EEG Correlates of Face Processing in a Large ASD Sample

Background: Social and communicative impairments are a core feature of ASD, and behavioural impairments in face processing are commonly reported (Dawson et al, 2005). In order to understand whether these impairments reflect atypicalities in the neural circuitry underlying face perception, some researchers have used the high temporal resolution of EEG to investigate individual stages of face processing in ASD. Latency and amplitude differences of face-sensitive event related potential (ERP) components have been reported in adults (e.g. McPartland et 2011) and children (e.g. Webb et al, 2005) with ASD. Here we describe the results from the Longitudinal European Autism Project (LEAP), a component of the EU-AIMS study.

Objectives: To characterise the nature and extent of atypicalities in EEG correlates of face processing in a large sample of individuals with ASD and age- and IQ-matched neurotypical controls.

Methods: Participants aged from 6-30 years of age watched 168 trials in which interleaved upright or inverted faces were presented, whilst their EEG was recorded. Data was centrally pooled, harmonised and segmented by trial, and artefacts were rejected. Neural responses to upright and inverted faces were averaged separately. The final analyses contain data from 496 individuals (271 with ASD).

Results: ERP responses to upright faces had slower latencies in ASD, but overall did not differ in amplitude. The effect of inversion was absent in children with ASD; the inversion effect emerged in adolescence and adulthood, but with a reduced magnitude compared to neurotypical controls. Face-sensitive ERP components were lateralised to the right hemisphere in both groups.

Conclusions: Longer ERP peak latencies suggests slower and/or less efficient processing of faces in ASD, from childhood to adulthood. An absence of an inversion effect in children with ASD, and a reduction in its magnitude in adolescence and adulthood, is suggestive of reduced cortical specialisation for faces. This may result from a lack of motivation to attend to other people, leading to the slower development of expertise for faces across development in ASD.