Rehabilitation Engineering Laboratory, Toronto Rehabilitation Institute, University Health Network, Toronto, Canada.
Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada.
Sci Rep. 2017 Mar 16;7:44658. doi: 10.1038/srep44658.
The precise role of the human primary motor cortex in walking is unknown. Our previous study showed that the primary motor cortex may contribute to specific requirements of walking (i.e., maintaining a constant movement frequency and bilaterally coordinating the feet). Because aging can impair (i) the ability to fulfill the aforementioned requirements and (ii) corticomuscular communication, we hypothesized that aging would impair the motoneuronal recruitment by the primary motor cortex during bilateral cyclical movements. Here, we used corticomuscular coherence (i.e., coherence between the primary motor cortex and the active muscles) to examine whether corticomuscular communication is affected in older individuals during cyclical movements that shared some functional requirements with walking. Fifteen young men and 9 older men performed cyclical, anti-phasic dorsiflexion and plantarflexion of the feet while seated. Coherence between the midline primary motor cortex and contracting leg muscles cyclically increased in both age groups. However, the coherence of older participants was characterized by (i) lower magnitude and (ii) mediolaterally broader and more rostrally centered cortical distributions. These characteristics suggest that aging changes how the primary motor cortex participates in the cyclical movements, and such change may extend to walking.
人类初级运动皮层在行走中的精确作用尚不清楚。我们之前的研究表明，初级运动皮层可能有助于行走的特定要求（即保持恒定的运动频率和双侧协调脚部）。由于衰老会损害（i）满足上述要求的能力和（ii）皮质-运动通讯的能力，我们假设衰老会损害初级运动皮层在双侧周期性运动中对运动神经元的募集。在这里，我们使用皮质-运动相干性（即初级运动皮层和活跃肌肉之间的相干性）来检查在周期性运动中，皮质-运动通讯是否会受到老年人的影响，这些运动与行走具有一些功能要求。15 名年轻男性和 9 名老年男性在坐姿下进行周期性、反向背屈和跖屈足部运动。在两个年龄组中，中线初级运动皮层与收缩腿部肌肉之间的相干性呈周期性增加。然而，老年参与者的相干性具有以下特征：（i）幅度较低，（ii）中-外侧更宽，更向前集中的皮质分布。这些特征表明，衰老改变了初级运动皮层参与周期性运动的方式，这种变化可能会扩展到行走。
