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Sketchpad Series

The impact of prefrontal tDCS on periodic and aperiodic contributions to resting-state EEG

Poster Session A - Saturday, March 29, 2025, 3:00 – 5:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Ashley R. Rosenfeld¹ (asrrosen@ucsc.edu), Cameron S. Carter², Megan A. Boudewyn¹; ¹University of California Santa Cruz, ²University of California Irvine

Studies exploring the effects of transcranial direct current stimulation (tDCS), a non-invasive neurostimulation technique, on cognitive performance have increased exponentially over the last decade. However, the mechanism by which tDCS modulates the underlying neural circuits is not yet understood. There is evidence that, rather than influencing neural spiking directly, tDCS modulates neural oscillations (Chase et al., 2020), and may also impact excitatory/inhibitory balance in cortex (Bunai et al., 2021). Interestingly, recent methodological advances have highlighted the contributions of periodic (rhythmic oscillatory activity) and aperiodic activity to the EEG signal, with aperiodic activity thought to be related to cortical excitatory/inhibitory balance (Gao et al., 2018). Thus, the goal of the current study is to examine tDCS-related changes in aperiodic contributions to the EEG signal and periodic oscillatory activity across several frequency bands of interest. We will examine resting-state EEG collected after a 20-minute tDCS protocol was administered in three conditions using a within-subjects design: PFC-targeted active stimulation, active control stimulation, and sham stimulation. Data collection is already complete (N=75). We will parameterize neural power spectra into periodic and aperiodic components using the spec-param method (Donoghue et al., 2020) for eyes-open and eyes-closed resting state EEG data separately. Of particular interest will be the slope of the aperiodic signal, which we hypothesize will vary as a function of tDCS protocol condition. This analysis is expected to provide new insights into the impact of tDCS on oscillatory dynamics in key neural circuits underlying higher-order cognition.

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