Eyes-closed resting state EEG reveals clearer and more stable group differences between autistic and neurotypical individuals than eyes-open resting state EEG

Background Resting-state electroencephalography (rs-EEG) has been widely used to explore neural dynamics in Autism Spectrum Condition (ASC). However, inconsistencies in findings across studies remain a challenge, partly due to variations in brain state, such as eye conditions (eyes-open vs. eyes-closed). This study aims to examine rs-EEG differences between ASC and neurotypical (NT) participants, focusing on the influence of eye condition. Methods A total of 300 participants (126 ASC) were included. Rs-EEG data were analysed across eyes-open, eyes-closed, and difference between eye conditions, with 726 variables assessed per participant. Linear regression and effect size (η 2 partial ) were used to identify group differences, complemented by cluster-based permutation testing and bootstrapped split-half validation for reliability. Results Group differences were most pronounced in the eyes-closed condition, particularly for relative power and multiscale entropy (MSE). Compared to neurotypical participants, ASC participants exhibited reduced frontal coarse-scale MSE, increased delta power, and decreased alpha power, suggesting altered local-global neural dynamics. Cross-validation revealed greater reliability of effects in the eyes-closed condition compared to eyes-open or difference between eye conditions. Conclusions Eye condition plays a critical role in detecting rs-EEG differences between ASC and NT groups, with the eyes-closed condition yielding more consistent and pronounced effects. These findings highlight the importance of controlling brain state in rs-EEG studies and suggest that integrating eye condition effects with other biomarkers may improve identification of neural differences associated with ASC.