EMG coherence between jaw and neck muscles during chewing performance

Method: Eight healthy subjects between the ages of 20 and 32 years were enrolled. Electromyography (Biomedical Amplifier, NEC Co.) examinations of jaw and neck muscles were conducted while chewing. Obtained data were then analyzed using the formula of transfer function (MultiScope EMG, Medical Trysystem) with the following input and output parameters used for interrelationships. Input consisted of EMG findings for chewing side Mm activities, while output was activities of other jaw muscles, including Mm, Ta, and AD, and neck muscle activities.

Result: Spectrum analysis showed a monomodal distributed frequency of power values in regard to jaw and neck muscles activities. As for phase characteristics in those, the 0.98, 1.22, and 1.46 frequencies as wave factors of jaw and neck muscle activities, and jaw closing muscle activities showed well-coordinated features, whereas the jaw opening muscles showed a half-cycle decline. Regarding coherent characteristics, the jaw muscles and chewing side SCM showed well-coordinated features. In contrast, the coherence between chewing side jaw muscle and non-chewing side neck muscle activities showed widespread distribution and significantly lower values as compared to chewing side SCM.

Conclusion: Our results indicated that jaw muscles and neck muscles are bilaterally and unilaterally coordinated, respectively. We speculate that jaw and neck muscle coordination on the non-chewing side participate in chewing and/or head stabilization.