Université de Bourgogne, Campus Universitaire, Unité de Formation et de Recherche en Sciences et Techniques des Activités Physiques et Sportives, BP 27877, F-21078 Dijon, France.
Neuroscience. 2011 Aug 25;189:269-76. doi: 10.1016/j.neuroscience.2011.04.055. Epub 2011 May 5.
Anticipatory grip force adjustments are a prime example of the predictive nature of motor control. An object held in precision grip is stabilized by fine adjustments of the grip force against changes in tangential load force arising from inertia during acceleration and deceleration. When an object is subject to sudden impact loads, prediction becomes critical as the time available for sensory feedback is very short. Here, we investigated the control of grip force when participants performed a targeted tapping task with a hand-held object. During the initial transport phase of the movement, load force varied smoothly with acceleration. In contrast, in the collision, load forces sharply increased to very large values. In the transport phase, grip force and load force were coupled in phase, as expected. However, in the collision, grip force did not parallel load force. Rather, it exhibited a stereotyped profile with maximum ∼65 ms after peak load at contact. By using catch trials and a virtual environment, we demonstrate that this peak of grip force is pre-programmed. This observation is validated across experimental manipulations involving different target stiffness and directions of movement. We suggest that the central nervous system optimizes stability in object manipulation-as in catching-by regulating mechanical parameters including stiffness and damping through grip force. This study provides novel insights about how the brain coordinates grip force in manipulation involving an object interacting with the environment.
预期握力调整是运动控制预测性质的一个主要例子。在精密握力中握住的物体通过精细调整握力来稳定，以抵抗由于加速和减速期间惯性引起的切向负载力的变化。当物体受到突然的冲击载荷时，由于用于感觉反馈的时间非常短，因此预测变得至关重要。在这里，我们研究了当参与者用手持物体执行目标敲击任务时握力的控制。在运动的初始传输阶段，负载力随加速度平稳变化。相比之下，在碰撞中，负载力急剧增加到非常大的值。在传输阶段，握力和负载力按预期相位耦合。然而，在碰撞中，握力并没有与负载力平行。相反，它表现出一种刻板的模式，在接触时峰值负载后的最大约 65 毫秒。通过使用捕获试验和虚拟环境，我们证明了这一握力峰值是预先编程的。通过涉及不同目标刚度和运动方向的实验操作，验证了这一观察结果。我们认为，中枢神经系统通过调节包括刚度和阻尼在内的机械参数来优化物体操纵中的稳定性——例如在抓握中。这项研究提供了关于大脑如何协调涉及与环境相互作用的物体的操纵中的握力的新见解。
