Modulation of phasic and tonic muscle synergies with reaching direction and speed
Modulation of phasic and tonic muscle synergies with reaching direction and speed
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DOI：
10.1152/jn.01377.2007
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发表时间：
2008-09-01
影响因子：
2.5
通讯作者：
Lacquaniti, Francesco
中科院分区：
文献类型：
--
作者：
d'Avella, Andrea;Fernandez, Laure;Lacquaniti, Francesco
中枢神经系统如何掌握肌肉骨骼系统的多个自由度来控制目标导向的运动是一个长期存在的问题。我们最近支持了CNS依赖于模块化控制架构的假设，证明了不同方向快速到达运动的相型肌肉模式是由几个时变肌肉协同作用产生的：具有特定激活特征的肌肉组的协调招募。然而，自然的伸展动作以不同的速度进行，需要控制动作和姿势。因此，我们调查了肌肉协同作用是否也是保持不同速度伸展和保持稳定手臂姿势的基础。记录了5名受试者在前额平面以不同速度达到8个目标时的手部运动学和肩肘部肌肉表面肌电。我们发现，三个时不变协同效应的幅度调制捕捉到了运动结束时姿势肌肉模式的变化。在运动过程中，三时相和三强直时变协同效应可以在所有条件下重建时间归一化的肌肉模式。时相协同效应受方向和速度的影响，在幅度和时序上均有调节。紧张性协同作用仅在幅度上受方向的调节。两种协同效应的方向性调整均可用单余弦函数或双余弦函数很好地描述。这些结果表明，肌肉协同作用是基本的控制模块，允许通过简单的调制和组合规则产生适当的肌肉模式。
How the CNS masters the many degrees of freedom of the musculoskeletal system to control goal-directed movements is a long-standing question. We have recently provided support to the hypothesis that the CNS relies on a modular control architecture by showing that the phasic muscle patterns for fast reaching movements in different directions are generated by combinations of a few time-varying muscle synergies: coordinated recruitment of groups of muscles with specific activation profiles. However, natural reaching movements occur at different speeds and require the control of both movement and posture. Thus we have investigated whether muscle synergies also underlie reaching at different speeds as well as the maintenance of stable arm postures. Hand kinematics and shoulder and elbow muscle surface EMGs were recorded in five subjects during reaches to eight targets in the frontal plane at different speeds. We found that the amplitude modulation of three time-invariant synergies captured the variations in the postural muscle patterns at the end of the movement. During movement, three phasic and three tonic time-varying synergies could reconstruct the time-normalized muscle pattern in all conditions. Phasic synergies were modulated in both amplitude and timing by direction and speed. Tonic synergies were modulated only in amplitude by direction. The directional tuning of both types of synergies was well described by a single or a double cosine function. These results suggest that muscle synergies are basic control modules that allow generating the appropriate muscle patterns through simple modulation and combination rules.