The Emergence of ADHD Comorbidity in School-Aged Children with ASD Impacts Resting-State Brain Networks Dynamics

Background: EEG microstates are defined in the literature as quasi-stable topographies of the electric fields in the ongoing EEG, lasting approximately 100 milliseconds and representing the sub-second coherent activation within global functional brain networks. Recently, we found early alterations in the spatio-temporal dynamics and syntax of brain states in toddlers and preschoolers with autism spectrum disorders (ASD) compared to their typically developing (TD) peers.Method: Here, we investigated how these alterations evolve over time and how they are impacted by the emergence of comorbid attention deficit/hyperactivity disorder (ADHD) in ASD among 49 school-aged children (19 children with ASD-only, 15 children with ASD+ADHD, and 15 TD children). Results: We found a decreased prevalence of all temporal parameters of microstate map B in school-aged children with ASD compared to TD peers. Children with ASD+ADHD had a significantly lower prevalence of map B compared to children with ASD-only. Moreover, children with ASD+ADHD had a higher prevalence in time coverage and occurrence for microstate map A than children with ASD-only and TD children. Map E of the ASD+ADHD group has a weaker spatial correlation with map E of ASD-only and TD groups. Moreover, the GEV of map E was significantly decreased for the ASD+ADHD group compared to the ASD-only group. We found that the transition probabilities between maps of the ASD+ADHD group, particularly for map B, differed from ASD-only and TD groups. Exploratory longitudinal analysis showed an increase in all temporal parameters of map B in TD children but a decrease in children with ASD, regardless of the ADHD comorbidity.Limitations: The present study has a small sample size and does not include a group of children with ADHD-only. Conclusion: Our results show that ADHD comorbidity in school-aged children with ASD impacts the spatial organization and the temporal dynamics of whole-brain networks. Further longitudinal studies are needed to understand better the impact of the emergence of ADHD comorbidity in ASD across ages.