People with Autism spectrum disorder (ASD) show difficulty in social communication, especially in the rapid assessment of emotion in faces. This study examined the processing of emotional faces in typically developing adults with high and low levels of autistic traits (measured using the Autism Spectrum Quotient—AQ). Event-related potentials (ERPs) were recorded during viewing of backward-masked neutral, fearful and happy faces presented under two conditions: subliminal (16 ms, below the level of visual conscious awareness) and supraliminal (166 ms, above the time required for visual conscious awareness). Individuals with low and high AQ differed in the processing of subliminal faces, with the low AQ group showing an enhanced N2 amplitude for subliminal happy faces. Some group differences were found in the condition effects, with the Low AQ showing shorter frontal P3b and N4 latencies for subliminal vs. supraliminal condition. Although results did not show any group differences on the face-specific N170 component, there were shorter N170 latencies for supraliminal vs. subliminal conditions across groups. The results observed on the N2, showing group differences in subliminal emotion processing, suggest that decreased sensitivity to the reward value of social stimuli is a common feature both of people with ASD as well as people with high autistic traits from the normal population.

Elevated “neural noise” has been advanced as an explanation of autism and autistic sensory experiences. However, functional neuroimaging measures of neural noise may be vulnerable to contamination by recording noise. This study explored variability of electrophysiological responses to tones of different intensities in 127 autistic and 79 typically-developing children aged 2–5 years old. A rigorous data processing pipeline, including advanced visualizations of different signal sources that were maximally independent across different time lags, was used to identify and eliminate putative recording noise. Inter-trial variability was measured using median absolute deviations (MADs) of EEG amplitudes across trials and inter-trial phase coherence (ITPC). ITPC was elevated in autism in the 50 and 60 dB intensity conditions, suggesting diminished (rather than elevated) neural noise in autism, although reduced ITPC to soft 50 dB sounds was associated with increased loudness discomfort. Autistic and non-autistic participants did not differ in MADs, and indeed, the vast majority of the statistical tests examined in this study yielded no significant effects. These results appear inconsistent with the neural noise account.

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LeDoux (1996 The Emotional Brain) has suggested that subconsciouss presentation of fearful emotional information is relayed to the amygdala along a rapid subcortical route. Rapid emotion processing is important because it alerts other parts of brain to emotionally salient information. It also produces immediate reflexive responses to threating stimuli in comparison to slower conscious appraisal, which is of important adaptive survival value. Current theoretical models of autism spectrum disorders (ASD) have linked impairments in the processing of emotional information to amygdala dysfunction. It can be suggested that impairment in face processing found in autism may be the result of impaired rapid subconscious processing of emotional information which does not make faces socially salient. Previous studies examined subconscious processing of emotional stimuli with backward masking paradigms by using very brief presentation of emotional face stimuli proceeded by a mask. We used an event-related potential (ERP) study within a backward masking paradigm with subjects with low and high autistic tendencies as measured by the Autism Spectrum Quotient (AQ) questionnaire. The time course of processing of fearful and happy facial expressions and an emotionally neutral face was investigated during subliminal (16 ms) and supraliminal (166 ms) stimuli presentation. The task consisted of an explicit categorization of emotional and neutral faces. We looked at ERP components N2, P3a, and also N170 for differences between subjects with low (< 12) and high (> 19) AQ.