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　　From The Economist

　　Aug. 2, 2007

　　Lest We Forget or Lest We Remember?

　　People remember emotionally charged events more easily than they recall the quotidian. A sexual encounter trumps doing the grocery shopping. A mugging trumps a journey to work. Witnessing a massacre trumps pretty well anything you can imagine.

　　That is hardly surprising. Rare events that might have an impact on an individual's survival or reproduction should have a special fast lane into the memory bank-and they do. It is called the a2b-adrenoceptor, and it is found in the amygdala, a part of the brain involved in processing strong emotions such as fear. The role of the α2b-adrenoceptor is to promote memory formation-but only if it is stimulated by adrenaline. Since emotionally charged events are often accompanied by adrenaline secretion, the α2b-adrenoceptor acts as a gatekeeper that decides what will be remembered and what discarded.

　　However, the gene that encodes this receptor comes in two varieties. That led Dominique de Quervain, of the University of Zurich, to wonder if people with one variant would have better emotional memories than those with the other. The short answer, just published in Nature Neuroscience, is that they do. Moreover, since the frequencies of the two variants are different in different groups of people, whole populations may have different mixtures of emotional memory.

　　The reason Dr de Quervain suspected the variants might work differently is that the rarer one looks like the commoner one when the latter has a memory-enhancing drug called yohimbine attached to it. His prediction, therefore, was that better emotional memory would be associated with the rarer version.

　　And that did, indeed, turn out to be the case in his first experiment. This involved showing students photographs of positive scenes such as families playing together, negative scenes such as car accidents, and neutral ones, such as people on the phone. Those students with at least one gene for the rarer version of the protein (everyone has two such genes, one from his father and one from his mother) were twice as good at remembering details of emotionally charged scenes than were those with only the common version. When phone- callers were the subject; there was no difference in the quality of recall.

　　That is an interesting result, but some of Dr de Quervain's colleagues at the University of Konstanz, in Germany, were able to take it further in a second experiment. In fact, they took it all the way along a dusty road in Uganda, to the Nakivale refugee camp. This camp is home to hundreds of refugees of the Rwandan civil war of 1994.

　　In this second experiment the researchers were not asking about photographs. With the help of specially trained interviewers, they recorded how often people in the camp suffered flashbacks and nightmares about their wartime experiences. They then compared those results with the α2b-adrenoceptor genes in their volunteers. As predicted, those with the rare version had significantly more flashbacks than those with only the common one.

　　Besides bolstering Dr de Quervain's original hypothesis, this result is interesting because only 12% of the refugees had the rarer gene. In Switzerland, by contrast, 30% of the population has the rare variety-and the Swiss are not normally regarded as an emotional people.

　　Whether that result has wider implications remains to be seen. Human genetics has a notorious history of jumping to extravagant conclusions from scant data, but that does not mean conclusions should be ducked if the data are good. In this case, the statistics suggest Rwanda may have been lucky: the long-term mental-health effects of the war may not be as widespread as they have been in people with a different genetic mix. On the other hand, are those who easily forget the horrors of history condemned to repeat them?

　　词汇注解

　　witness /'witnis/

　　【文中释义】v目击

　　【大纲全义】n.目击者，证人;证据，证明。v目击，目睹;作证

　　impact /'impækt/

　　【文中释义】 n.影响，作用

　　【大纲全义】n.冲击，碰撞;影响v影响;挤入，压紧

　　process / prə'ses/

　　【文中释义】v.加工，处理

　　【大纲全义】n.过程;工序;工艺;(法律)程序，(诉讼)手续v.加工，处理，办理

　　promote /prə'məut/

　　【文中释义】v.促进，增进

　　【大纲全义】v.促进，发扬;提升，提拔;增进，助长;宣传，推销(商品)

　　charged/tʃa:dʒd/

　　【文中释义 】adj.充满感情的，(气氛)紧张的

　　【大纲全义】adj.(颜色)过重的，(笔法)夸张的;充满感情的，(气氛)紧张的，(物)带电的

　　accompany /ə' kʌmpəni/

　　【文中释义】v.与某事物同时存在或发生

　　【大纲全义】v.陪伴,陪同;伴随，和…一起发生;伴奏

　　discard /dis'ka:d/

　　【文中释义】v.丢弃，抛弃

　　【大纲全义】v.丢弃，抛弃，遗弃

　　variety/və'raiəti/

　　【文中释义】n. 品种，种类

　　【大纲全义】n.种种，多种多样;种类，品种

　　mixture /'mikstʃə/

　　【文中释义】n.混合物

　　【大纲全义】n.混合;混合物，混合剂

　　suspect / səs'pekt/

　　【文中释义】v.推测，怀疑

　　【大纲全义】v.猜想;怀疑;察觉 n.嫌疑犯 adj.可疑的

　　enhance / in'ha:ns/

　　【文中释义】v.提高，增加，加强

　　【大纲全义】v.提高，增强

　　attached /ə'tætʃt/

　　【文中释义】adj.附加的

　　【大纲全义】adj.依恋的，充满爱心的;附上......的

　　neutral /'nju:trəl/

　　【文中释义】adj.中性的

　　【大纲全义】adj.中立的，不偏不倚的;中性的，中和的

　　recall /ri'kɔ:l/

　　【文中释义】n.记忆力，记性

　　【大纲全义】n.回忆，召回，取消v回忆，记得，回想;撤消，收回

　　dusty /'dʌsti/

　　【文中释义】adj.满是灰尘的

　　【大纲全义】adj.多灰尘的，灰尘厚积的;灰色的;(酒)浊的;灰尘一般的;粉末状的;无聊的，干巴巴的;含糊的，不明朗的，无价值的

　　refugee /¸refju(︰) ˊdʒi: /

　　【文中释义】n.难民

　　【大纲全义】n.(政治上的)避难者，难民

　　超纲单词

　　quotidian n.每天发生的事 amygdala n.扁桃体

　　adrenaline n.肾上腺素 commoner n.平民

　　flashback n.例叙，闪回 yohimbine n.育亨宾

　　重点段落译文

　　和日常发生的事情比起来，人们往往会记住引起强烈情绪反应的事件。而路遇行凶抢劫的记忆也比平常去上班的记忆更深刻。目击一场大杀戮在你心中留下的烙印可能也是其他任何

　　事情所不可比拟的。

　　这不足为奇。对于那些可能影响个体生存和繁衍的不寻常事件，它们理应有一个能够优先进入人的记忆库的快速通道，而事实也是如此—这个快速通道叫做α 2b肾上腺素受体，是在人的扁桃体中发现的。扁桃体是人大脑中处理强烈情绪(如恐惧)的部分。α 2b肾上腺素受体所扮演的角色是促进记忆的形成，但必须是在它受到肾上腺素的刺激之后。由于引起情绪很大波动的事件通常伴随着肾上腺素的分泌，α 2b肾上腺素受体就像看门人一样要决定记住哪些事而舍弃哪些事

　　然而，对这些受体进行编码的基因有两种变体。那么，携带其中一种变体的人是否比携带另一种变体的人对引起情绪反应的事情记忆得更深刻呢?苏黎世大学的多米尼克·德凯尔万教授对此提出质疑。答案是肯定的—这一结论刚刚发表在《自然—神经科学》杂志上。此外，由于在不同的人群体内，这两种变体的分布频率不同，因此从总体来看，人们的情绪记忆存在着各种不同的状况。

　　德凯尔万博士之所以怀疑不同的变体有不同的作用是有一定的依据的。这两种变体中，一种是较少见的变体，另一种是较常见的变体;而后者与一种叫做育亨宾的可增强记忆的药物相结合时，其作用与较少见的变体表现得一样。因此，他推测:较少见的那种变体会促成较好的情绪记忆。

　　这种情况也确实在他第一次的实验中得到了验证。在该实验中，他给学生们展示了各种积极情绪的图片(如一家人在一起戏耍的情景)、消极情绪的图片(如车祸)，以及中性的图片(如正在打电话的人)。那些学生中有的人至少携带有一个少见的变体基因(每个人都有一对这样的基因，一个来自来父亲，另一个来自于母亲)，他们对于情绪事件的记忆力是那些只有常见变体基因的学生的两倍。而当记忆的对象是打电话的人时，学生们的记忆力水平没有出现差异。

　　这是一个有趣的结果，但德凯尔万博士在德国康斯坦茨大学的一些同事又进一步地做了第二个实验。事实上，他们带着这个实验穿过了乌干达灰蒙蒙的公路，来到了纳基瓦莱难民营。那里居住着1994年卢旺达内战后成百上千的难民。

　　在这第二个实验中，研究者们没有使用图片。在经过专门训练的调查人员的帮助下，他们记录了难民们脑海中战时情景闪回的次数，以及关于战时经历的噩梦的次数。然后，他们将记录结果与研究对象中所携带的α 2b肾上腺索受体基因进行了比较。正如之前所预计的一样，那些带有少见变体基因的难民所经历的记忆闪回次数，比起只有常见变休基因的难民要多得多。

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