Tongue-Palate Electromyographic Synchronization Related to Swallowing, Mastication, and Speech

The specific oscillatory dynamics of intermuscular coupling involved in swallowing, mastication, speech production, and respiration have not been elucidated. This study aimed to explore intermuscular coupling between the tongue and palate that underlies oral functions by analyzing the event-related coherence (ERC) of electromyography (EMG) signals before swallowing, mastication, and speech production. Twenty-two healthy participants performed three oral tasks: swallowing, speech production, and mastication. Sixteen of these participants also completed a combined task involving swallowing immediately after speech. EMG signals were recorded from the tongue and palate, and ERC between tongue and palate EMG was analyzed. Peak ERC was compared across tasks for alpha (8-14 Hz), beta (16-30 Hz), and gamma (32-46 Hz) frequency bands. In all participants, ERC showed significant peaks in all frequency bands before the onset of swallowing, mastication, and speech. Only the ERC values in the beta band were significantly larger for swallowing than for mastication, but not for speech. Moreover, the ERC values for the combined task of swallowing after speech production were significantly smaller than those for the simple swallowing task in the alpha, beta, and gamma bands. The intermuscular oscillatory regulation is more critical for swallowing than for mastication.