Poster D18, Wednesday, August 21, 2019, 5:15 – 7:00 pm, Restaurant Hall
Neural Synchronization During Language Processing in Listeners with Aphasia
Lisa Johnson1, Stephen Wilson4, Grigori Yourganov1, Alexandra Basilakos1, Brielle Stark2, Dana Eriksson5, Roger Newman-Norlund1, Chris Rorden1, Julius Fridriksson1;1University of South Carolina Department of Communication Sciences and Disorders, 2University of South Carolina Department of Psychology, 3Indiana University, Bloomington, 4Vanderbilt University Medical Center, 5University of Arizona
Background Listening to meaningful speech results in extensive reliable activity shared across multiple listeners (Silbert et al., 2014), and this neural coupling during language processing is integral for successful comprehension and social communication (Hasson et al., 2012). In persons with aphasia (PWA), receptive language is often impaired, thus affecting auditory comprehension. A possible explanation is that damage to certain cortical language areas affects the ability of the listener with aphasia to synchronize cortical ocsillations similarly to neurotypical listeners. The present study tests this hypothesis by investigating neural synchrony during comprehension in the right hemisphere (RH) ventral stream regions in PWA and neurotypical individuals. Aims The purpose of this study was to investigate (1) differences in neural synchrony in RH ventral stream regions between PWA and neurotypical controls, and (2) the relationship between neural synchrony in the contralesional hemisphere and aphasia severity. Methods Seven PWA (1 F, age M = 60.7±9.7 years) in the chronic phase of left-hemisphere stroke (months post-onset, M = 85±103.7) and 5 neurotypical controls (NT; 4 F, age M = 63.5±5.8) were included in the study. Participants underwent a battery of language and working memory assessments. In addition to structural MRI scans, we performed two functional MRI scans where participants watched an abbreviated television show (7 minutes in length). We computed mean BOLD response across RH ventral-stream regions of interest (ROIs) (Fridriksson et a., 2016). Neural synchrony within a group (PWA, NT) was estimated as correlation between individual timecourses. We also computed the correlation between the PWA’s individual timecourses and the mean of the NT timecourses as a measure of similarity of each PWA to the NT group. Results Timecourses were positively correlated across subjects within NT (r = .73) but not PWA (r = -.09) groups. A t-test between z-transformed correlation coefficients revealed a significant difference between groups (t(45.82) = 2.7; p = .009). To identify which PWA were demonstrating successful neural synchrony, timecourses from each PWA were correlated with a NT timeseries, which was the average of all members of the NT group. Therefore, PWA with higher correlations to the NT timeseries were thought to demonstrate neural synchrony success. PWA demonstrating neural synchrony success were those with greater spontaneous speech (r = .65, p = .11), naming (r = .66, p = .10) and repetition (r = .60, p = .15) abilities, as well as milder aphasia (r = .68, p = .09). These correlations did not reach statistical significance, likely due to a small sample size. Summary These preliminary results confirm results shown elsewhere: the typical listeners, over the course of a naturalistic comprehension paradigm, demonstrate neural coupling in reasonable regions (e.g. RH ventral stream). Here, we extend this to PWA who showed heterogeneity in timecourses in the contralesional hemisphere. PWA whose timecourses most resembled neurotypical listeners demonstrated milder aphasia and milder impairments of naming, spontaneous speech and repetition. More broadly, this early finding suggests that neural activation within the intact hemisphere in PWA is related to an impairment in language processing.
Themes: Disorders: Acquired, Speech Perception
Method: Functional Imaging