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Speech motor programming in apraxia of speech: A reaction time approach
Edwin Maas, Donald A. Robin, Kirrie J. Ballard, Curt E. Magnuson, & David L. Wright

Apraxia of Speech (AOS) is considered a motor programming disorder. The present study examines the nature of this motor programming disorder by testing the hypothesis that AOS reflects a deficit in a specific motor programming process, based on a contemporary model. Specifically, we hypothesize that AOS reflects a problem with organizing and integrating muscle commands for a unit (process INT), and not in sequencing units into their correct serial order (process SEQ). The current study first seeks to establish that our reaction time paradigm captures both processes for speech production, and thus to determine its utility for examining speech motor programming. Second, we use the paradigm to determine whether AOS reflects a specific deficit in INT, while SEQ remains intact. Previous findings using limb movements in this paradigm support the idea that individuals with AOS have an INT-deficit. Preliminary results of control subjects indicate that the paradigm is indeed sensitive to both processes. Consistent with limb findings, INT-demand increased for longer syllables and SEQ-demand increased as the number of syllables in the speech task was increased. Results from speakers with AOS will be available at the conference and will speak to our main hypothesis of an INT-deficit in AOS.

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