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.

　　译文：

　　前额皮质位于前额之后区域，作用于高级认知，比如，回忆是否听过或读过某个单词。大多数人右侧大脑皮层更发达。而研究显示，一些老年人均衡使用左右脑，因此左右脑相当。

　　产生了两种截然不同理论来解释这一发现。一种理论是这种改变是因为整体机能衰退，大脑协调分工失常。另一种观点则认为左脑协助右脑工作，是在弥补更活跃的右脑机能的衰退，也就是说，这种情况是在弥补大脑自身机能的衰退。

　　科学家针对60岁到70岁的老人做过一组认知测试。从中删选出两小组：一组测试表现好的;一组测试表现差的。科学家对这两组老人和一组年龄在20岁到35岁的受试者进行相同测试，并扫描受试者大脑。结果发现，比起其他两组，测试表现好的老人均衡使用左右脑。

　　研究结果表明后者观点是正确的，左右脑合作是为了弥补因为年老衰退的右侧大脑机能。研究的下一步是证明个体能否通过训练或服用药物提高左右脑功能均衡发展，预防老年痴呆症。

　　prefrontal cortex: 前额皮质

　　PET: 性能鉴定(positron emission tomography)

　　Alzheimer's: 老年痴呆症

　　compensate：弥补