雅思閱讀精讀：人類大腦與機器實驗

　　Brain-computer interfaces sound like the stuff of science fiction. Andrew Palmer sorts the reality from the hype

　　腦機接口聽起來像是科幻小說中的東西。在喧囂的炒作中，安德魯·帕爾默幫我們厘清現(xiàn)實狀況

　　IN THE gleaming facilities of the Wyss Centre for Bio and Neuro engineering in Geneva, a lab technician takes a well plate out of an incubator. Each well contains a tiny piece of brain tissue derived from human stem cells and sitting on top of an array of electrodes. A screen displays what the electrodes are picking up: the characteristic peak-and-trough wave forms of firing neurons.

　　在日內(nèi)瓦韋斯(Wyss)生物和神經(jīng)工程中心那閃閃發(fā)光的大樓中，一名實驗室技術(shù)人員從培養(yǎng)箱中取出一塊多孔板。每個孔中都有小小一塊來源于人類干細(xì)胞的腦組織放在一個電極陣列上。一塊屏幕上顯示著電極拾取的信息：神經(jīng)元放電的特征峰谷波形。

　　To see these signals emanating from disembodied tissue is weird. The firing of a neuron is the basic building block of intelligence. Aggregated and combined, such “action potentials” retrieve every memory, guide every movement and marshal every thought. As you read this sentence, neurons are firing all over your brain: to make sense of the shapes of the letters on the page; to turn those shapes into phonemes and those phonemes into words; and to confer meaning on those words.

　　看到這些脫離身體的組織會發(fā)射信號讓人感到有些怪異。神經(jīng)元的放電是構(gòu)建智力的基本材料。這些“動作電位”匯集和組合起來，就可拾取每一個記憶，支配每一個動作，組織每一個想法。在你讀這句話的時候，你整個大腦中的神經(jīng)元就在不停地放電：理解頁面上的字母形狀，把這些形狀變成音素，把音素組成單詞，再賦予這些單詞意義。

　　This symphony of signals is bewilderingly complex. There are as many as 85bn neurons in an adult human brain, and a typical neuron has 10,000 connections to other such cells. The job of mapping these connections is still in its early stages. But as the brain gives up its secrets, remarkable possibilities have opened up: of decoding neural activity and using that code to control external devices.

　　這曲“信號交響樂”的復(fù)雜程度令人暈眩。成年人腦中有多達(dá)850億個神經(jīng)元，而一個典型的神經(jīng)元細(xì)胞會連接到10000個同類細(xì)胞。描繪這些連接的工作還處于初期階段。但是隨著大腦秘密的逐步揭示，人們已經(jīng)創(chuàng)造出非凡的可能性：解碼神經(jīng)活動并用這些密碼控制外部設(shè)備。

　　A channel of communication of this sort requires a brain-computer interface (BCI). Such things are already in use. Since 2004, 13 paralysed people have been implanted with a system called Brain Gate, first developed at Brown University (a handful of others have been given a similar device). An array of small electrodes, called a Utah array, is implanted into the motor cortex, a strip of the brain that governs movement. These electrodes detect the neurons that fire when someone intends to move his hands and arms. These signals are sent through wires that poke out of the person’s skull to a decoder, where they are translated into a variety of outputs, from moving a cursor to controlling a limb.

　　要建立這樣的溝通渠道，就需要一個腦機接口(BCI)。人們已經(jīng)在使用這種東西了。自2004年以來，已有13位癱瘓者被植入了一個名為Brain Gate的系統(tǒng)，它是由布朗大學(xué)首先開發(fā)的(還有少數(shù)其他人也植入了類似的設(shè)備)。一組被稱為猶他(Utah)陣列的小電極被植入到運動皮層，即大腦中管理運動的部分。如果有人想動動他的手和手臂，這些電極會檢測到放電的神經(jīng)元。信號通過穿出顱骨的電線傳送到解碼器，再轉(zhuǎn)換成各種輸出，如移動光標(biāo)或控制肢體。

　　The system has allowed a woman paralysed by a stroke to use a robotic arm to take her first sip of coffee without help from a caregiver. It has also been used by a paralysed person to type at a rate of eight words a minute. It has even reanimated useless human limbs. In a study led by Bob Kirsch of Case Western Reserve University, published in the Lancetthis year, Brain Gate was deployed artificially to stimulate muscles in the arms of William Kochevar, who was paralysed in a cycling accident. As a result, he was able to feed himself for the first time in eight years.

　　該系統(tǒng)讓一名中風(fēng)癱瘓的婦女在沒有看護者幫助的情況下用機器人手臂喝到了第一口咖啡。還有一位癱瘓者能以每分鐘八個字的速度打字。它甚至讓本已無用的肢體再次活動起來。由凱斯西儲大學(xué)的鮑勃·基爾希(Bob Kirsch)領(lǐng)導(dǎo)的一項研究今年在《柳葉刀》上發(fā)表了論文，為在一次騎車事故中癱瘓的威廉·科切瓦(William Kochevar)人為部署了BrainGate，以刺激他手臂上的肌肉。結(jié)果八年來他第一次能夠自己吃飯了。

　　Interactions between brains and machines have changed lives in other ways, too. The opening ceremony of the football World Cup in Brazil in 2014 featured a paraplegic man who used a mind-controlled robotic exoskeleton to kick a ball. A recent study by Ujwal Chaudhary of the University of Tübingen and four co-authors relied on a technique called functional near-infrared spectroscopy (fNIRS), which beams infrared light into the brain, to put yes/no questions to four locked-in patients who had been completely immobilized by Lou Gehrig’s disease; the patients’ mental responses showed up as identifiable patterns of blood oxygenation.

　　大腦和機器之間的互動還以其他方式改變了人們的生活。2014年，在巴西舉行的世界杯足球賽開幕式上，一名截癱男子用思維控制機器人外骨骼來踢球。在最近的一項研究中，圖賓根大學(xué)的烏吉瓦·喬杜里(Ujwal Chaudhary)和四位合著者使用一種可將紅外光束照進(jìn)大腦的“近紅外光譜”(fNIRS)技術(shù)，向四名因盧·賈里格癥(Lou Gehrig's disease，又稱肌萎縮性脊髓側(cè)索硬化癥、漸凍癥)而完全失去行動能力的閉鎖綜合癥患者提出是非問題，患者的思維反應(yīng)表現(xiàn)為可辨認(rèn)的血氧模式。

　　Neural activity can be stimulated as well as recorded. Cochlear implants convert sound into electrical signals and send them into the brain. Deep-brain stimulation uses electrical pulses, delivered via implanted electrodes, to help control Parkinson’s disease. The technique has also been used to treat other movement disorders and mental-health conditions. NeuroPace, a Silicon Valley firm, monitors brain activity for signs of imminent epileptic seizures and delivers electrical stimulation to stop them.

　　神經(jīng)活動可以被刺激，也可以被記錄。人工耳蝸將聲音轉(zhuǎn)換為電信號并將其送入大腦。深度腦刺激通過植入電極傳送電脈沖來幫助控制帕金森病，該技術(shù)也被用于治療其他運動障礙和精神疾病。硅谷的NeuroPace公司監(jiān)測大腦活動來判斷癲癇即將發(fā)作的跡象，并通過電刺激來阻止它們。

　　It is easy to see how brain-computer interfaces could be applied to other sensory inputs and outputs. Researchers at the University of California, Berkeley, have deconstructed electrical activity in the temporal lobe when someone is listening to conversation; these patterns can be used to predict what word someone has heard. The brain also produces similar signals when someone imagines hearing spoken words, which may open the door to a speech-processing device for people with conditions such as aphasia (the inability to understand or produce speech).

　　我們很容易想象出腦機接口可以如何應(yīng)用于其他感官的輸入和輸出。加州大學(xué)伯克利分校的研究人員解析了聆聽對話時大腦顳葉的電活動;這些模式可以用來推測聽到的單詞。當(dāng)人們想象聽到某些單詞時，大腦也會產(chǎn)生類似的信號，這可能為患有失語癥(無法理解或產(chǎn)生言語)的人開啟語音處理設(shè)備的大門。

　　Researchers at the same university have used changes in blood oxygenation in the brain to reconstruct, fuzzily, film clips that people were watching. Now imagine a device that could work the other way, stimulating the visual cortex of blind people in order to project images into their mind’s eye.

　　這所大學(xué)的另一些研究人員利用大腦中的血氧變化來模糊地重建人們正在觀看的電影片段。想想看，要是有一種設(shè)備能夠反向工作，刺激盲人的視覺皮層，就可將圖像投射到他們的頭腦中。

　　If the possibilities of BCIs are enormous, however, so are the problems. The most advanced science is being conducted in animals. Tiny silicon probes called Neuropixels have been developed by researchers at the Howard Hughes Institute, the Allen Institute and University College London to monitor cellular-level activity in multiple brain regions in mice and rats. Scientists at the University of California, San Diego, have built a BCI that can predict from prior neural activity what song a zebra finch will sing. Researchers at the California Institute of Technology have worked out how cells in the visual cortex of macaque monkeys encoded 50 different aspects of a person’s face, from skin color to eye spacing. That enabled them to predict the appearance of faces that monkeys were shown from the brain signals they detected, with a spooky degree of accuracy. But conducting scientific research on human brains is harder, for regulatory reasons and because they are larger and more complex.

　　不過，如果BCI有巨大的可能性，那么問題也同樣巨大。最前沿的科學(xué)研究正在動物身上進(jìn)行�；羧A德·休斯研究所、艾倫研究所和倫敦大學(xué)學(xué)院的研究人員開發(fā)出了一種稱為神經(jīng)像素(Neuropixel)的微小硅探針，用于監(jiān)測小鼠和大鼠多個腦區(qū)中細(xì)胞層面的活動。加州大學(xué)圣地亞哥分校的科學(xué)家已經(jīng)造出了一個BCI，可以從先前的神經(jīng)活動中預(yù)測斑馬雀將會唱什么歌。加州理工學(xué)院的研究人員已經(jīng)揭示了獼猴視覺皮層中的細(xì)胞如何編碼人臉從膚色到眼間距的50個不同特征。這使得他們能夠根據(jù)檢測到的大腦信號，以讓人驚恐的準(zhǔn)確度預(yù)測猴子看到的面部外觀。但是由于監(jiān)管方面的原因，加上人類大腦更大、更復(fù)雜，要在人腦上進(jìn)行科學(xué)研究更為困難。

　　Even when BCI breakthroughs are made on humans in the lab, they are difficult to translate into clinical practice. Wired magazine first reported breathlessly on the then new Brain Gate system back in 2005. An early attempt to commercialize the technology, by a company called Cyberkinetics, foundered. It took NeuroPace 20 years to develop its technologies and negotiate regulatory approval, and it expects that only 500 people will have its electrodes implanted this year.

　　即使實驗室中的人類BCI獲得突破，它們也很難轉(zhuǎn)化為臨床實踐。早在2005年，《連線》(Wired)雜志就首先興奮地報道了當(dāng)時新推出的BrainGate系統(tǒng)。一家名為Cyberkinetics的公司初步試圖將這項技術(shù)商業(yè)化，卻遭到慘敗。NeuroPace花費了整整20年來開發(fā)技術(shù)并與監(jiān)管審批部門談判，它預(yù)計今年只有500人將植入它的電極。

　　Current BCI technologies often require experts to operate them. “It is not much use if you have to have someone with a masters in neural engineering standing next to the patient,” says Leigh Hochberg, a neurologist and professor at Brown University, who is one of the key figures behind BrainGate. Whenever wires pass through the skull and scalp, there is an infection risk. Implants also tend to move slightly within the brain, which can harm the cells it is recording from; and the brain’s immune response to foreign bodies can create scarring around electrodes, making them less effective.

　　目前的BCI技術(shù)通常需要專家來操作。BrainGate的關(guān)鍵人物之一，布朗大學(xué)的神經(jīng)學(xué)家李·霍赫貝格(Leigh Hochberg)教授說：“如果你必須讓一個神經(jīng)工程學(xué)碩士站在患者旁邊，那它的用處就不大了�！敝灰�是電線穿過頭骨和頭皮的地方就有感染的風(fēng)險。植入物也可能在腦內(nèi)輕微移動，這可能會傷害它正在記錄的細(xì)胞;大腦對異物的免疫反應(yīng)會在電極周圍產(chǎn)生瘢痕，讓它們的效果變差。

　　Moreover, existing implants record only a tiny selection of the brain’s signals. The Utah arrays used by the BrainGate consortium, for example, might pick up the firing of just a couple of hundred neurons out of that 85bn total. In a paper published in 2011, Ian Stevenson and Konrad Kording of Northwestern University showed that the number of simultaneously recorded neurons had doubled every seven years since the 1950s (see chart). This falls far short of Moore’s law, which has seen computing power double every two years.

　　而且，現(xiàn)有的植入物只記錄了大腦信號中很小的一部分。例如，BrainGate財團使用的猶他陣列也許僅僅拾取了幾百個神經(jīng)元放電的信號，而神經(jīng)元總計有850億個。在2011年發(fā)表的一篇論文中，西北大學(xué)的伊恩·史蒂文森(Ian Stevenson)和康拉德·科爾丁(Konrad Kording)提出，自20世紀(jì)50年代以來，能一次被同時記錄的神經(jīng)元數(shù)量每七年翻一番(見圖表)。這與摩爾定律也就是計算能力每兩年翻一番相差甚遠(yuǎn)。

　　雅思閱讀高頻詞匯

　　symphony 交響樂團

　　regulatory 監(jiān)管

　　Neuro engineering 神經(jīng)工程

　　interfaces 接口

　　infection 感染

　　deploy 部署

　　cortex 皮質(zhì)

　　array 數(shù)組