how does our brain work to distinguish between sweet and salty?

What in our brain makes us feel the sweet taste of watermelon or the bitterness of quinine? Researchers from New York University in Stony Brook (United States) have analyzed the brain’s response to taste perception, which goes against what we thought. Their findings were published in the journal Current biology November 12, 2020.

Until now, the scientific community believed that taste was governed by specific groups of neurons in the brain. It would seem to be more complex.

The specific “hot spots” hypothesis

When we eat, neural activity travels from the tongue through the brain stem to the taste cortex. Presumably, it is the activation of this bark that contributes to our perception of taste and flavor.

During the first experiments with brain imaging, researchers believed that clusters of neurons specifically encoded certain tastes. Thus, these clusters, called hot spots, foreshadowed a menu with a hot spot for sweet, another for bitter, a third for salty, and a last for flavor.

“Our experiments show that there is no map with hot spots in the gustatory cortex of animals., said Alfredo Fontanini, director of the neurobiology and behavioral department at Stony Brook University. Rather, each taste is represented by series of neurons distributed in space and “sprinkled” throughout the cortex. Neurons can represent one or more taste sensations and form what is called an ensemble code. Basically, neurons behave like instruments in an orchestra playing different notes to form a chord.“

No taste “mapping” in the brain

On several occasions, the researchers were able to demonstrate activation of these neurons in mice. Therefore, they were able to see that some neurons react to only one taste, while others identify several.

Their analysis confirmed that neuron responses appear on multiple spatial scales in our brains, with no sign of clustering. The idea that taste is “mapped” in our brain is therefore wrong.

“Our findings are important because they address one of the basic organizing principles of brain function, underlines Alfredo Fontanini. Topographic maps are a ubiquitous feature of brain organization. Demonstrating that the spatial organization of taste responses is not as simple as previously thought makes us re-evaluate the neurobiological processes that underlie the perception of taste and brain functions related to taste “.