Department of Kinesiology, Health, and Nutrition, College of Education and Human Development, The University of Texas at San Antonio San Antonio, TX, USA.
Research Imaging Institute, The University of Texas Health Science Center at San Antonio San Antonio, TX, USA.
Front Aging Neurosci. 2014 May 9;6:86. doi: 10.3389/fnagi.2014.00086. eCollection 2014.
Previous studies report greater activation in the cortical motor network in controlling eccentric contraction (EC) than concentric contraction (CC) despite lower muscle activation level associated with EC vs. CC in healthy, young individuals. It is unknown, however, whether elderly people exhibiting increased difficulties in performing EC than CC possess this unique cortical control mechanism for EC movements. To address this question, we examined functional magnetic resonance imaging (fMRI) data acquired during EC and CC of the first dorsal interosseous (FDI) muscle in 11 young (20-32 years) and 9 old (67-73 years) individuals. During the fMRI experiment, all subjects performed 20 CC and 20 EC of the right FDI with the same angular distance and velocity. The major findings from the behavioral and fMRI data analysis were that (1) movement stability was poorer in EC than CC in the old but not the young group; (2) similar to previous electrophysiological and fMRI reports, the EC resulted in significantly stronger activation in the motor control network consisting of primary, secondary and association motor cortices than CC in the young and old groups; (3) the biased stronger activation towards EC was significantly greater in the old than the young group especially in the secondary and association cortices such as supplementary and premotor motor areas and anterior cingulate cortex; and (4) in the primary motor and sensory cortices, the biased activation towards EC was significantly greater in the young than the old group. Greater activation in higher-order cortical fields for controlling EC movement by elderly adults may reflect activities in these regions to compensate for aging-related impairments in the ability to control complex EC movements. Our finding is useful for potentially guiding the development of targeted therapies to counteract age-related movement deficits and to prevent injury.
先前的研究报告表明，尽管在健康的年轻人中，离心收缩（EC）的肌肉激活水平较低，但与向心收缩（CC）相比，EC 会引起皮质运动网络更大的激活。然而，尚不清楚在执行 EC 时比 CC 表现出更大困难的老年人是否具有这种独特的 EC 运动皮质控制机制。为了解决这个问题，我们检查了 11 名年轻（20-32 岁）和 9 名老年（67-73 岁）个体在进行第一背侧骨间（FDI）肌的 EC 和 CC 时获得的功能磁共振成像（fMRI）数据。在 fMRI 实验中，所有受试者均以相同的角度距离和速度进行 20 次 CC 和 20 次 EC 的右 FDI 运动。行为和 fMRI 数据分析的主要发现是：（1）在老年人中，EC 的运动稳定性比 CC 差，但在年轻人中则没有；（2）与之前的电生理学和 fMRI 报告一致，EC 会导致运动控制网络（包括初级、次级和联合运动皮层）的激活显著增强，而 CC 在年轻和老年组中则没有；（3）老年人的 EC 偏向激活明显大于年轻人，特别是在次级和联合皮层中，如补充运动区和前运动区以及前扣带皮层；（4）在初级运动和感觉皮层中，年轻人的 EC 偏向激活明显大于老年人。老年人控制 EC 运动的皮质高级区域的激活增强可能反映了这些区域的活动，以补偿与年龄相关的控制复杂 EC 运动能力的损伤。我们的发现有助于潜在地指导靶向治疗的发展，以对抗与年龄相关的运动缺陷并预防损伤。
