Effects of gravity on velopharyngeal muscle activity during speech

Assessment of the role of gravitational forces in the motor control of the velopharyngeal mechanism was the focus of this study. Specifically, the effect of gravity on activation levels of the levator veli palatini and palatoglossus muscles was assessed. Nineteen volunteers repeated a CV syllable in upright and supine body positions. Overall, lower peak activation levels of levator veli palatini were observed in the supine body position. The results suggest that less muscle activity was seen in the levator veli palatini in the supine body posture, where gravitational effects worked in the same direction (i.e., toward closure). No statistically significant group effects were seen in muscle activation levels of palatoglossus across the two body postures, although clear gravity effects were observed in some subjects. The implications of these findings from a speech motor control perspective are discussed in relation to normal and disordered velopharyngeal function.