Auditory-Somatosensory Influences on Vocal Motor Control in Primary Muscle Tension Dysphonia.

PURPOSE: Auditory and somatosensory systems jointly support vocal motor control, yet their relative contributions in primary muscle tension dysphonia (pMTD) remain poorly understood. This study examined how auditory and somatosensory feedback influence vocal motor control and adaptation in individuals with and without pMTD.

METHOD: Fifty-eight participants (pMTD: n = 17; controls: n = 41) completed a 200-trial altered auditory feedback paradigm involving sustained vowel productions with fundamental frequency downward shifts at -100 cents. The task was repeated with nebulized lidocaine to transiently attenuate laryngeal somatosensory input. Data were analyzed to extract the magnitude and direction of vocal adjustments across baseline, ramp, hold, and aftereffect phases.

RESULTS

Vocally healthy controls demonstrated robust adaptive vocal responses to fundamental frequency feedback alterations in the hold phase, followed by an adaptive aftereffect during the washout phase, particularly when somatosensation was intact. In contrast, when somatosensation was intact, individuals with pMTD displayed greater vocal responses in the opposing direction compared to controls during the hold phase, did not adapt within the hold phase, and showed greater variability overall. Notably, somatosensory disruption stabilized adaptation during the hold phase in pMTD with nebulized lidocaine.

CONCLUSIONS

Individuals with pMTD demonstrated differences in sensory weighting, with evidence that attenuating somatosensory input facilitated better vocal motor adaptation. Framing pMTD within models of sensorimotor control advances our theoretical understanding of the disorder and highlights aberrant somatosensory processing as a potential mechanism underlying vocal instability. Future research is needed to further elucidate sensorimotor interactions and determine whether targeted recalibration of sensory feedback has therapeutic benefit.