supplemented by observations in humans.
The scientists focused on dopamine, a substance that allows nerve cells to communicate and plays a role in learning. In mice, the arrival of nutrients in the digestive system triggers its release in a small region of the brain. This area belongs to the amygdala, known in particular for its role in emotions and memories.
The surprising detail concerns the location of this reaction. It occurs mainly in a part located on the left side of the mice's brains. Other regions often associated with dopamine do not respond in the same way to these digestive signals. The brain therefore does not seem to process all food-related messages through a single circuit.
To verify its role, the researchers modified the activity of certain nerve cells in the mice. When the circuit was interrupted, the animals struggled to learn that a flavor signaled a nutritional benefit. Conversely, stimulating it could promote this learning.
In other words, this circuit helps memorize the relationship between a flavor and the nutritional benefits that follow. It does not by itself control hunger or the pleasure of eating. This distinction matters because a food preference can develop gradually.
The researchers also examined human brain responses after consuming nutritious drinks. They observed activity in a comparable region, with a stronger response on the left in some measurements.
Future research will need to clarify how these digestive signals influence our meal choices.