重建大脑

许多年来,大家一直认为我们的脑细胞(神经细胞)是在出生前产生的,也有一些例外的是在出生后一两年产生的,但是其后这一进程就被认为是终止了。大多数脑科学家认为,从那时起,大脑回路只能通过改变突触或者已有的细胞之间的联系来得以修改。按照这种观点,所有用来补充的细胞按照功能在结构上被组合在一起并形成主要的路径,组成大脑的“硬件”。而细胞之间具体的联系性质以及可以改变的突触是软件。

从二十世纪六十年代起,证据显示新的神经细胞可以在这一早期过后,甚至在成年期被添加进来。到了八十年代,在研究歌鸟的大脑与获取和产生学来的歌曲相关的部分时所获得的一些发现使这一证据变得更有说服力。这一发现一开始受到了质疑,但是歌鸟的数据证明这是可信的。

那么如何来证明一个神经细胞是在某个特定时间产生的呢?身体内每个细胞都包含有DNA,它负责产生细胞要形成其功能所必需的蛋白质。尽管身体内的所有细胞的NDA都是相同的,但是不同的细胞类型只含有带有DNA密码的某个基因子集,这样就产生了皮肤细胞、肝细胞和脑细胞之间的区别。

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