Abstract：
Balance control is an important indicator of mobility and independence in activities of daily living. How the functional coupling between the cortex and the muscle for balance control is affected following stroke remains to be known. We investigated the changes in coupling between the cortex and leg muscles during a challenging balance task over multiple frequency bands in chronic stroke survivors. Fourteen participants with stroke and ten healthy controls performed a challenging balance task. They stood on a computerized support surface that was either fixed (low difficulty condition) or sway-referenced with varying gain (medium and high difficulty conditions). We computed corticomuscular coherence between electrodes placed over the sensorimotor area (electroencephalography) and leg muscles (electromyography) and assessed balance performance using clinical and laboratory-based tests. We found significantly lower delta frequency band coherence in stroke participants when compared with healthy controls under medium difficulty condition, but not during low and high difficulty conditions. These differences were found for most of the distal but not for proximal leg muscle groups. No differences were found at other frequency bands. Participants with stroke showed poor balance clinical scores when compared with healthy controls, but no differences were found for laboratory-based tests. The observation of effects at distal but not at proximal muscle groups suggests differences in the (re)organization of the descending connections across two muscle groups for balance control. We argue that the observed group difference in delta band coherence indicates balance context-dependent alteration in mechanisms for the detection of somatosensory modulation resulting from sway-referencing of the support surface for balance maintenance following stroke.
摘要：
平衡控制是日常生活活动中流动性和独立性的重要指标。中风后如何影响皮质和肌肉之间的功能耦合以进行平衡控制仍是已知的。我们调查了慢性中风幸存者在具有挑战性的平衡任务中在多个频带上的皮质和腿部肌肉之间的耦合变化。14名中风患者和10名健康对照者执行了一项具有挑战性的平衡任务。他们站在一个计算机化的支持表面上，该表面是固定的（低难度条件）或具有不同增益的摇摆参考（中等和高难度条件）。我们计算了放置在感觉运动区域（脑电图）和腿部肌肉（肌电图）上的电极之间的皮质醇相干性，并使用临床和实验室测试评估了平衡性能。我们发现，在中等困难条件下，与健康对照相比，卒中参与者的δ频带相干性明显降低。但不是在低和高难度条件下。在大多数远端腿部肌肉群中发现了这些差异，但在近端腿部肌肉群中却没有。在其他频带没有发现差异。与健康对照组相比，中风参与者的平衡临床评分较差，但实验室检测没有发现差异。对远端而非近端肌肉组的影响的观察表明，用于平衡控制的两个肌肉组之间的下降连接的（重新）组织存在差异。我们认为，观察到的δ带相干性的组差异表明，由于中风后支撑表面的摇摆参考以维持平衡而导致的体感调节检测机制的平衡上下文依赖性改变。
