外刊 | 腦細胞能充值嗎？

相關知識

神經元(Neurons / Nerve Cells)是什麼？

• Neurons are the basic data processing units, the chips, of the brain.
• Each neuron receives electrical inputs from about 1000 other neurons.

視頻：神經元工作原理(這裡本來有視頻，有需要可以見公號)

# 經濟學人 #

Neuroscience: Brain teaser

神經科學：你說你的，我講我的

One paper says 「yes」. Another says 「no」

* brain teaser: a difficult question or problem that you try to solve for fun

TWO papers with starkly contradictory conclusions, published three weeks apart, have reignited debate about whether adult human brains can grow new neurons. For over a century, neuroscientists believed brains have acquired all the neurons they will ever have shortly after birth. But research over the past two decades has questioned this, producing evidence that new neurons are indeed generated in the adults of several species, people included. The matter is of more than just theoretical concern. Understanding how neurons are generated might lead to new ways of dealing with cognitive decline in ageing, neurodegenerative disease and even depression.

兩份研究結論完全相反的文章，在時隔三周內相繼發表；激發了新一輪的有關成年人是否可以生長出新神經元的爭論。在長達一個世紀的時間裡，神經科學家認為人類在出生後不久就已經獲得了所有需要的神經元。但經過近二十年的研究，這種想法開始被質疑；並且有證據表明有些物種在成年後會繼續生長神經元，包括人類。這並非單純的理論之爭，更重要的是如果理解了神經元的生長機制，諸如上了年紀的人認知能力下降，神經退化疾病，甚至抑鬱這些問題都有可能得到新的解決方案。

* be of: possess intrinsically / give rise to, e.g. This work is of great interest and value.

* neurodegenerative: relating to conditions such as Alzheimers disease or

Parkinsons disease that cause someone』s nerves to be damaged

The conflicting studies both involved inspecting post-mortem brain samples using a technique calledimmunostaining. The first to press, by Arturo Alverez-Buylla and Shawn Sorrells of the University of California, San Francisco, was published on March 15th in Nature. It claims that neurogenesis happens rarely, if at all, in adults. The other, by Maura Boldrini and René Hen at Columbia University, was published on April 5th in Cell Stem Cell. It claims neurogenesis persists through adulthood at a largely unchanged rate.

結論衝突的兩組研究都是以免疫染色的技術對已死亡大腦的樣本進行檢測。最先發表的是加州大學的Arturo Alverez-Buylla和Shawn Sorrells，他們在3月15日把結論發表在了Nature期刊上。他們的結論是：成年人的神經生長硬要說有的話，也是極其罕見。另一個結論來自哥倫比亞大學的Maura Boldrini和René Hen，4月5日發表在Cell Stem Cell 期刊上。他們的結論是：成年人的神經生長會繼續，且生長速率大致上保持穩定。

* immunostaining = immuno-(免疫的) + stain-ing(染色), was originally used to refer to the immunohistochemical staining of tissue sections

* neurogenesis = neuro(神經) + genesis(發生), the development of nerve tissues

Immunostaining uses antibodies that bind to particular proteins and fluoresce in particular colours. Employing it, both teams focused their attention on DCX and PSA-NCAM, two proteins found more abundantly in newly generated nerve cells than in older ones. They looked, in particular, at thehippocampuses, two parts of the brain (see picture) involved in memory formation—a process that might easily be assisted by the generation of new neurons.

免疫染色是用熒光著色與特定蛋白質結合的抗體。兩組研究都使用了這種方法，重點檢測DCX 和 PSA-NCAM這兩種蛋白質。因為這兩種蛋白質在新生成的神經元中比較多。他們特別觀察了大腦的兩個海馬體（見上圖紅色部分）。海馬體負責記憶形成，而這個過程中如果能有新生成的神經元的幫助，或許可以讓記憶形成更加容易。

* fluoresce [flu?res]: vi. exhibit or undergo fluorescence, 發熒光

* hippocampus [?h?p?(?)k?mp?s]: a complex neural structure (shaped like a sea horse) 海馬體（大腦有兩個海馬體，負責記憶和情感）

Using DCX and PSA-NCAM as indicators of youthful nerve cells, Dr Alverez-Buylla and Dr Sorrells describe a picture of abundant neurogenesis in prenatal and infant brains, which then declines sharply in the first year of life. The oldest hippocampus in which they saw new neurons had come from a 13-year-old. This supports the historical belief that adult brains do not generate new neurons. Dr Boldrini and Dr Hen, in contrast, saw signs of youthful neurons in people up to the age of 79.

把DCX和PSA-NCAM這兩種蛋白質作為衡量神經元"新鮮度"的指標，加州大學研究小組指出，在胎兒和嬰兒的大腦里有豐富的新生神經元，但在1歲之後開始銳減。他們在海馬體里能發現新生神經元的年齡最大為13歲。這個結論跟歷史上的看法一致。但是，哥倫比亞大學研究小組卻在成年人的大腦中發現了年輕的神經元，而且能發現這一現象的最大年齡提高到了79歲。

* prenatal: relating to the period of time when a woman is pregnant

How such contradictory conclusions emerged from similar approaches is now being debated. One difference was that Dr Alverez-Buylla and Dr Sorrells used samples collected up to 48 hours after death, whereas the upper limit used by Dr Boldrini and Dr Hen was 26 hours. That might be important. Studies on rats suggest DCX can break down within hours of death.

為什麼同樣的研究方法會得出對立的結果？有一點值得注意的是：加州大學小組使用的大腦樣本是在死後48小時收集的，而哥倫比亞大學小組把時間縮短到了死後26小時。這也許就是關鍵所在。曾經有對老鼠的研究表明，DCX蛋白質在死後數小時之內就能被分解。

Moreover, though both teams used immunostaining, their procedures differed in other respects. In particular, Dr Boldrini and Dr Hen looked only at teenagers and adults, so could not have picked up the change that Dr Alverez-Buylla and Dr Sorrells saw in the earliest years, which provided an important reference point for the effectiveness of immunostaining. Conversely, Dr Boldrini and Dr Hen used other lines of evidence, such as the volume of the hippocampus (which did not seem smaller in old brains than in young ones), to support their conclusions.

雖然兩個小組都使用了免疫染色的方法，他們在實施過程也有其他方面的差異。哥大小組的研究主體是青少年和成年人，並沒有涉及到加州大學小組有去觀察的胎兒和嬰兒時期，而這個時期的數據為免疫染色的有效性提供了重要參考。另外，哥大為了支持自己的結論，還提供了其他證據，比如海馬體的大小，並沒有因為上了年紀而變小。

The upshot is that old scientific cliché: 「more research is needed」. But the coincident publication of these two papers, each plausible in itself, is a useful reminder of the requirement, in science, to check the work. Then check it. Then check it again.

兩個結論都遠沒達到蓋棺定論，還需要更多的研究。不過能得出這種截然相反的結論，而且各自還有各自的合理性，就很值得在科學研究上一而再、再而三的多檢查了。

* upshot: the result of a process or an event

p.s. AI都在學神經了，人類不打算做點什麼嗎？讓大腦充值來得更猛烈些吧。