Areas of the tongue and different tastes - myth?

[Revtim]

I was reading this old Cecil column about salt and pepper and Cecil mentions “the salt-sensing taste buds at the tip of the tongue”.

I could have sworn that the idea that different parts of the tongue were responsible for different tastes (salt, sweet, sour, etc) had been debunked, even though the idea and the same picture showing the areas still shows up in modern texts and webpages. But a web search came up with nothing, and a SDMB search came up with this thread from about a year and a half ago asking the very same question, but no clear answer.

I did a quick experiment with salt, and I clearly tasted it on the back of my tongue, and the sides near the back.

Did I catch Cecil in an error? I’d have put this in the “Comments on Cecil’s Columns” forum but the column wasn’t really about this. Plus, I think the question needs the traffic of GQ to get answered (although it didn’t do the trick in the other thread). Of course, if the mods decide to move this, it’s their call.

[GorillaMan]

No knowledge to impart…but I always thought the tip of the tongue had the sweet receptors, and the back the salt.

[Dr.Lao]

All of your tastesbuds are capable of tasting all four tastes (sweet, salt, sour, bitter), but ones on certain areas of the tongue are more sensitive to one taste over the others.

[Colibri]

There are actually five kinds of taste receptors, the recently-discovered fifth one, called “umami,” being to MSG.

From here

• A single taste bud contains 50-100 taste cells representing all 5 taste sensations (so the classic textbook pictures showing separate taste areas on the tongue are wrong).

’ ’ ’

• Although a single taste cell may have representatives of several types of receptor, one type may be more active than the others on that cell. And, no single taste cell contains receptors for both bitter and sweet.

[Colibri]

From here

There has been some controversy as to whether the familiar taste maps of the human tongue, which appear in every textbook, are correct. Taste sensation can be localised on the tongue but does the tongue have regions that are more sensitive to one taste modality than another? Fungiform papillae are concentrated on the anterior tip of the tongue and anterior lateral margins in humans and it has been demonstrated that NaCl threshold was inversely related to the number of fungiform papillae (more papillae = more sensitivity, lower threshold). In a study of human fungiform papillae it was found that taste buds can respond to NaCl only or to both NaCl and sucrose. The responses to NaCl and sucrose occurred in different cells within the taste bud. Thus, one can infer that fungiform papillae are salt-sensitive but this does not mean they are insensitive to other tastes. Bitter receptors are not uniformly distributed over the tongue. In rats the bitter receptors are expressed in a subset of taste cells in all papillae but they are more concentrated in foliate and circumvallate papillae situated at the sides and the back of the tongue. Furthermore, alpha-gustducin, which is the G-protein coupled to the T2R bitter receptors (see below), is expressed more in circumvallate than fungiform papillae in the rat. One rather more empirical approach to resolving this question is to stimulate the different areas of the tongue directly. Thermal stimulation of the anterior sides of the tongue in humans (fungiform papillae and the chorda tympani nerve) evokes sweet and salt/sour taste. While thermal stimulation of the rear of the tongue (foliate/circumvallate papillae and glossopharyngeal nerve) causes a different relationship between temperature and taste to the anterior stimulation. One can conclude that the classical “taste map” is an over simplification. Sensitivity to all tastes is distributed across the whole tongue and indeed to other regions of the mouth where there are taste buds (epiglottis, soft palate), but some areas are indeed more responsive to certain tastes than others.

[Revtim]

Excellent Colibri, thank you.