阅读理解   You can have too much of a good thing, it seems—at least when it comes to physiotherapy after a stroke. Many doctors believe that it is the key to recovery: exercising a partially paralyzed limb can help the brain 'rewire' itself and replace neural connections destroyed by a clot in the brain.
    But the latest animal experiments suggest that too much exercise too soon after a brain injury can make the damage worse. 'It's something that clinicians are not aware of,' says Timothy Schallert of the University of Texas at Austin, who led the research.
    In some trials, stroke victims asked to put their good arm in a sling—to force them to use their partially paralyzed limb—had made much better recoveries than those who used their good arm. But these patients were treated many months after their strokes. Earlier intervention, Schallert reasoned, should lead to even more dramatic improvements.
    To test this theory, Schallert and his colleagues placed tiny casts on the good forelimbs of rats for two weeks immediately after they were given a small brain injury that partially paralyzed one forelimb. Several weeks later, the researchers were astonished to find that brain tissue surrounding the original injury had also died. 'The size of the injury doubled. It's a very dramatic effect.' says Schallert.
    Brain-injured rats that were not forced to overuse their partially paralyzed limbs showed no similar damage, and the casts did not cause a dramatic loss of brain tissue in animals that had not already suffered minor brain damage, In subsequent experiments, the researchers have found that the critical period for exercise-induced damage in rats is the first week after the initial brain injury.
    The spreading brain damage witnessed by Schallert's team was probably caused by the release of glutamate, a neurotransmitter, from brain cells stimulated during Limb movement. At high doses, glutamate is toxic even to healthy nerve cells. And Schallert believes that a brain injury makes neighboring cells unusually susceptible to the neurotransmitter's toxic effects.
    Randolph Nudo of the University of Texas Health Science Center at Houston, who studies brain injury in primates, agrees that glutamate is the most likely culprit. In experiments with squirrel monkeys suffering from stroke-like damage. Nudo tried beginning rehabilitation within five days of injury. Although the treatment was beneficial in the long run, Nudo noticed an initial worsening of the paralysis that might also have been due to brain damage brought on by exercise.
    Schallert stresses that mild exercise is likely to be beneficial however soon it begins. He adds that it is unclear whether human victims of strokes, like brain injured rats, could make their problems worse by exercising too vigorously, too soon.
    Some clinics do encourage patients to begin physiotherapy with a few weeks of suffering a traumatic head injury or stroke, says David Hovda, director of brain injury research at the University of California, Los Angeles. But even if humans do have a similar period of vulnerability to rats, he speculates that it might be possible to use drugs to block the effects of glutamate.
单选题     Schallert issued a warning to those who ______.
 
【正确答案】 C
【答案解析】 推断题。题意为：Schallert向______人发出警告。第一段第二句话告诉我们：很多医生都相信物理疗法是康复的关键，通过训练半瘫的肢体可以帮助大脑神经再连接起来(rewire)并代替由脑中血凝块破坏的神经线路。第二段话则告诉我们Schallert进行的动物实验暗示大脑损伤后太早进行康复训练会使损害更严重，从而对那些对偏瘫肢体进行训练的人发出警告。所以选C。
单选题     Which of the following is Schallert's hypothesis for his investigation?
 
【正确答案】 A
【答案解析】 细节题。题意是：哪个选项是Schallert的假设?根据Schaller对动物做的实验可以看出，早期康复练习才会对大脑加重损伤，而受伤一周后，过了危险期再进行干预，就不会出现这个问题。参见第四、第五段。所以选A。
单选题     The results from Schallert's research ______.
 
【正确答案】 C
【答案解析】 推断题。题意是：Schallert研究的结论______。参见第三段和第四段。在第三段最后一句话中，Schallert认为早期干预应该能使肢体获得更大的恢复。为证实这一想法，Schallert用老鼠做了实验。而在第四段的实验中Schallert等人吃惊地发现brain tissue surrounding the original injury had also died(损伤脑部周围的细胞组织也死了)。从此处我们可以看出，Schallert的实验与他的设想相反。所以选C。
单选题     The results made Schallert's team aware of the fact that ______.
 
【正确答案】 B
【答案解析】 细节题。题意是：实验结果让Schaller研究人员意识到______。参见第六段。第六段告诉我们Schaller得出的研究结论是，脑部伤害使得周边细胞往往易受神经传递素的毒性作用影响，而这种神经传递素就是glutamate。本段第一句话...a neurotransmitter, from brain cells stimulated during Limb movement(神经传递素，由于肢体运动而刺激大脑细胞而产生的)告诉我们此题选B。A和C是科学事实，不是本次研究结果。
单选题     Schaller would probably advise clinicians ______.
 
【正确答案】 B
【答案解析】 细节题。题意是：Schaller可能会建议临床医生______。A选项“使用药物来阻断glutamate的影响。这是David Hovda的想法，而不是Schaller的(参见最后一段)。选项B“中风病人应该对运动量慎重。”参见第八段第一句话“Schaller强调适度运动对于无论何时开始的康复训练都有好处。”选项C“给受伤一周后的中风病人开强度训练的处方。”参见第五段最后一句话“对于老鼠来说，大脑受伤后最后的一星期是训练诱发损伤的关键期。”文中并没有提到人的关键期具体是什么时间。选项D“重新考虑物理疗法对大脑带来的损伤。”也不正确，所以选B。