Decoded: How tongue keeps its tastes right

Signals sent by tongue's taste cells prevent the brain from confusing between bitter and sweet tastes, a study has showed. Humans perceive taste through thousands of tiny sensory organs called taste buds, which are located mostly on the upper surface of the tongue.

Each taste bud contains 50 to 100 taste cells, which contain molecules, known as receptors, that can detect each type of taste -- sweet, bitter, sour, salty, or umami (savory). These taste cells then relay this information from the tongue to the brain.

Using this knowledge, the scientists were able to rewire the taste-system of mice to perceive sweet stimuli as bitter tastes, and vice versa. The discovery provides new insights into how the tongue keeps its sense of taste organised despite the rapid turnover of the cells in its taste buds, the researchers said.

"Most portions of the brain circuits that govern taste are hardwired at birth, except in the tongue, where the cells in our taste buds -- taste receptor cells -- connect to taste neurons," said Hojoon Lee, Associate Research Scientist at Columbia University Medical Center (CUMC) in the US.
"It's a highly dynamic process. Taste cells are replaced every one to three weeks, and one type of receptor may be replaced by a different type.

Each time a new taste receptor cell is made, it needs to make the right connection with the brain," Lee added, in the paper detailed in the journal Nature. When taste receptor cells are produced, the cells most likely express dedicated molecular signals that attract the right complement of taste neurons.

"The taste system gives us a unique opportunity to explore how connections between taste cells and neurons are wired and preserved, in the face of random turnover of our sensory cells" Zuker said.