『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 55 Lec 2听力练习：What is the main purpose of the lecture?原文题目答案解析，TPO/Official 55 Lec 2听力原文范文音频翻译。

托福TPO/Official 55 Lec 2听力原文What is the main purpose of the lecture?【新东方在线】

旁白：听健康科学课上的部分讲座。

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

女教授：我们都听说经常锻炼对健康有好处。

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

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？

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?

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。

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

有一些假说可以解释运动如何影响我们的大脑。

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

但在我们开始讨论之前，我需要谈谈神经发生。

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

神经发生是在大脑中产生新的神经元、神经细胞。

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

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。

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.

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。

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

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。

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.

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。

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

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。

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

但是运动到底是如何适应这里的呢？

But, how exactly does exercise fit in here?

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。

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

一种这样的蛋白质称为脑源性神经营养因子，或 BDNF。

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

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。

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

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？

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?

好吧，让我们考虑一些动物研究表明什么。

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

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。

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

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。

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

女学生：嗯……那项研究是用老鼠做的。

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

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。

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

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。

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

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。

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.

这表明神经元正在分支并与其它神经元建立联系。

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

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。

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.

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。

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.

你知道的，你需要保持精神上的刺激和学习新事物。

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

女教授：是的。似乎获得知识或能力是另一个关键。

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

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。

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.

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。

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

这似乎是一种“使用它或失去它”的事情。

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

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？

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?

女教授：嗯，有趣的是，一些研究表明这里少即是多。

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

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。

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.

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。

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

What did researchers decide to investigate as a result of the research on songbirds?

What is the professor’s opinion about the research findings on rats that were administered BDNF?

What does the professor imply may be important to prevent new neurons from dying in adult humans?

What point does the professor make when she discusses stress hormones?

NARRATORListen to part of a lecture in a health science class.FEMALE PROFESSOR We’ve all heard that there are health benefits to regular exercise. 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? Now we’re hearing that exercise also has a positive effect on our high-level intellectual abilities. There’re a few hypotheses that may explain how exercise affects our brain. But before we get into that, I need to talk a little bit about neurogenesis.Neurogenesis is the creation of new neurons, nerve cells, in the brain. 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. But some decades ago, research on the ability of adult songbirds to learn new songs changed that whole paradigm. 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. These findings on songbirds opened up the question of whether the same processes that occurred in birds also occurred in humans. And subsequent research confirmed that the adult human brain indeed generates new neurons in the memory center of the brain.But, how exactly does exercise fit in here? Well, probably the most studied hypothesis out there proposes that exercise increases the production of important proteins in the brain. One such protein is called brain-derived neurotrophic factor, or BDNF.Brain-derived neurotrophic factor helps neurons grow, multiply, connect, and transmit signals. 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? Well, let’s consider what some animal studies indicate. In one important rat study, brain signals and responsiveness to those signals were enhanced within just seconds after rats were administered doses of BDNF. And physical activity in rats, even just a few minutes of swimming, has been shown to increase BDNF levels. Yes, Susan.FEMALE STUDENT Ah… that study was done on rats.FEMALE PROFESSOR Well, it’s true that a direct connection between BDNF, physical exercise, and brain performance in people hasn’t been proven yet. But the sheer numbers of studies that indicate a connection in animals say a lot, in my view.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. Uh, suggesting that neurons are branching and making connections with other neurons. 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.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. You know, that you need to stay mentally stimulated and learn new things.FEMALE PROFESSOR Yes, it seems that gaining knowledge or abilities is another key. 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. Animal studies have shown a correlation between acquiring new skills and new neurons actually surviving in the brain. It seems to be a use it or lose it kind of thing. So good point. Yes, Matt?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?FEMALE PROFESSOR Well… interestingly, some studies suggest that less is more here. 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. Stress hormones have been implicated in reducing BDNF levels and can also create a cascade of other problems in the human body.

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