NARRATOR:Listen to part of a lecture in a health science class.

旁白：听健康科学课上的部分讲座。

FEMALE PROFESSOR:We’ve all heard that there are health benefits to regular exercise.

女教授：我们都听说经常锻炼对健康有好处。

It’s hard even to know where to begin: increased strength, a sense of well-being, weight maintenance, a healthy heart and cardiovascular system, need I go on?

这些好处多得不知从哪说起：增强力量，增加幸福感，保持体重，健康的心脏和心血管系统，还用我多说吗？

Now we’re hearing that exercise also has a positive effect on our high-level intellectual abilities.

现在我们听说锻炼对我们的高水平智力能力也有积极影响。

There’re a few hypotheses that may explain how exercise affects our brain.

有一些假说可以解释运动如何影响我们的大脑。

But before we get into that, I need to talk a little bit about neurogenesis.

但在我们开始讨论之前，我需要谈谈神经发生。

Neurogenesis is the creation of new neurons, nerve cells, in the brain.

神经发生是在大脑中产生新的神经元、神经细胞。

Now, maybe you’ve heard that the human brain doesn’t generate new neurons after fetal development, that the neurons you have when you’re born are all you’ll ever have… unlike what’s true of cells in most tissues, which are generated and replaced throughout life.

现在，你可能听说了，人脑在胎儿发育后不会产生新的神经元，你出生时的神经元就是你所有的全部了。与大多数组织中的细胞不同，细胞在整个生命中都会被产生和被更替。

But some decades ago, research on the ability of adult songbirds to learn new songs changed that whole paradigm.

但几十年前，对成年鸣禽学习新歌曲能力的研究改变了整个范式。

The research showed that in adulthood, the songbirds’ brains created new neurons and that these new cells helped them remember how to sing new songs.

研究表明，在成年期，鸣禽的大脑会产生新的神经元，这些新细胞帮助它们记住如何唱新歌。

These findings on songbirds opened up the question of whether the same processes that occurred in birds also occurred in humans.

这些关于鸣禽的发现提出了一个问题，即鸟类中发生的相同过程是否也发生在人类身上。

And subsequent research confirmed that the adult human brain indeed generates new neurons in the memory center of the brain.

随后的研究证实，成年人的大脑确实在大脑的记忆中心产生了新的神经元。

But, how exactly does exercise fit in here?

但是运动到底是如何适应这里的呢？

Well, probably the most studied hypothesis out there proposes that exercise increases the production of important proteins in the brain.

好吧，可能是被研究最多的假说提出运动会增加大脑中重要蛋白质的产生。

One such protein is called brain-derived neurotrophic factor, or BDNF.

一种这样的蛋白质称为脑源性神经营养因子，或 BDNF。

Brain-derived neurotrophic factor helps neurons grow, multiply, connect, and transmit signals.

脑源性神经营养因子帮助神经元生长、繁殖、连接和传递信号。

We’ve always known that it served this function during fetal development. But does it play a role in the proliferation of adult neurons as well?

我们一直都知道它在胎儿发育过程中发挥了这种作用，但它是否也在成人神经元的增殖中发挥作用？

Well, let’s consider what some animal studies indicate.

好吧，让我们考虑一些动物研究表明什么。

In one important rat study, brain signals and responsiveness to those signals were enhanced within just seconds after rats were administered doses of BDNF.

在一项重要的大鼠研究中，大脑信号和对这些信号的反应在大鼠被给予 BDNF 剂量后的几秒钟内得到增强。

And physical activity in rats, even just a few minutes of swimming, has been shown to increase BDNF levels.

老鼠的身体活动即使只是游泳几分钟也被证明会增加 BDNF 水平。

Yes, Susan.

好的，苏珊？

FEMALE STUDENT:Ah… that study was done on rats.

女学生：嗯……那项研究是用老鼠做的。

FEMALE PROFESSOR:Well, it’s true that a direct connection between BDNF, physical exercise, and brain performance in people hasn’t been proven yet.

女教授：嗯，确实，BDNF 体育锻炼与人的大脑性能之间的直接联系尚未得到证实。

But the sheer numbers of studies that indicate a connection in animals say a lot, in my view.

但在我看来，表明动物之间存在联系的研究数量之多说明了很多。

And exercise does seem to have an effect on the human brain: the research done with brain imaging techniques shows that the brains of people who exercise are much denser compared to those who don’t.

运动似乎确实对人脑有影响：使用大脑成像技术进行的研究表明，与不锻炼的人相比，锻炼的人的大脑密度要大得多。

Uh, suggesting that neurons are branching and making connections with other neurons.

这表明神经元正在分支并与其它神经元建立联系。

Also, in clinical studies involving active and inactive adults, the active adults scored much higher on cognitive tests that measured high-level thinking skills than inactive adults did.

同样在涉及活跃和不活跃成年人的临床研究中，活跃的成年人在衡量高水平思维能力的认知测试中得分比不活跃的成年人高得多。

FEMALE STUDENT:But I’ve always thought that doing crossword puzzles and… like, reading a lot was important if you wanted to maintain your thinking abilities.

女学生：但是我一直认为，如果你想保持你的思维能力，做填字游戏，比如多读书是很重要的。

You know, that you need to stay mentally stimulated and learn new things.

你知道的，你需要保持精神上的刺激和学习新事物。

FEMALE PROFESSOR:Yes, it seems that gaining knowledge or abilities is another key.

女教授：是的。似乎获得知识或能力是另一个关键。

While it’s true that thousands of new neurons are produced in the brain’s memory center each day and that exercise promotes their generation, those new neurons will just die off if they’re not being used for anything.

虽然确实每天大脑的记忆中心会产生数千个新神经元，而运动会促进它们的生成，但如果这些新神经元不被用于任何事情，它们就会死掉。

Animal studies have shown a correlation between acquiring new skills and new neurons actually surviving in the brain.

动物研究表明，获得新技能与大脑中实际存活的新神经元之间存在相关性。

It seems to be a use it or lose it kind of thing.

这似乎是一种“使用它或失去它”的事情。

So good point. Yes, Matt?

不错的观点。是的，马特？

MALE STUDENT:I was just wondering: how much exercise do we need to keep our brains making neurons? I imagine the more, the better, right?

男学生：我只是想知道我们需要多少运动才能让我们的大脑保持神经元的生成？我想越多越好，是吗？

FEMALE PROFESSOR:Well… interestingly, some studies suggest that less is more here.

女教授：嗯，有趣的是，一些研究表明这里少即是多。

You see, there’s a particular stress hormone that’s elevated in response to all methods of exercise, but more so with more intense regimens.

你会看到有一种特殊的压力荷尔蒙会随着所有的运动方式而升高，但在更激烈的训练中更是如此。

Stress hormones have been implicated in reducing BDNF levels and can also create a cascade of other problems in the human body.

压力荷尔蒙与降低 BDNF 水平有关，并且还会在人体中产生一系列其它问题。