Page 21 - Science Focus (Issue 018)

5IF 4JHOBUVSF 4VNNFS 1BJO

By Yasine Malki 馬建生

Brain freeze, the signature summer pain we 大腦凍結（brain freeze） — 亦即是廣東話裡的「凍
experience when we are enthusiastically gulping 上腦」，是一種夏日限定的頭痛。每當我們貪婪地吞下一碗
down a large bowl of ice-cream, or slurping down 雪糕，或是大口地啜飲一杯沙冰的時候 — 突然一陣刺痛
a cup of refreshing slush…then you suddenly feel a 侵襲你的前額，彷彿要把整個腦袋冰封！
sharp, searing pain in your forehead, almost like your
brain has turned to ice! 眼見這個現象甚為普遍，而事實上我們亦齊備一系列
治療頭痛和偏頭痛 的藥物，你可能會覺得我們對此會有一
１
Seeing that it is so common, and the fact that
we have a massive repertoire of medication for 個清晰的解釋。可是，科學家卻不太肯定導致大腦凍結的
headaches and migraines , you may expect that we 詳細原因。在探討其可能原因之前，讓我先介紹甚麼是大
1
would have a clear explanation for this. However, 腦凍結吧！
scientists are still not sure of the specific mechanism 大腦 凍 結 科 學 上 叫「 翼 齶 神 經 節 疼 痛
that causes brain freeze. Before exploring its possible
causes, let’s first talk about what brain freeze is! （sphenopalatine ganglioneuralgia）」 [1]，有時又被
稱為「雪糕頭痛（ice-cream headache）」或「冷刺激頭
The scientific term for brain freeze is sphenopalatine 痛（cold-stimulus headache）」，它是出現在大腦額葉
ganglioneuralgia [1], or sometimes referred to as 和顳葉（眼睛後面）區域的短暫性頭痛 [2]，持續時間為數
ice-cream headache or cold-stimulus headache. 秒至數十秒不等，有時更會長達一至兩分鐘，誘發的原因
Induced by the consumption of a cold product, like
an iced beverage or ice cream, at a very rapid rate, 是因為我們狼吞虎嚥地吃或喝下冰凍飲料、雪糕等冷凍食
brain freeze is a short-term headache in the frontal 品。這現象正常並不會為身體帶來長遠的影響，它被認為
and temporal (behind the eyes) regions of our head [2] 可能是從進化而來的機制，提醒我們要減慢進食冰凍食品
that lasts for seconds, or sometimes up to one or two 的速度 [3]。
minutes. Not normally leaving any long-term effects,
this phenomenon is suspected to be an evolutionary 那問題來了，既然食物是應該進入消化道的，那麼它跟
temperature regulator, telling the body to slow down 頭部有著甚麼關係，可以引致大腦凍結？而且，我們的大腦
the consumption of cold products [3]. 並不像皮膚那樣具有能探測冷熱的結構，那麼它又怎樣能
感覺到嘴裡的冰冷呢？
The question is, given that food travels down our
digestive tract, how does it connect with our 答案在於冷凍物與口腔頂部和喉
head and cause brain freeze? Also, our 嚨後方，一個叫「顎（palate）」的
brains are not equipped with sensory 區域接觸後所觸發的反應。那個
components to detect heat as we do 區域有著很多血管，高密度的血
in our skin, so how can it sense the 管穿梭往來該處。其中一個主
cold in our mouth?
流理論建基於喝下冰水後通

19