Perception of limb position and motion combines sensory information from spindles in muscles that span one joint (monoarticulars) and two joints (biarticulars). This anatomical organization should create interactions in estimating limb position. We developed two models, one with only monoarticulars (MO Model) and one with monoarticulars and biarticulars (MB Model), to explore how biarticulars influence estimates of arm position in hand (x,y) and joint (shoulder,elbow) coordinates. In hand coordinates, both models predicted larger medial-lateral than proximal-distal errors, though the MB Model predicted that biarticulars would reduce this bias. In contrast, the two models made significantly different predictions in joint coordinates. The MO Model predicted that errors would be uniformly distributed because estimates of angles at each joint would be independent. In contrast, the MB Model predicted that errors would be coupled between the two joints, resulting in smaller errors for combinations of flexion or extension at both joints and larger errors for combinations of flexion at one joint and extension at the other joint. We also carried out two experiments to examine errors made by human subjects during an arm position matching task in which an robot passively moved one arm to different positions and the subjects moved their other arm to mirror-match each position. Errors in hand coordinates were similar to those predicted by both models. Critically, however, errors in joint coordinates were only similar to those predicted by the MB Model. These results highlight how biarticulars influence perceptual estimates of limb position by helping to minimize medial-lateral errors.

中文翻译：

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位置感的关节间耦合反映双关节肌肉的感觉贡献

肢体位置和运动的感知结合了跨越一个关节（单关节）和两个关节（双关节）的肌肉纺锤体的感觉信息。这种解剖组织应该在估计肢体位置时产生相互作用。我们开发了两种模型，一种只有单关节（MO 模型），另一种具有单关节和双关节（MB 模型），以探索双关节如何影响手臂位置（x，y）和关节（肩，肘）坐标的估计。在手坐标中，两个模型预测的内侧-外侧误差大于近端-远端误差，尽管 MB 模型预测双关节会减少这种偏差。相比之下，这两个模型在关节坐标上做出了明显不同的预测。MO 模型预测误差将均匀分布，因为每个关节的角度估计是独立的。相比之下，MB 模型预测误差将在两个关节之间耦合，导致两个关节的屈曲或伸展组合的误差较小，而一个关节的屈曲和另一关节的伸展组合的误差较大。我们还进行了两个实验来检查人类受试者在手臂位置匹配任务中所犯的错误，其中机器人被动地将一只手臂移动到不同的位置，而受试者移动另一只手臂以镜像匹配每个位置。手坐标中的误差与两种模型预测的误差相似。然而，至关重要的是，关节坐标中的误差仅与 MB 模型预测的误差相似。