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Mapping the Role of Right Pars Triangularis in Post-Stroke Aphasia: A Planned GIMME Analysis of TMS-Induced Connectivity Changes
Poster Session C, Saturday, September 13, 11:00 am - 12:30 pm, Field House
This poster is part of the Sandbox Series.
Harrison Stoll1, Apoorva Kelkar1, Denise Harvey2, Olu Faseyitan2, Roy Hamilton2, Branch Coslett2, John Medaglia1,2; 1Drexel University, 2University of Pennsylvania
Introduction: Noninvasive brain stimulation to the right pars triangularis (rPTr) has been explored as a treatment for post-stroke aphasia, with mixed outcomes across individuals. While inhibitory rPTr stimulation has sometimes improved naming, the underlying neural mechanisms remain unclear. Traditional interhemispheric inhibition (IHI) models suggest a maladaptive role for the rPTr. Still, recent evidence points to a more nuanced, potentially compensatory function in the context of perisylvian language regions and their right hemisphere homotopes. This project aims to clarify the functional role of the rPTr by examining its directed connectivity with bilateral language-related regions before and after TMS using Group Iterative Multiple Model Estimation (GIMME). Critically, an advantage of GIMME is that it allows us to uncover valid group and individual connections that relate to TMS efficacy. Thus, we can identify individual differences in the rPTr connectivity to the language network, which should improve our ability to determine what connections are necessary for effective TMS stimulation to the rPTr. Study Design and Planned Analysis: We recruited 21 individuals with chronic aphasia due to left hemisphere stroke and administered inhibitory TMS to the rPTr. Resting-state fMRI data were collected pre- and post-TMS. GIMME will be used to model individual-level directed connectivity between key language nodes (bilateral IFG pars triangularis, MTG, SMG, and precentral sulcus). Behavioral responses to TMS will be indexed by changes in naming accuracy, focusing on phonological errors. We are particularly interested in whether individual differences in connectivity profiles (e.g., inhibitory rPTr → lPTr vs. excitatory rPTr → rMTG connections) relate to TMS outcomes. Preliminary Direction and Interpretation: Data collection is in progress, and analytic strategies are being finalized. Our pilot analyses and prior work suggest that specific rPTr connectivity patterns may explain TMS-induced naming changes. We hypothesize that inhibitory connections from rPTr to left hemisphere language areas may reflect maladaptive interference, while excitatory connections to the right hemisphere language nodes could indicate compensatory recruitment. We anticipate identifying multiple connectivity “phenotypes” across individuals, reflecting divergent neural strategies for supporting naming after stroke. Value of Sandbox Participation: This work is in the planning and early analysis phase. Sandbox feedback will be instrumental in refining our model space, selecting optimal ROIs, and interpreting observed connectivity patterns. We hope to discuss the use of GIMME for modeling individual variability in network dynamics, the challenges of targeting multifaceted regions like rPTr, and the broader implications for tailoring TMS protocols in aphasia rehabilitation.
Topic Areas: Speech-Language Treatment, Disorders: Acquired