考研

You hop into your car， but， wait， where are the keys? You meet someone new， but her name is gone before the handshake's over. Those are failures of your short-term， or “working，” memory——the place you file information for immediate， everyday retrieval. It isn't perfect. But researchers are increasingly convinced that the hormone estrogen could play a key role in maintaining and perhaps even improving memory. Last week a team of Yale scientists provided dramatic new evidence that bolsters the theory. Using MRIs——detailed snapshots of the brain——researchers found that women taking estrogen show significantly more activity in brain areas associated with memory than women on a placebo. “This is very exciting，” says Yale's Dr. Sally Shaywitz. “It means that the brain circuitry for memory had altered.”

After menopause， when estrogen levels plummet， some women become forgetful. Past research has demonstrated that those who take estrogen do better on memory tests than their nonmedicated peers do. The hormone may even reduce the risk of Alzheimer's. The new study， published in last week's Journal of the American Medical Association， is the first to visually compare the neurocircuitry of memory both on and off estrogen. The drug made a big difference to participant Bernadette Settelmeyer： “All of a sudden I was remembering things.”

The women (whose average age was 51) lay down in a brain-imaging machine where they were shown two types of information： nonsense words (“BAZ” or “DOB”) to test verbal memory and geometric patterns to assess visual memory. After a 20-second “storage” period， participants saw a mix of old and new and were asked if anything looked familiar. During each stage of the test——as the women encoded， stored and retrieved data——researchers took pictures of their brains. The 46 women underwent the test twice——once while taking a standard daily dose of estrogen and again while taking a placebo. Beyond the power of estrogen， the difference in MRIs suggests that the adult brain maintains “plasticity”——the ability to rewire itself——even as it ages.

There is still plenty of research to be done. Scientists can't yet be sure estrogen is directly responsible for better memory performance. Despite the difference in brain activity on and off estrogen， participants' scores did not change. Researchers say that is probably because the tasks were so simple (the women got more than 90 percent correct overall)。 Other studies on estrogen and cognition are short term——and their findings have been inconsistent. And scientists still can't answer the question facing millions of women： should I take hormone-replacement therapy? The new study may make estrogen more appealing， but it should be just “one part of the equation，” says Shaywitz. Still， it's a memorable one.

注(1)：本文選自Newsweek; 04/19/99， p50;

注(2)：本文習(xí)題命題模仿對象2002年真題Text 3;

1. The following are the examples of the failures of short-term memory， except that ___________.

[A]you are not sure whether you‘ve locked the door or not

[B]you cannot recall all your previous experience

[C]you cannot find the key to your car when starting it

[D]you forget the name of a stranger before the greeting is over

2. It can be inferred from the text that women‘s working memory could probably be improved if _________.

[A]they overuse estrogen

[B]they participate in the experiment

[C]their minds are kept active

[D]the estrogen level is raised

3. The experiment involving 46 ladies shows that _______.

[A]the women should take a normal dose of estrogen

[B]the women‘s brains still have the ability of creation

[C]the estrogen level determines their memory bad or good

[D]the estrogen makes the brain work more actively

4. We can draw a conclusion from the text that ________.

[A]the connection between estrogen and memory is still an open study

[B]the hormone estrogen plays a key role in improving memory.

[C]the low level estrogen makes a woman forgetful

[D]raising the estrogen level can improve the women‘s short-term memory

5. From the text we can see the writer seems ________.

[A]objective

[B]optimistic

[C]sensitive

[D]gloomy

答案：BDDAA

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（責(zé)任編輯：昆凌）

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