Klein Breteler Mary D, Meulenbroek Ruud G J, Gielen Stan C A M
Department of Experimental Psychology at the University of Nijmegen, The Netherlands.
Motor Control. 2002 Jan;6(1):69-83. doi: 10.1123/mcj.6.1.69.
In the present study we evaluated the minimum jerk and the minimum torque-change model at the path, trajectory, and movement-cost levels. To date, most evaluations of these models have mainly been restricted to path comparisons. Assessments of the time courses of realized jerk and torque changes are surprisingly lacking. Moreover, the extent to which the presumed optimized parameters change as a function of the duration and other temporal features of aiming movements has never been investigated, most probably because the models presuppose movement time. In order to fill this gap, we analyzed a subset of the data of an earlier experiment in which 12 participants performed leftward and rightward planar pointing movements. Hand displacements and joint excursions were recorded with a 3D motion-tracking system and subsequently evaluated by means of model-based analyses. The results show that despite a good agreement between observed paths and predicted paths, especially by the minimum torque-change model, the time courses of jerk and torque changes of observed and modeled movements differed considerably. These differences could mainly be attributed to asymmetrical properties of the time functions of slow movements. Variations of movement costs as a function of movement time and skewness of tangential velocity profiles show that, especially at high movement speed, costs increase exponentially with departures of symmetry. It is concluded that trajectory-formation models have limited explanatory power in situations that require demanding information processing during the homing-in phase of goal-directed movements. However, for slow movements, deviations from the optimal timing profiles require little extra costs in terms of jerk or torque change.
在本研究中，我们在路径、轨迹和运动成本层面评估了最小冲击模型和最小扭矩变化模型。迄今为止，对这些模型的大多数评估主要局限于路径比较。令人惊讶的是，对实际冲击和扭矩变化的时间进程缺乏评估。此外，假定的优化参数随瞄准运动的持续时间和其他时间特征而变化的程度从未被研究过，很可能是因为这些模型预先假定了运动时间。为了填补这一空白，我们分析了早期一项实验的数据子集，在该实验中，12名参与者进行了向左和向右的平面指向运动。用三维运动跟踪系统记录手部位移和关节偏移，随后通过基于模型的分析进行评估。结果表明，尽管观察到的路径与预测路径之间有很好的一致性，尤其是最小扭矩变化模型，但观察到的运动与建模运动在冲击和扭矩变化的时间进程上有很大差异。这些差异主要可归因于慢速运动时间函数的不对称特性。运动成本随运动时间的变化以及切向速度分布的偏度表明，尤其是在高运动速度下，成本随着对称性的偏离呈指数增加。得出的结论是，在目标导向运动的归位阶段需要大量信息处理的情况下，轨迹形成模型的解释力有限。然而，对于慢速运动，与最优时间分布的偏差在冲击或扭矩变化方面几乎不需要额外成本。
