You would probably remember the diagram from school – a pink tongue with different regions marked for different tastes – bitter across the back, sweet across the front, salty at sides near the front and sour at the sides towards the back.
Even that biology experiment where we made sugar and salt solutions and touched different parts of our tongues to confirm the map was right!
The famous tongue diagram has appeared in hundreds of textbooks over the decades and the theory behind this map originated from a book written by Harvard psychologist Edwin Boring in 1942, which included a translation of a German paper, Zur Psychophysik des Geschmackssinnes, by Dirk P. Hänig, written in 1901.
BUT You will be surprised to know that the tongue may not have different regions specialized for different tastes!
In fact Neuroscientists and taste experts recently concluded that all regions of the tongue that detect taste respond to all five taste qualities with mild regional differences! Then again it is not so simple!
Messages about taste are sent to the brain via two cranial nerves – one at the back of the tongue and one at the front. As a further counter to the idea that different parts of the tongue detected different tastes, it was shown that even if the front nerve, the chorda tympani, is anaesthetised, people can still taste sweetness, which in the traditional tongue map is found at the tip of the tongue!
The next mystery has been how the brain decodes these messages delivered via the cranial nerve and in 2015 a team at Columbia University found that mice have specialist brain cells which respond to each taste!
So it is true that we have specialist equipment for each taste. But rather than being clusters of taste buds in particular regions of the tongue, they are specialized receptor cells with matching neurons in the brain, each attuned to a particular taste!
Different areas of the tongue can taste anything, but although some regions are slightly more sensitive to certain tastes though those difference are minute!
Taste thresholds have been also been shown to differ at different locations within the oral cavity where gustatory receptors are found. However, the relationship between the stimulation of particular taste receptors and the subjective spatially-localized experience of taste qualities is uncertain.
So although the existence of the ‘tongue map’ has long been discredited, the psychophysical evidence clearly demonstrates significant differences in taste sensitivity across the tongue, soft palate, and pharynx which are the sites where taste buds have been documented.
If, however, the claim is instead taken to relate to the perceived
spatial localization of taste qualities, and/or about sensitivity differences on different parts of the tongue, then psychophysics is more likely
to provide a meaningful answer than neurophysiology.
Indeed, it is worth remembering that Hanig (1901) original work was titled Zur Psychophysik des Geschmackssinnes which actually meant ‘The Psychophysics of Taste‘
So the actual idea behind the tongue taste map could have been lost in translation! Because in the original work Hanig: “believed that if the thresholds for his four stimuli (sucrose salt, quinine sulfate, and hydrochloric acid) could be shown to vary differentially around the perimeter of the tongue, then this would support the argument that these four tastes had distinct physiological mechanisms.
For those who interpret the tongue map as highlighting differences in
sensitivity, the relevant question to ask then becomes one of whether the
spatial differences in sensitivity are sufficiently great to merit consideration or not.
At the same time, however, there has also been growing interest in
the relationship between the composition of oral microbiota and taste
perception. There is also more studies between Gut health and taste perception! In fact even between individuals, there is a difference in taste perception! Some can even taste a food being bitter or going bad or on the verge of it (Like my dad, wife and son! in that order!)
You also have the fact that you need a good nose for getting a proper taste! Which is why your food taste bad in a cold or even in the sky! Beyond all that the most important is your mood and hunger! Even the tastiest food is bland when you are down! While a simple curd rice is tasty when you are in a good mood (Though for an average south Indian, curd rice is always tasty!).
Now do not worry about any map of the tongue! If you are hungry, simply eat!
And if you are bond then simply shoot! A quick sketch inspired by Pierce Brosnan’s bond!
He will always be my favourite bond at least for now!
Remember that intelligence and secret agents in real life do not look or act like bond! They gel with the crowd and do not stand out!
Big salute to those scores of intelligence agents who do the work of national security in the shadows!
Jai hind!
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