虽然失去了嗅觉神经，但仍能闻到气味

这些女人虽然失去了嗅觉神经，但仍能闻到气味

Fresh-baked bread. Rain falling onto warm soil. Cut grass in the summer. We can relish in these fragrances thanks to a bundle of nerves deep inside each nostril called an olfactory bulb - or so we thought, anyway.

新鲜的烤面包、雨水落在温暖的土壤上、夏天割草。我们可以享受这些香味，这要归功于每个鼻孔深处的一束神经，叫做嗅球——至少我们是这么认为的。

Among brain scans from over 1,000 subjects, researchers have now identified a handful of cases where individuals appear to lack this structure. Nevertheless, these people can identify smells surprisingly well.

在对1000多名受试者的脑部扫描中，研究人员现在发现了少数人似乎缺乏这种结构。然而，这些人却能很好地辨别气味。

Neurologists from the Weizmann Institute of Science in Israel and the Florey Institute of Neuroscience and Mental Health in Australia initially stumbled across two strange cases of missing olfactory bulbs while reviewing MRIs for a different study.

以色列魏茨曼科学研究所(Weizmann Institute of Science)和澳大利亚弗洛里神经科学与心理健康研究所(Florey Institute of Neuroscience and Mental Health)的神经学家在为另一项研究进行核磁共振检查时，最初偶然发现了两个奇怪的嗅球丢失病例。

Since their research required left-handed female volunteers with a sense of smell, the absences stood out as particularly odd, warranting further investigation.

由于他们的研究需要有嗅觉的左撇子女性志愿者，这些缺席显得特别奇怪，值得进一步调查。

The olfactory bulbs, located deep inside most of our skulls, could be described as a pair of upside-down toothbrushes. Their handles reach back into our brain, and their bristles poke into the roof of our nasal cavities.

嗅球位于我们大多数头骨的深处，可以说是一对倒置的牙刷。它们的手柄伸进我们的大脑，鬃毛伸进我们的鼻腔。

The purpose of this bulb of sensory nerves is to catch volatile particles floating about in the air we inhale and send messages into various parts of the brain, including sections responsible for memory and emotion.

这种感觉神经球的目的是捕捉漂浮在我们吸入空气中的挥发性颗粒，并将信息发送到大脑的各个部分，包括负责记忆和情感的部分。

The result can fill us with pleasure or disgust, summoning memories of fear or recollection of grandma's hugs. If this is the olfactory bulb's function, it stands to reason that should it be damaged – or missing altogether – our ability to detect any trace of a scent should be seriously affected.

结果会让我们充满愉悦或厌恶，唤起恐惧的回忆或是对祖母拥抱的回忆。如果这是嗅球的功能，那么如果它被损坏或者完全丢失，我们探测气味痕迹的能力应该受到严重影响。

Yet controversial studies on rodents raise some interesting questions. Even when olfactory bulbs have been eaten away by lesions, or removed altogether, researchers have found their lab animals could still respond to scent-oriented tasks.

然而，关于啮齿动物的有争议的研究提出了一些有趣的问题。即使嗅球被病变吞噬，或者被完全移除，研究人员发现他们的实验动物仍然可以对气味导向的任务做出反应。

Unfortunately, lab animals are crafty subjects, who might find ways to navigate that test for a tasty treat – smell or no smell. That leaves plenty of room for doubt over whether such results should be taken seriously

不幸的是，实验动物是狡猾的实验对象，他们可能会想办法在测试中找到美味的食物——闻或不闻。这就给人们留下了很大的怀疑空间，怀疑是否应该认真对待这样的结果。

Having now stumbled across two volunteers who had no olfactory bulbs and still seemed to have a sense of smell, neurologists had an opportunity.

现在，在无意中发现了两个志愿者，他们没有嗅球，但似乎仍然有嗅觉，神经学家有了一个机会。

In spite of what you might think, we humans are pretty good smellers, discriminating between maybe as many as a trillion different odours. And, unlike rats, people can be quizzed on their experiences.

不管你怎么想，我们人类的嗅觉很好，分辨出的气味可能多达一万亿种。而且，与老鼠不同的是，可以问到他们的经历。

So the research team used their unexpected finds as a starting point to hunt down more examples in a massive public collection of MRIs aimed at mapping connections in the human brain.

因此，研究小组以他们意想不到的发现为起点，在一个旨在绘制人类大脑连接图谱的大规模公共核磁共振成像集合中，寻找更多的例子。

Sifting through 1,113 scans, they uncovered a further three.

通过1113次扫描，他们又发现了3例。

The new examples were also all women, with one also being left-handed. It's not at all clear what these biases mean, but the fact that the records all reported they had a sense of smell was startling.

新的例子也都是女性，其中一个也是左撇子。目前还不清楚这些偏见意味着什么，但记录显示他们都有嗅觉，这一事实令人震惊。

To confirm suspicions, the team went back to their original two volunteers and recruited a third woman who lacked olfactory bulbs but also happened to have anosmia – an inability to detect scents.

为了证实这一怀疑，研究小组又找来了最初的两名志愿者，并招募了第三名女性志愿者。这名女性没有嗅球，但碰巧也患有嗅觉缺失症，即无法察觉气味。

More detailed scans of the volunteers' brains found their entire olfactory bulb structures were indeed diminished. The team concluded that they had to be tiny, if the women had any olfactory bulbs at all.

对志愿者大脑的更详细扫描发现，他们的整个嗅球结构确实被削弱了。研究小组得出结论，如果这些女性身上有嗅球，那么她们的鼻子就必须很小。

They then gave the women a whiff of 10 odorants and asked them to rate them according to 11 different descriptors. Their results were compared with those taken from 140 other women who all had completely functional olfactory bulbs.

然后，研究人员给这些女性闻了10种气味，并要求她们根据11种不同的描述对这些气味进行评级。研究人员将他们的研究结果与另外140名拥有完全正常功能的嗅球的女性的研究结果进行了比较。

The results provided by the two bulb-less women who could still smell were remarkable, but only in that they shouldn't have the ability to smell at all.

两位没有嗅球的女性提供的结果是显著的，但仅仅是她们不应该有嗅觉的能力。

There was one other curiosity. The descriptors they each provided were eerily similar to one another's.

还有一件怪事。他们各自提供的描述符出奇地相似。

It's hard to tell exactly what's going on, and what – if any – olfactory nerves these women might have retained. But it does reinforce the notion that our brains are capable of doing a lot with very little.

很难确切地说出到底发生了什么，以及这些女性可能保留了什么(如果有的话)嗅觉神经。但它确实强化了这样一种观念，即我们的大脑可以用很少的东西做很多事情。

"The simplest interpretation of our findings is that these women were born without an olfactory bulb, but thanks to the extreme plasticity of the developing brain, they developed an alternative glomeruli map somewhere else in the brain, not in the olfactory bulb," says Sobel.

索贝尔说：“对于我们的发现，最简单的解释是，这些女性出生时没有嗅球，但由于发育中大脑的极度可塑性，她们在大脑的其他地方，而不是嗅球中，形成了另一种肾小球图。”。

This research was published in Neuron.

这项研究发表在《神经元》杂志上。