Transactions of the Illinois State Academy of Science [Volume 110 (2017)]
Masticatory and Brux-like Motor Patterns in the Freely Behaving Rat: Electromyography and Phase Analysis
Authors: Jaclyn E Taylor, J Devin Wall, Dan B Welch (110-01MS1776Final)
Our objective was to develop an experimental platform to examine brainstem commands, and trigeminal neural networks that underlie activation and switching of masticatory and brux-like motor patterns of the jaw. This characterization could help us understand the underlying mechanisms of human bruxism. Sixteen male rats (200-224 g) had EMGs implanted into right superficial masseter (mass: jaw closing, n=16), temporalis (temp: jaw closing, n=8), and anterior digastric (dig: jaw opening, n=8) muscles. We conducted a dual-referent phase analysis in order to assess coordination. We used Rayleigh test to discriminate between uniform and unimodal-clustered phase distributions, and Williams F-test to determine if mean angles differed significantly. We found: 1) Phase differences between jaw closing muscles, the temp and mass (p<.05). During a brux-like event, temp and mass fire almost simultaneously. However, during mastication the onset for the EMG burst for the temp occurs after the onset for the mass muscle. 2) Phase differences between jaw opening (dig) and jaw closing (mass) muscles. During mastication we can observe an alternation of jaw opening and jaw closing muscles (p<.05). However, during a brux-like event, dig and mass exhibit co-contraction. 3) Brux-like motor patterns elicit shorter, more rapid bursts (p<.05), and occurred at a cycle frequency higher than the masticatory patterns (p<.05).