Localization of mRNAs for synaptojanin isoforms in the brain of developing and mature rats

STATEMENT OF PROBLEM: Knowledge of mastication is based on studies that use jaw tracking equipment in nonroutine settings. Ethologists would argue that such data probably does not reflect routine masticatory function. If jaw movements could be tracked noninvasively, then the hypothesis that jaw tracking equipment and nonroutine settings alter mastication could be investigated. PURPOSE: This study quantitatively evaluated the relationship between chin and jaw movements during a gum-chewing task. MATERIAL AND METHODS: Masticatory chin and jaw movements of 50 subjects were tracked in the x-, y-, and z-axes for 15 seconds, which resulted in approximately 15 chewing cycles obtained per subject. For each chewing cycle, magnitude and timing of displacement, velocity, and acceleration extrema in each axis were computed for both jaw and chin movement data. Extrema means were calculated for each 15-second trial. The respective means representing chin versus jaw movements were compared with linear regression and correlation analyses. RESULTS: All mean extrema were significantly correlated (r range 0. 30-0.99; P <.05). Magnitude correlations were larger than timing correlations for acceleration extrema. In contrast, magnitude correlations were smaller than timing correlations for displacement extrema. The highest correlation occurred for chewing rate. CONCLUSIONS: Chin and jaw movements were correlated during chewing; however, only chewing rate was highly predictable from chin movement data.