Altered spectral patterns of aperiodic electroencephalography in autism

The altered ratio of neural excitation (E) and inhibition (I) has been proposed to the etiology of autism spectrum disorder (ASD). Previous studies suggested a lower E/I ratio in autistic individuals compared to non-autistic comparisons (NACs) in specific brain regions. Whether the E/I imbalance was present in ASD in adolescence and adulthood and how the ratio correlated with clinical manifestations are unclear. This study aimed to investigate the E/I ratio in autistic adolescents and adults by using resting-state electroencephalography (EEG) signals.

The study recruited 63 autistic adolescents and adults, and 53 NAC. EEG was recorded while participants were asked to stare at the cross mark on the monitor and close their eyes for 3 min each. We used fitting oscillations and one-over-F function to separate periodic and aperiodic components, then fitting the curve to a linear line.

Autistic participants exhibited a flatter spectrum power slope and a smaller offset compared to NAC. Group differences existed in the relationship between slope and Autism Spectrum Quotient (AQ) scores, with higher AQ total scores correlated with lower aperiodic exponent in ASD. In ASD, a lower aperiodic exponent was significantly correlated with greater difficulty in mindreading, low registration, and working memory difficulty.

The slope of the aperiodic component in ASD was flatter across frontal and posterior regions, supporting that the ASD group may have an E/I imbalance. Besides, the slope might be associated with overall autistic severity, empathy, sensory characteristics, and real-world working memory difficulties that warrants further investigation.