Ketamine alters the aperiodic EEG exponent in major depression: implications for cortical E/I balance and treatment prediction.
Therapeutic advances in psychopharmacology January 1, 2026 Yujuan Liu, Xiaorong Liu, Sebastian Olbrich et al.
Ketamine, a rapid-acting antidepressant for treatment-resistant depression, may work by altering the brain's excitation-inhibition balance, measurable via the aperiodic exponent of EEG power spectra. In a placebo-controlled trial of 24 patients with major depressive disorder, ketamine infusion significantly reduced the aperiodic exponent across the scalp. Patients who responded to treatment had steeper pretreatment occipital aperiodic exponents, which predicted better outcomes. A meta-analysis within the study revealed substantial variability in ketamine's effect on this measure. The occipital aperiodic exponent may serve as a biomarker for predicting antidepressant response, but further large-scale studies are needed.