Department of Kinesiology, Pennsylvania State University, Rec Hall 27, Burrowes Rd., University Park, PA, 16802, USA.
Department of Neurology, Penn State College of Medicine, Hershey, USA.
Exp Brain Res. 2020 Mar;238(3):713-725. doi: 10.1007/s00221-020-05743-9. Epub 2020 Feb 14.
We have previously proposed a model of motor lateralization that attributes specialization for predictive control of intersegmental coordination to the dominant hemisphere/limb system, and control of limb impedance to the non-dominant system. This hypothesis was developed based on visually targeted discrete reaching movement made predominantly with the shoulder and elbow joints. The purpose of this experiment was to determine whether dominant arm advantages for multi-degree of freedom coordination also occur during continuous distal movements of the wrist that do not involve visual guidance. In other words, are the advantages of the dominant arm restricted to controlling intersegmental coordination during discrete visually targeted reaching movements, or are they more generally related to coordination of multiple degrees of freedom at other joints, regardless of whether the movements are discrete or invoke visual guidance? Eight right-handed participants were instructed to perform alternating wrist ulnar/radial deviation movements at two instructed speeds, slow and fast, with the dominant or the non-dominant arm, and were instructed not to rotate the forearm (pronation/supination) or move the wrist up and down (flexion/extension). This was explained by slowly and passively moving the wrist in each plane during the instructions. Because all the muscles that cross the wrist have moment arms with respect to more than one axis of rotation, intermuscular coordination is required to prevent motion about non-instructed axes of rotation. We included two conditions, a very slow condition, as a control condition, to demonstrate understanding of the task, and an as-fast-as-possible condition to challenge predictive aspect of control, which we hypothesize are specialized to the dominant controller. Our results indicated that during as-fast-as-possible conditions the non-dominant arm incorporated significantly more non-instructed motion, which resulted in greater circumduction at the non-dominant than the dominant wrist. These findings extend the dynamic dominance hypothesis, indicating that the dominant hemisphere-arm system is specialized for predictive control of multiple degrees of freedom, even in movements of the distal arm and made in the absence of visual guidance.
我们之前提出了一个运动偏侧化模型，该模型将节段间协调的预测控制专业化归因于优势半球/肢体系统，将肢体阻抗控制归因于非优势系统。这个假设是基于主要使用肩部和肘部关节进行的视觉靶向离散到达运动发展起来的。本实验的目的是确定在不涉及视觉引导的情况下，腕部的连续远距离运动是否也存在多自由度协调的优势手臂。换句话说，优势手臂的优势仅限于在离散的视觉靶向到达运动中控制节段间协调，还是更普遍地与其他关节的多个自由度的协调相关，无论运动是离散的还是涉及视觉引导？八名右利手参与者被指示以两种指令速度（慢和快）用优势手或非优势手交替进行腕部尺侧/桡侧偏斜运动，并被指示不要旋转前臂（旋前/旋后）或上下移动手腕（弯曲/伸展）。这是通过在指令期间缓慢而被动地移动手腕来解释的。由于穿过手腕的所有肌肉都相对于一个以上的旋转轴具有力臂，因此需要肌肉间协调来防止非指令旋转轴的运动。我们包括两个条件，一个非常慢的条件作为对照条件，以证明对任务的理解，以及一个尽可能快的条件，以挑战控制的预测方面，我们假设这是专门针对优势控制器的。我们的结果表明，在尽可能快的条件下，非优势手臂纳入了明显更多的非指令运动，这导致非优势手腕的环绕运动明显大于优势手腕。这些发现扩展了动态优势假说，表明优势半球-手臂系统专门用于预测控制多个自由度，即使在没有视觉引导的情况下，也可以进行远距离手臂运动。
