Yoon Tejin, Vanden Noven Marnie L, Nielson Kristy A, Hunter Sandra K
Exercise Science Program, Department of Physical Therapy, Marquette University, P.O. Box 1881, Milwaukee, WI, 53201, USA.
Exp Brain Res. 2014 Oct;232(10):3133-45. doi: 10.1007/s00221-014-3976-z. Epub 2014 Jun 6.
Although maintenance of steady contractions is required for many daily tasks, there is little understanding of brain areas that modulate lower limb force accuracy. Functional magnetic resonance imaging was used to determine brain areas associated with steadiness and force during static (isometric) lower limb target-matching contractions at low and high intensities. Fourteen young adults (6 men and 8 women; 27.1 ± 9.1 years) performed three sets of 16-s isometric contractions with the ankle dorsiflexor muscles at 10, 30, 50, and 70 % of maximal voluntary contraction (MVC). Percent signal changes (PSCs, %) of the blood oxygenation level-dependent response were extracted for each contraction using region of interest analysis. Mean PSC increased with contraction intensity in the contralateral primary motor area (M1), supplementary motor area, putamen, pallidum cingulate cortex, and ipsilateral cerebellum (p < 0.05). The amplitude of force fluctuations (standard deviation, SD) increased from 10 to 70 % MVC but relative to the mean force (coefficient of variation, CV %) was greatest at 10 % MVC. The CV of force was associated with PSC in the ipsilateral parietal lobule (r = -0.28), putamen (r = -0.29), insula (r = -0.33), and contralateral superior frontal gyrus (r = -0.33, p < 0.05). There were minimal sex differences in brain activation across the isometric motor tasks indicating men and women were similarly motivated and able to activate cortical motor centers during static tasks. Control of steady lower limb contractions involves cortical and subcortical motor areas in both men and women and provides insight into key areas for potential cortical plasticity with impaired or enhanced leg function.
尽管许多日常任务都需要维持稳定的收缩，但对于调节下肢力量准确性的脑区却知之甚少。功能磁共振成像被用于确定在低强度和高强度静态（等长）下肢目标匹配收缩过程中与稳定性和力量相关的脑区。14名年轻人（6名男性和8名女性；年龄27.1±9.1岁）使用踝背屈肌进行三组16秒的等长收缩，收缩强度分别为最大自主收缩（MVC）的10%、30%、50%和70%。使用感兴趣区域分析提取每次收缩的血氧水平依赖反应的百分比信号变化（PSCs，%）。在对侧初级运动区（M1）、辅助运动区、壳核、苍白球扣带回皮质和同侧小脑，平均PSCs随收缩强度增加（p<0.05）。力量波动幅度（标准差，SD）从10%MVC增加到70%MVC，但相对于平均力量（变异系数，CV%）在10%MVC时最大。力量的CV与同侧顶叶小叶（r=-0.28）、壳核（r=-0.29）、岛叶（r=-0.33）和对侧额上回（r=-0.33，p<0.05）的PSCs相关。在等长运动任务中，大脑激活的性别差异最小，表明男性和女性在静态任务中具有相似的动机，并且能够激活皮质运动中心。稳定下肢收缩的控制涉及男性和女性的皮质和皮质下运动区，并为腿部功能受损或增强时潜在皮质可塑性的关键区域提供了见解。
