PROJECT SUMMARY Speech motor disorders have profound impacts on an individual’s ability to communicate, often leading to a significant reduction in quality of life35,49. Since the advent of personalized medicine, clinical phenotypes have become an increasingly important construct in rehabilitation research, as they facilitate the identification of treatment targets that are individualized to a patient’s unique impairment profile3. There is, however, currently no established set of objective measures that to phenotype the articulation impairments observed in speech motor disorders32. Consequently, clinicians employ broad treatment strategies for patients with distinct articulatory deficits, which often result in variable therapy outcomes97. Given the links between specific articulatory abnormalities and pathophysiologies1,16,81,90 and the impact of the articulatory subsystem on intelligibility14,53,69,77, there is a critical need to determine the articulatory impairment phenotypes across the spectrum of speech motor disorders. The proposed study will comprehensively characterize articulatory impairments in four neurologic populations (compared to healthy controls) with hypothetically divergent motor deficits: (1) the nonfluent variant of primary progressive aphasia (nfvPPA) or primary progressive apraxia of speech (PPAOS), (2) amyotrophic lateral sclerosis (ALS), (3) Parkinson’s disease (PD), and (4) spinocerebellar ataxia (SCA). Articulatory impairments will be characterized based on a hypothesis-driven framework of motor control (i.e., Coordination, Consistency, Speed, Precision, and Rate) composed of a semi-automated acoustic feature set. Aim 1 will use a linear discriminant analysis (LDA) to compare the articulatory performance (as indexed by the acoustic feature set) of the groups during the sequential motion rate (SMR) task. The LDA will be adjusted for speech severity to determine the true discriminatory power of the acoustic features and ensure that severity differences are not driving phenotype differences. Aim 2 will use a multiple regression analysis (MRA) to determine the articulatory deficits most associated with intelligibility in the four neurologic populations by correlating performance on each acoustic feature with performance on the Sentence Intelligibility Test (SIT)96. The overall goal of the proposed research is to advance our knowledge of the diversity of articulatory impairment phenotypes in different speech motor subtypes. Results from this research will (1) facilitate the development of impairment-based approaches, (2) yield more granular outcome measures for evaluating the efficacy of behavioral or pharmaceutical treatments, and (3) elucidate the contribution of distinct articulatory mechanisms to declines in functional communication. This project falls under NIDCD’s Priority Area 3 in Voice, Speech, and Language Research, as it investigates biomarkers that could support diagnosis, treatment, and progress monitoring in in...