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  3. (46) It is known that the brain shrinks as the body ages, but the effects on mental ability are different from person to person.

(46) It is known that the brain shrinks as the body ages, but the effects on mental ability are different from person to person.

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问题     (46) It is known that the brain shrinks as the body ages, but the effects on mental ability are different from person to person. Interestingly, in a study of elderly men and women, those who had more education actually had more brain shrinkage.
    "That may seem like bad news," said study author Dr. Edward Coffey, a professor of psychiatry and of neurology at Henry Ford Health System in Detroit. (47) However, he explained, the finding suggests that education allows people to withstand more brain tissue loss before their mental functioning begins to break down.
    The study, published in the July issue of Neurology, is the first to provide biological evidence to support a concept called the "reserve" hypothesis, according to the researchers. In recent years, investigators have developed the idea that people who are more educated have greater cognitive reserves to draw upon as the brain ages; in essence, they have more brain tissue to spare.
    (48) Examining brain scans of 320 healthy men and women aged 66 to 90, researchers found that for each year of education the subjects had, there was greater shrink age of the outer layer of the brain known as the cortex. Yet on tests of cognition and memory, all participants scored in the range indicating normal.
    "Everyone has some degree of brain shrinkage," Coffey said. "People lose (on average) 2.5 percent per decade starting in adulthood."
    There is, however, a "remarkable range "of shrinkage among people who show no signs of mental decline, Coffey noted. Overall health, he said, accounts for some differences in brain size. Alcohol or drug use, as well as medical conditions such as diabetes and high blood pressure, contribute to brain tissue loss throughout adulthood.
    In the absence of such medical conditions, Coffey said, education level helps explain the range of brain shrinkage exhibited among the mentally-fit elderly. The more-educated can withstand greater loss.
    (49) Coffey and colleagues gauged shrinkage of the cortex by measuring the cerebrospinal fluid surrounding the brain. The greater the amount of fluid, the greater the cortical shrinkage.
    Controlling for the health factors that contribute to brain injury, the researchers found that education was related to the severity of brain shrinkage. For each year of education from first grade on, subjects had an average of 1.77 milliliters 11 more cerebrospinal fluid around the brain.
    Just how education might affect brain cells is unknown. (50) In their report, the researchers speculated that in people with more education, certain brain structures deeper than the cortex may stay intact to compensate for cortical shrinkage.
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答案研究人员对320名年龄在66岁到90岁的身体健康的男子和女子的脑部扫描X光片研究后发现，受试者的受教育经历每多一年，其大脑外层叫做脑皮层的部位就多一份萎缩。
解析     句子的框架是Examining brain scans…，researchers found that…there was greater shrink age of the outer layer of the brain known as the cortex(脑皮层)。examining…是现在分词结构作时间状语，that引导宾语从句。此从句是个there be句型；the subjects had作为定语从句修饰education；known as the cortex作定语，修饰the outer layer of the brain。
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