Parikh Pranav J, Cole Kelly J
School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, 85226, United States of America.
Motor Control Laboratories, Department of Health and Human Physiology, University of Iowa, IA 52242, United States of America.
PLoS One. 2015 Apr 9;10(4):e0124137. doi: 10.1371/journal.pone.0124137. eCollection 2015.
The contribution of poor finger force control to age-related decline in manual dexterity is above and beyond ubiquitous behavioral slowing. Altered control of the finger forces can impart unwanted torque on the object affecting its orientation, thus impairing manual performance. Anodal transcranial direct current stimulation (tDCS) over primary motor cortex (M1) has been shown to improve the performance speed on manual tasks in older adults. However, the effects of anodal tDCS over M1 on the finger force control during object manipulation in older adults remain to be fully explored. Here we determined the effects of anodal tDCS over M1 on the control of grip force in older adults while they manipulated an object with an uncertain mechanical property. Eight healthy older adults were instructed to grip and lift an object whose contact surfaces were unexpectedly made more or less slippery across trials using acetate and sandpaper surfaces, respectively. Subjects performed this task before and after receiving anodal or sham tDCS over M1 on two separate sessions using a cross-over design. We found that older adults used significantly lower grip force following anodal tDCS compared to sham tDCS. Friction measured at the finger-object interface remained invariant after anodal and sham tDCS. These findings suggest that anodal tDCS over M1 improved the control of grip force during object manipulation in healthy older adults. Although the cortical networks for representing objects and manipulative actions are complex, the reduction in grip force following anodal tDCS over M1 might be due to a cortical excitation yielding improved processing of object-specific sensory information and its integration with the motor commands for production of manipulative forces. Our findings indicate that tDCS has a potential to improve the control of finger force during dexterous manipulation in older adults.
手指力量控制不佳对与年龄相关的手部灵活性下降的影响，超出了普遍存在的行为迟缓的范畴。手指力量控制的改变会在物体上施加不必要的扭矩，影响其方向，从而损害手部操作表现。经颅直流电刺激（tDCS）阳极刺激初级运动皮层（M1）已被证明可提高老年人手部任务的执行速度。然而，阳极tDCS对M1刺激对老年人在物体操作过程中手指力量控制的影响仍有待充分探索。在此，我们确定了阳极tDCS对M1刺激对老年人在操作具有不确定机械特性的物体时握力控制的影响。八名健康的老年人被指示握住并提起一个物体，该物体的接触面在不同试验中分别意外地使用醋酸纤维和砂纸表面，变得或多或少更滑。受试者在两个单独的时段接受M1区域的阳极或伪tDCS刺激后，采用交叉设计执行此任务。我们发现，与伪tDCS相比，老年人在接受阳极tDCS后使用的握力显著降低。在手指与物体界面处测量的摩擦力在阳极和伪tDCS后保持不变。这些发现表明，阳极tDCS对M1刺激改善了健康老年人在物体操作过程中的握力控制。尽管用于表征物体和操作动作的皮层网络很复杂，但阳极tDCS对M1刺激后握力的降低可能是由于皮层兴奋导致对物体特定感觉信息的处理改善及其与用于产生操作力的运动指令的整合。我们的研究结果表明，tDCS有潜力改善老年人在灵巧操作过程中手指力量的控制。
