Department of Bioengineering Department, University of Illinois at Urbana-Champaign, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA.
Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA.
Neuroimage. 2014 Aug 1;96:81-7. doi: 10.1016/j.neuroimage.2014.03.045. Epub 2014 Mar 20.
Changes in fine motor control that eventually compromise dexterity accompany advanced age; however there is evidence that age-related decline in motor control may not be uniform across effectors. Particularly, the role of central mechanisms in effector-specific decline has not been examined but is relevant for placing age-related motor declines into the growing literature of age-related changes in brain function. We examined sub-maximal force control across three different effectors (fingers, lips, and tongue) in 18 young and 14 older adults. In parallel with the force variability measures we examined changes in white matter structural integrity in effector-specific pathways in the brain with diffusion tensor imaging (DTI). Motor pathways for each effector were identified by using an fMRI localizer task followed by tractography to identify the fiber tracts propagating to the midbrain. Increases in force control variability were found with age in all three effectors but the effectors showed different degrees of age-related variability. Motor control changes were accompanied by a decline in white matter structural integrity with age shown by measures of fractional anisotropy and radial diffusivity. The DTI metrics appear to mediate some of the age-related declines in motor control. Our findings indicate that the structural integrity of descending motor systems may play a significant role in age-related increases in motor performance variability, but that differential age-related declines in oral and manual effectors are not likely due to structural integrity of descending motor pathways in the brain.
精细运动控制的变化最终会影响到灵活性，随着年龄的增长而出现；然而，有证据表明，与年龄相关的运动控制下降在不同效应器中可能并不均匀。特别是，中央机制在效应器特异性下降中的作用尚未得到检验，但对于将与年龄相关的运动下降纳入大脑功能与年龄相关变化的不断增长的文献中具有重要意义。我们检查了 18 名年轻成年人和 14 名老年成年人在三个不同效应器（手指、嘴唇和舌头）上的亚最大力控制。与力变异性测量同时，我们使用扩散张量成像（DTI）检查了大脑中与效应器特异性通路相关的白质结构完整性的变化。每个效应器的运动通路是通过使用 fMRI 局部器任务来识别的，然后通过跟踪来识别传播到中脑的纤维束。在所有三个效应器中，随着年龄的增长，力控制变异性都有所增加，但效应器显示出不同程度的与年龄相关的变异性。运动控制变化伴随着与年龄相关的白质结构完整性下降，这表现为各向异性分数和径向扩散率的测量。DTI 指标似乎介导了一些与年龄相关的运动控制下降。我们的研究结果表明，下行运动系统的结构完整性可能在与年龄相关的运动性能变异性增加中起着重要作用，但口腔和手动效应器的与年龄相关的下降不太可能是由于大脑中下行运动通路的结构完整性造成的。
