665: Repetition-Related Early ERP Dynamics During Emotion�Attention Processing in Within-Subject tDCS

Topic: Experimental (Non-clinical) Human Studies
Subtopic: Non -specific to any diagnosis, Neuromodulation (e.g. rTMS, tDCS, FUS, DBS, biofeedback)

Background and Aims: Background

Transcranial direct current stimulation (tDCS) is widely used to probe causal links between cortical excitability and cognition, but reliable single-session effects in healthy adults remain debated. Emotion–attention tasks are especially useful for testing neuromodulatory claims because task-irrelevant emotional stimuli can interfere with goal-directed behavior. Event-related potentials (ERPs) provide temporally precise markers of this processing cascade, from early perceptual gain to later emotional evaluation. However, repeated exposure to the same task can itself alter ERP amplitudes, making it important to separate stimulation-specific effects from repetition-related neural dynamics.

Aims

This study examined whether a single session of anodal tDCS modulates behavioral performance and ERP markers of emotion–attention processing in healthy adults. A second aim was to test whether a within-subject, double-blind crossover design could dissociate acute neuromodulatory effects from changes driven by task repetition.

Methods: Fifty-three healthy adults completed a color-detection task during EEG recording. Emotional faces showing neutral, pain, anger, or happy expressions were presented as task-irrelevant distractors inside colored frames, and participants responded to the frame color. Each session included three identical task blocks: baseline, post–first stimulation, and post–second stimulation. Participants received both active anodal tDCS and sham stimulation in counterbalanced order within the same session. Active tDCS was delivered for 20 min at 1.5 mA, with the anode over C3 and the cathode over the supraorbital region. Reaction times and ERP components indexing early sensory processing, face encoding, attentional evaluation, and sustained emotional processing were analyzed across predefined regions of interest.

Results: Reaction times decreased from baseline to the first post-stimulation block, F(1,51)=8.53, p=.005, ηp²=.143, indicating practice-related improvement. Across all three time points, responses improved from baseline to the first repetition but showed no further facilitation thereafter. No behavioral differences emerged between active and sham stimulation. For ERPs, no component showed reliable active-versus-sham modulation. Instead, P1 amplitudes increased after the first task repetition, F(1,51)=8.91, p=.004, ηp²=.15, and remained elevated across the session, particularly at posterior sites. N170 amplitudes were modulated by facial emotion, with pain faces eliciting larger responses than neutral and angry faces, but were unaffected by stimulation. P2 and late positive potential amplitudes showed no reliable stimulation-related effects.

Conclusions: In healthy adults, a single session of anodal tDCS did not measurably alter behavioral performance or ERP markers of emotion–attention processing beyond repetition-related changes. Early perceptual ERP responses were sensitive to repeated task exposure, whereas later emotion-related components remained comparatively stable. These findings highlight the need to model practice and repetition effects when interpreting short-term EEG changes in tDCS studies.

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Presenting Author: Behzad Rostami Sani
Submitting Author: Behzad Rostami Sani

Senior Author: Pedro José Montoya Jiménez

IASP 2026 Global Year theme of Neuropathic Pain: No

• Juan Lorenzo Terrasa Navarro: PhD - University of the Balearic Islands(UIB)
• Ana María González Roldán: PhD - University of the Balearic Islands(UIB)
• Pedro José Montoya Jiménez: PhD - University of the Balearic Islands(UIB)