Biggs J, Horch K, Clark F J
Department of Bioengineering, University of Utah, Salt Lake City 84112-9202, USA.
Exp Brain Res. 1999 Apr;125(3):221-30. doi: 10.1007/s002210050677.
Studies have demonstrated that muscle spindle organs provide the majority of the proprioceptive information available to the nervous system about limb position. Other studies suggest that a sense of position may be lacking in the fingers, as subjects were unaware of rather large excursions of finger joints if the excursions were made slowly enough. We sought to investigate the basis for this unexpected finding with a biomechanical model of the human long finger and the forearm muscles which actuate it, in order to study potential contributions of spindle organs in the extrinsic muscles of the hand to a sense of position of the finger. The model, based on cadaver data, allowed us to determine how precisely estimates of the lengths of the extrinsic finger muscles can be transformed into estimates of: (1) the flexion/extension angles of the individual finger joints, and (2) the location of the fingertip in the flexion/extension plane. We found that, for some finger positions, length information from all three extrinsic muscles was not sufficient to precisely estimate the flexion angles of all finger joints. Precision of joint angle estimates could be as poor as +/- 18% of joint range of motion. However, length information from just two of the extrinsic muscles taken together could always provide information sufficient to estimate the location of the fingertip relative to the metacarpophalangeal joint within a reasonably small tolerance (+/- one-half thickness of the fingertip). Furthermore, it was possible to make this estimate without determining any of the finger joint angles. These results suggest that spindles in the extrinsic muscles alone can signal fingertip location, even though they may not provide sufficient information to estimate the individual joint angles that set the position of the fingertip. Thus, an absence of position sense for individual joints (the sense many studies have tried to measure) may say little about a sense of location of the tip of the finger.
研究表明，肌梭器官为神经系统提供了有关肢体位置的大部分本体感觉信息。其他研究表明，手指可能缺乏位置感，因为如果手指关节的移动足够缓慢，受试者并未意识到相当大的关节移动。我们试图用人类食指和驱动它的前臂肌肉的生物力学模型来研究这一意外发现的基础，以便研究手部外在肌肉中的梭器官对手指位置感的潜在贡献。该模型基于尸体数据，使我们能够确定外在手指肌肉长度的精确估计值如何转化为以下方面的估计值：（1）各个手指关节的屈伸角度，以及（2）指尖在屈伸平面中的位置。我们发现，对于某些手指位置，来自所有三块外在肌肉的长度信息不足以精确估计所有手指关节的屈伸角度。关节角度估计的精度可能低至关节活动范围的+/-18%。然而，仅将两块外在肌肉的长度信息结合起来，总是能够提供足够的信息，以在相当小的公差范围内（+/-指尖厚度的一半）估计指尖相对于掌指关节的位置。此外，无需确定任何手指关节角度就可以进行这种估计。这些结果表明，仅外在肌肉中的梭就能发出指尖位置的信号，即使它们可能无法提供足够的信息来估计确定指尖位置的各个关节角度。因此，单个关节缺乏位置感（许多研究试图测量的感觉）可能与手指尖的位置感关系不大。
