Discovery that the tongue can ‘smell’ challenges age-old senses theory
When it comes to taste and smell, the brain has been getting far too much credit, according to new research published to Chemical Senses.
Scientists from the Monell Chemical Senses Center in the US have discovered that sensors used to detect odours in the nose – called functional olfactory receptors – are also found in human taste cells on the tongue.
This discovery suggests that the body’s primary interactions between the senses of taste and smell may begin in the tongue, rather than the brain.
While it would seem logical to assume that flavour equates to taste, in fact, the distinctive flavour of most food and drink actually comes more from smell. While taste has evolved to become a gatekeeper of a food type’s nutritional value or potential toxicity, smell helps us determine the quality of a food. When combined together and with other senses, it creates the multimodal sensation of flavour.
Until now, taste and smell were considered to be independent sensory systems that did not interact until their respective information reached the brain. However, Hakan Ozdener, senior author of the study, was inspired to look into the topic further after his young son asked if snakes extend their tongues to smell.
To make the discovery, Ozdener and his fellow researchers maintained living human taste cells in culture, which were probed using genetic and biochemical methods. They found that the human taste cells contain many key molecules known to be present in olfactory receptors.
Then, using a method known as calcium imaging, they showed that these taste cells responded to odour molecules, thus showing olfactory receptors may play a role in the taste system by interacting with taste receptor cells on the tongue.
“This [discovery] may lead to the development of odour-based taste modifiers that can help combat the excess salt, sugar and fat intake associated with diet-related diseases such as obesity and diabetes,” said Ozdener.
The next step for the research is to see whether olfactory receptors are preferentially located on a specific taste cell type – for example, sweet- or salt-detecting cells.
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