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DAVID GREENE, HOST:

Athletes take a shot to the head. It is hard to know exactly what will happen to their brains. NPR's Jon Hamilton spent some time with a scientist who is trying to understand why certain head impacts are worse than others.

JON HAMILTON, BYLINE¹: Philip Bayly's interest in brain injuries began with a question about soccer players. Bayly's a mechanical engineer at Washington University in St. Louis. And in the 2000s, he met with some doctors who treat injured athletes.

PHILIP BAYLY: They said, well, we've got some kids who have concussions². And they want to know if they can go back to play, and we don't know what's happening to their head when they're heading a soccer ball.

HAMILTON: Was it a big impact or a small one? The doctors thought Bayly might have the answer.

BAYLY: I said that's really interesting. I play soccer, and my kids play soccer. And I don't know what's happening when you head a soccer ball, either. But I know how we can find out.

HAMILTON: Bayly brought some soccer players into the lab to find out how much acceleration³ their heads experienced. The answer - 15 to 20 times the force of gravity. Bayly says that's a moderate impact.

BAYLY: Jump up and down, you're maybe feeling 4 or 5 Gs when you hit the ground. When you play football - you have a hard collision with someone else, it's maybe 50 to 100 Gs.

HAMILTON: But Bayly realized these numbers didn't mean much unless he knew how much of this force was reaching a person's brain. So he spent more than a decade trying to figure that out. It's an effort that has involved jiggling a lot of living human brains. Charlotte Guertler, a graduate student in Bayly's lab, shows one way to do that.

CHARLOTTE GUERTLER: So your head is resting on this. And so now if I turn it on, it'll make it vibrate again.

(SOUNDBITE OF MACHINE VIBRATING)

GUERTLER: Can you feel it vibrating? Yeah, that's what vibrates the back of your head, and that's how we see the waves inside your head.

HAMILTON: A special type of MRI shows how moving a person's head causes their brain to deform⁴ slightly. And Bayly says the research has revealed something about head impacts he didn't expect.

BAYLY: And so what we saw surprisingly was that the brain wasn't, you know, colliding and bouncing against the walls of the skull⁵. But it was pulling away from points of attachment⁶.

HAMILTON: These points of attachment anchor the brain to the skull, and Bayly says they usually act like the shock absorbers on a car.

BAYLY: Your brain is much better protected and suspended than it would be if it was just, you know, rattling⁷ around inside your skull. But like any suspension system, it can fail.

HAMILTON: Especially with certain types of impacts. One is a blow that causes a person's head to rotate. Another is an impact to the back of the head. This can actually tear the attachment points at the front of the brain and cause dangerous bleeding. Bayly says the brain's suspension system probably works pretty well when someone heads a soccer ball. What's still not clear, he says, is whether that's enough to prevent damage when players head the ball over and over again as they often do in practice.

BAYLY: So understanding the mechanical behavior of the brain at relatively⁸ low accelerations⁹ is more important than we ever thought.

HAMILTON: Jon Hamilton, NPR News.

1 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

2 concussions   

n.震荡( concussion的名词复数 )；脑震荡；冲击；震动

参考例句：

• People who have concussions often trouble thinking or remembering. 患脑震荡的人通常存在思考和记忆障碍。 来自互联网
• Concussions also make a person feel very tired or angry. 脑震荡也会使人感觉疲倦或愤怒。 来自互联网

3 acceleration   

n.加速，加速度

参考例句：

• All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
• He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。

4 deform   

vt.损坏…的形状；使变形，使变丑；vi.变形

参考例句：

• Shoes that are too tight deform the feet.(穿)太紧的鞋子会使脚变形。
• Ice crystals begin to deform measurably.冰晶就产生某种程度的变形了。

5 skull   

n.头骨；颅骨

参考例句：

• The skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
• He fell out of the window and cracked his skull.他从窗子摔了出去，跌裂了颅骨。

6 attachment   

n.附属物，附件；依恋；依附

参考例句：

• She has a great attachment to her sister.她十分依恋她的姐姐。
• She's on attachment to the Ministry of Defense.她现在隶属于国防部。

7 rattling   

adj. 格格作响的, 活泼的, 很好的 adv. 极其, 很, 非常 动词rattle的现在分词

参考例句：

• This book is a rattling good read. 这是一本非常好的读物。
• At that same instant,a deafening explosion set the windows rattling. 正在这时，一声震耳欲聋的爆炸突然袭来，把窗玻璃震得当当地响。

8 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

9 accelerations   

n.加速( acceleration的名词复数 )；加速度；（车辆）加速能力；（优秀学生的）跳级

参考例句：

• The two particles will undergo accelerations as a result of their interaction. 这两个粒子由于相互作用将获得加速度。 来自辞典例句
• Since the cord connecting the two blocks is inextensible, the accelerations are the same. 由于连接两物块的绳子无伸缩性，因此它们的加速度相同。 来自辞典例句