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　　High Stress May Damage Memory

　　According to a report issued in May 1998， elderly people who consistently high blood levels of the stress hormone. What's more ，high levels of cortisol are also associated with shrinking of the hippocampus（海马区）， a region of the brain that plays a key role in learning and memory.

    The findings suggest that even cortisol levels in the normal, "healthy" range can actually accelerate brain aging.

　　The study results "now provide substantial evidence that long-term exposure to adrenal（肾上腺） stress hormones may promote hippocampal aging in normal elderly humans， "write Nada porter and Phillip Landfield. Cortisol is a hormone releases in response to stress by the adrenal glands（腺）， which sit on top of the kidneys （肾）。

    Over a 5-to 6-year period, dr. Sonia lupine and his colleagues measures 24-hour cortisol levels in 51 healthy volunteers, most whom were in their 70s.

    The researchers tested the volunteers' memory on six people in the increasing/high category and five people in the decreasing/moderate group. The groups did not differ in tests of immediate memory, but the increasing/high cortisol group had other memory problems compared with those in the decreasing/moderate group.

    The researchers also found that the total volume of the hippocampus in those in the increasing/high group was 14% lower than those in the decreasing/moderate group, although there were no differences in other brain regions.

　　The results suggest that "…brain aging can be accelerated by levels of adrenal hormones that are not generally regarded as pathological（病态的） and that variation within this normal range is related to variation in the rate of brain aging." write porter and landfield." This further suggests that chronic stress may accelerate the worsening of the hippocampus.

　　6　which of the following plays a key role in one's learning and memory？

　　A　the kidneys

　　B　the adrenal hormone

　　C　the stress hormone

　　D　the hippocampus

　　7　when the levels of cortisol go high ，the hippocampus

　　A　may expand

　　B　 may shrink

　　C　 may disappear

　　D　 may function better

　　8　according to the passage， when people are under stress，

　　A　the adrenal glands will produce cortisol

　　B　the kidneys will shrink rapidly

　　C　the hippocampus will produce cortisol

　　D　the brain will work more efficiently

　　9　it app ears that when the hippocampus shrinks sue to high levels of cortisol， other brain regions

　　A　may change dramatically

　　B　may stop functioning

　　C　may remain unaffected

　　D　may be seriously damaged

    10 the research conducted by porter and land field showed that

　　A　the levels of adrenal hormones have nothing to do with brain aging

　　B　changes in the levels of adrenal hormones can affect brain aging

　　C　chronic stress may strengthen one's memory

　　D　the rate of brain aging always remains stable

　　同时按下ctrl+A键查看答案

　　31. A　 32. D　 33. C　 34. C　 35. B

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