Department of Physiology, University of Montreal, Montreal, Quebec, Canada.
J Neurophysiol. 2012 Sep;108(6):1764-80. doi: 10.1152/jn.00081.2012. Epub 2012 Jul 5.
Recent work has shown that human subjects are able to predict the biomechanical ease of potential reaching movements and use these predictions to influence their choices. Here, we examined how reach decisions are influenced by specific biomechanical factors related to the control of end-point stability, such as aiming accuracy or stopping control. Human subjects made free choices between two potential reaching movements that varied in terms of path distance and biomechanical cost in four separate blocks that additionally varied two constraints: the width of the targets (narrow or wide) and the requirement of stopping in them. When movements were unconstrained (very wide targets and no requirement of stopping), subjects' choices were strongly biased toward directions aligned with the direction of maximal mobility. However, as the movements became progressively constrained, factors related to the control of the end point gained relevance, thus reducing this bias. This demonstrates that, before movement onset, constraints such as stopping and aiming participate in a remarkably adaptive and flexible action selection process that trades off the advantage of moving along directions of maximal mobility for unconstrained movements against exploiting biomechanical anisotropies to facilitate control of end-point stability whenever the movement constraints require it. These results support a view of decision making between motor actions as a highly context-dependent gradual process in which the subjective desirability of potential actions is influenced by their dynamic properties in relation to the intrinsic properties of the motor apparatus.
最近的研究表明，人类受试者能够预测潜在的运动的生物力学易感性，并利用这些预测来影响他们的选择。在这里，我们研究了特定的生物力学因素如何影响到达决策，这些因素与端点稳定性的控制有关，例如瞄准精度或停止控制。在四个不同的块中，人类被试在两种潜在的运动之间进行自由选择，这些运动在路径距离和生物力学成本方面有所不同，此外还改变了两个约束条件：目标的宽度（窄或宽）和在其中停止的要求。当运动不受约束时（目标非常宽，没有停止的要求），被试的选择强烈偏向于与最大可移动性方向一致的方向。然而，随着运动变得越来越受约束，与端点控制有关的因素变得更加重要，从而减少了这种偏差。这表明，在运动开始之前，停止和瞄准等约束条件参与了一个非常自适应和灵活的动作选择过程，该过程权衡了沿着最大可移动性方向移动的优势，以换取不受约束的运动，以利用生物力学各向异性来帮助控制端点稳定性，只要运动约束需要。这些结果支持了一种观点，即运动动作之间的决策是一个高度依赖上下文的渐进过程，潜在动作的主观可取性受到它们与运动装置固有特性相关的动态特性的影响。
