The association between infant EEG aperiodic exponent and the trajectory of restricted and repetitive behaviors for toddlers with and without autism.

Background: Restricted and repetitive behaviors (RRB) are core features of autism but are also observed in typical development. Our understanding of the neural underpinnings of RRBs is limited. Given that excitation-inhibition (E/I) balance may underlie RRBs, we aimed to evaluate the relationship between aperiodic exponent (as a proxy of E/I balance) and changes in RRBs over time in infants with and without elevated likelihood of autism.

Methods: Resting-state EEG data were collected from 12-to-14-month-old infants and aperiodic exponent was calculated. Parent-reported RRBs were obtained using the Repetitive Behavior Scale-Revised questionnaire to measure the severity and change in RRBs from 12-to-36 months. Multiple linear regressions were conducted to assess relationships between aperiodic and change in RRBs.

Results: Marginal effects analysis of linear regressions revealed significant associations such that lower aperiodic exponent was associated with elevated RRBs reported over time across the whole sample ([Formula: see text]=0.31, β= -0.21, p = 0.01), which was more prominently observed in the infants who later received an autism diagnosis (δy/δx = -15.57, p < .001).

Conclusions: Results suggest that early EEG aperiodic activity may serve as a potential correlate of increased manifestation of RRBs. Longitudinal studies are needed to elucidate whether the early trajectory of aperiodic activity in development influences the severity of RRBs in childhood.