大腦中那些神經的連接構成億萬世界

So many things come down to connections -- especially the ones in your brain.
很多事情歸根結底都是連接――尤其是你大腦中的那些神經。

Women and men display distinctive differences in how nerve fibers connect various regions of their brains, according to a half-dozen recent studies that highlight gender variation in the brain's wiring diagram. There are trillions of these critical connections, and they are shaped by the interplay of heredity, experience and biochemistry.
近來，有半打之多的研究着重探索了大腦接線圖中的性別差異。這些研究表明，在神經纖維如何連接大腦各個區域方面，男性和女性顯得截然不同。人腦中遍佈着上萬億這樣的關鍵連接，而遺傳因素、人生經歷和生物化學的相互影響、相互作用又塑造了這些連接的形成。

No one knows how gender variations in brain wiring might translate into thought and behavior -- whether they might influence the way men and women generally perceive reality, process information, form judgments and behave socially -- but they are sparking controversy.
目前尚不清楚，大腦連接中的性別差異可能會如何傳導至人們的言行中――它們是否可能會影響一般男性與女性解讀現實、處理信息、社交行爲和形成判斷的方式――但它們現在卻引發了爭議。

'It certainly is incendiary,' said Paul Thompson, a professor of neurology and director of the University of Southern California's Imaging Genetics Center. He is directing an effort to assemble a database of 26,000 brain scans from 20 countries to cross-check neuroimaging findings. 'People who look at findings about sex differences are excited or enraged,' he said.
南加州大學(University of Southern California)基因影像學中心(Imaging Genetics Center)負責人、神經學教授保羅・湯普森(Paul Thompson)說：“那肯定會點燃爭議的導火索。”爲了反覆覈對神經影像學的研究成果，湯普森正帶頭致力於組建一個數據庫，該數據庫將包含26,000份來自20個國家的腦部掃描資料。他說：“那些查看有關性別差異研究成果的人，有些興奮不已，有些則忿怒填胸。”

Researchers are looking at the variations to explain the different ways men and women respond to health issues ranging from autism, which is more common among men, and multiple sclerosis, which is more common among women, to strokes, aging and depression. 'We have to find the differences first before we can try to understand them,' said Neda Jahanshad, a neurologist at USC who led the research while at the University of California, Los Angeles.
研究人員正在查看這些變化以解釋男性和女性對健康問題的不同反應方式。這些問題包括從在男性中更常見的孤獨症到女性中更常見的多發性硬化症、再到中風、衰老和抑鬱症。南加州大學(USC)神經病學家妮達・扎哈沙德(Neda Jahanshad)在加州大學洛杉磯分校(the University of California, Los Angeles) 帶領團隊完成了上述研究，她說：“在我們試着弄清這些問題之前，我們得先找到它們的區別。”

Dr. Jahanshad and her UCLA collaborators conducted a 2011 brain-imaging study of healthy twins, including 147 women and 87 men, to trace connections in the brain. She discovered 'significant' sex differences in areas of the brain's frontal lobe, which is associated with self-control, speech and decision-making.
2011年，扎哈沙德與她在加州大學洛杉磯分校的同仁們進行了一項針對健康雙胞胎的腦成像研究以追蹤大腦中的連接情況，該研究共涉及147名女性和87名男性。她後來發現，在人腦額葉區中存在着“顯著”的性別差異，該區域與自控力、決策力和演講能力都息息相關。

In the most comprehensive study so far, scientists led by biomedical analyst Ragini Verma at the University of Pennsylvania found the myriad connections between important parts of the brain developed differently in girls and boys as they grow, resulting in different patterns of brain connections among young women and young men.
在目前爲止最全面的一項研究中，以賓夕法尼亞大學(the University of Pennsylvania)生物醫學分析專家拉吉尼・維爾馬(Ragini Verma)爲首的科學家們發現，大腦重要部位之間的諸多連接隨着男孩、女孩的成長而演化出差異，導致年輕女性和男性的腦內連接模式不同。

The team imaged the brains of 949 healthy young people, 521 females and 428 males, ranging in age from 8 to 22. Like Dr. Jahanshad's team, Dr. Verma employed a technique called Diffusion Tensor Imaging to trace how water molecules align along the brain's white-matter nerve fibers, which form the physical scaffolding of thought. The study was reported earlier this month in the journal the Proceedings of the National Academy of Sciences.
該團隊對949名健康的年輕人進行了腦成像掃描，其中包括521名女性和428名男性，他們的年齡從8到22歲不等。同扎哈沙德的團隊一樣，維爾馬也採用了一種名爲“彌散張量成像(Diffusion Tensor Imaging)”的技術來追蹤水分子是如何同腦白質神經纖維相應移動的，這形成了該想法的理論框架。這一研究於本月早些時候發表在《美國國家科學院院刊》(Proceedings of the National Academy of Sciences)上。

The neural patterns emerged only when combining results from hundreds of people, experts said. In any one person, gender patterns may be subsumed by the individual variations in brain shape and structure that help make every person unique.
專家們稱，只有將來自成百上千人的結果歸納結合起來看時，纔會出現上述的神經模式。在任何某一個人身上，性別模式可能會被歸爲大腦結構和形態方面的個體差異，這些個體差異會使每個人都顯得獨一無二。

Dr. Verma's maps of neural circuitry document the brain at moments when it is in a fury of creation. Starting in infancy, the brain normally produces neurons at a rate of half a million a minute, and reaches out to make connections two million times a second. By age 5, brain size on average has grown to about 90% of adult size. By age 20, the average brain is packed with about 109,000 miles of white matter tissue fibers, according to a 2003 Danish study reported in the Journal of Comparative Neurology.
在創造思潮難抑之時，維爾馬的神經迴路圖會即時記錄下大腦的情況。據2003年發表在《比較神經外科學雜誌》(Journal of Comparative Neurology)上的一項丹麥研究表明，從嬰兒時期開始，人腦通常就會以每分鐘50萬個的速度長出神經元，並以每秒鐘200萬次的速度伸展、形成連接。到了五歲的時候，大腦的尺寸一般會長到成年人腦的90%。到了20歲的時候，平均而言，大腦中會佈滿長達109,000英里（約合175,418千米）的白質組織纖維。

Spurred by the effects of diet, experience and biochemistry, neurons and synapses are ruthlessly pruned, starting in childhood. The winnowing continues in fits and starts throughout adolescence, then picks up again in middle age. 'In childhood, we did not see much difference' between male and female, Dr. Verma said. 'Most of the changes we see start happening in adolescence. That is when most of the male-female differences come about.'
在飲食習慣、生活經歷和生物化學的影響刺激下，神經元與突觸從童年時期就開始被無情地修剪。這場篩選一陣一陣地繼續，然後開始貫穿整個青春期。維爾馬說：“童年時期，我們在男孩女孩身上看不到太多的差別。我們看到的大多數變化都發生在青春期。也就是那個時候，男女之間的大多數差別顯現出來了。”

Broadly speaking, women in their 20s had more connections between the two brain hemispheres while men of the same age had more connective fibers within each hemisphere. 'Women are mostly better connected left-to-right and right-to-left across the two brain hemispheres,' Dr. Verma said. 'Men are better connected within each hemisphere and from back-to-front.'
從廣義上說，女性在20歲時左右腦之間的連接更多，而同齡的男性則是左、右腦各自內部的連接纖維更多。維爾馬稱：“女性大腦兩個半球之間無論是從左至右、還是從右至左的連接都更好些。男性則是左、右腦各自內部的連接和後腦到前腦的連接更佳。”

That suggests women might be better wired for multitasking and analytical thought, which require coordination of activity in both hemispheres. Men, in turn, may be better wired for more-focused tasks that require attention to one thing a time. But the researchers cautioned such conclusions are speculative.
這就表明了女性可能在完成多重任務和分析思維方面更出色，而這需要左右腦之間的協作活動。反過來，男性可能在集中思維方面更爲出色，這需要他們將注意力一次只放在一件事情上。但研究人員謹慎表示，這些結論都是推測性的，並非定論。

Experts also cautioned that subtle gender differences in connections can be thrown off by normal disparities in brain size between men and women and in the density of brain tissue. Other factors, such as whether one is left- or right-handed, also affect brain structure.
專家們還警告稱，連接方面微小的性別差異會被當成男女大腦尺寸及腦組織密度方面的正常差異而被摒棄。其他一些因素，如一個人是不是左撇子或右撇子，也會影響大腦結構。

Also affecting results are differences in how computer calculations are carried out from one lab to the next. 'With neuroimaging, there are so many ways to process the data that when you do process things differently and get the same result, it is fantastic,' Dr. Jahanshad said.
影響結果的還有：從這個實驗室到下個實驗室，這其中如何進行電腦運算。扎哈沙德說：“關於神經影像，有很多方式都能用來處理其相關數據，所以當你使用不同的方法處理數據還能得到相同的結果時，那簡直不可思議。”