Courtine Grégoire, Papaxanthis Charalambos, Schieppati Marco
Dipartimento di Medicina Sperimentale, Sezione di Fisiologia, Università di Pavia, Pavia, Italy.
Exp Brain Res. 2006 Apr;170(3):320-35. doi: 10.1007/s00221-005-0215-7. Epub 2005 Nov 19.
We describe the muscle synergies accompanying steering of walking along curved trajectories, in order to analyze the simultaneous control of progression and balance-threatening emerging forces. For this purpose, we bilaterally recorded in ten subjects the electromyograms (EMGs) of a representative sample of leg and trunk muscles (n=16) during continuous walking along one straight and two curved trajectories at natural speed. Curvilinear locomotion involved a graded, limb-dependent modulation of amplitude and timing of activity of the muscles of the legs and trunk. The turn-related modulation of the motor pattern was highly coordinated amongst muscles and body sides. For all muscles, linear relationships were detected between the spatial and temporal features of muscle EMG activity. The largest modulation of EMG was observed in gastrocnemius medialis and lateralis muscles, which showed opposite changes in timing and amplitude during curve-walking. Moreover, amplitude and timing characteristics of muscle activities were significantly correlated with the spatial and temporal gait adaptations that are associated with curvilinear locomotion. The present results reveal that fine-modulation of the muscle synergies underlying straight-ahead locomotion is enough to generate the adequate propulsive forces to steer walking and maintain balance. These findings suggest that the turn-related command operates by modulation of the phase relationships between the tightly coupled neuronal assemblies that drive motor neuron activity during walking. This would produce the invariant templates for locomotion kinematics that are at the base of human navigation in space.
我们描述了沿着弯曲轨迹行走时转向所伴随的肌肉协同作用，以便分析对前进和威胁平衡的新兴力的同时控制。为此，我们在十名受试者双侧记录了腿部和躯干肌肉代表性样本（n = 16）的肌电图（EMG），这些受试者以自然速度沿着一条直线轨迹和两条弯曲轨迹连续行走。曲线运动涉及腿部和躯干肌肉活动幅度和时间的分级、肢体依赖性调制。运动模式与转弯相关的调制在肌肉和身体两侧之间高度协调。对于所有肌肉，在肌电图活动的空间和时间特征之间检测到线性关系。在腓肠肌内侧和外侧肌肉中观察到最大的肌电图调制，它们在曲线行走期间在时间和幅度上表现出相反的变化。此外，肌肉活动的幅度和时间特征与与曲线运动相关的空间和时间步态适应显著相关。目前的结果表明，直线前进运动背后的肌肉协同作用的精细调制足以产生足够的推进力来引导行走并保持平衡。这些发现表明，与转弯相关的指令通过调节在行走期间驱动运动神经元活动的紧密耦合神经元组件之间的相位关系来起作用。这将产生运动运动学的不变模板，这些模板是人类在空间中导航的基础。
