Touched

爱抚是神经元的抒情诗

We ride a stream of naked neurons, stripped of their sheaths, to the most blissful moments and deepest intimacies of life

沿着神经信号的溪流，我们乘着赤裸的神经元追溯，享受生命中的亲密，直至最幸福的时刻。

by Steven M Phelps + BIO

Steven M Phelps | 撰文

橘子汁 | 翻译

神经现实（ID：neureality）| 来源

As a student of neuroanatomy, I was provided with a human brain in a half-gallon tub. Our lab manual depicted a brain in situ, half-exposed in the head of an aged Irishman cut open along the midline, where his part might have run.

当我还是一名神经解剖学学生的时候，曾解剖过一颗装在半加仑桶内的人脑。我们的实验室手册绘制出了大脑的原位图，那是沿中线切开的半颗爱尔兰老人的头颅，图谱画出了各个部位正常工作时该有的样子。

My lab partner and I spent a semester peeling away layers of our stranger’s accumulated experience. We sketched coarse outlines to label in Latin and Greek. In an exam, we might find pins in the pons and medulla, in their minor partitions. We might be asked to diagram the flow of information as a child touches a hot stove then withdraws her hand in a thin sliver of a second.

我和实验室的合作伙伴花了整整一个学期，层层剥开那颗头颅，了解它所积累的经历。我们用拉丁语和希腊语给出粗略的轮廓标签。在考试中，我们可能会在脑桥和延髓的小分区里寻找如针一般的细小结构，可能会被要求描绘出小孩碰到热炉后瞬间缩手时的信息流。

This is the allure of neuroscience: it offers an atlas of experience, one whose pages can be laid out for view with a scalpel and steady hand. At 21, I was overwhelmed and enthralled.

这正是神经科学的魅力：它提供了一份用经验绘制的图谱，一份用柳叶刀和稳健的双手打开的图谱。那年我21岁，在这张美妙的图谱面前快要窒息。

Roughly a year later, I joined several graduate students for an afternoon spent kicking our way through ankle- and waist-deep waters, seining for tiny varieties of fishes. We were led by an ichthyology professor who was opinionated and clever. He taught me how to hold the seine, placing my hands on the posts in proper position, tilting them so the net could billow behind me.

大概过了一年，我加入了几名研究生的午后活动，在小河中捕捞各式各样的鱼，任水流亲吻过我们的脚踝和腰间。带领我们的是一位见解独特、思维灵活的鱼类学教授，他手把手教我怎样使用围网：把手放在合适的位置上，倾斜渔网，让它在我的身后漂荡。

He showed me how to move through the water to drive fish into our net. And despite my ignorance, he addressed me with deference. ‘You’re a neurobiologist,’ he began, as I watched the Vermillion River work its way across a flat Illinois acre. ‘Why is water so mesmerising?’

他向我演示如何在水里移动，把鱼儿赶进渔网中去。尽管我完全是个门外汉，但他仍然悉心指导。我正看着费米利恩河在伊利诺伊的平原蜿蜒，他转过头问我：“你是个神经生物学家对吧，那你告诉我：为何这水流会如此迷人？”

Maybe it was the way light and sound leapt from the stream, at once constant and unpredictable. I kept this thought to myself. We could not have anticipated that we would discuss his strange question and our awkward silence for the next 20 years.

或许是因为那溪水潺涓、浮光跃金，时而平静时而捉摸不定，我把这个答案留在了心里。那时的我们没有意料到，在今后的20年里，我们会继续讨论他这个奇怪的问题，以及当时尴尬的沉默。

Perhaps we have become too easily ashamed of our wonder. Neuroscientists want more than ever to chart the brain’s navigable waters, its every tributary and purling riffle. We have performed meta-analyses of brains lit with love and desire.

也许我们太羞于谈论自己的奇思妙想。神经科学家想要的不仅仅是绘制大脑的“通航水域”，条条支流，潺潺涟漪。我们对大脑中负责情爱与欲望的区域完成了元分析。

And when we have these maps, these intimate geographies, what then? As Walt Whitman has written, ‘Your facts are useful, and yet they are not my dwelling.’ Can we learn how a fleeting touch drives a frenzied heart, or why the delay between contact and withdrawal can span a decade? An answer worthy of our effort should begin at the skin’s surface, yet somehow end in poetry.

可即便我们能绘制出爱和欲望的“地形图”，那又有什么意义呢？正如沃尔特·惠特曼（Walt Whitman）所写：“你们掌握的那些事实很有用，但它们并不是我的信仰。”我们是否真能明白，为何刹那间的触碰会让心脏狂跳不止；为何那一瞬间的接合，会感觉像是过了好几个世纪？答案应该始于皮肤，止于诗歌。

While walking on a Japanese beach at the end of the 19th century, the Scottish doctor Henry Faulds found pottery fragments that bore impressions from the fingertips of prehistoric craftsmen. Contemporary pots made by similar methods revealed finer details and alerted him to the minute variations of the human hand.

19世纪末，苏格兰医生亨利·福尔德斯（Henry Faulds）在日本海滩漫步时，发现陶器碎片中留有史前工匠的指痕。当代陶艺通过类似方法制作的壶器可以展现更多的细节，这让他开始注意人手之间的微妙差异。

Naturalists of the time often documented the delicate forms of exotic ferns by transferring a thin layer of printer’s ink from frond to paper. Faulds made similar records of the intricate ridges of fingers and palms, noting the variety of patterns he observed among the digits of his friends and colleagues.

当时的博物学家通常在叶子表层刷上薄层印刷油墨，把植物的纹路转印到纸上，以记录异国蕨类植物的微妙形态。福尔德斯对手指和手掌的复杂纹路做了类似的记录，发现他的朋友和同事们都不一样。

Faulds published his observations in 1880, in an article that proposes the use of handprints in criminology. He suggested printing furrow patterns onto glass in different colours of ink, so the superposition could be projected by magic lantern. Impressions recovered from soot or blood could be used to incriminate or absolve a suspect. A mutilated, headless body could be identified.

1880年，福尔德斯发表了他的发现，并在提出将手印运用到犯罪学中。他建议使用不同颜色的墨水把手印印在玻璃上，重叠处就可以利用幻灯投影出来。从烟灰或血液中采集到的信息可用于确定或排除嫌疑人，而残缺无头尸体的身份也可以因此而得以鉴别。

In response to his publication, Faulds soon learned that Sir William Herschel had used fingerprints for the identification of Bengalese prisoners and pensioners. Herschel’s large collection of prints was passed on to Sir Francis Galton, a younger cousin of Charles Darwin and a pioneer in statistics. In 1892, Galton compared the arches, loops and whorls that define the central, bulbous part of the fingertip, the triangular spaces where ridges converge, their infinite permutations.

德斯很快收到了威廉·赫歇尔爵士（Sir William Herschel）的回应：他已经开始用指纹识别孟加拉国的囚犯和抚恤金领取者。赫歇尔把收集到的大量指纹数据传递给了弗朗西斯·高尔顿（Sir Francis Galton）。高尔顿是查尔斯·达尔文的表亲，同时也是数据统计的先驱。1892年，高尔顿比较了指尖中央球部的斗形、箕形和弓形纹路，在这个小小的三角区域里，细纹交汇于一点，发出无数种排列组合。

Galton estimated the probability of two fingerprints being identical at approximately one in 64 billion. Apparently, it matters so little exactly how the ridges of our palms and fingers are arranged that there are more ways to make a fingerprint than there are fingers. Fingerprints seem to have become metonyms for identity by evolutionary accident.

福尔高尔顿估计出现两枚指纹相同的概率大约是六十四亿分之一。显然，我们的手纹线和指纹的组合比世界上存在的手指的数量还要多的多。至此，在进化过程中产生的指纹似乎已成为身份的代名词。

For every spike in voltage there was a small but predictable increase in pleasure

With so much variety, it is telling when something remains constant. Try an experiment: lick your fingers as though you were about to turn a page. Instinctively, you’ve licked the spot where fingers grip light objects, and at its centre are the concentric ridges and grooves that define your fingerprint. If you move your finger over an object in most directions, the object will run roughly perpendicular to these ridges, allowing friction to tug on each ridge as though toppling a wall.

指纹拥有多样性，也就意味着同样存在恒常性。做个小实验：舔一下手指，就像你看书翻页时做的那样。你会本能地舔在手指捏住轻小物体的地方，在这个区域的中央，绕着中心一圈圈堆砌起来的脊线和凹纹，正是指纹的重要组成部分。如果你在物体上往任意方向移动手指，物体将沿垂直于指纹脊线的方向运动，这样能保证摩擦力作用在每一条脊线上，好似推墙一样。

This central, bulbous part of your fingertip also contains the finest, densest set of ridges. You can see this if you follow your finger a short distance toward your palm, where the ridges become progressively wider. It is no coincidence that the ridges are finest, most centred on the part of your finger that first makes contact with an object. It is also where the nerve endings that sense touch are most dense. If you’re the caressing sort, recall how you have touched a lover, your fingertips scanning as they glide slowly over skin. Perhaps your palm lay flat, presenting the largest possible surface for contact.

指尖中心的球形部分包含了最精细、最密集的脊线。如果你沿着手指往掌心看，可以清楚地发现脊线越来越宽。我们手指上最最精细的脊线正好位于我们手指最先触碰到物体的区域中央，这绝非巧合——那里同样也是触觉神经末梢最密集的地方。回想一下你是如何爱抚恋人的——指尖慢慢地滑过皮肤，抑或展开手掌，最大面积接触恋人的肌肤。

The ridges of our fingers and hands are densely innervated by sensory neurons, nerve cells that translate pressure into changes in voltage. These sensory neurons come in a variety of forms suited for their tasks, named after neuroscientists like Merkel, Ruffini, Meissner and Pacini. Nerve endings can be capped with structures called disks, capsules or corpuscles – each defined by a distinctive weight or stiffness. These tips make the neurons more or less sensitive to pressure. The nerve endings that sense touch can be buried deep in the skin or can be so near the surface you could find them within the ridge of a fingerprint.

我们的手指和手掌受密集分布的感觉神经元控制，它们将压力变化转化为电压。这些感觉神经元根据传递任务的不同，具有各种形态，并以神经科学家的名字命名，如Merkel感受器，Ruffini小体，Meissner小体和Pacini小体等。神经末梢可以根据结构的重量或刚度分为盘、囊或小体。这些结构保证神经末梢或多或少对压力敏感。感受触觉的神经末梢可以埋在皮肤深处，或者处于皮肤表面，当然也可以在指纹的脊部找到它们。

When the pressure and depth of touch are just right, the surface of the sensing neuron is deformed, stretched until the tension opens channels that let electrically charged salt ions flow in and out of the cell.

当触觉的压力和深度达到一定程度时，受体神经元的表面变形、细胞拉伸，直到压力大到足以打开相关通道，让盐离子流入和流出细胞。

The voltage change caused by the flow of ions zips along a cable-like projection to the spinal cord, where it gets passed on to other nerve cells and eventually to the brain. We can judge how smooth or pliant something is because voltages conveying the complex patterns of pressure arrive quickly enough for our brains to perceive subtle variation in timing.

离子流引起的电压变化沿着神经轴索传入脊髓，继而传递到其他神经细胞，最终到达大脑。我们之所以能判断物体的光滑程度和柔韧程度，是因为传递压力分布状况的神经冲动可以快速到达我们的大脑，从而在短时间内分辨触觉的变化。

Without this ability, touch would feel like a surveillance tape played at half-speed: blurred and coarse. Like other species, we gain this speed by insulating our cables. Nerve cells are highly specialised, and require companion cells to help them with the daily details of cellular living. Some of these companions have developed means of enveloping the cable-like projections of neurons, becoming flat and wrapping themselves around the exterior of the cable again and again, like a king-sized sheet swaddling an infant. Or like rubber coating wire.

假如没有这种能力，触觉感受就会像半速播放的磁带那样，模糊又粗糙。和其他物种一样，我们通过让“导线”绝缘来达到这一传递速度。神经细胞高度分化，需要伴细胞（companion cell）辅助维持生存。一些伴细胞分化成了包封轴突的形式，一层层扁平地包裹在轴突的外侧，就像包裹着小宝宝的特大号襁褓，又像电线的橡胶涂层。

Insulated neurons are responsible for fine touch, but there is a second class of receptors that remain bare. These bare nerve endings are slower, and respond to coarser kinds of stimuli.

绝缘神经元（译者注：有髓神经纤维）负责细微的触觉，但是人体内还有第二类感觉神经元没有髓鞘包裹。这些裸露的神经末梢反应较慢，会对较粗糙的刺激作出反应。

Science has long known that these unmyelinated neurons respond to temperature, pain, tickle and itch. But we have only recently learned that they also respond to the pleasurable sensation of caress. Researchers in Sweden recorded data from neurons in the skin of human subjects as they exposed them to soft slow touch.

科学早已证明，这些无髓鞘神经元能回应温度、疼痛和瘙/痒。但直到最近研究才发现，它们也能回应爱/抚带来的愉悦感。当人类被试的皮肤被轻缓抚/摸时，瑞典的研究人员记录下了神经元的相关数据。

For every spike in voltage there was a small but predictable increase in pleasure. While these naked neurons are missing in the hairless skin of our fingers and palms, they are found on the rest of the body, on the places you might touch with affection or consolation. And naked fibres are particularly abundant in the places we like to juxtapose – our lips, nipples, genitals and anus. The clitoris and the glans are enmeshed in the unmyelinated ends of sensory neurons. Inexplicably, we have often assumed these naked fibres were there for the sensation of pain, as though we had never known the joy of sexual touch.

电压每次激增，都对应一分微小但可预测的愉悦感受。虽然在手指和手掌上的无毛皮肤中未发现这类神经元，但它们存在于身体的其他部分；也许你会带着爱意抚慰它们。无髓鞘神经纤维大量存在于某些部位，我们常常把它们放在一起讨论：嘴唇、乳/头、生/殖/器和肛/门。这些无髓末端在阴/di和gui/头里尤为密集。令人不解的是，我们下意识地认为这些神经元通常只负责痛觉，就仿佛我们从未感受过性/接触的快感。

Every Friday I joined a group of ichthyologists for happy hour at a neighbourhood pub. I loved the boozy debates, the elaborate arguments diagrammed on damp napkins, the raised voices and laughter.

每个星期五，我都和一群鱼类学家在附近的酒吧聚会。我喜欢在微醺中辩论，在湿纸巾上记录精心构思的论据，热爱喧嚣和嬉笑。

On one of these evenings I ran into my former neuroanatomy partner. We were both animated and friendly. When we shook hands and said goodbye, I pretended not to notice as his middle finger scratched my palm. This concealed touch within a touch was strange – in the Midwest at least, it’s a childhood code for romantic interest. How peculiar to receive this gesture from an adult man.

某天晚上，我偶遇了从前的神经解剖学搭档，感觉亲切又激动。当我们握手再见时，我假装没注意到他在悄悄用中指挠我的手掌心。这种隐晦的触摸很奇怪，至少在美国中西部是这样，这是一个童年时期表示暧昧的暗示。从成年男子那里收到这个手势真是很独特的体验。

I dissected its meaning with friends. This was not his only unusual behaviour: He knew I didn’t own a motorcycle, for example, yet had invited me to go riding with him more than once.

我和朋友一起分析了手势的涵义。这并不是他唯一一次的特殊举动：他知道我没有摩托车，但还是不止一次地邀请我和他一起骑车兜风。

In my extended public analysis, I did not mention how his touch seemed to leap from my palm to spine. Privately I wrote of the jolt I felt. Objectively, I noted in a spiral notebook now tucked away in a box, its effect seemed likely to have resulted from the sudden realisation that I was an object of sexual interest, of anyone’s interest.

在公开分析中，我并没有提及，他对我的抚摸从手掌心传到了背脊。但私下里，我记录下了内心雀跃。我在笔记本上这样写道：客观来说，产生这样的情绪波动，是因为我突然意识到，原来我是某个人的性///趣对象。现在这个笔记本已经被我藏到了一个小盒子里。

This shock, coupled with the sexualised context, would naturally bear some erotic charge. Add to this my own pent-up energies, and such a charge could easily explain both my rise in heart rate and transient tumescence.

这种情绪波动配合上具有性意味的语境，自然会产生“性感的”电荷；这些电荷释放了我体内积压已久的情感能量，很好地解释了为什么我会心率上升、下/体/微/硬。

Although I could accept this unlikely explanation for my response to a classmate, I found it increasingly difficult to deny my infatuation with the biologist who had been so mesmerised by running water. It was his company I sought every Friday. I delighted in the accidental intimacy of a crowded table. One happy hour stretched late into the evening, into a drunken discussion on the biology of sexual orientation.