Are grapes sour? How brain decodes taste

Current Biology report says The ability to taste is crucial for food choice and the formation of food preferences

Researchers have discovered how taste is encoded in patterns of neural activity in the human brain.

A team of researchers from the German Institute of Human Nutrition in Potsdam and the Charite University Hospital in Berlin made the discovery.

The ability to taste is crucial for food choice and the formation of food preferences.

"Impairments in taste perception or hedonic experience of taste can cause deviant eating behaviour, and may lead to malnutrition or supernutrition," said lead researcher Kathrin Ohla.

"This knowledge is essential for the development of strategies to moderate deviant eating behaviour," Ohla noted.

Tastants in the mouth activate specific receptors on the tongue corresponding to each of the basic tastes: sweet, salty, sour, bitter, and savoury. The signal is then transduced further to the brain.

"This would be an important step to understanding how individual taste preferences are coded in the brain and of high relevance for clinical applications such as weight loss programmes," said co-researcher Niko Busch.

In the study, participants discriminated between sweet, salty, sour, and bitter tastants while their brain activity was recorded with electroencephalography (EEG) - a method that measures minuscule electrical signals generated by billions of neurons in the human neocortex.

Different tastes evoked different dynamic patterns of electrical activity. A machine learning algorithm could be trained to discriminate between these patterns.

Thus, given a piece of data, the algorithm could decode from the pattern of brain-wide activity which taste a participant had received in that moment.

This form of "mind reading" even made it possible to decode which of four tastants participants thought to have tasted when they were, in fact, incorrect.

The tastes that participants frequently confused with each other (e.g. sour and salty) were also frequently confused by the algorithm.

"The findings suggest that quality is among the first attributes of a taste represented in the central gustatory system," Ohla said.

The study was published in Current Biology.