The overarching goal of this dissertation was to assess a set of sensorimotor, acoustic, and functional speech measures to inform the understanding of the mechanisms underlying two common speech disorders with evidence of disrupted sensory function: hyperfunctional voice disorders (HVDs) and hypokinetic dysarthria resulting from Parkinson’s disease (PD). The purpose of the first and second study was to elucidate the mechanisms underlying speech symptoms in HVDs. The aim of the first study was to examine whether auditory discrimination and vocal responses to altered auditory feedback (indicative of vocal motor control) differed in a large set of speakers with HVDs (N = 62) compared to controls (N = 62). The results directly implicate disrupted auditory processing in impairments to vocal motor control in HVDs. Building on this finding, the second study sought to compare the same auditory and vocal motor control measures in speakers with HVDs pre- and post-therapy (N = 11) to assess whether successful therapy (i.e., voice symptom improvement) resulted in improvements to auditory-motor function. On average, vocal motor control improved after therapy but there were little changes to measures of auditory processing, which suggests that therapeutic improvements in HVDs may be compensatory rather than a result of resolving the underlying auditory processing deficits. The collective findings from the first and second study improve the understanding of the development of HVDs and highlight the need to consider auditory processing in assessment and treatment of HVDs. The third and fourth study objectives were to characterize auditory-motor control and longitudinal changes to speech acoustics in PD. In the third study, auditory-motor control of both voice and articulatory parameters of speech were assessed in speakers with PD on medication (N = 28) compared to controls (N = 28) and compared to measures of speech function (intelligibility and naturalness ratings). No group differences were found in auditory-motor measures, regardless of speech domain. These results, which describe findings from the largest sample of PD patients completing auditory-motor tasks to-date (N=28), suggest that auditory-motor control is intact in individuals with PD on their typical medication cycle. This work also provided the first evidence that auditory-motor measures reflect measures of speech function (speech intelligibility and naturalness). The fourth and final study in this dissertation examined whether longitudinal changes to speech acoustics in PD were associated with the specific time (in months) between speech samples. Although prior work has examined speech decline in PD, no study to-date has assessed whether speech acoustics are sensitive to disease progression within an individual with PD. The current study examined acoustic speech samples collected from speakers with PD (N = 30) at two separate time points. Longitudinal changes to speech acoustics were examined by time between speech samples, motor phenotype and sex assigned at birth, to shed light on the relationships between acoustic measures of speech, disease progression, motor symptoms, and sex. The study revealed that longitudinal decline in second formant slope, articulation rate (syllables per second) across The Rainbow Passage, and relative fundamental frequency offset values were all associated with increased time between sessions within a speaker. In addition, longitudinal increases in percent pause time in conversational speech were more likely in the PIGD motor phenotype, and longitudinal increases mean fo across conversational speech were more likely in males compared to females with PD. This work provides the first report of acoustic measures of speech that reflect the specific time, in months, of PD progression, as well as acoustic measures of speech that appear to be differentially impacted over time by motor phenotype and by sex. The findings provide evidence that three acoustic measures of speech show promise as measures of PD progression in months and support the notion that speech symptom decline differs by motor phenotype and by sex assigned at birth, which should be considered when planning therapeutic interventions. / 2026-08-31T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/45040 |
| Date | 24 August 2022 |
| Creators | Abur, Defne |
| Contributors | Stepp, Cara E. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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