Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Theta-Burst Stimulation to Left SMG Slows Pseudoword Processing in Young Adults
Poster Session A, Friday, September 12, 11:00 am - 12:30 pm, Field House
Rachael Harrington1, Katie Wallace1, Adianes Herrera-Diaz1, C. Nikki Arrington1; 1Georgia State University
Introduction: Theta-burst stimulation has significant potential for improving outcomes after intervention across disordered populations. By upregulating or downregulating regions with atypical activity or connectivity, we may be able to induce plasticity to encourage more typical neural patterns which can improve behavioral outcomes. Previous data from our lab has shown that the mechanisms of theta-burst stimulation in complex cognitive networks differs from the mechanisms in the motor system, from which we primarily derive stimulation protocols and interpretation. Specifically, we have shown an inconsistent facilitative effect from continuous theta-burst stimulation (cTBS) which is often described as inhibitory (Harrington et al. 2023). In this study, we examine the effects of cTBS versus sham stimulation to left supramarginal gyrus (SMG) on a lexical decision and phonological decoding task. We hypothesized that cTBS stimulation of SMG would inhibit accuracy and reaction time on pseudoword decisions during forced-choice computerized reading tasks as compared to sham stimulation. Methods: Eleven participants were included in this analysis (21.5 +/- 2.1; 7 females, 4 males; Woodcock-Johnson IV Broad: 104.7 +/- 14.5 (77-127); WASI FSIQ-2: 103.1 +/- 13.5 (85-121). Participants were pseudorandomized into stimulation order for active or sham stimulation. cTBS was delivered via standardized paradigm (Huang et al., 2025) with a Magventure Magpro MCF-B65 coil and Neurolite Neuronavigation software using individual neuroanatomical landmarks. Sham stimulation was delivered with the MCF-P-B65 coil. Post stimulation, participants performed two computerized forced-choice reading tasks. The phonological decoding task required participants to determine if a pseudohomophone (target) or pseudoword (foil) could be pronounced like a real word (i.e. “roze” vs “filk”). The lexical decision task required participants to determine if a word (target) or pseudoword (foil) is a real word (“rose” vs “filk”). Reaction time and accuracy data for each task were collected via E-Prime. Paired t-tests of accurate responses for the whole task, target words, and foil words were computed using R with the t.test function. Results: No significant differences were found for accuracy in either condition. Reaction time was slower after stimulation in all conditions involving pseudowords (foils in the lexical decision task, foils and targets in the phonological decoding tasks). Slower reaction time reached significance for the pseudowords in the phonological decoding task (t(6) = 2.74, p = 0.03) with all participants decreasing reaction time from the sham to the active condition. Surprisingly, while the pseudowords in the lexical decision task trended toward significance (t(10) = 1.25, p = 0.2), there was not a significant trend for pseudohomophones in the phonological decoding task (t(6) = 0.73, p = 0.5). Conclusions: cTBS stimulation to SMG slowed pseudoword decision making processes. This effect, however, was specific to pseudowords and did not extend to pseudohomophones. Previous research from our lab has found that iTBS stimulation of SMG preferentially affects decision-making of pseudohomophones. Taken together, these findings suggest that stimulation type may differentially modulate subcomponents of phonological decoding. This dissociation underscores the need to refine stimulation protocols based on the cognitive architecture of the target task.
Topic Areas: Reading,