时差N小时:选择性记忆
雅艾尔：你有过不愉快的记忆吗，唐?
Don: Sure. Who doesn't?
唐：当然。谁都会有。
Yael: What would you say to having thempermanently erased from your brain?
雅艾尔：如果把它们从大脑里永久得清除，你会怎么看?
Don: Without losing other memories?
唐：不会丧失其它记忆吗?
Yael: Right. Scientists did just that with rats. They trained rats to fear two different sounds bysending a mild electric shock through the rats' paws when they played the sounds. ThisPavlovian technique resulted in the rats freezing up in nervous anticipation of the shocksevery time they heard either sound. Scientists wanted to know whether they could erase one ofthe memories without erasing the other one, even though both sounds result in the same fear.
雅艾尔：对。科学家对老鼠做过这样的实验。当他们弹奏音乐时，科学家使温和的电流震动传送到它们的爪子，以这种方式训练老鼠害怕两种不同的声音。这种巴普洛夫的技术导致老鼠每次听到其中一种声音就因害怕点电击而紧张地发抖。科学家想知道在两种声响同样使它们恐惧的前提下，它们是否能够在消除一种记忆的同时而不丧失另一种记忆。
Don: I didn't know scientists knew how to erase memories at all.
唐：我一点都不认为科学家们知道怎么去除记忆。
Yael: They do. You see, long-term memories aren't nearly as solid as we like to think. They'reactually very fragile. Every time we recall a long-term memory, it becomes malleable. Justbefore playing one of the sounds, scientists injected half the rats with a chemical that interfereswith memory reconsolidation. Thus, when they were in the process of remembering whataccompanies the sound, the drug went to work.
雅艾尔：他们知道。显而易见，长期性记忆并非我们想象的那么牢固。每当我们回忆一段长期记忆时，它就会继续延展。在播放其中任一种声音之前，科学家们给一半的老鼠注射了干扰记忆的化学物质。这样，在老鼠回忆伴随声音所发生的事情时，这种药物就会起作用。
Don: Then what?
唐：那又怎么样?
Yael: When they played both sounds a day later, the rats that had been injected with thechemical did not freeze up when they heard the sound that had accompanied the drug. Theyfroze as usual when they heard the second sound.
雅艾尔：一天后科学家再次播放这两种声音，当被注射药物的老鼠听到注射时的声音后没有表现出害怕。但听到第二种声音时还是像往常一样呆住了。
Don: They had forgotten to be afraid. Hmm. This business makes me kind of nervous.
唐：他们忘记了害怕。嗯。这个实验听起来有点恐惧。
Yael: I know what you mean, but for people with post-traumatic stress disorder, selectivememory erasure could prove enormously useful.
雅艾尔：我明白你的想法，但选择性记忆对于患上创伤后精神失调的人有很大的帮助。
Don: True. I guess some fears are best laid to rest.
唐：那倒是真的。我认为有的恐惧最好将它埋葬掉。
