A small protein, sometimes called the 'love hormone' might play a much wider role in how we learn to bond.

有時這種微小的蛋白質(zhì)又被稱為“愛情荷爾蒙”，它在我們學(xué)習(xí)如何建立親密關(guān)系過程中可能發(fā)揮著更廣泛的作用。

When love is in the air, what's happening in the brain? For many years, biologists would answer, "Oxytocin!" This small protein — just nine amino acids long — has sometimes been called "the love hormone" because it has been implicated in pair-bonding, maternal care and other positive, love-like social behaviours.

當(dāng)空氣中彌漫著愛情時，大腦里正在發(fā)生什么？多年來生物學(xué)家給出的回答是：“后葉催產(chǎn)素”！這種微小的蛋白質(zhì)——僅為9個氨基酸長度——有時又被稱為“愛情荷爾蒙”，因為它與配對結(jié)合、母愛及其他建設(shè)性的、有感情特征的社會行為密切相關(guān)。

But lately, neuroscientists have been revising their thinking about oxytocin. Experiments with mice and other lab animals suggest that instead of acting as a trigger for pro-social behaviour, the molecule may simply sharpen the perception of social cues, so that mice can learn to target their social behaviour more accurately. "It turns out it’s not as simple and straightforward as 'oxytocin equals love'," says Gül D?len, a neuroscientist at Johns Hopkins University. If something similar is true of humans, that may, among other things, add a fresh wrinkle in attempts to treat social disorders such as autism by tinkering with the oxytocin system.

但最近，神經(jīng)科學(xué)家對后葉催產(chǎn)素的觀念有所轉(zhuǎn)變。老鼠及其他動物試驗表明，這種分子的作用不是觸發(fā)親社會行為，而是可能提高對社交信號的感知力，這樣老鼠就能學(xué)會更準(zhǔn)確地定位社交行為?！笆聦嵶C明，這并不像后葉催產(chǎn)素等于愛情那么簡單明了”，美國約翰霍普金斯大學(xué)的神經(jīng)科學(xué)家葛蘭·德倫說道。如果人類也有類似的情況，那么除此以外，還能給治療孤獨(dú)癥等社交障礙提供新的思路，即修復(fù)后葉催產(chǎn)素系統(tǒng)。

Neuroscientists have long believed that the release of oxytocin in the brain could be triggered by social interactions with certain individuals such as offspring or mates that are important to us and other animals. And when researchers experimentally block the action of oxytocin, mice lose the ability to recognise socially important individuals. This suggests that the molecule plays a central role in social learning — but researchers haven't known exactly how oxytocin does its job.

神經(jīng)學(xué)家一直認(rèn)為，與某些個體的社會交往可能觸發(fā)大腦釋放后葉催產(chǎn)素，例如對我們?nèi)祟惣捌渌麆游锓浅Ｖ匾暮蟠蚺渑?。?dāng)科學(xué)家在試驗中阻止后葉催產(chǎn)素發(fā)揮作用時，老鼠失去了辨認(rèn)重要的社交個體的能力。這表明這種分子在社交學(xué)習(xí)中發(fā)揮著核心作用——但科學(xué)家尚不清楚后葉催產(chǎn)素究竟是如何做到的。

That is changing, thanks to advances in neuroscience techniques, which in recent years have allowed researchers to identify and record the activity of individual oxytocin-producing neurons deep within the brain. And those recordings tell a story that differs from the old view — in subtle but important ways.

得益于神經(jīng)科學(xué)技術(shù)的進(jìn)步，這種境況正在得到改善，近年來科學(xué)家能夠識別和記錄大腦深處的個體神經(jīng)元釋放后葉催產(chǎn)素的活動，記錄的情形與傳統(tǒng)觀點(diǎn)之間有重要的細(xì)微差異。

In the main smell centre of rats' brains, for example, measurements show that oxytocin inhibits the random, noisy firing of nerve cells, thus allowing the neural signals of actual odours to stand out more prominently. (It does this in a backhanded way, by exciting nerve cells known as granule cells, which inhibit other nerve cells.)

以老鼠的嗅覺中樞為例，測量結(jié)果顯示后葉催產(chǎn)素抑制神經(jīng)元隨意傳遞嘈雜的信號，這樣能使真正氣味的神經(jīng)信號更為突出（后葉催產(chǎn)素是以間接的方式做到的，它刺激被稱為粒細(xì)胞的神經(jīng)元，而粒細(xì)胞能抑制其他神經(jīng)元）。


Like tuning in to the sound of your child, oxytocin might help our brains to focus on the most important signals – cutting out noise

正如聽到自己孩子的聲音一般，后葉催產(chǎn)素可能幫助我們的大腦關(guān)注最重要的信號——濾掉噪音。
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Robert Froemke, a neuroscientist at New York University Grossman School of Medicine and Young's coauthor, uses hearing his baby crying over background noise as an analogy to the clarity oxytocin creates in our brain. "I've got two little kids," he says. "Even two rooms away, air conditioner on, and I'm deep asleep, the baby starts crying and right away I'm awake and attending, full-pupil-dilated."

羅伯特·弗羅姆克是紐約大學(xué)格羅斯曼醫(yī)學(xué)院的神經(jīng)科學(xué)家，他把后葉催產(chǎn)素在大腦中創(chuàng)造的清晰環(huán)境比作從背景噪聲中聽到嬰兒的啼哭聲?！拔矣袃蓚€孩子”，他說道?！凹词瓜喔魞蓚€房間，空調(diào)開著，我在熟睡，當(dāng)嬰兒開始啼哭時，我馬上就醒了，專注聲音，瞳孔放大”。

Oxytocin also enhances the response of the brain's reward system, says Yevgenia Kozorovitskiy, a neuroscientist at Northwestern University. This effect could shift the animal's behaviour away from seeking out new things in the environment, and toward focusing on social rewards.

后葉催產(chǎn)素還能強(qiáng)化大腦的獎賞系統(tǒng)，來自美國西北大學(xué)的神經(jīng)科學(xué)家葉夫吉尼亞·科佐羅維茨基說道。這種效應(yīng)可能使動物避免在環(huán)境中物色新事物，并專注于社交獎賞。

In prairie voles, for example — which intrigue researchers for their monogamous behaviour, rare in rodents — this shift facilitates pair-bonding. Among other effects, some of the oxytocin-sensitive cells lix a mate's odour to the reward system. "Pair-bonding is kind of like becoming addicted to a partner," says Young. "The partner becomes inherently rewarding." Promiscuous species such as mice and meadow voles lack those oxytocin receptors but, tantalisingly, they're there in the brains of people, suggesting that we may respond more like prairie voles than mice. (Oxytocin's molecular cousin, vasopressin, also plays a role in pair-bonding.)

以草原田鼠為例，它們一夫一妻制的行為激起了科學(xué)家的興趣，這種行為在嚙齒動物中罕見——這有利于配對結(jié)合。除了其他效應(yīng)以外，某些對后葉催產(chǎn)素敏感的細(xì)胞將配偶的氣味與獎賞系統(tǒng)相關(guān)聯(lián)?！芭鋵Y(jié)合有點(diǎn)類似于對配偶上癮”，楊先生說道。“配偶本身成為獎賞”。老鼠、普通田鼠等濫交物種缺少后葉催產(chǎn)素受體，但可喜的是存在于人類大腦中，這表明我們的反應(yīng)可能更像草原田鼠，而不是老鼠。（與后葉催產(chǎn)素有關(guān)的分子后葉加壓素在配對結(jié)合中也發(fā)揮著作用）。
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Like some species of vole, pair-bonding might make us 'addicted' to our partners, reducing promiscuous behaviours

正如某些種類的田鼠，結(jié)合配對可能使我們對伴侶“上癮”，減少濫交行為。

There's a further complication here, and an important one: If oxytocin's real role is to clarify social-related sensory perceptions, not simply to promote sociality, then the chemical is likely to have different effects in different contexts. For example, Young notes, oxytocin enhances maternal care in mice — clearly a pro-social behaviour — but it also increases maternal aggression toward unfamiliar individuals.

這里還有一個復(fù)雜的問題，并且很重要：如果后葉催產(chǎn)素的真正作用是凈化與社交有關(guān)的感官知覺，而不只是促進(jìn)對社交的向往，那么后葉催產(chǎn)素在不同的環(huán)境下可能產(chǎn)生不同的效應(yīng)。例如楊先生指出，后葉催產(chǎn)素能增強(qiáng)老鼠的母性——這是明顯的親社會行為——但也增加了對陌生個體的母性攻擊行為。

Moreover, female prairie voles respond differently to oxytocin depending on whether they have formed a pair bond yet, Young and his colleagues have found. In unbonded females, oxytocin reduces noise in the reward system, allowing them to learn to like a potential partner's odour. In females that have already bonded with a partner, the molecule turns up the volume on the reward system to make the partner more rewarding, thus reducing aggression toward the partner.

另外，楊先生及其同事發(fā)現(xiàn)，雌性草原田鼠對后葉催產(chǎn)素有不同的反應(yīng)，這取決于它們是否擁有伴侶。在沒有伴侶的雌性中，后葉催產(chǎn)素減少獎賞系統(tǒng)的噪音，使它們學(xué)著喜歡上某只潛在伴侶的氣味。在已擁有伴侶的雌性中，后葉催產(chǎn)素增大獎賞系統(tǒng)的音量，使伴侶更有價值，從而減少對伴侶的攻擊行為。

Something similar may apply to people, too. In one study from 2012, 30 men who were in monogamous relationships maintained a slightly greater social distance from an attractive female stranger when they received an intranasal oxytocin spray than when they got a placebo. The effect wasn't seen in a similar group of 27 single men.

人類可能也有類似的情況。在2012年的一項研究中，30名男性在接受催產(chǎn)素鼻噴霧劑后，與接受安慰劑相比，他們與陌生美女保持的社交距離更遠(yuǎn)一些。這種效應(yīng)在27名單身男性組中沒有出現(xiàn)。
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The context-dependence of oxytocin may complicate efforts to use oxytocin to treat autism-spectrum disorder. Some therapists already use intranasal oxytocin sprays to treat people with autism, on the theory that it should enhance their response to social stimuli. However, a large clinical trial recently found no demonstrable effect.

后葉催產(chǎn)素有賴于環(huán)境，利用它治療孤獨(dú)癥譜系障礙可能因此變得復(fù)雜。有些醫(yī)療專家已經(jīng)利用催產(chǎn)素鼻噴霧劑治療孤獨(dú)癥患者，理論依據(jù)是應(yīng)該能增強(qiáng)患者對社交刺激的反應(yīng)。但是，最近開展的大規(guī)模臨床試驗并未發(fā)現(xiàn)顯著療效。

That's not surprising, Young says, because the trial did not control the context in which patients received the sprays. If a child is being bullied at school, for example, the proposed treatment might not help but instead might intensify that negative experience, he notes. Instead, Young thinks that any oxytocin-based therapies would need to be carefully delivered in the safety of a therapy session.

這并不奇怪，楊先生說道，因為該試驗沒有控制患者接受噴霧劑治療的環(huán)境。例如，如果孩子在學(xué)校受欺負(fù)了，該療法可能無濟(jì)于事，反而強(qiáng)化負(fù)面經(jīng)歷。楊先生認(rèn)為，任何催產(chǎn)素類療法都需要在療程安全的情況下謹(jǐn)慎實施。

Neuroscientists also note that even though oxytocin clearly plays an important role in regulating social behaviors like pair-bonding and parental care, it's not the only actor. "Falling in love is a full brain and body experience," says Kozorovitskiy. "It has sensory elements and cognitive elements, and memory is important. Is oxytocin one of the many modulators that is mediating all those changes? Absolutely. But can we pin it all on oxytocin? That's definitely an oversimplification."

神經(jīng)科學(xué)家也指出，盡管后葉催產(chǎn)素在調(diào)節(jié)配對結(jié)合、母愛等社交行為方面明顯發(fā)揮著重要作用，但它不是唯一的因素?！皦嬋霅酆邮侨硇牡捏w驗”，科佐羅維茨基說道?！皭矍樯婕案泄俸驼J(rèn)知因素，回憶很重要。后葉催產(chǎn)素是調(diào)節(jié)這一切變化的因素之一嗎？確實是。但我們能把愛情完全歸因于后葉催產(chǎn)素嗎？那肯定是過于簡單化了。