Force synergies for multifingered grasping: effect of predictability in object center of mass and handedness
Force synergies for multifingered grasping: effect of predictability in object center of mass and handedness
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DOI：
10.1007/s00221-002-1024-x
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发表时间：
2002-05-01
影响因子：
2
通讯作者：
Santello, M
中科院分区：
文献类型：
--
作者：
Rearick, MP;Santello, M
要用手的五个手指抓握，需要有效地分配接触力，以便在举起和握住物体时保持静态平衡。在先前的研究中，受试者被要求达到，抓住并举起一个五位数的抓握装置，其质心（CM）位置在每个试验区组中都会发生变化。尽管调制的力量分配模式之间的数字作为一个功能的质心位置，一致的同相和异相之间的关系正常的力量被发现在频域。在本研究中，我们使用了相同的任务，以评估（a）预测的对象的CM位置（随机与封锁介绍）和（B）利手（优势与非优势手）的影响。与我们最初的预期相反，我们发现在所有条件下的保持阶段，法向力对CM位置的调制类似。具体而言，力分担模式，即，由每个手指贡献的力的等级顺序在抓握序列中很早就出现，在整个提起和保持的持续时间内保持相对稳定。然而，在何种程度上可以区分力共享模式作为一个功能的CM位置是较低的随机比在封锁的条件。最后，由手指对施加的法向力趋于同步，在所有条件下，在大部分功能频率范围（高达10 Hz）内都是同相（拇指和手指）和异相（手指对）。这些研究结果表明，在抓握过程中，中枢神经系统使用刻板的控制策略来协调多种抓握力。这些方案的特定方面似乎受到对象CM位置的可预测性的影响，但不受手的优势的影响。
To grasp with five digits of the hand requires an efficient parceling of contact forces in order to maintain static equilibrium as an object is lifted and held. In a previous study, subjects were asked to reach, grasp and lift a five-digit grip apparatus whose center of mass (CM) location was changed for each block of trials. Despite a modulation of force sharing patterns among the digits as a function of center of mass location, consistent in-phase and out-of-phase relationships between normal forces were found in the frequency domain. In the present study, we have used the same task to assess the effect of (a) predictability of an object's CM location (random vs blocked presentation) and (b) handedness (dominant vs non-dominant hand). Contrary to our original expectations, we found a similar modulation of normal forces to CM location during the hold phase across all conditions. Specifically, the force sharing pattern, i.e., the rank order of force contributed by each digit, emerged very early in the grasp sequence, remaining relatively stable throughout the duration of the lift and hold. Nevertheless, the extent to which force sharing patterns could be discriminated as a function of CM location was lower in the random than in the blocked conditions. Lastly, normal forces exerted by pairs of digits tended to be synchronized, both in-phase (thumb and fingers) and out-of-phase (pairs of digits) across a large proportion of the functional frequency range (up to 10 Hz) in all conditions. The composite of these findings suggests that the central nervous system uses stereotyped control strategies for coordinating multiple grip forces during grasping. Specific aspects of these schemes appear to be affected by predictability of object CM location, but not by hand dominance.