Differences In Electrophysiological Indices of Cognitive Control In the Younger Siblings of Children with Autism

Background: Younger siblings of children with autism (Sibs-ASD) are at a heightened risk for the development of clinical and subclinical cognitive and social deficits characteristic of the Broader Autism Phenotype (BAP).  In typically developing young children, the development of executive attention skills (e.g., cognitive control) are important for social development.  An understanding of executive attention in Sibs-ASD may provide a foundation for further exploring the social variability observed among Sibs-ASD and the BAP.

Objectives: The aims of the current study were to identify behavioral and electrophysiological differences between Sibs-ASD and a sample of younger siblings of children without a diagnosis of an ASD (Sibs-COM) on a modified version of the Children’s Attention Network Task (ANT).  It was hypothesized that a) Sibs-ASD would display a greater number of errors and slower reaction time on incompatible trials of the Children’s ANT and b) they would display atypical electrophysiological indices of executive attention (smaller N2 and larger P300).

Methods: Preliminary data was collected on 28 preschoolers: 14 Sibs-ASD (8 males) and 14 Sibs-COM (8males). Groups were matched on age, t(26)=.06,ns and verbal IQ, t(26)= .96, ns.  Participants completed the Children’s ANT while Electroencephalograph (EEG) was collected continuously using a 128-channel dense array system.  The N2 and P300 were analyzed at midline scalp sites on correct compatible and incompatible trials. The N2 was analyzed as the mean amplitude ±50 ms of the largest negative peak between 250 and 400 ms while the P300 was analyzed as the mean amplitude ±50 of the largest positive peak between 500-700 ms after stimulus onset.

Results: Behaviorally, there were no difference between groups on performance on the Children’s ANT. Both groups made significantly fewer errors on compatible compared to incompatible trials F(1,26)= 16.43, p<.01, η²= .39. Separate 2(Group: Sibs-ASD vs Sibs-COM) X 2 (Compatibility: Incompatible vs. Compatible) X 4(Scalp Site: Fz, FCz, Cz, and Pz) repeated measures ANOVAs were conducted for the mean amplictue N2 and P300.  No significant group differences in N2 mean amplitude were observed; however, the P300 amplitude was predicted by the interaction of compatibility and diagnostic group, F(1,23)=4.89, p<.05, η²= .18.  Post hoc analyses revealed that for Sibs-ASD, the P300 amplitude was enhanced (more positive) on compatible compared to incompatible trials, t(14)= -2.17, p<.05. In contrast, this was not observed for Sibs-COM.  Also, a marginal effect of diagnostic group on P300amplitude was observed for compatible trials such that Sibs-ASD demonstrated larger P300 mean amplitude compared to Sibs-COM, t(23)=1.95, p=.06. 

Conclusions: Overall, Sibs-ASD and Sibs-COM were comparable on behavioral performance of the Children’s ANT; however, compatibility of ERPs differentiated the two groups.  Behaviorally, compatible trials were easier (faster response time and fewer errors) than incompatible trials for both Sibs-ASD and Sibs-COM; however, the enhanced amplitude P300 on compatible trials for the Sibs-ASD may reflect inefficient attention allocation or a compensatory strategy.  Due to the importance of executive attention in social development, poorly developed executive attention may contribute to the social variability in Sibs-ASD and provide a model for exploring social deficits in ASD.