Tagliabue Michele, Ciancio Anna Lisa, Brochier Thomas, Eskiizmirliler Selim, Maier Marc A
Neuroscience Research Federation FR3636, CNRS, Université Paris Descartes Paris, France ; Centre de Neurophysique, Physiologie et Pathologie, UMR 8119, CNRS, Université Paris Descartes Sorbonne Paris Cité, Paris, France.
Laboratory of Biomedical Robotic and Biomicrosystem, Università Campus Bio-Medico di Roma Roma, Italy.
Front Hum Neurosci. 2015 Mar 26;9:165. doi: 10.3389/fnhum.2015.00165. eCollection 2015.
The large number of mechanical degrees of freedom of the hand is not fully exploited during actual movements such as grasping. Usually, angular movements in various joints tend to be coupled, and EMG activities in different hand muscles tend to be correlated. The occurrence of covariation in the former was termed kinematic synergies, in the latter muscle synergies. This study addresses two questions: (i) Whether kinematic and muscle synergies can simultaneously accommodate for kinematic and kinetic constraints. (ii) If so, whether there is an interrelation between kinematic and muscle synergies. We used a reach-grasp-and-pull paradigm and recorded the hand kinematics as well as eight surface EMGs. Subjects had to either perform a precision grip or side grip and had to modify their grip force in order to displace an object against a low or high load. The analysis was subdivided into three epochs: reach, grasp-and-pull, and static hold. Principal component analysis (PCA, temporal or static) was performed separately for all three epochs, in the kinematic and in the EMG domain. PCA revealed that (i) Kinematic- and muscle-synergies can simultaneously accommodate kinematic (grip type) and kinetic task constraints (load condition). (ii) Upcoming grip and load conditions of the grasp are represented in kinematic- and muscle-synergies already during reach. Phase plane plots of the principal muscle-synergy against the principal kinematic synergy revealed (iii) that the muscle-synergy is linked (correlated, and in phase advance) to the kinematic synergy during reach and during grasp-and-pull. Furthermore (iv), pair-wise correlations of EMGs during hold suggest that muscle-synergies are (in part) implemented by coactivation of muscles through common input. Together, these results suggest that kinematic synergies have (at least in part) their origin not just in muscular activation, but in synergistic muscle activation. In short: kinematic synergies may result from muscle synergies.
在诸如抓握等实际运动过程中，手部大量的机械自由度并未得到充分利用。通常，各个关节的角运动往往相互耦合，不同手部肌肉的肌电图活动也往往相互关联。前者共变现象的出现被称为运动协同，后者则被称为肌肉协同。本研究探讨了两个问题：（i）运动协同和肌肉协同是否能同时适应运动学和动力学约束。（ii）如果是这样，运动协同和肌肉协同之间是否存在相互关系。我们采用了伸手 - 抓握 - 拉动范式，并记录了手部运动学以及八个表面肌电图。受试者必须执行精确抓握或侧握，并必须调整握力以对抗低或高负荷来移动物体。分析分为三个阶段：伸手、抓握 - 拉动和静态握持。对运动学和肌电图领域的所有三个阶段分别进行主成分分析（PCA，时间或静态）。PCA 显示：（i）运动协同和肌肉协同可以同时适应运动学（抓握类型）和动力学任务约束（负荷条件）。（ii）在伸手阶段，抓握即将到来的抓握和负荷条件已经在运动协同和肌肉协同中得到体现。主肌肉协同相对于主运动协同的相平面图显示：（iii）在伸手和抓握 - 拉动阶段，肌肉协同与运动协同相关联（相关且相位超前）。此外，（iv）握持期间肌电图的成对相关性表明，肌肉协同（部分）是通过共同输入对肌肉的共同激活来实现的。总之，这些结果表明运动协同（至少部分）不仅源于肌肉激活，还源于协同的肌肉激活。简而言之：运动协同可能源于肌肉协同。
