Evidence for motor cortex dedifferentiation in older adults.
Evidence for motor cortex dedifferentiation in older adults.
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DOI：
10.1016/j.neurobiolaging.2011.06.021
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发表时间：
2012-09
影响因子：
4.2
通讯作者：
Seidler RD
中科院分区：
文献类型：
--
作者：
Bernard JA;Seidler RD
在认知、运动和知觉任务的执行过程中，老年人（OA）比年轻人（YA）表现出更多的弥散性脑活动。目前尚不清楚这种过度激活是否反映了补偿或去分化。通常情况下，这些研究没有评估休息时大脑的组织，这有助于确定更弥散的表征是否反映了生理或任务依赖性效应。在本研究中，我们使用经颅磁刺激（TMS），以确定是否有不同的运动皮层组织的两个大脑半球的YA和OA。我们测量了静息运动阈值，运动诱发电位（MEP）的潜伏期和振幅，以及第一背侧骨间代表的程度，除了反应时间的计算机测量。在运动阈值方面没有显著的年龄差异，但我们确实发现OA具有更大的对侧MEP振幅和更长的对侧MEP潜伏期。此外，OA的运动表征的空间范围更大。我们发现，OA中较大的优势半球运动表征与较高的反应时间相关，这表明去分化而不是补偿效应。
Older adults (OA) show more diffuse brain activity than young adults (YA) during the performance of cognitive, motor, and perceptual tasks. It is unclear whether this over-activation reflects compensation or dedifferentiation. Typically, these investigations have not evaluated the organization of the resting brain, which can help to determine whether more diffuse representations reflect physiological or task- dependent effects. In the present study we used transcranial magnetic stimulation (TMS) to determine whether there are differences in motor cortex organization of both brain hemispheres in YA and OA. We measured resting motor threshold, motor evoked potential (MEP) latency and amplitude, and extent of first dorsal interosseous representations, in addition to a computerized measure of reaction time. There was no significant age difference in motor threshold, but we did find that OA had larger contralateral MEP amplitudes and a longer contralateral MEP latency. Furthermore, the spatial extent of motor representations in OA was larger. We found that larger dominant hemisphere motor representations in OA were associated with higher reaction times, suggesting dedifferentiation rather than compensation effects.
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