Directional Perilaryngeal Functional Muscle Network Indicates Sequential Patterns of Muscle Coordination During Vocal...

This study, for the first time, investigates the response of a directional perilaryngeal muscle network to a variety of vocal tasks.

Twelve surface electromyography (sEMG) signals were recorded bilaterally from six muscles around the larynx during ten vocal tasks. Eight subjects (four females) without a history of voice disorders participated in the study. The vocal tasks were divided into three groups, including (i) phonation at distinct levels of loudness and pitch, (ii) single-repetition tasks such as pitch glide, and (iii) reading at different levels of loudness.

For the muscle-wise comparison, the network out-degree was higher than the in-degree for all four regions of infrahyoid muscles (p<0.001). For the task-wise comparison, the network weighted clustering coefficient monotonically ascended in proportion to increasing loudness and elevating pitch during sustained phonation (p<0.003).

The partial directed coherence analysis robustly indicated outward flow from the four regions of infrahyoid muscles to the other eight muscles. In the context of muscle networks, the outward flow means the infrahyoid muscles receive the neural drive before other muscles. Additionally, the directional muscle network responded in proportion to vocal task parameters such as loudness and pitch.

This work illuminates the chain of events during vocal tasks and identifies the infrahyoid muscles as leading the coordinated efforts during phonation. This study indicates the potential of the presented method for assessing vocal health and performance.