Motor planning of arm movements is direction-dependent in the gravity field
Motor planning of arm movements is direction-dependent in the gravity field
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DOI：
10.1016/j.neuroscience.2006.11.035
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发表时间：
2007-03-02
期刊：
影响因子：
3.3
通讯作者：
Papaxanthis, C.
中科院分区：
文献类型：
--
作者：
Gentili, R.;Cahouet, V.;Papaxanthis, C.
在本研究中，我们分析了手臂运动的运动学和动力学特征，以更好地阐明运动系统如何将环境约束（重力）整合到运动规划和控制过程中。为了达到这一目标，我们实验性地操纵重力对手臂的机械效应，同时保持手臂惯性恒定（即肩关节周围的质量分布）。6名受试者在矢状面（向上，U与向下，D）和水平面（左，L与右，R）进行单关节手臂运动（围绕肩关节旋转），幅度不同，初始位置不同。在这些条件下，肩关节重力扭矩（SGTs）显着变化时，手臂运动进行矢状面，而不是在水平面。与SGT相反，手臂惯性保持恒定，水平和矢状面相似，因为受试者仅以一个自由度进行手臂运动。所有受试者，无论运动方向如何，根据运动幅度适当缩放肩关节运动学参数。此外，水平和矢状面的峰值速度和运动持续时间相等。有趣的是，一些运动学参数显着不同，根据U/D，但不是L/R方向。具体而言，加速持续时间大于U运动的D，而相反的是真正的峰值加速度。因此，虽然垂直和水平臂运动共享一个一般的共同策略（即缩放定律），U和D臂运动之间的运动学不对称性，特别是那些反映中央规划过程（即峰值加速度），表示不同的电机意图即将到来的运动的方向。这些研究结果表明，手臂与环境的动态的相互作用是内部表示在生成的手臂轨迹。(c)2006年IBRO。由爱思唯尔有限公司出版。保留所有权利。
In the present study we analyzed kinematic and dynamic features of arm movements in order to better elucidate how the motor system integrates environmental constraints (gravity) into motor planning and control processes. To reach this aim, we experimentally manipulated the mechanical effects of gravity on the arm while maintaining arm inertia constant (i.e. the distribution of the mass around the shoulder joint). Six subjects performed single-joint arm movements (rotation around the shoulder joint) in both sagittal (upward, U, versus downward, D) and horizontal (left, L, versus right, R) planes, at different amplitudes and from different initial positions. Under these conditions, shoulder gravitational torques (SGTs) significantly varied when arm movements were performed in the sagittal but not in the horizontal plane. Contrary to SGTs, arm inertia remained constant and similar for both horizontal and sagittal planes since subjects performed arm movements with only one degree of freedom. All subjects, whatever the movement direction, appropriately scaled shoulder joint kinematic parameters according to movement amplitude. Furthermore, peak velocity and movement duration were equivalent for both horizontal and sagittal planes. Interestingly, some kinematic parameters significantly differed according to U/D but not L/R directions. Specifically, acceleration duration was greater for D than U movements, while the opposite was true for peak acceleration. Consequently, although vertical and horizontal arm movements shared a general common strategy (i.e. scaling law), the kinematic asymmetries between U and D arm movements, especially those that reflect central planning process (i.e. peak acceleration), indicated different motor intentions regarding the direction of the upcoming movement. These findings indicate that the interaction of the arm with the dynamics of the environment is internally represented during the generation of arm trajectories. (c) 2006 IBRO. Published by Elsevier Ltd. All rights reserved.