Evaluation of the corticomuscular coherence underlying ankle force production stability

Abstract

Objectives Maintaining postural balance sollicits a large set of muscles and, especially, the muscles acting around the ankles. Impaired ankle muscle force control severly impacts postural stability. Electroencephalography (EEG) and electromyography (EMG) are useful tools to investigate the neural control underlying muscle activations. The corticomuscular coherence, i.e., the spectral correlation of EEG recorded over the motor cortex and EMG signals, particularly helps quantifying the involvment of the corticospinal pathway in such tasks. This study investigated the relationship between the magnitude of the corticomuscular coherence and the force production around the ankle joint. Methods Force production, EMG from ankle extensors and flexors and EEG over the motor cortex were recorded in 11 participants performing 50 isometric ankle extension at submaximal force level. A feedback of the force production was displayed on a screen. Participants had to follow a target line which was composed of an increasing, a holding and a decreasing force phase (IFP, HFP and DFP). The average and the variability of the force production and the magnitude of the corticomuscular coherence with ankle extensors and flexors were computed for each phase. The correlation between the variables was tested using Pearson's correlation coefficient. Results The corticomuscular coherence with ankle extensors significantly decreases with increased variability of the force production (r2 = 0.23; P Conclusion Results suggest that corticomuscular coherence is sensitive to the modulation of force production independently depending on the targeted muscles. The control of ankle extensors, acting in the direction of the force production, appears to be directly associated with the modulation of force production. On the contrary, the control of ankle flexors, acting against the direction of the force production, appears to be associated with the stability of the force production This may have potential clinical applications, e.g., for patients with balance disorders.