ERP Responses to Social Stimuli and ASD Symptoms in “Unaffected” Siblings of Children with Autism Spectrum Disorder

Background: Siblings of children with autism spectrum disorder (ASD), even those who are not later diagnosed with ASD themselves (non-ASD ASIBs), often exhibit elevated ASD-related social-behavioral difficulties, known as the broad autism phenotype (BAP). Few studies have characterized the BAP in young children or investigated underlying neurophysiological mechanisms.

Objectives: The objectives of the present study were to a) characterize ERP responses to social and non-social stimuli and b) investigate the relationship between ERP responses and social-behavioral phenotypes in non-ASD ASIBs.

Methods: Twenty-six participants, ranging from 4 to 8 years old, were included in this study (non-ASD ASIBs: n = 11, 81.8% male, Mage = 5.96 years; TD controls: n = 15, 100% male, Mage = 5.60 years). Non-ASD ASIBs had an older sibling with a diagnosis of ASD but were not diagnosed with ASD themselves. TD controls had no family history of ASD. Participants completed an EEG experiment in which they passively viewed upright faces, inverted faces, upright houses, and inverted houses. The latency and amplitude of P1 was measured at the central occipital (OZ) electrodes. The latency and amplitude of N170 was measured at right posterior lateral electrodes (P8). Participants completed a battery of social-behavioral measures that included the Autism Diagnostic Observation Schedule – Second Edition (ADOS-2), the Childhood Autism Rating Scale (CARS), and the Social Responsiveness Scale (SRS). ERP component latencies and amplitudes were examined across conditions and groups in repeated measures ANOVAs. Correlations between ERP responses and social-behavioral variables were investigated using Pearson correlations.

Results: No main or interaction effects were observed for P1 latency or amplitude. For N170 latency, no main or interaction effects were observed. For N170 amplitude, the main effect of condition was significant, F(3, 69) = 10.22, p < .001, with faces eliciting larger amplitudes than houses, ps < .037, but no main effect of group or group by condition interaction was present. In TD controls, P1 and N170 latencies and amplitudes were not significantly correlated with any social-behavioral measures. In non-ASD ASIBs, several significant correlations emerged. Shorter N170 latency to upright faces was associated with higher ADOS-2 Social Affect severity score, r = -.71, p = .021 and marginally correlated with higher CARS total score, r = -.620, p = .056 and SRS total score, r = -.63, p = .068. Greater (i.e., more negative) N170 amplitude to inverted faces was correlated with higher ADOS-2 Social Affect severity score, r = -.66, p = .050 and higher SRS total score, r = -.80, p = .009, whereas greater N170 amplitude to upright faces was marginally correlated with higher ADOS-2 Social Affect severity score, r =-.62, p =.057, and higher SRS total score, r = -.62, p = .076.

Conclusions: These results indicate that ERP responses to social and non-social stimuli are similar in non-ASD ASIBs and TD controls. In contrast, correlations between ERP responses and BAP symptoms in non-ASD ASIBs suggest distinct relationships among neurophysiological functioning and behavior in ASD-related behavior in those at elevated genetic risk for ASD relative to TD controls.