Eadie, TanyaKapsner-Smith, Mara2024-09-092024-09-092024KapsnerSmith_washington_0250E_27156.pdfhttps://hdl.handle.net/1773/52188Thesis (Ph.D.)--University of Washington, 2024Voice disorders are experienced by nearly a third of people at some point in their lifetimes. Recent evidence suggests impaired auditory-motor function may be a factor in the development or evolution of hyperfunctional voice disorders (HVDs), the most common category. The series of studies outlined in this dissertation form a program of research that focused on further describing the role and nature of such auditory-motor (dys)function in HVDs. In chapter 1, we explored the reliability of common methods used to assess auditory-motor function for speech. Prior to this study, test-retest reliability had never been examined for these methods, which was important for interpretation of study findings across studies outlined in chapters 1 and 3. Results from the study outlined in chapter 1 showed different patterns of reliability of assays of speech auditory-motor control between the domains of voice and articulation, and supported the use of a categorical measure of fundamental frequency (fo) adaptation employed in chapter 3. In chapter 2, we developed a protocol to assess volitional control of small changes in vocal fo and intensity, and tested for group differences between people with and without HVDs. Prior studies of auditory-motor impairment in HVDs found unusually large involuntary changes in vocal fo during auditory-motor adaptive learning tasks. The study outlined in chapter 2 evaluated the possibility that people with HVDs simply are not able to make smaller changes, even when asked to do so volitionally. We found no significant differences in volitional control of fo and intensity between people with and without HVDs. In chapter 3, we evaluated the specificity of vocal auditory-motor impairment in people with HVDs, by replicating studies of fo discrimination and adaptive vocal learning, and extending findings to a second vocal parameter, intensity. In addition, we tested a novel hypothesis that manipulations of auditory feedback, particularly of fo, may elicit a stabilization response in muscles around the larynx, as a form of vocal control. We posited that if this type of response exists, it may be dysregulated in people with HVDs. The results of these studies replicated and extended findings of prior work. Specifically, we found impaired auditory-motor adaptive learning for fo that was similar to prior findings, and a trend for a significant difference from controls in adaptive learning for intensity that was qualitatively different. These findings occurred in the absence of differences in volitional control of small changes in fo and intensity, as reported in chapter 2. Taken together, the results of this series of studies may suggest differences in the causal vs. compensatory nature of these impairments in people with HVDs, which should be explored in future studies. We also found preliminary evidence for laryngeal stabilization as a mechanism of control of vocal fo, which was not present in measures of vocal intensity. Taken together with differences in vocal and articulatory auditory-motor control described in chapter 2, these findings reinforce the importance of refining theoretical models of speech sensorimotor control to account for differences across different parameters of speech. Future directions for research and clinical implications also are discussed.application/pdfen-USnoneauditory discriminationdysphoniamotor controlspeechvoiceNeurosciencesSpeech therapySpeechThesis