Brain matter

1.大腦里的物質(zhì)

Throughout history, the human brain has been remarkably good at dismissing itself. Everyone from ancient Egyptians to Aristotle has downplayed the role of the mysterious stuff between our ears. Famed anatomist Galen gave the brain credit as commander of movement and speech, but even he brushed aside the white and gray matter, figuring the fluid-filled ventricles inside the brain did most of the work.

縱觀歷史，人類的大腦總是很喜歡把自己“隱身”。從古埃及人一直到亞里斯多德，沒有人對我們兩耳之間的神秘器官給以應(yīng)有的重視。著名的的解剖學(xué)家蓋倫曾給與大腦行為和語言的指揮官的贊譽，但是他始終認為是充滿液體狀物質(zhì)的腦室在起主要作用，而把白質(zhì)灰質(zhì)晾在了一邊。

Human brains are big...

2.人腦很大...

The average adult brain weighs just under 3 pounds (between 1.3 and 1.4 kilograms). Some neurosurgeons describe the texture of a living brain as that of toothpaste, but according to neurosurgeon Katrina Firlik, a better analogy can be found in the local health-food store.

成年人的大腦平均重量接近3磅（1.3-1.4千克）。有神經(jīng)外科醫(yī)師把大腦的質(zhì)感形象的描述為牙膏，但是據(jù)卡特麗娜·弗里克（Katrina Firlik）醫(yī)生說，在保健食品店里可以找到與人腦極其相似的東西。

"[The brain] doesn't spread like toothpaste. It doesn't adhere to your fingers the way toothpaste does," Firlik writes in her memoir, "Another Day in the Frotal : A Brain Surgeon Exposes Life on the Inside" (Random House, 2006). "Tofu — the soft variety, if you know tofu — may be a more accurate comparison."

“（大腦）不會像牙膏一樣攤開，也不會像牙膏一樣黏在你的手指上”弗里克在她的文章中寫道?！赌X外科醫(yī)生的一天》（蘭登書屋，2006）這本書中寫道：“豆腐——軟的那一種，如果你見過的話——可能用來比喻大腦更為準確。

If you aren't charmed by that description, consider this: About 80 percent of the contents of your cranium is brain, while equal amounts of blood and cerebrospinal fluid, the clear liquid that buffers neural tissue, make up the rest. If you were to blend up all of that brain, blood and fluid, it would come to about 1.7 liters, or not quite enough to fill a 2-liter soda bottle.

如果你對上面的描述不感興趣，那么試著這樣想：你的頭蓋骨里80%的物質(zhì)都是你的大腦，剩下的是10%的血液和10%脊髓液（一種透亮的液體，用來緩沖神經(jīng)組織）。如果你把大腦、血液和脊髓液都攪在一起，大約有1.7公升，可能裝不滿一個2公升的蘇打飲料瓶。

...But they're getting smaller

3....但它們在變小

Don't get too cocky about your soda-bottle-sized brain. Humans 5,000 years ago had brains that were even larger.

不要以為自己有著蘇打飲料瓶那么大的腦子就無敵了。五千年前，人類的大腦比現(xiàn)在還要大。

"We do know from archaeological data that pretty much everywhere we can measure — Europe, China, South Africa, Australia — that brains have shrunk about 9 cubic inches (150 cubic centimeters), from an average of about 82 in3 (1,350 cm3). That's roughly 10 percent," University of Wisconsin at Madison paleoanthropologist John Hawks told LiveScience in 2009.

2009年，人類學(xué)家約翰 考克（John Hawks）來自位于麥迪遜市的威斯康星州立大學(xué)，他告訴科學(xué)在線說，“我們的確從所能測量到的所有考古學(xué)數(shù)據(jù)中——包括歐洲、中國、南非、澳大利亞——可以得出人類的大腦從原來的大約82立方英寸（1，350立方厘米），到現(xiàn)在縮小了大約9立方英寸（150立方厘米）。粗略的算都有10%了?！?/p>

Researchers don't know why brains might be shrinking, but some theorize that they're evolving to be more efficient. Others think our skulls are getting smaller because our diets include more easily chewable foods and so large, strong jaws are no longer required.

研究人員還不清楚為什么人類的大腦會越來越小，但有些人提出理論說，大腦正在向高效性進化。另一些人認為由于我們的飲食更加趨向于那些易咀嚼的食物，導(dǎo)致原來寬大、強勁的頜骨逐漸退化，進而使得我們的頭蓋骨也隨之縮小了。

Whatever the reason, brain size doesn't directly correlate with intellect, so there's no evidence that ancient man was brainier than humans of today.

無論是什么原因，人腦的大小和智力并沒有直接的聯(lián)系，所以也沒有證據(jù)表明古代人就比現(xiàn)代人更聰明。

Our brains burn through energy

4. 我們的大腦燃燒能量

The modern brain is an energy hog. The organ accounts for about 2 percent of body weight, but it uses about 20 percent of the oxygen in our blood and 25 percent of the glucose (sugars) circulating in our bloodstream, according to the American College of Neuropsychopharmacology.

現(xiàn)代人的大腦是個能量的“貪吃鬼”。根據(jù)美國神經(jīng)精神藥理學(xué)會稱，大腦雖然才占到人類體重的2%左右，卻消耗著我們血液中20%的氧氣，以及循環(huán)在血流中25%的葡萄糖。

These energy requirements have spurred a debate among anthropologists about what fueled the evolution of big brains in the first place. Many researchers credit meat, citing evidence of hunting in our early ancestors. But meat would have been an unreliable food source, say other scientists. A 2007 study published in the Proceedings of the National Academy of Science found that modern-day chimps know how to dig for calorie-rich tubers on the savanna. Perhaps our ancestors did the same, boosting their brainpower with veggies.

這些能量需求在人類學(xué)家之間引起了一場唇槍舌劍，爭論的焦點是：是什么首先加速了大腦的進化。一些學(xué)者認為這都是肉的功勞，證據(jù)就是人類祖先早期以狩獵為生。但其他科學(xué)家們認為，肉這種食物來源在當時是極其不穩(wěn)定的。2007年，發(fā)表在《國家科學(xué)院學(xué)報》的一項研究發(fā)現(xiàn)，當今生活在熱帶（亞熱帶）稀樹大草原上的黑猩猩知道怎樣挖出富含卡路里的塊莖。也許我們祖先就是這樣做的，通過吃蔬菜來促進智力的發(fā)育。

As for what motivated the brain to balloon in size, there are three major hypotheses: climate change, the demands of ecology, and social competition.

至于是什么推動了人腦的大幅增長，現(xiàn)在存在三種假設(shè)：氣候變化、生態(tài)需求和社會競爭。

Wrinkles make us smart

5. “皺紋”使我們更聰明

What's the secret to our species' smarts? The answer may be wrinkles. The surface of the human brain is convoluted by deep fissures, smaller grooves called sulci, and ridges called gyri. This surface is called the cerebral cortex and is home to about 100 billion neurons, or nerve cells.

我們?nèi)祟惵斆鞯拿卦E是什么？答案也許就是“皺紋”。人腦的表面錯綜復(fù)雜，有深的裂紋，淺的溝槽，又叫做腦溝，還有凸起，學(xué)名叫腦回。這層表面叫做大腦皮層，上面有大約1000億個神經(jīng)元，或神經(jīng)細胞。

The folded, meandering surface allows the brain to pack in more surface area — and thus, more processing power — into the limited confines of the skull. Our primate relatives show varying degrees of convolution in their brains, as do other intelligent creatures like elephants. In fact, research done by Emory University neuroscientist Lori Marino has found that dolphins have even more pronounced brain wrinkles than humans.

這種褶皺、蜿蜒的表面使得人腦，在有限的頭骨空間里，具有更大的表面積——進而，具有更強的數(shù)據(jù)處理能力。作為人類近親們的靈長動物，他們的大腦也呈現(xiàn)出不同程度的褶皺，其它聰明的動物，如大象亦是如此。事實上，埃默里大學(xué)的神經(jīng)學(xué)家勞瑞 馬瑞諾（Lori Marino）曾在一項研究中發(fā)現(xiàn)，海豚大腦上的褶皺要比人類的更加明顯。

Most of our brain cells aren't neurons

6.絕大部分的腦細胞不是神經(jīng)元

The old saw that we use just 10 percent of our brainpower isn't true, but we now know that neurons make up just 10 percent of our brain cells.

以前有種說法是：我們只利用了10%的大腦智能，但這只是個謬論。而我們現(xiàn)在知道了神經(jīng)元只占到大腦細胞的10%。

The other 90 percent, which account for about half the brain's weight, are called glia, which means "glue" in Greek. Neuroscientists used to think glia were simply the sticky stuff that holds neurons together. But recent research has shown glia to be much more. A 2005 paper in the journal Current Opinions in Neurobiology laid out the roles of these unsung cells, which range from mopping up excess neurotransmitters to providing immune protection to actually promoting and modulating synapse growth and function. (Synapses are the connections between neurons.) It turns out the silent majority isn't so silent after all.

剩下的90%叫做神經(jīng)膠質(zhì)（glia這個詞在希臘語里意思是“膠水（glue）”），占了大腦總重的一半左右。神經(jīng)學(xué)家過去認為這些粘糊糊的膠質(zhì)只是用來把神經(jīng)元黏合在一起。但最新的研究表明，神經(jīng)膠質(zhì)的作用要遠遠大得多。2005年，發(fā)表在《心理科學(xué)進展》上的一篇論文指出，這些默默無聞的細胞所承擔(dān)的任務(wù)包括：吸收多余的神經(jīng)傳遞素、保護免疫系統(tǒng)以及促進和調(diào)整神經(jīng)鍵的成長和功用等。（神經(jīng)鍵是神經(jīng)元之間的連接部分）看來這些少言寡語的大多數(shù)干起活來一點兒也不含糊。

The brain is an exclusive club

7. 大腦是個VIP會所

Like bouncers at a night club, an assembly of cells in the brain's blood system, called the blood-brain barrier, lets only a few molecules into the nervous system's inner sanctum – the brain. The capillaries that feed the brain are lined with tightly bound cells, which keep out large molecules. Special proteins in the barrier transport necessary nutrients and substances into the brain. Only an elite few make it through.

就像夜總會門口的保鏢一樣，在大腦的血液系統(tǒng)中也有這樣一組細胞叫做血-腦屏障，它們只允許少數(shù)分子進入神經(jīng)系統(tǒng)的密室——大腦。為大腦提供補給的毛細血管里緊密排列著相連的細胞，以防止大分子的進入。屏障中的特殊蛋白質(zhì)負責(zé)運輸大腦所需的營養(yǎng)及物質(zhì)。只有“精英”才能過得去。

The blood-brain barrier protects the brain, but it can also keep out lifesaving medications. Physicians trying to treat brain tumors can use drugs to open the junctions between cells, but that leaves the brain temporarily vulnerable to infection. One new way to sneak meds past the barrier might be nanotechnology. A 2009 study published in the journal Cancer Research showed that specially-engineered nanoparticles can cross the barrier and attach to tumor tissue. In the future, combining nanoparticles with chemotherapy drugs could be one way to target tumors.

雖說血-腦屏障保護著大腦，但有時它也會把救命的藥物拒之門外。治療腦部腫瘤的醫(yī)生雖然能夠利用藥物打開細胞間的接縫，但這也會使得大腦暫時很容易受到感染。把藥物送入大腦的一個新的方法可能會是納米技術(shù)。2009年，發(fā)表在《癌癥研究》上的一篇論文指出，新型的納米粒子可以穿過屏障，并附著在腫瘤組織上。未來，把納米粒子與化療藥物相結(jié)合的手段可能成為治療腫瘤的方法之一。

The brain starts as a tube

 

8.大腦最初的形狀像根管子

The foundation for the brain is set early. Three weeks after conception, a sheet of embryonic cells called the neural plate folds and fuses into the neural tube. This tissue will become the central nervous system.

大腦開始形成的時間很早，懷孕三個星期后，一系列胚細胞，又叫神經(jīng)板，交疊融合進神經(jīng)管。這一組織將來會成為中樞神經(jīng)系統(tǒng)。

The neural tube grows and differentiates throughout the first trimester. (When cells differentiate they specialize into various tissues needed to create body parts.) It isn't until the second trimester that glia and neurons begin to form. The brain doesn't wrinkle up until even later. At 24 weeks, magnetic resonance imaging shows just a few nascent grooves in the otherwise smooth surface of the fetal brain, according to a 2000 study in the journal Radiology. As the third trimester begins in week 26, the grooves deepen and the brain begins to look more like that of a newborn.

在前三個月，神經(jīng)管會一直生長、分化。（細胞分化，即細胞逐漸具備不同的特性，以形成不同的器官）直到第四個月，神經(jīng)膠質(zhì)和神經(jīng)元才開始形成。再往后，大腦逐漸形成褶皺。根據(jù)2000年發(fā)表在《放射線學(xué)》一項研究，孕期第24周時，磁共振成像顯示，在胎兒原本平滑的大腦皮層上出現(xiàn)了一些新的溝槽。懷孕第7個月，也就是差不多在26周的時候，這些溝槽越來越深，嬰兒的大腦就開始成形了。

Teen brains aren't fully formed

9. 青少年的大腦還沒有完全定型

Parents of stubborn teenagers rejoice, or at least relax: That adolescent attitude stems, in part, from the vagaries of brain development.

能讓整日為孩子頭疼的家長們高興，或起碼松口氣兒的事兒是：青少年叛逆的性格，一部分

是由于大腦發(fā)育期時的異常而造成的。

The gray matter of the brain peaks just before puberty and is pruned back down throughout adolescence, with some of the most dramatic development happening in the frontal lobes, the seat of judgment and decision-making.

大腦中的灰質(zhì)會在青春期前開始縮減，并且這一進程將貫穿整個青少年時期，同時大腦額葉

部，也就是控制人的判斷和決策的部位，也會發(fā)生非常大的改變。

A 2005 study published in the journal Child Development found that the parts of the brain responsible for multitasking don't fully mature until we're 16 or 17 years old. And research presented at the BA Festival of Science in 2006 revealed that teens also have a neural excuse for self-centeredness. When considering an action that would affect others, teens were less likely than adults to use the medial prefrontal cortex, an area associated with empathy and guilt. Teens learn empathy by practicing socializing, the researchers said. So much for grounding them until they're 20.

2005年，發(fā)表在《兒童發(fā)展》上的一項研究發(fā)現(xiàn)，人腦中負責(zé)多任務(wù)處理的部分在人們16或

17歲時才會發(fā)育成熟。2006年，在BA科學(xué)節(jié)上展示的研究也指出，青少年的自我主義是可以

用神經(jīng)學(xué)來解釋的。研究人員表明，當處在青春期的孩子在考慮做一件有可能會影響到他人

的事情時，他們多半不會像成年人一樣，會用到中前額葉皮質(zhì)，這一會讓人產(chǎn)生同情和內(nèi)疚

的大腦部位，來思考這件事。青少年需要通過社會實踐才能學(xué)會什么是同情。所以等到

了20歲，就不必對他們禁足了。

Brains never stop changing

10.大腦時刻在改變

Scientific wisdom once held that once you hit adulthood, your brain lost all ability to form new neural connections. This ability, called plasticity, was thought to be confined to infancy and childhood.

過去一個普遍的科學(xué)常識是：一個人一旦成年，其大腦就喪失了建立新的神經(jīng)聯(lián)系的能力

了。這種稱作“可塑性”的能力，被認為只存在于人的嬰兒和孩童時期。

Wrong. A 2007 study on a stroke patient found that her brain had adapted to the damage to nerves carrying visual information by pulling similar information from other nerves. This followed several studies showing that adult mice could form new neurons. Later studies found more evidence of human neurons making new connections into adulthood; meanwhile, research on meditation showed that intense mental training can change both the structure and function of the brain.

以上說法是錯誤的。2007年，一項對一位中風(fēng)患者的研究發(fā)現(xiàn)，她的大腦通過連接其他未受

損的神經(jīng)，獲取受損神經(jīng)無法傳遞的視覺信息，從而對損傷進行修復(fù)。接下來的幾個研究也

表明，成年小白鼠是可以再生新的神經(jīng)元細胞的。后來的研究進一步證實了成年人的神經(jīng)元

可以建立新的連接這一說法。與此同時，通過對冥想的探究，科學(xué)家發(fā)現(xiàn)，集中的腦部訓(xùn)練

不僅可以改變大腦的結(jié)構(gòu)，還可以改變其功能。

Women aren't from Venus after all

11.原來女人不是金星人?。ㄗⅲ涸从谝槐緯拿帧赌信蟛煌腥藦幕鹦莵?，女

人從金星來）》）

Popular culture tells us that women and men's brains are just different. It's true that male and female hormones affect brain development differently, and imaging studies have found brain differences in the ways women and men feel pain, make social decisions and cope with stress. The extent to which these differences are genetic versus shaped by experience — the old nature-versus-nurture debate — is unknown.

大眾文化普遍認為男人和女人的大腦是不同的。的確，雄性和雌性激素對大腦的發(fā)育的影響不同，并且成像研究也表明男人和女人在感知疼痛、做出決定以及應(yīng)對壓力時，大腦的反應(yīng)有所差異。但是，這些差異到底多少是由基因決定的，又有多少是經(jīng)驗塑造的——即，由來已久的先天VS后天的論戰(zhàn)——就不得而知了。

But for the most part, male and female brains (and brainpower) are similar. A 2005 American Psychologist analysis of research on gender differences found that in 78 percent of gender differences reported in other studies, the effect of gender on the behavior was in the small or close-to-zero range. And recent studies have debunked myths about the genders' divergent abilities. A study published in the January 2010 Psychological Bulletin looked at almost half a million boys and girls from 69 countries and found no overall gap in math ability. Focusing on our differences may make for catchy book titles, but in neuroscience, nothing is ever that simple.

事實上，男人和女人的大腦（和智力）是極其相似的。2005年，美國心理學(xué)家通過對性別差異研究的分析發(fā)現(xiàn)，在研究性別差異的78%的成果中，性別對行為的影響可以算是小之又小，幾乎接近于零。并且，最新的研究也已經(jīng)打破了性別不同能力也不同的這一迷信說法。發(fā)表在2010年1月《心理學(xué)公報（美）》的一項研究，對來自69個國家，接近50萬名男孩和女孩進行測試，發(fā)現(xiàn)他們整體上不存在數(shù)學(xué)能力上的差異。這些有關(guān)人類差異的研究或許更容易起個吸引人的書名，（從而賣的更好）。但在神經(jīng)系統(tǒng)科學(xué)領(lǐng)域中，事情遠不是如此簡單。