ABSTRACT The purpose of the proposed research is to strengthen the impact of a current project on speech profiles after left hemisphere stroke (R01DC018569). Specifically, we seek to expand its scope to primary progressive aphasia as seen in some phenotypes of frontotemporal lobar degeneration and Alzheimer’s disease. Recent research at The University of North Carolina at Chapel Hill has demonstrated a spectrum of quantitative speech profiles in stroke-induced aphasia. These profiles include apraxia of speech—a disorder of motor programming that has been notoriously difficult to diagnose with traditional perceptual methods. Though apraxia of speech is usually caused by stroke, it also occurs in degenerative disease, where its presence or absence is central to the behavioral differentiation among variants of primary progressive aphasia and is predictive of underlying pathology1,2. As such, the diagnosis is essential to early prognostication and treatment. Through collaboration with colleagues at The University of Texas at Austin and The University of New Mexico, we plan to apply experimental conditions and analysis procedures from the parent stroke project to persons with primary progressive aphasia. We expect this expansion will facilitate synergistic neurobehavioral research across distinct pathologies that affect overlapping brain regions and networks. In Aim 1 we will evaluate the extent to which the speech assessment we are developing for stroke-induced apraxia of speech is applicable to primary progressive aphasia. We plan to adjust parameters as needed to ensure psychometric rigor and clinical feasibility for both etiologies. Anticipated tools and procedures will be of value to all researchers and clinicians whose work involves either of these clinical populations. In Aim 2, we will determine to what extent apraxia of speech and related speech profiles predict responsiveness to behavioral cueing strategies. By replicating experimental conditions utilized in the stroke-focused parent grant, we will contribute to converging evidence about cognitive compensation and capacity for learning after diverse left hemisphere pathology. In conjunction with the parent project, these two aims will establish a foundation for collaborative research beyond traditional boundaries of disorder etiology.