The notion of a “tongue map” for different tastes is a myth, according to scientists who have found that specialist brain cells handle different tastes.
Researchers at Columbia University in the US, found that every one of the thousands of sensors on the tongue can sense the full range of sweet, salty, bitter, sour, and umami (the savoury taste of glutamate).
Taste buds each have 50 to 100 receptors attuned to each category, which have a matching partner in the brain that receives signals.
Prof Charles Zuker, a lead author of the study, told BBC News: “The cells were beautifully tuned to discrete individual taste qualities, so you have a very nice match between the nature of the cells in your tongue and the quality they represent [in the brain].”
Scientists hope that the findings, published in Nature, could be used to help reverse the loss of taste sensation in old age.
The human tongue is popularly thought to have distinct zones for discerning sweet, bitter, sour, salty and savoury tastes, with the so-called “tongue map”, often seen in primary school textbooks.
But the theory, based on dodgy research published in 1901 by a German scientist named DP Hanig, was first debunked in 1974.
The new research also dismissed the alternative theory that brain cells respond to multiple tastes by finding “fine selectivity” in neurons.
Researchers tested communication between taste buds and the brain by engineering mice so their taste neurons would become fluorescent when activated.
When the mice were fed chemicals with specific tastes, scientists monitored the neuron response at the base of the brain with endoscopes.
The study said it revealed a “fine selectivity in the taste preference of ganglion neurons”, as well as a strong match between taste bud receptors and sensory neurons relaying information to the brain.
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