Get Smart
 
　　Many people dream of having a smarter brain. Princeton neurobiologist Joseph Z. Tsien found the key. In September he announced that he’d built a better mouse by altering a gene¹ that affects learning and memory. A similar process of gene manipulation might conceivably be used one day to boost intelligence in humans. 

　　The secret lies in a feature of brain cells called the nmda receptor, which Tsien likens[1] to a cylindrical² tube or window that mediates[2] the flow of information. When the window is open, chemicals called neurotransmitters flow through easily and memory is registered and stored. But as organisms mature, the window begins to close. (This may explain why children lose their facility for learning new languages when they reach sexual maturity³ and why some people suffer memory loss as they age.) 

　　Tsien noticed that the receptor worked more efficiently⁴ when teamed[3] with the gene NR2B, so he introduced extra NR2B genes⁵ into a batch⁶ of fertilized⁷ mouse eggs. In a normal mouse, the memory window is open for just 150-thousandths of a second. In Tsien’s specially⁸ engineered mice, the window opens for 250-thousandths of a second, long enough to make a remarkable⁹ difference in memory retention¹⁰. When he pitted[4] his mice against common mice, they won paws down. Ordinary mice could recognize a Lego block for 12 hours, but smart mice could remember the block for up to three days. "That’s a profound enhancement," Tsien says. 

　　Can it be done with humans? Maybe, but genetic¹¹ engineering will have to make some extraordinary advances first. And some thorny¹² ethical¹³ issues will have to be resolved. Meanwhile, Tsien promises to keep his furry¹⁴ little geniuses locked up in a lab, far from your larder¹⁵. "Otherwise," he says, "you might need a smart cat or a smart mousetrap to catch them."

　　许多人都希望自己能变成更聪明。普林斯顿神经生物学家Joseph Z. Tsien就找到了这把开启智慧之门的钥匙：他于九月宣布，通过改变影响学习和记忆能力的基因培养出了一只聪明的老鼠。类似的基因处理技术有望在未来日子里运用到人脑，以推动人类智慧的飞跃。
 
　　该技术的奥秘就在于名为nmda感受器的脑细胞的功能。Tsien将其比作一个传递信息流的圆柱通道或窗口。当窗口开放时，某种称为神经传递素的化学物质就能轻易流过，记忆因此登记并存储了下来。然而，当器官成熟时，这扇窗口就开始关闭。（这也能解释为何儿童长大后（性器官成熟之时）会失去掌握新语言的能力，以及为何某些人年老时会患失忆）。 

　　Tsien注意到，当感受器与名为NR2B的基因协作时效率会更高。因此，他将NR2B基因植入一批老鼠的受精卵中。一只普通老鼠的记忆之窗仅开放千分之150秒。而经Tsien植入基因的老鼠，记忆之窗能开放千分之250秒，这已经能够使其记忆力发生惊人的改变。当他让自己的老鼠与普通老鼠互斗时，它们竟能轻而易举地取胜。普通老鼠能够保留关于Lego block的记忆12小时，而聪明的老鼠居然能将记忆保持三天。“这可是一个意义深远的进步。”Tsien这样说。 

　　那么，人类也能接受这种基因移植吗？ 或许可以，但前提是基因工程得首先做出非凡的成就，还必须解决一系列棘手的伦理问题。Tsien保证他一定会将那些披着毛皮的小天才锁入实验室，远离人们的食品柜。“否则，”他说，“为了捉住他们，人们就不得不去寻找更聪明的猫或者功能更强的捕鼠器了。” 

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