托福閱讀材料之The Prefrontal Cortex with Age

　　The prefrontal cortex is the region of the brain located just behind the forehead, where higher-level cognition occurs, such as recalling whether a word was heard aloud or read. Most people show evidence of more processing on one side of the cortex, the right side. However, research has shown that many elderly people use both hemispheres more equally, thus processing bilaterally.

　　This discovery led to two opposing theories as to why. One theory supposes that this change in the prefrontal cortex is part of the general decline of the body, that bilateral processing is evidence of malfunctioning. The other theory supposes that enlisting the help of the other hemisphere of the prefrontal cortex is a way to compensate for reduced capacity in the more active hemisphere; that is, the brain is making up for its own failings.

　　Scientists conducted a range of cognitive tests with older adults in their 60’s and 70’s. Then chose two smaller groups from those subjects–those who performed high on the tests, and those who performed low. The scientists then administered two of the same tests to the two groups of older adults, as well as to a group of young adults between the ages of 20 and 35 while the subjects’ brains were PET scanned. What they found was that the high-performing older adults showed significantly more use of bilateral processing than did anyone else.

　　The research supports the theory that bilateral processing is a way to compensate for reduced capacity of the right hemisphere with age. Further research may examine how training individuals or using drugs to enhance bilateral processing affects diseases such as Alzheimer’s.

　　前額皮質(zhì)位于前額之后區(qū)域，作用于高級認知，比如，回憶是否聽過或讀過某個單詞。大多數(shù)人右側(cè)大腦皮層更發(fā)達。而研究顯示，一些老年人均衡使用左右腦，因此左右腦相當。

　　產(chǎn)生了兩種截然不同理論來解釋這一發(fā)現(xiàn)。一種理論是這種改變是因為整體機能衰退，大腦協(xié)調(diào)分工失常。另一種觀點則認為左腦協(xié)助右腦工作，是在彌補更活躍的右腦機能的衰退，也就是說，這種情況是在彌補大腦自身機能的衰退。

　　科學家針對60歲到70歲的老人做過一組認知測試。從中刪選出兩小組：一組測試表現(xiàn)好的;一組測試表現(xiàn)差的。科學家對這兩組老人和一組年齡在20歲到35歲的受試者進行相同測試，并掃描受試者大腦。結(jié)果發(fā)現(xiàn)，比起其他兩組，測試表現(xiàn)好的老人均衡使用左右腦。

　　研究結(jié)果表明后者觀點是正確的，左右腦合作是為了彌補因為年老衰退的右側(cè)大腦機能。研究的下一步是證明個體能否通過訓練或服用藥物提高左右腦功能均衡發(fā)展，預防老年癡呆癥。

　　prefrontal cortex: 前額皮質(zhì)

　　PET: 性能鑒定(positron emission tomography)

　　Alzheimer's: 老年癡呆癥

　　compensate：彌補