Stability of steady hand force production explored across spaces and methods of analysis
Stability of steady hand force production explored across spaces and methods of analysis
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DOI：
10.1007/s00221-018-5238-y
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发表时间：
2018-06-01
影响因子：
2
通讯作者：
Latash, Mark L.
中科院分区：
文献类型：
--
作者：
de Freitas, Paulo B.;Freitas, Sandra M. S. F.;Latash, Mark L.
我们使用的框架不受控制的流形（UCM）的假设，并探讨了几个结果变量的可靠性，在一个非常简单的四指精确的力生产任务在不同的分析空间。14名健康的年轻成年人在3天内用每只手执行精确的力量生产任务。小的空间手指扰动产生的“逆钢琴”装置，每次试验三次（提高手指1厘米/0.5秒，并降低它们）。数据分析使用以下主要方法：（1）计算指力和指模空间中的试验间方差和运动等效性结构指数，以及（2）分析手的参考坐标和表观刚度值。最大自愿力和奴役指数（无意手指力生产）表现出良好的可靠性。强协同稳定总力量反映在方差结构和运动等效指数。UCM内的方差和运动等效运动指数在试验持续时间内下降，并显示出良好的可靠性。方差正交的UCM和非运动等效运动的指数下降超过3天，表现出较差的中度可靠性。参考坐标和表观刚度指数共同变化强烈，都表现出良好的可靠性。相反，计算的力稳定指数显示出较差的可靠性。研究结果被解释内的神经控制与涉及两个基本的命令，r-命令和c-命令的层次结构的参照坐标的计划。这些数据表明手指力空间中的自然漂移，特别是在UCM内。我们将这些漂移解释为稳定性和优化行动之间的权衡的反映。这些发现的UCM框架和未来的临床应用的影响进行了探讨的讨论。方差结构指标和运动等效性指标具有较好的信度，可推荐用于应用研究。
We used the framework of the uncontrolled manifold (UCM) hypothesis and explored the reliability of several outcome variables across different spaces of analysis during a very simple four-finger accurate force production task. Fourteen healthy, young adults performed the accurate force production task with each hand on 3 days. Small spatial finger perturbations were generated by the "inverse piano" device three times per trial (lifting the fingers 1 cm/0.5 s and lowering them). The data were analyzed using the following main methods: (1) computation of indices of the structure of inter-trial variance and motor equivalence in the space of finger forces and finger modes, and (2) analysis of referent coordinates and apparent stiffness values for the hand. Maximal voluntary force and the index of enslaving (unintentional finger force production) showed good to excellent reliability. Strong synergies stabilizing total force were reflected in both structure of variance and motor equivalence indices. Variance within the UCM and the index of motor equivalent motion dropped over the trial duration and showed good to excellent reliability. Variance orthogonal to the UCM and the index of non-motor equivalent motion dropped over the 3 days and showed poor to moderate reliability. Referent coordinate and apparent stiffness indices co-varied strongly and both showed good reliability. In contrast, the computed index of force stabilization showed poor reliability. The findings are interpreted within the scheme of neural control with referent coordinates involving the hierarchy of two basic commands, the r-command and c-command. The data suggest natural drifts in the finger force space, particularly within the UCM. We interpret these drifts as reflections of a trade-off between stability and optimization of action. The implications of these findings for the UCM framework and future clinical applications are explored in the discussion. Indices of the structure of variance and motor equivalence show good reliability and can be recommended for applied studies.