Opposing Modulation of EEG Aperiodic Component by Ketamine and Thiopental: Implications for the Noninvasive Assessment of Cortical E/I Balance in Humans.
bioRxiv : the preprint server for biology August 22, 2025 Jose A Cortes-Briones, Juan Urrutia-Gandolfo, Pablo A Estevez et al. preprint
The balance between excitatory and inhibitory (E/I) activity in the brain is important for normal function, and its disruption is linked to psychiatric disorders. In a randomized, double-blind, placebo-controlled study, healthy volunteers received low doses of ketamine (which shifts E/I balance toward excitation) and thiopental (which shifts it toward inhibition) while their brain activity was recorded with EEG. The drugs altered the aperiodic exponent of the power spectrum in opposite directions, matching computational predictions. Changes in the exponent correlated with subjective and cognitive effects, suggesting that this measure could serve as a noninvasive EEG biomarker for transient shifts in cortical E/I balance.