許多人都希望自己能變成更聰明。這也是各種健腦、補腦藥品和營養品大行其道的原因。普林斯頓的一位神經生物學家Joseph Z. Tsien則宣稱找到了開啟智慧之門的鑰匙——基因。

    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 gene 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 to a cylindrical tube or window that mediates 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 maturity and why some people suffer memory loss as they age.)

    Tsien noticed that the receptor worked more efficiently when teamed with the gene NR2B, so he introduced extra NR2B genes into a batch of fertilized mouse eggs. In a normal mouse, the memory window is open for just 150-thousandths of a second. In Tsien’s specially engineered mice, the window opens for 250-thousandths of a second, long enough to make a remarkable difference in memory retention. When he pitted 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 genetic engineering will have to make some extraordinary advances first. And some thorny ethical issues will have to be resolved. Meanwhile, Tsien promises to keep his furry little geniuses locked up in a lab, far from your larder. "Otherwise," he says, "you might need a smart cat or a smart mousetrap to catch them."

    liken: 把……比作