大脑为何有那么多沟壑【阅读听力】

Why The Brain Has So Many Folds

"Dear A Moment of Science, I know the human brain is an incredible thing, the most complex object in the known universe. But, honestly, it’s not much to look at. Just a big, gray, foldy lump. And what’s with all those folds? Why does the brain look a lot like a scrunched up piece of paper?"

Our brains, and the brains of some other animals, have a lot more in common with a balled up piece of paper than you might think.

First, though, it’s worth mentioning that not all brains look the same. Some animals, including rats and mice, have smooth brains. No folds or wrinkles. Humans and other animals, such as pigs, have brains with many folds.

Scientists at the University of Rio de Janeiro have been trying to figure out what accounts for the folds. One idea postulated that as brains evolve and the more neurons they have, the more folds are required to allow neurons to form connections. But elephants have nearly twice as many folds in their brains yet have fewer neurons than we do, so that theory seems improbable.

The researchers have, however, determined that how human brains fold follows the same physical principles guiding folds and creases resulting from crumpling a sheet of paper. That’s interesting because it enabled the scientists to reason that the two main factors determining a brain’s shape are the surface area and thickness of the outer layer cortex. The larger the cortex surface area, the more folds a brain will have. But greater thickness results in fewer folds.

Same goes for a piece of paper.

译文：

为什么大脑有那么多沟壑

亲爱的科学一刻，我知道人脑非常不可思议，是已知的宇宙世界中最复杂的构造。但是，说实话从表面看根本看不出来，只是一个体积较大的灰色有沟壑的团状物。这些沟壑究竟是什么呢？为什么大脑看起来就像一张揉成一团的纸？

事实上你可能不知道，我们的大脑与个别动物的大脑一样，和揉成一团的纸有许多相似之处。

首先，值得一提的是并非所有大脑都长得一样。一些动物，例如老鼠，他们的大脑就很平整，并没有沟壑和褶皱。人类的大脑与猪等其他动物的大脑都有许多沟壑。

里约热内卢大学的科学家试图找出沟壑的成因。目前有一个理论认为随着大脑进化，产生越来越多地神经元，就需要更多的沟壑让神经元连接起来。但大象的沟壑几乎是人类的2倍多，但神经元却比我们少的多，因此这项理论并不成立。

但那些科学家从揉成团的纸中推论出，人脑形成沟壑与纸的折叠和起皱遵循同样的物理学规律。这很有意思，科学家通过2个要素推论出大脑的形状是由外皮质层的表面积和厚度决定的。外皮质层的表面积越大，大脑的沟壑就越多。而厚度越大，沟壑就越少。

纸张也是同样的原理。（略有修改）

【本译文由普特网友小辰JODY提供】