21405
Event-Related Potential and Induced Gamma 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. There are several theories describing the neurobiology of underlying deficits. 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.
Objectives:
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, SD= 4.9 yrs) and typically developing children (CNT group, N=21,14.9 yrs, SD= 4.5 yrs) in behavioral (reaction time and accuracy), induced gamma and ERP correlates of processing emotional information from facial expressions. Children with ADHD (N=14, 14.4 yrs, SD=3.9 yrs) served as a contrast group in induced gamma analysis.
Methods:
Task had 4 different conditions: either to identify the gender or the emotion of the face. Dense-array EEG was recorded using 128 channel 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.
Results:
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).
Conclusions:
The results of the study 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 autism. The results of the study contributes to better understanding of possible neurobiological mechanisms resulting in abnormal processing of facial information resulting in deficient social communication and mentalizing abnormalities in autism spectrum disorders. Analysis revealed larger difference waves in ASD subjects in the N170 component from the occipital cortex and in the P3a component from the frontal cortex. The parietal P3b measurements also showed a larger amplitude and shorter latency when viewing emotion in autism, representing more evaluation of one’s performance after a task. The measurement of single trial induced gamma oscillations with advanced alignment technique provides confirmation that differences exist between how children with autism, and those with typical development process emotional stimuli.