Compensatory tongue-jaw strategies during speech in response to intra-oral perturbation

Abstract

When normal speech production is disrupted by perturbing devices, such as dental prosthesis or appliances, a compensatory motor strategy must emerge using unaffected speech articulators. The purpose of this study was to use a unique methodology to measure compensatory oral motor function in response to oral articulatory perturbation. Compensatory speech was evaluated for the fricative "s" in three different vowel contexts, while the oral cavity was perturbed using two different five millimeter thickened devices. Measurements were made of the acoustical spectral properties, ultrasonographic images of mid-sagittal tongue movement, and electrognathographic jaw displacement during speech. Recordings were made at baseline, immediately upon insertion, after 15 minutes, and after two weeks and upon removal of the perturbing device. A Within-Subject 2-way Repeated Measures ANOVA was performed to statistical evaluate the significance of the mean acoustical output, mandibular displacement, and change in tongue height at four time intervals and between each type device with a significance level of p < 0.05. The results revealed that compensatory motor control of speech organs is time and task dependent, and that for /s/ the acoustic output and jaw displacement sensitive. However, the tongue was used to create long-term compensation in response to oral perturbation. Therefore, changes in the oral cavity, such as prosthesis, appliances, and surgery may initially impact speech function. However, the tongue and the jaw movement is altered to compensate for perturbation resulting in new motor control strategies.