Sense of taste comes from brain, not tongue

The ability to perceive the five basic tastes — sweet, sour, salty, bitter and umami (savoury) — is hardwired in our brains, according to scientists who were able to switch taste on and off through brain manipulation.

“Taste, the way you and I think of it, is ultimately in the brain,” said study leader Charles S. Zuker, from the Columbia University Medical Centre (CUMC) in US.

“Dedicated taste receptors in the tongue detect sweet or bitter and so on, but it’s the brain that affords meaning to these chemicals,” said Zuker. The scientists used optogenetics, which allowed them to directly activate specific neurones with laser light.

Yueqing Peng, a postdoctoral associate in Zuker’s lab, examined whether manipulating the neurones in these brain regions could evoke the perception of sweet or bitter, without the mouse actually tasting either.

Sweet and bitter tastes were chosen because they are most critical and recognisable tastes for humans and other animals. When scientists injected a substance into the mice to silence the sweet neurones, the animals could not reliably identify sweet. They could, however, still detect bitter.

The animals regained their ability to taste sweet when the drug was flushed from the brain. The researchers were also able to make the animals think they were tasting bitter or sweet, even when the animal was only drinking water.