According to the HHMI, the Howard Hughes Medical Institute and NIH scientists have discovered how different tastes are processed by distinct areas of the brain.

The researchers published their work in the September 2, 2011, issue of the journal Science.

From the HHMI website —

Zuker, Ryba, and other collaborators had previously identified unique taste receptors and taste receptor cells for each taste – uncovering a “one taste, one cell class” coding scheme. Activating these receptor cells triggered innate behaviors in mice: attraction to sweet, umami, and low salt and aversion to bitter, sour, and high salt.

With this clear link between taste and “hardwired” behaviors, the researchers wondered why different tastes would be processed by the same neurons in the brain. They suspected that the previous experiments had missed something.

So Xiaoke Chen, a postdoctoral associate in Zuker’s lab tried a powerful new technique, called two-photon calcium imaging, to determine which neurons responded when an animal is exposed to different taste qualities.

When a neuron is activated, it releases a wave of calcium throughout the cell. So the level of calcium can serve as a proxy for measuring activation of neurons. The researchers injected dye into the neurons of mice that made those cells light up with fluorescence every time calcium was released.

Then, they looked at the brains of the mice under high-powered microscopes that allowed them to watch hundreds of nerve cells at a time deep within the brain of mice. When a cell was activated, the researchers saw it fluoresce.

This allowed them to monitor the activity of large ensembles of cells, as opposed to previous methods, which tracked only a few cells at a time. They observed that when a mouse is given something bitter to taste, or the receptors on its tongue that sense bitter are stimulated, many neurons in one small, specific area of the brain light up.

When the mouse is given something salty, an area a few millimeters away is activated. Each taste corresponded to a different hotspot in the brain. None of the areas overlapped—in fact, there was space between all of them.

These findings indicate that neurons that respond to specific tastes are arranged in a “gustotopic map.” Scientists are reveling that this is the first map that shows how taste is represented in the mammalian brain.

For more on this story see: New Map Shows Where Tastes are Coded in the Brain