科学家们过去常常认为，大脑因为其复杂性而呈现出静止状态。
Once the brainmatured, it essentially stoppedgrowing and changing.
一旦成熟，大脑基本上就会停止生长和变化。
And when neurons, or brain cells, were lostordamaged, they were gone for good.
当神经元或大脑细胞丢失或损坏时，大脑就会坏死掉。
But recent discoveries have caused neuroscientists tochange their tune.
但是最近的发现让神经学家改变了看法。
The human brain isanything but static-in fact, it's constantly growing and changing as itadapts to new informationand circumstances.
人类的大脑绝不是静止的，事实上，它是随着对新信息和新环境的适应不断生长和变化的。
For example, scientists now know that there's a mechanism in the hippocampus a brainpartinvolved with memory, among other things that gives birth to new brain cells.
举个例子来说，现在科学家们知道大脑内存在一种叫做海马体的记忆机制，可以产成新的大脑细胞。
Scientists don'tknow exactly why the brain makes new cells or what the cells do.
但是，科学家们不能确切地知道大脑为什么能生成新细胞，而这些细胞又能做什么。
They may have something todo with forming memories, or be used to replace dead ordamaged cells.
它们可能和形成记忆有关，或者被用于代替老去或损坏的细胞。
In any case, in a recent experiment, scientists working with mice shut down their brains' abilitytomake new cells.
不管怎样，在最近的一次实验中，科学家们用老鼠进行实验，他们消除了这些老鼠们大脑生成新细胞的能力。
At first, the researchers observed that the mice had reduced functioning in cellularmechanismsin the brain important for memory formation.
起初，研究人员观测到，老鼠大脑中对记忆生成非常重要的细胞机制的功能降低了。
But after about six weeks, they noticed that the mice's brains had begun to compensatebymaking existing neurons more active.
但是大约六周之后他们又发现，老鼠的大脑通过使现有的神经元变得更加活跃从而弥补之前的损失。
Relatively newborn neurons created before the researchersshut down the neuron birthingprocess reacted by living longer than they normally would-almostas though they knew thatreplacements would not be forthcoming and so they had to workovertime to help the brain getback on course.
相对地，在研究人员阻止神经元生成之前生成的神经元比一般生成的存活更长—就好像它们知道自己不会被很快代替，所以它们必须延时工作来帮助大脑回到正轨上。
This research is of the most basic, foundational kind. But knowing more about how thebrainresponds to changes could eventually have profound implications for how doctorsunderstandand treat Alzheimer's, dementia, and other brain illnesses.
这项研究是最为基础的研究。但是，对大脑是如何变化的了解越多，就会对医生了解与治疗老年痴呆症、痴呆和其它大脑疾病产生更为深远的意义。
