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The effects of transcranial direct current stimulation on speech production in individuals with acquired apraxia of speech
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- Author / Creator
- Ehr, Sarah
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Background. Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, has been used as an adjunct to speech and language therapy to facilitate neuroplasticity in individuals with language impairments due to stroke. The extent to which these therapeutic results extend to motor speech disorders, particularly acquired apraxia of speech (AOS), is limited. AOS is a motor speech disorder that results in difficulties planning and sequencing the motor patterns required for speech production. Treatment for AOS typically involves using speech motor learning and/or phoneme placement strategies, and while these interventions have been shown to generalize to phoneme and word accuracy, the required dosage is intense and results between patients are highly variable. The present study seeks to assess the potential efficacy of anodal tDCS (A-tDCS) over the primary motor cortex coupled with training to improve both precision and consistency of speech production, as measured by percentage of phonemes correct (PPC) on tasks of increasing speech motor complexity.
Methods. A modified repeated measures single case study design was conducted across two participants, one receiving A-tDCS and a control receiving sham-tDCS (S-tDCS). Differences in speech accuracy, as measured by change in percentage of phonemes correct (PPC) within sessions, between conditions pre- and post-stimulation were examined using descriptive analyses and visual representations. Data was collected across four weekly sessions.
Results. The main findings included: 1) A-tDCS over the motor cortex resulted in a moderate intervention effect for motorically complex speech tasks over the S-tDCS condition, 2) A-tDCS resulted in an unanticipated positive effect for simple tasks during the first session over the S-tDCS condition, potentially reflecting an added improvement in linguistic as well as motor speech ability, and 3) effectiveness of A-tDCS was highly variable and appeared to diminish across sessions, while the S-tDCS condition showed greater consistency.
Conclusion. Bihemispheric stimulation of tDCS to the motor cortex has potential to simultaneously improve both chronic speech and language deficits during behavioural interventions, due to the spreading effect and lack of focal specificity inherent in neuromodulation. Future research is needed on the dose-response of tDCS and individual factors that may influence outcomes. -
- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.