Four of the five basic tastes — bitter, salty, sweet and umami — are processed at different hot spots in the brain.

Charles Zuker at Columbia University in New York and his colleagues used fluorescence microscopy to image neural activity in the partially exposed brains of anaesthetised mice while administering different-tasting chemicals to the animals' tongues. The images show discrete regions of neural activity in the primary taste cortex, each specific to a particular taste category and responsive to a range of chemicals within that category.

The authors could not pinpoint a hot spot for sour taste; they think that it may be outside the brain areas studied, or that acid stimuli act on other pathways, such as that for pain. The map could help researchers to understand how taste perception is integrated with other brain functions such as emotion and feeding behaviour, the authors say.

Science 333, 1262–1266 (2011)