Resting State Aperiodic and Periodic EEG Activity in Preschool-aged Autistic Children: Differences from Neurotypical Peers and Links to Language Skills

Background: The neural mechanisms underpinning language development in autism spectrum disorder remain unclear. While prior studies have identified associations between resting-state EEG absolute power and language skills in autistic children, none have examined the distinct roles of aperiodic and periodic activity decomposed from the absolute power spectra on language development in autistic children. Methods: At the group level, we examined resting-state power spectra differences between 64 neurotypical and 64 autistic children age-matched from 2 to 6 years old, as well as within the autistic group based on language impairment status. At the individual level, we examined whether aperiodic and periodic EEG features were associated with concurrent language skills measured by natural language samples and a standardized language assessment in participants with autism spectrum disorder. Results: Autistic children exhibited higher aperiodic offset, but not aperiodic slope, compared to their neurotypical peers. Autistic children with lower aperiodic offset demonstrated better concurrent expressive and receptive language skills, but not nonverbal cognition. While we did not find significant differences in peak alpha frequency and peak alpha periodic power between neurotypical and autistic children, after separating the autistic group by language impairment status, we found that autistic children with language impairment had significantly lower peak alpha periodic power compared to autistic children without language impairment and their age-matched neurotypical peers. Autistic children with higher peak alpha periodic power demonstrated better concurrent language and nonverbal cognitive abilities. Limitations: Findings were based on cross-sectional data. Future longitudinal studies are needed to explore whether early variations in resting-state EEG aperiodic and periodic features are predictive of later language development in autistic children or vice versa. Conclusions: The characteristic features of resting-state power differences vary when comparing autistic children to neurotypical peers versus comparing within the autistic subgroup based on language phenotypes. These findings underscore the importance of considering the heterogeneity of the autism spectrum when investigating the neural mechanisms underlying language development in autistic children.