EEG resting-state gamma power as a potential biomarker of excitation / inhibition imbalance in autism: Evidence from the Autism Biomarkers Consortium for Clinical Trials.

Identification of neural biomarkers is one of the central challenges in autism research as they could significantly advance our understanding of the brain mechanisms of symptom trajectories, serve as objective markers in clinical trials (e.g., for subgrouping children, or use for prognostic relationship), and lead to targeted treatment development. The Autism Biomarkers Consortium for Clinical Trials (ABCCT) is a naturalistic longitudinal study assessing a set of candidate electroencephalographic (EEG) biomarkers, their change over time, utility for group discrimination, and relation to clinical phenotype. Here, we focused on one of the ABCCT biomarkers - resting-state gamma-band neural activity - as a measure of excitation-inhibition balance, which is considered a key neurophysiological mechanism in autism. A total of 1597 EEGs were analyzed resulting in 399 autistic children and typically developing (TD) peers with resting-state EEG and behavioral measures at four timepoints: baseline, +6 weeks, +6 months, and +4 years. The results revealed a significantly increased gamma power in autistic children, suggesting an excitation-inhibition imbalance. This elevation was longitudinally associated with lower non-verbal IQ and memory for faces. Finally, males had higher gamma power in comparison to females and gamma power decreased with age in both groups. The study demonstrates that resting-state gamma power is related to cognitive ability across ages and timepoints of our study in autistic youth.