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Sketchpad Series

A Transcranial Direct Current Stimulation Study of Speech Error Monitoring

Poster Session E - Monday, March 31, 2025, 2:30 – 4:30 pm EDT, Back Bay Ballroom/Republic Ballroom

Nathan Caines¹ (ncaines@ucsc.edu), Megan Boudewyn²; ¹University of California Santa Cruz

Speech production is a complex, multi-step process, and yet speech error rates are surprisingly low. This is thought to be attributable to an error monitoring mechanism, although accounts differ as to the nature of this mechanism and the extent to which error monitoring during speech relies on domain-general cognitive control processes. The goal of the current study was to use transcranial direct current stimulation (tDCS) to test the hypothesis that prefrontal-cortex-supported error monitoring circuits (and their electrophysiological correlates) support error monitoring during speech. Specifically, we will assess speech error rates and neural oscillations in the theta band (4-7 Hz) during a tongue twister task. In this within-participants study (current N = 13), participants will complete the tongue twister task while EEG is recorded after receiving 20 minutes of prefrontally-targeted tDCS stimulation versus sham. Preliminary results suggest that prefrontal-cortex-targeted tDCS reduces speech error rates on the tongue twister task compared to sham (Stim:2.39%, Sham:6.8%). Once data collection is complete, behavioral analysis will compare error rates across tDCS protocol conditions. EEG data analysis will examine theta power in the period immediately preceding speech production on tongue-twister trials. We predict that speech error rates will be significantly reduced for PFC tDCS compared to sham stimulation. We also predict that increased theta power in the pre-production period of tongue twister trials will be elicited in the PFC tDCS conditions compared to sham stimulation. This pattern of results would align with speech production models that posit prefrontally-mediated error monitoring mechanisms.

Topic Area: LANGUAGE: Other