ERP and EEG Oscillations Study of Facial Expression Processing Deficits in Autism

Autism spectrum disorder (ASD) is one of neurodevelopment disorders, which presents with impairments in communication and social skills, and stereotyped, repetitive patterns of behavior. Disturbances of affective reactivity and innate inability to perceive and respond to the social cues including facial emotional expressions in a typical and appropriate manner are the hallmark deficits of ASD. The study used event-related potentials (ERP) and single-trial induced EEG gamma oscillations recording in a modification of a "Theory-of-mind" (ToM) test using facial emotional expression recognition to test emotional responsiveness in children with autism and typical age-matched children. Autism is featured by difficulty in decoding affective facial cues. The goal of the study was to find the differences between ASD group (N = 19, mean age 16.3 4.9 years) and typically developing children (CNT group, N = 21, 14.9 4.5 years) in behavioral (reaction time and accuracy), induced gamma and ERP correlates of processing emotional information from facial expressions. The task had four different conditions: either to identify the gender or the emotion of the face. Dense-array EEG was recorded using EGI system. The ERP components analyzed in the study were parieto-occipital N170, frontal P3a, and parietal P3b, while induced gamma oscillations were recorded at 8 frontal and parietal sites. ERP measures yielded following group differences: N170 showed a more negative amplitude in the ASD group than controls when identifying emotional faces (F = 5.66, p = 0.023). The latency of N170 was prolonged in the ASD group (F = 7.54, p = 0.01). The ASD group had a larger frontal P3a amplitude as compared to controls when differentiating emotions (F = 5.15, p = 0.03). In the emotion recognition conditions, P3b had larger amplitude in autism (F = 4.17, p = 0.049). Induced gamma (35-45 Hz) oscillations in ASD showed significant differences from controls at all 8 sites of recording in facial emotion discrimination condition (p < 0.05). These results indicate that more effort is required for an individual with autism to recognize emotion rather than gender from viewing a face. Abnormal processing of emotional stimuli may provide an explanation for some of the social and communicative deficits observed in children with autism. Keywords * Event related potentials * Single trial induced EEG * Autism spectrum disorder * Emotional recognition