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Shifts in the right pars triangularis network controllability and phonological errors in post-stroke aphasia

Poster C60 in Poster Session C, Friday, October 7, 10:15 am - 12:00 pm EDT, Millennium Hall

Harrison Stoll¹, Denise Harvey², Haley Dresang^2,3, Adelyn Brecher³, Olu Faseyitan², Daniela Sacchetti², Roy Hamilton², H. Branch Coslett², Peter Turkeltaub^4,5, John Medaglia^1,2; ¹Drexel University, ²University of Pennsylvania, ³Moss Research Rehabilitation Institute, ⁴Georgetown University, ⁵Medstar National Rehabilitation Hospital

Aphasia after a stroke impacts an individual’s ability to work and quality of life. Due to a stroke, the brain can recruit new regions to assist with language processing demands and preserve cognitive functions. One region that displays post-stroke changes in persons with aphasia (PWA) is the right pars triangularis (rPTr). This region has higher functional activity in persons with aphasia (PWA) relative to healthy controls, but the increased connectivity is associated with worse language performance. The goal of the current study was to further clarify the role of rPTr in PWA by investigating if the neuro-plastic changes after stroke are associated with language deficits. To that end, we measured the boundary controllability (BC) of rPTr; BC quantifies the capacity of a region to integrate and segregate the activities of different networks. We hypothesized that BC would be higher in rPTr for PWA than age-matched controls, representing a relatively higher role of this region in the context of stroke. Prior research has found rPTr activity is associated with phonological errors. Furthermore, research has also found that higher BC in healthy individuals is associated with worse performance on tasks with higher semantic demands. In light of these results, we sought to understand whether different types of naming errors corresponded to BC at rPTr. We hypothesized that BC would relate to a specific error type in PWA, and based on prior neuromodulation work, we predicted that it would relate to phonological errors. We tested our hypothesis in 60 chronic post-stroke aphasia patients and 62 matched controls. All PWA completed the Western Aphasia Battery (WAB) and the Philadelphia Naming Test (PNT). With PNT data, we calculated the overall accuracy and proportion of error type (phonological, semantic, and mixed). Consistent with our first hypothesis, we found PWA had higher BC than age-matched controls at rPTr (t(120) = -2.52, p < .01). A regression model yielded a statistically significant negative relationship between BC and phonological errors that could not be accounted for by lesion volume (R2 = .11, F(1,48) = 6.21, p < .05). Our results provide new insight into the network-level changes after a stroke causing aphasia. Specifically, the results demonstrate that changes to rPTr after stroke extend beyond functional activity. The shift in the fundamental anatomical role of rPTr suggests the region becomes more critical for integrating and segregating communication across networks of the brain. Moreover, the stronger an anatomical integrator the rPTr is, the better it can help process language information efficiently. This could be because the rPTr has an increased role in mediating communication among language regions of the brain more generally. Compared to findings in the left PTr in healthy subjects, our data suggest that homotopic recruitment may involve shifts in this anatomical property. Changes in BC may also predict functional neuroplasticity observed in prior research. Research has yet to investigate how BC relates to functional activity, and future work is needed to understand this relationship. Moreover, future work should also consider BC in PWA moderates neuromodulation treatment efficacy.

Topic Areas: Phonology and Phonological Working Memory, Computational Approaches