Neural Correlates of Individual Facial Feature Processing in ASD

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition, characterized by difficulties in social communication alongside narrow interests, repetitive behaviors, and sensory sensitivities (American Psychiatric Association, 2013). Atypical neural responses to faces is thought to contribute to social deficits in ASD (Kang et al., 2018). Compared to typically developing (TD) controls, individuals with ASD exhibit delayed brain responses to upright faces at a face-sensitive event-related potential (ERP) known as the N170 (Bentin et al., 1996; McPartland et al., 2004). Yet, questions persist regarding how those with ASD respond to different classes of facial stimuli. Thus, investigating the physiology of the N170 to distinct facial percepts may provide additional insight on nature of atypical face perception in ASD and its relation to the clinical phenotype.

Objectives: To confirm previous findings that temporal processing of upright faces are delayed in individuals with ASD and examine differential response patterns for classes of facial stimuli across TD and ASD groups.

Methods: ERPs were recorded from 11 adolescents and adults with ASD (10 male and 1 female) and 21 TD controls (18 male and 3 female) using a 128-channel Geodesic Sensor Net. The sample was matched on age (ASD: M=22.44, SD=8.45; TD: M=25.57, SD=7.77) and IQ (ASD: M=101.82, SD=19.43; TD: M=112.81, SD=14.3051). Participants were presented with two stimulus blocks each composed of 240 gray-scale digital images on a computer monitor with a black background. The first block included eyes, upright faces, inverted faces, and distorted faces. The second block was composed of hands, noses, lips, and faces. The N170 was extracted from six electrodes over the right occipitotemporal scalp. Peak amplitude and latency were analyzed in response to eyes, upright faces, inverted faces, and distorted faces. Data analysis for N170 amplitude and latency in response to hand, nose, lips, and face stimuli is ongoing. ASD symptomology was measured using the Autism Diagnostic Interview-Revised (ADI-R) and DSM-IV clinical diagnosis was determined by the senior author.

Results: There was a significant main effect of condition on N170 latency (F(3, 28)=9.135, p<0.001) and N170 amplitude (F(3, 28.00)=16.387, p<0.001) across groups, with faster N170 components to eyes than upright faces, distorted faces, and inverted faces. Additionally, participants with ASD exhibited slower right N170 latency for upright faces than TD individuals (ASD: M=172.00, SD=24.27; TD: M=150.48, SD=26.09; p=0.031). However, no significant associations were found between groups in eyes, distorted face, and inverted face conditions.

Conclusions: Consistent with previous research, individuals with ASD exhibit longer N170 latencies to upright faces than TD individuals. Our findings also show that both groups display enhanced response to eye conditions, suggesting shared salience of eye stimuli. Comparable neural responses between groups for other stimuli suggests atypical neural responses to faces in ASD may depend on prototypic face configuration. Additional EEG research studying top-down face processing is needed to elucidate the relationship among holistic and configural face processing in ASD.