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Modulation of Target-Related Spectral Dynamics Induced by Methylphenidate During an Oddball Task: A Pilot Study in a Mexican ADHD Population

Poster Session D - Monday, March 9, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Paloma Acacia Guzman Garcia^1,2, Claudia Xochitl Perez Ortiz¹, Ricardo Caraza¹; ¹Neurociencias Cognitivas y Neuroplasticidad, Hospital Zambrano-Hellion, ²Escuela de Medicina y Ciencias de la Salud, Tecnológico de Monterrey

Attention-deficit/hyperactivity disorder (ADHD) affects approximately 7% of Mexican youth, underscoring the need for context-specific neurophysiological markers. ​​We investigated whether quantitative EEG (qEEG) during a visual oddball task captures changes in time–frequency dynamics in ADHD and their modulation after methylphenidate administration in a Mexican cohort. This pilot study enrolled 11 ADHD patients (7F/4M; 8–23 years, 15.18 ± 6.12) and 11 controls (4F/7M; 8–29 years, 19.80 ± 7.83), each completing two EEG sessions; the ADHD group performed pre- and post-methylphenidate recordings. EEG (16-channel, g.tec, 10/20) was processed in MATLAB/EEGLAB. We computed event-related spectral perturbation (ERSP), inter-trial phase coherence (ITPC), and sensor-level coherence, and compared intra- and inter-group differences (α = 0.05). At baseline, ADHD showed greater delta-band event-related synchronization (ERS) at Fz relative to controls, consistent with slow-wave frontal predominance. After methylphenidate, low-frequency ERS increased over frontocentral sites, while lateral/posterior electrodes showed stronger event-related desynchronization (ERD), suggesting task-specific suppression of ongoing rhythms. Alpha-band ERS also rose at posterior sensors (PO7, Oz, Pz, P4) with medication, consistent with enhanced visuospatial attentional engagement. ITPC increased at higher frequencies, most prominently over right centro-parietal regions, indicating improved stimulus-locked phase alignment. Coherence was greater in controls across bands at baseline; in ADHD, methylphenidate produced notable parieto-occipital gains (e.g. P4–PO8), suggesting partial normalization of attentional-visual network coupling. These results support methylphenidate-related shifts toward more organized, phase-locked, goal-directed cortical dynamics during attention. Future work will expand the cohort and examine associations between oscillatory/phase metrics and neurocognitive performance to refine the clinical utility of qEEG biomarkers.

Topic Area: ATTENTION: Development & aging