The sight of taste: live observations of taste buds in action

Scientists have for the first time captured live images of taste buds in the process of taste sensation thanks to a new method of multiphoton imaging.

The research, published in Nature's Scientific Reports, shows how an international team of researchers were able to image single cells on the tongue of a mouse, with a specially designed microscope.

Two-photon microscopy – a form of multiphoton imaging – is an advanced high-resolution fluorescence imaging technique that allows imaging of living tissues at higher depths than conventional optical microscopy

On the human tongue there are approximately 2,000 taste buds that can distinguish between at least five tastes: sweet, sour, salty, bitter and umami.

However, the relationship between the cells within a taste bud and our perception of taste is not well understood. Professor Seok-Hyun Yun, from Harvard Medical School, said: "With this new tool we have shown that each taste bud contains taste cells for different tastes."

Surprisingly, they also found that taste cells not only responded to molecules on the cells surface but also with molecules within the bloodstream.

Assistant Professor Myunghwan (Mark) Choi, from the Sungkyunkwan University in South Korea, said: "We think that tasting might be more complex than we expected, and involve an interaction between the food taken orally and blood composition."

The team developed a special imaging window to facilitate microscopic access to the tongue of a living mouse. They then used an infrared laser to activate fluorescence on the tongue. Doing this at the same time as administering flavour molecules to the tongue, allowed the researchers to gather three dimensional microanatomy of functioning taste buds up to 0.25 mm into the surface of the tissue.

Other studies have helped to identify the areas of the brain associated with taste. The group is now trying to develop an experiment where they can monitor the brain while imaging the tongue to track the full sensation of taste.

Dr Steve Lee, from The Australian National University, said: "We've watched live taste cells capture and process molecules with different tastes."

He added that this new technique means that we can now simultaneously capture the neurological and physiological events involved in taste and fully unravel the logic behind it.