Electrophysiological Marker of a Potential Excitatory/Inhibitory Imbalance in Children with Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social interaction and the presence of stereotypic behaviors or restricted interests. To explore possible consequences of an excitatory/inhibitory (E/I) imbalance on the visual system in ASD, we investigated spatial suppression in 16 children with ASD and 16 neurotypical comparison children from 6 - 12 years of age using a visual motion processing task during high-density electroencephalography (EEG) recording in order to derive the N1 event related potential (ERP). Consistent with prior behavioral research, neurotypical participants displayed spatial suppression in conditions of large, high-contrast sinusoidal gratings as indexed by delayed N1 response latency. As predicted, children with ASD displayed weakened surround suppression, i.e. shorter N1 response latency to large, high-contrast sinusoidal gratings. However, this study also unexpectedly revealed that children with ASD showed longer N1 latencies in response to small, high-contrast sinusoidal gratings as compared to neurotypical control children. Although there were no statistically significant differences between children with ASD and NT children for N1 peak amplitude, there was a strong negative correlation between N1 amplitude represented in absolute values for large, high-contrast sinusoidal gratings and hyper-responsiveness item mean scores on the Sensory Experiences Questionnaire for children with ASD, but not for NT children. As predicted, no significant differences were found within or between groups in the low-contrast experiment. Our results are indicative of weakened spatial suppression and deficits in contrast gain in children with ASD, suggestive of an underlying E/I imbalance in ASD.