經濟學人 | 眼睛是大腦的窗戶(認知能力衰退或許有跡可循)

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題圖來自The Simpsons

經濟學人

6.30- 7.6 / 2018

專欄 |Science and Technology

Cognitive decline: Windows to the brain

眼睛是大腦的窗戶

BECAUSE it islocked awayinside the skull, the brain is hard to study. Looking at it requiresfinickymachines which use magnetism or electricity or both tobypassthe bone. There is just onetendrilof brain tissue that can be seen from outside the bodywithout anymucking aboutof this sort. That is theretina. Look into someone』s eyes and you are, in some small way, looking at their brain.

【要點】被「鎖在」頭骨里的大腦是很難進行研究的。( 美劇《生活大爆炸》里Penny問Amy為什麼像Sheldon這麼聰明的人會喜歡玩玩具火車，Amy說得把Shedlon大腦切開研究才能回答這個問題。) 使用磁或電的繁瑣機器可以繞過頭骨看到大腦。但其實有一個腦組織的邊角我們不需要藉助任何設備就可以從外界看到——視網膜。當你看著一個人的眼睛的時候，或許大概可能，你看著的是Ta的大腦。

lock away: to put sth. in a place or container which you fasten with a lock

e.g. Valuable items should belocked away.

finicky: adj. more complicated than necessary and difficult to deal with 繁瑣的

tendril: n. tendrils are thin organs of plants that wrap around (纏繞) other objects for support 卷鬚

muck about: to cause trouble or problems for someone

retina: n. the part at the back of your eye that sends light signals to your brain, where they are changed into images 視網膜

This being so, a group of researchers at Moorfields Eye Hospital in London, working with others around the world, decided to study the structure of the eye for signs of cognitive decline.Changes in the brain, they reasoned,might lead to changes in the nervous tissue connected to it.They focused on a part of the eye called theretinal nerve-fibre layer(RNFL). This is the lowest layer of the retina and serves to link thelight-sensitive tissueabove to thesynapses which lead to the brain. The team』s results, published in JAMA Neurology this week, show thatpeople with a thin RNFL are more likely to fail cognitive teststhan those with a thick one. They are also more likely to suffer cognitive decline as they age.

【要點】既然有這麼直接的研究對象，研究人員當然不會放過，他們決定研究眼睛的結構與認知能力下降的跡象是否相關。在大腦發生的改變，或許也會改變連接大腦的神經組織。對眼睛的主要研究集中在視網膜神經纖維層(RNFL)，這裡連接了光敏組織和神經突觸，向大腦傳輸信號。發布在JAMA Neurology上的研究結果發現視網膜神經纖維層(RNFL)薄的人群比厚的人群更不容易通過認知測試。隨著年齡的增長，他們也更容易出現認知能力衰退。

synapse/"sa?n?ps/: a synapse is the tiny gap across which a nerve cell, or neuron, can send an impulse to another neuron. 神經突觸

To discover this, the researchers relied on Britain』s Biobank, arepositoryof medical data from half a million volunteers. Of these, 32,000 aged between 40 and 69 had provided informationpertinentto the study, namelyocularscans and relevant scores from cognitive tests. None of these people had been diagnosed withdiabetesor aneurodegenerative disease, both of which could have interfered with the results.

【要點】研究人員使用了英國Biobank的資料庫，這裡有50萬志願者的醫療數據。從中獲取了32000名年齡在40-69歲志願者的眼部掃描數據和認知測試的相關分數。而且這些人中沒有糖尿病患者或神經退化疾病患者，這兩種都可能干擾結果。

repository/r?"p?z?t(?)r?/: n. a person, book, library etc considered as a store of information and knowledge 庫

pertinent: adj. relevant or applicable to a particular matter

ocular: adj. of or connected with the eyes or vision 眼睛的

The eye scans had been conducted using a technique calledoptical coherencetomography. This employslong-wavelength lighttopenetrate intoandscatter frombiological tissues,building upa three-dimensional picture of that tissue. Comparing the scans and the cognitive tests showed that those people whose RNFL was in the thinnest fifth of the group were 11% more likely to fail at least one cognitive test than those with an RNFL in the thickest fifth. A small portion of the originalcohortsat a second cognitive test three years later. This showed that those in the bottom two-fifths of RNFL thickness were twice as likely to have suffered a decline in cognitive function as those in the top fifth.

【要點】這裡的眼部掃描使用的是光學相干斷層掃描(optical coherence tomography)。這項技術採用了長波光穿透生物組織並從生物組織中散射，從而構建該組織的三維圖像。眼部掃描和認知測試數據表明，視網膜神經纖維層(RNFL)在該組中處於最薄的五分之一處的人在認知測試中失敗的比例比處在最厚的五分之一處的人多11%。三年後，這群人里的一小部分進行了第二次認知測試。結果表明，視網膜神經纖維層(RNFL)厚度處在底部五分之二的人可能出現認知能力衰退是處在頂部五分之一人的兩倍。

tomography:a technique for displaying a representation of a cross section through a human body or other solid object using X-rays or ultrasound 斷層攝影術

cohort/"k??h??t/: n.a group of people with a common statistical characteristic

e.g.the 1940–4 birthcohortof women

Although these results show only a correlation between eye structure and brain health,without an underlying explanation, they do suggest that scanning eyes is a fruitful road to diagnosing and even predicting cognitive decline. That would be warmly welcomed, especially fordementia, which currently lacks any form of predictive test.

【要點】這些結果顯示了眼睛結構和大腦健康之間的相關性，還無法進行解釋。(不過相關性有時候可以很迷惑人，比如每次用鋼筆寫作文都能得高分，高分和鋼筆有沒有相關性呢？也許只是因為用鋼筆字寫得比較工整)。但研究人員相信掃描眼睛是診斷甚至預測認知衰退的有效途徑。這對於無法預測的痴呆症是個福音。

In the future, then, a visit to theopticians might also lead to a diagnosis about mental health. Poets say thatthe eyes are the window to the soul.Perhaps. But this work suggests they are surely a window to the brain.

【要點】今後或許配眼鏡的時候也可以順便檢查下心智健康了。詩人說「眼睛是心靈的窗戶」，然而從研究結果看，更準備的應該是「眼睛是大腦的窗戶」。

optician: a person qualified to prescribe and dispense glasses and contact lenses 配鏡師

Cya ~

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