Coordination of velopharyngeal muscle activity during positioning of the soft palate.

The relative contributions of the levator veli palatini, palatoglossus, and palatopharyngeus muscles were assessed relative to a range of positions of the velopharynx during production of the vowels [a] and [i] by four normal adult speakers. The results indicate that velopharyngeal positioning is determined by the relative contributions of the levator veli palatini, palatoglossus, and palatopharyngeus muscles. There was an increase in coefficients of determination (i.e., amount of closure level variability explained) when activity levels of all three muscles are included in the statistical model compared to activity in any one muscle analyzed independently. Both consistent and inconsistent relations among activity levels in the three velopharyngeal muscles studied were observed across speaker and vowel produced.