Poster A8, Tuesday, August 20, 2019, 10:15 am – 12:00 pm, Restaurant Hall
Propagation speed within the ventral stream predicts treatment response in chronic post-stroke aphasia
Janina Wilmskoetter1, Barbara Marebwa1, Graham Warner2, Alexandra Basilakos3, Julius Fridriksson3, Chris Rorden4, Leonardo Bonilha1;1Department of Neurology, College of Medicine, Medical University of South Carolina, 2Department of Neuroscience, College of Graduate Studies, Medical University of South Carolina, 3Department of Communication Sciences and Disorders, University of South Carolina, 4Department of Psychology, University of South Carolina
Background: The preservation of direct, white-matter connections between language-related brain regions has been linked to aphasia recovery after stroke. However, little is known about the importance of indirect, alternative pathways when direct connections are lost or not existent. We hypothesized that the propagation speed (number of steps between two regions) within the ventral and dorsal streams of language processing is predictive of the treatment response of individuals with chronic post-stroke aphasia. Specifically, we hypothesized that the propagation speed within the ventral stream and dorsal stream is predictive of a change in semantic and phonological errors, respectively. Methods: We leveraged data from 69 individuals with chronic, left-hemisphere, post-stroke aphasia who were enrolled in a clinical trial assessing the futility of transcranial direct current stimulation (tDCS) in aphasia treatment. We measured individuals’ naming abilities with the standardized Philadelphia Naming Test (PNT) before and one week after the three-week-long computerized anomia treatment. Using probabilistic tractography individuals’ whole brain connectomes were constructed based on diffusion tensor MRIs acquired before treatment. We calculated the number of steps (nodes) between brain regions of the ventral and dorsal language processing stream as a proxy for the propagation speed of information spreading between regions. The sum of all internodal shortest connections was calculated for the ventral and dorsal stream separately. We performed multivariable linear regression modeling to predict the change in naming performance from pre- to post-treatment. Results: The propagation speed within the ventral stream significantly predicted the change in correct naming responses (standardized coefficients beta: -.522, p=.023) and semantic errors (standardized coefficients beta: .654, p=.003) from pre- to post-treatment, while controlling for dorsal stream propagation speed, lesion volume, age, education, and treatment type. The ventral stream did not predict change in phonological errors, nor did the dorsal stream predict change in correct naming, semantic or phonological errors. Conclusions: In this study we demonstrate that the propagation speed between brain regions of the language network is a crucial marker for treatment responses in individuals with chronic post-stroke aphasia. Specifically, a faster propagation speed between regions belonging to the ventral stream was linked to more correct naming responses and less semantic errors. Propagation speed is a useful measure that compliments traditional lesion symptom mapping by assessing the integrity of residual neural networks.
Themes: Disorders: Acquired, Language Production
Method: White Matter Imaging (dMRI, DSI, DKI)