Contraction patterns of facial and neck muscles in speaking tasks using high-density electromyography

Speaking activities requires coordinated neuromuscular activation of the facial and neck muscles, so that natural and intelligible speeches could be produced for human communication. Given that any problem of these muscles will lead to speaking difficulties, understanding the contraction patterns of the facial and neck muscles is helpful to explore the muscular mechanism of various speaking problems. In this study, the high-density surface electromyography (HD sEMG) technique was proposed to examine the muscular activities associated with speaking. The HD sEMG signals were acquired when the human subjects were speaking English daily words by 120 channels of closely-spaced electrodes, symmetrically placed on the left and right sides of the facial/neck muscles. The results showed that the energy maps calculated from normalized RMS values of the sEMG signals could illustrate the dynamic spatiotemporal properties of the muscle activities during different speaking tasks. There were high left-right symmetric properties for the RMS curves and energy maps, and further analyses of the correlation coefficients confirmed a significant left-right correlation for the facial and neck muscles during the speaking. The findings of this study suggested that the HD sEMG signals would be useful to evaluate the muscle contraction patterns related to speaking activities and could be a potential tool for diagnosing the muscular functions of speaking difficulties.