Klein Joshua, Whitsell Bryan, Artemiadis Panagiotis K, Buneo Christopher A
Interdisciplinary Graduate Program in Neuroscience, Arizona State University, Tempe, AZ, United States.
Alliance for Person-Centered Accessible Technologies, Arizona State University, Tempe, AZ, United States.
Front Hum Neurosci. 2018 Aug 21;12:331. doi: 10.3389/fnhum.2018.00331. eCollection 2018.
Proprioception refers to the senses of body position, movement, force and effort. Previous studies have demonstrated workspace and direction-dependent differences in arm proprioceptive sensitivity within the horizontal plane. In addition, studies of reaching in the vertical plane have shown that proprioception plays a key role in anticipating arm configuration dependent effects of gravity. This suggests that proprioceptive sensitivity could vary with the direction of arm displacement relative to the gravitational vector, as well as with arm configuration. To test these hypotheses, and to characterize proprioception more generally, we assessed the direction-dependence and arm postural-dependence of proprioceptive sensitivity in 3D space using a novel robotic paradigm. A subject's right arm was coupled to a 7-df robot through a trough that stabilized the wrist and forearm, allowing for changes in configuration largely at the elbow and shoulder. Sensitivity was evaluated using a "same-different" task, where the subject's hand was moved 1-4 cm away from an initial "test" position to a 2nd "judgment" position. The proportion of trials where subjects responded "different" when the positions were different ("hit rate"), and where they responded "different" when the positions were the same, ("false alarm rate"), were used to calculate d', a measure of sensitivity derived from signal detection theory (SDT). Initially, a single initial arm posture was used and displacements were performed in six directions: upward, downward, forward, backward, leftward and rightward of the test position. In a follow-up experiment, data were obtained for four directions and two initial arm postures. As expected, sensitivity (d') increased monotonically with distance for all six directions. Sensitivity also varied between directions, particularly at position differences of 2 and 3 cm. Overall, sensitivity reached near maximal values in this task at 2 cm for the leftward/rightward directions, 3 cm for upward/forward and 4 cm for the downward/backward directions. In addition, when data were grouped together for opposing directions, sensitivity showed a dependence upon arm posture. These data suggest arm proprioceptive sensitivity is both anisotropic in 3D space and configuration-dependent, which has important implications for sensorimotor control of the arm and human-robot interactions.
本体感觉是指身体位置、运动、力量和努力的感觉。先前的研究已经证明，在水平面内，手臂本体感觉灵敏度存在工作空间和方向依赖性差异。此外，在垂直平面内进行伸手动作的研究表明，本体感觉在预测重力对手臂形态的影响方面起着关键作用。这表明本体感觉灵敏度可能会随着手臂相对于重力矢量的位移方向以及手臂形态而变化。为了验证这些假设，并更全面地描述本体感觉，我们使用一种新颖的机器人范式评估了三维空间中本体感觉灵敏度的方向依赖性和手臂姿势依赖性。受试者的右臂通过一个稳定手腕和前臂的槽与一个7自由度机器人相连，使得手臂形态的变化主要发生在肘部和肩部。使用“相同-不同”任务评估灵敏度，即受试者的手从初始“测试”位置移动1-4厘米到第二个“判断”位置。当位置不同时受试者回答“不同”的试验比例（“命中率”），以及当位置相同时受试者回答“不同”的试验比例（“误报率”），用于计算d'，这是一种源自信号检测理论（SDT）的灵敏度度量。最初，使用单一的初始手臂姿势，并在六个方向上进行位移：测试位置的向上、向下、向前、向后、向左和向右。在后续实验中，获取了四个方向和两种初始手臂姿势的数据。正如预期的那样，所有六个方向上的灵敏度（d'）都随着距离单调增加。灵敏度在不同方向之间也有所变化，特别是在位置差异为2厘米和3厘米时。总体而言，在该任务中，向左/向右方向在2厘米时、向上/向前方向在3厘米时以及向下/向后方向在4厘米时，灵敏度接近最大值。此外，当将相反方向的数据分组在一起时，灵敏度显示出对手臂姿势的依赖性。这些数据表明，手臂本体感觉灵敏度在三维空间中既是各向异性的，也是形态依赖性的，这对手臂的感觉运动控制和人机交互具有重要意义。
