據(jù)livescience網(wǎng)站8月29日報道,，將舌頭味覺分成甜,、酸,、咸和苦4個區(qū)域是錯誤的?，F(xiàn)在舌頭能品嘗出五種基本味道已經(jīng)得到確認,，舌頭的任何部分都具備幾乎一樣的品嘗出這些味道的能力。
正如本月《自然》雜志所報道的,，科學們已經(jīng)確認舌頭上的一種蛋白質(zhì)能探測出酸味,。這是一種相當重要的蛋白質(zhì)，因為它使我們和其它哺乳動物能區(qū)別出腐爛或者未成熟食物,。此項研究發(fā)現(xiàn)獲得了高度贊譽,，因為這項對基因工程老鼠為期數(shù)年的不懈研究使科學家在鑒別味覺機理上取得了一個小小的突破。
這聽起來可能會讓人覺得過于簡單,，但是這項研究卻相當重要,。因為此項研究將有助于我們對比味覺更為復雜的視覺、聽覺及其它感覺的了解,。
只是在最近幾年我們才確認出味覺受體,。味覺研究取得的首次突破是在1974年，它糾正了一個多世紀以來無人能改變的錯誤舌頭“地圖”,。你可能也知道這個錯誤的舌頭“地圖”：能品嘗出“甜”味的味蕾位于舌尖,；“咸”味味蕾位于舌頭前部的一側(cè)；“酸”味味蕾在“咸”味味蕾的后面,；“苦”味味蕾在舌頭的后半部分,。據(jù)說葡萄酒杯就可以測試出這樣的舌頭味覺部位安排。
在家里就可以很容易檢驗出這種舌頭地圖是錯誤的,。放鹽在你的舌尖上,，你將品嘗出咸味。因為這樣或者那樣的原因,，科學家們從來就不愿意為爭論這種麻煩真相而自尋煩惱,。
這幅舌頭地圖誤導了包括我在內(nèi)的許多小學生，它使我們無法在科學課上獲得正確的經(jīng)驗。我也沒有能堅持自己的想法,，我能用我的舌頭后部分品嘗出甜味,。事實上舌頭除了甜、酸,、咸和苦外還可以品嘗出其它味道,。大多數(shù)科學家都同意20世紀初一位名叫池田的科學家所發(fā)現(xiàn)的第五種味道，即鮮味的存在,。此項研究發(fā)現(xiàn)在二十世紀的絕大多時間一直被西方所忽視,。這種味道就是谷氨酸鹽，它廣泛存在于日本食物中,，特別是昆布（一種類似于海菜的海藻）,、熏肉和味精中。池田教授分離出了這種物質(zhì)并獲得專利?，F(xiàn)在人們正就第六種油膩味覺受體的存在與否展開爭論,。
舌頭地圖研究可以追溯到1901年一名名叫D.P.哈尼格的德國科學家所發(fā)表的論文。盡管并不熟悉日本烹飪,，但是哈尼格還是著手測試舌頭對四種已知味道的相關(guān)敏感部位,。根據(jù)自愿者的主觀奇想，他得出了甜味敏感區(qū)域在舌尖等等一系列結(jié)論,。1942年,，一位著名的哈佛大學心理歷史學家愛德溫?波林同樣對日本烹飪毫不熟悉，他利用哈尼格的原始數(shù)據(jù)計算出了不同敏感水平的真實數(shù)量,。這些數(shù)量僅僅對應相關(guān)的靈敏度,，但是一些科學家卻利用這些數(shù)據(jù)繪制了一幅舌頭味覺地圖，而其它科學家卻又假定這些低靈敏度區(qū)域是不存在靈敏性的?，F(xiàn)代舌頭地圖就這樣誕生了,。
1974年，一名名叫維吉尼亞?庫林斯的科學家重新論證了哈尼格的研究,，并贊同哈尼格的大部分觀點：舌頭周圍的各個部分對四種基本味覺的靈敏度存在差異性,。（這使葡萄酒杯的制造者們欣喜若狂）。但是這種差異性卻相當小,，基本上可以忽略,。（葡萄酒杯制造者忽略這部分）。庫林斯發(fā)現(xiàn)舌頭周圍任何有味覺受體的部分都能品嘗出所有味道,，比如口腔上層后半部分的軟上腭，甚至會厭軟骨和防止食物進入氣管的口蓋都能品嘗出所有味道,。
后來的研究發(fā)現(xiàn)味蕾似乎包含了針對每種味道的50至100個受體,。盡管差異的程度仍然面臨爭議，但是以味覺的種類方式來描繪舌頭地圖卻顯得過于簡單化。為什么現(xiàn)在教科書還繼續(xù)使用舌頭舊地圖真是一個令人費解的迷,。
至于神話中所描述的,，舌頭是人體中最強壯的肌肉，以“力量”來定義似乎并不符合事實,。嚼肌或者顎肌是最強壯的肌肉主要得力于它的機械優(yōu)勢,，肌肉依附在顎上構(gòu)成了一種杠桿。如果進行純粹的力量測試,，四頭肌和臀大肌則是人體中橫紋肌纖維密度最高的地區(qū),。如果你以持續(xù)無疲勞為標準測量肌肉力量，那么心肌將是最強壯的肌肉,。從另一方面來講,，舌頭是會很快疲勞的，至少有些人是這樣,。
英文原文：
The Tongue Map: Tasteless Myth Debunked
The notion that the tongue is mapped into four areas—sweet, sour, salty and bitter—is wrong. There are five basic tastes identified so far, and the entire tongue can sense all of these tastes more or less equally.
As reported in the journal Nature this month, scientists have identified a protein that detects sour taste on the tongue. This is a rather important protein, for it enables us and other mammals to recognize spoiled or unripe food. The finding has been hailed as a minor breakthrough in identifying taste mechanisms, involving years of research with genetically engineered mice.
This may sound straightforward but, remarkably, more is known about vision and hearing, far more complicated senses, than taste.
Only in recent years have taste receptors been identified. One of the first breakthroughs in taste research came in 1974 with the realization that the tongue map was essentially a century-old misunderstanding that no one challenged.
You might know the map: The taste buds for "sweet" are on the tip of the tongue; the "salt" taste buds are on either side of the front of the tongue; "sour" taste buds are behind this; and "bitter" taste buds are way in the back. Wineglasses are said to cater to this arrangement.
The tongue map is easy enough to prove wrong at home. Place salt on the tip of your tongue. You'll taste salt. For reasons unknown, scientists never bothered to dispute this inconvenient truth.
The map has frustrated many a grade-schooler, including me, who couldn't get the experiment right in science class. I failed for insisting I could taste sugar in the back of my tongue.
In fact, there's more to taste than sweet, sour, salty and bitter. Most scientists agree that there's a fifth distinct taste, called umami, identified by a Japanese scientist named Kikunae Ikeda in the early 1900s (and ignored by the West for most of the twentieth century). This is the taste of glutamate. It is common in Japanese foods, particularly kombu, a type of sea vegetable similar to kelp, and in bacon and monosodium glutamate (MSG), which Ikeda isolated and patented. There's considerable debate about the existence of a sixth taste receptor for fat, too.
The tongue map dates back to research by a German scientist named D.P. Hanig, published in 1901. Not familiar with Japanese cuisine, Hanig set out to measure the relative sensitivity on the tongue for the four known basic tastes. Based on the subjective whims of his volunteers, he concluded that sensitivity to the four tastes varied around the tongue, with sweet sensations peaking in the tip, etc. That's all.
In 1942, Edwin Boring, a noted psychology historian at Harvard University, also apparently unfamiliar with Japanese cuisine, took Hanig's raw data and calculated real numbers for the levels of sensitivity. These numbers merely denoted relative sensitivities, but they were plotted on a graph in such a way that other scientists assumed areas of lower sensitivity were areas of no sensitivity. The modern tongue-map was born.
In 1974, a scientist named Virginia Collings re-examined Hanig's work and agreed with his main point: There were variations in sensitivity to the four basic tastes around the tongue. (Wineglass makers rejoiced.) But the variations were small and insignificant. (Wineglass makers ignored this part.) Collings found that all tastes can be detected anywhere there are taste receptors—around the tongue, on the soft palate at back roof of the mouth, and even in the epiglottis, the flap that blocks food from the windpipe.
Later research has revealed that taste bud seems to contain 50 to 100 receptors for each taste. The degree of variation is still debated, but the kindest way to describe the tongue map is an oversimplification. Why textbooks continue to print the tongue map is the real mystery now.
As for the myth that the tongue is the strongest muscle in the body, this doesn't seem to be true by any definition of "strength." The masseter, or jaw muscle, is the strongest due its mechanical advantage, in which the muscles attach to the jaw to form a lever. The quadriceps and gluteus maximus have the highest concentration of striated muscle fibers, a pure measure of strength. The heart is the strongest muscle if you measure strength as continuous activity without fatigue.
The tongue, on the other hand, wears out quickly—at least with some people.
