Institute of Movement Sciences, Centre National de la Recherche Scientifique and Université de la Méditerranée, Marseille, France.
J Neurophysiol. 2010 Aug;104(2):641-53. doi: 10.1152/jn.00174.2010. Epub 2010 Jun 10.
When we manipulate an object, grip force is adjusted in anticipation of the mechanical consequences of hand motion (i.e., load force) to prevent the object from slipping. This predictive behavior is assumed to rely on an internal representation of the object dynamic properties, which would be elaborated via visual information before the object is grasped and via somatosensory feedback once the object is grasped. Here we examined this view by investigating the effect of delayed visual feedback during dextrous object manipulation. Adult participants manually tracked a sinusoidal target by oscillating a handheld object whose current position was displayed as a cursor on a screen along with the visual target. A delay was introduced between actual object displacement and cursor motion. This delay was linearly increased (from 0 to 300 ms) and decreased within 2-min trials. As previously reported, delayed visual feedback altered performance in manual tracking. Importantly, although the physical properties of the object remained unchanged, delayed visual feedback altered the timing of grip force relative to load force by about 50 ms. Additional experiments showed that this effect was not due to task complexity nor to manual tracking. A model inspired by the behavior of mass-spring systems suggests that delayed visual feedback may have biased the representation of object dynamics. Overall, our findings support the idea that visual feedback of object motion can influence the predictive control of grip force even when the object is grasped.
当我们操纵物体时，握力会根据手的运动（即负载力）的机械后果进行调整，以防止物体滑落。这种预测行为被认为依赖于对物体动态特性的内部表示，在抓住物体之前，这种内部表示会通过视觉信息进行阐述，而在抓住物体之后，则会通过躯体感觉反馈进行阐述。在这里，我们通过研究在灵巧的物体操纵过程中延迟视觉反馈的效果来检验这种观点。成年参与者通过对手持物体进行摆动来手动跟踪正弦波目标，该物体的当前位置会显示为屏幕上的光标以及视觉目标。在实际物体位移和光标运动之间引入了延迟。该延迟以线性方式增加（从 0 到 300 毫秒），并在 2 分钟的试验中减少。如前所述，延迟的视觉反馈会改变手动跟踪的性能。重要的是，尽管物体的物理特性保持不变，但延迟的视觉反馈会使握力相对于负载力的时间延迟约 50 毫秒。进一步的实验表明，这种效果不是由于任务复杂性或手动跟踪造成的。受质量弹簧系统行为启发的模型表明，延迟的视觉反馈可能会影响物体动力学的表示。总的来说，我们的研究结果支持了这样一种观点，即即使在抓住物体时，物体运动的视觉反馈也可以影响握力的预测控制。
