The emergence and disappearance of multi-digit synergies during force-production tasks
The emergence and disappearance of multi-digit synergies during force-production tasks
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DOI：
10.1007/s00221-005-2248-3
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发表时间：
2005-07-01
影响因子：
2
通讯作者：
Latash, ML
中科院分区：
文献类型：
--
作者：
Shim, JK;Olafsdottir, H;Latash, ML
我们分析了人手五个手指在任务中产生的力之间的协变模式，这些任务需要产生一种由斜坡上升，恒定力，和斜坡-下降段的斜坡时间范围从0到3000毫秒。模式的方差的总的力量和总和的方差的个别数字的力量进行了比较，超过12组在每一个任务中。斜坡上升段的开始与手指力的正协变相关。负协变手指的力量（力稳定的协同作用）出现后的关键时间为600-800毫秒，这是只有弱依赖于斜坡时间。这些协同作用在稳态阶段持续存在。一个定量指标的手指力协变的介绍，它显示了下降约100毫秒开始前的斜坡下降阶段，我们称之为“预期协变”（ACV）的现象。斜降阶段与在0至600 ms范围内的时间段内的力稳定协同作用的快速消失相关，并且随着力斜升的持续时间而强烈缩放。拇指-虚拟手指协同显示出与多手指协同定性相似的行为（虚拟手指是一个想象的手指，其动作在机械上等同于四个手指的动作）。我们的结论是，在总力的时间曲线的突然变化与瞬态不稳定的总力。力稳定协同作用的变化可能发生在总力变化的准备过程中。
We analyzed patterns of covariation among forces produced by the five digits of the human hand during tasks that required the production of a pattern of the total force consisting of ramp-up, constant force, and ramp-down segments with the time of the ramps ranging from 0 to 3000 ms. Patterns of the variance of the total force and the sum of the variances of individual digit forces were compared over sets of 12 trials at each task. The initiation of the ramp-up segment was associated with positive covariation of digit forces. Negative covariation among digit forces (force-stabilizing synergies) emerged after a critical time of 600-800 ms, which was only weakly dependent on the ramp time. These synergies persisted over the steady-state phase. A quantitative index of digit force covariation was introduced; it showed a drop about 100 ms before initiation of the ramp-down phase; we termed this phenomenon "anticipatory covariation" (ACV). The ramp-down phase was associated with rapid disappearance of the force-stabilizing synergy over a time period that ranged from 0 to 600 ms and scaled strongly with the duration of the force ramp. Thumb-virtual finger synergies showed qualitatively similar behavior to the multi-finger synergies (virtual finger is an imagined digit whose action is mechanically equivalent to the action of the four fingers). We conclude that abrupt changes in a time profile of total force are associated with transient destabilization of the total force. Changes in force-stabilizing synergies may occur in preparation to changes in the total force.