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  3. Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a singl

Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a singl

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问题     Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a single memory. Working with rats, LeDoux’s team first【B1】______the animals to fear both a beep and a siren【B2】______giving them an electric shock every time either of the tones sounded. Then LeDoux gave half the rats the drug U0126, which is known to【B3】______with memory storage, and replayed the beep【B4】______electric shocks.
    A day later, when LeDoux【B5】______back both tones to the rats, the animals that hadn’t been given the drug were still fearful of both sounds.【B6】______the rats that had been given the memory-blocking drug weren’t【B7】______of the beep, which they had last heard while【B8】______the influence of U0126.
    【B9】______how U0126 exerts its amnesiac effect is【B10】______, but it may block the synthesis of proteins that help strengthen【B11】______between neurons and establish memories. The opportunity for erasure【B12】______during the act of retrieving a memory, because that’s【B13】______the memory is being updated and【B14】______again for long-term storage. " Only those memories that are activated are【B15】______," LeDoux says.
    Drugs like U0126 may someday【B16】______sufferers of traumatic memories. A small group of human studies have been done on a drug called propranolol, which blocks the action of stress neurotransmitters that help【B17】______memories in the brain, but LeDoux’s work shows the【B18】______for greater precision. " You might be able to【B19】______the traumatic impact of memories in people," says LeDoux. " The good news is you wouldn’t be【B20】______off their memory bank. "
【B2】
选项 A、in
B、at
C、upon
D、by
答案D
解析 介词辨析题。本空前后分句结构并不复杂，但信息量较大，解题关键在于正确理解前后文意，并理清前后信息的相互关系。空格前指出研究小组要让老鼠对两种声音都产生恐惧感，空格后则说明了让老鼠产生这种恐惧感的具体做法，故后文是说明方式的，而四个选项中只有by才能引导方式状语，故[D]为答案。[A]in表示“在内部或在某范围之内”，显然不符合题意。[B]at表示“在具体的地点或时间”，也可表示“朝着具体的方向”，也不符合此处文意。而[C]after则表示“在……之后”，说明的是时间关系，而不是方式，故也应排除。
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