Evidence for auditory-motor impairment in individuals with hyperfunctional voice disorders

Purpose: The vocal auditory-motor control of individuals with hyperfunctional voice disorders was examined using a sensorimotor adaptation paradigm. Method: Nine individuals with hyperfunctional voice disorders and 9 individuals with typical voices produced sustained vowels over 160 trials in 2 separate conditions: (a) while experiencing gradual upward perturbations in the fundamental frequency (f_o) of their auditory feedback (shift-up) and (b) under no auditory perturbation (control). The shift-up condition consisted of 4 ordered (fixed) phases: baseline (no perturbation), ramp (gradual increases in heard f_o), hold (a consistently higher heard f_o), and after-effect (no perturbation). Adaptive responses were defined as the difference in produced f_o during control and shift-up conditions. Results: Adaptive responses were significantly different between groups. Individuals with typical voices generally showed compensatory adaptive responses, with decreased f_o during the ramp and hold phases. Conversely, many individuals with hyperfunctional voice disorders instead displayed the opposite effect by following the direction of the perturbation. When f_o was experimentally increased speakers further increased their f_o. Conclusion: Results indicate that some individuals diagnosed with hyperfunctional voice disorders have disrupted auditory-motor control, suggesting atypical neurological function. These findings may eventually allow for the development of new interventions for hyperfunctional voice disorders.