Abstract:
Past research has found evidence for face processing differences between individuals with Asperger's syndrome (AS) and Neurotypical (NT) controls at the neurophysiological and behavioural levels. The aim of the first three experiments in this thesis was to further investigate the neurophysiological basis of face processing in AS and NT controls (matched for age and gender) through the analysis of event-related potential (ERP) data. ERPs were recorded from a) NT and AS adults and children during the explicit identification of basic expressions and neutral faces, b) AS and NT adults during the explicit identification of scared and neutral expressions filtered at low and high-pass spatial frequencies and c) AS and NT adults during the identification of objects, neutral faces, isolated eyes and mouths. Results found adults with AS to elicit significantly delayed N170 latencies to faces, isolated eyes and mouths, regardless of expression or spatial frequency in comparison to NT controls. However, adults with AS did not elicit delayed N170 latencies to objects. These findings suggest AS adults are slower to recruit neuronal networks involved in processing both facial configurations and features. In contrast to adults, ERPs to facial expressions did not differ significantly between NT and AS children, which may result from incomplete development of the neuronal generators of these components and/or intervention. In the last two experiments, NT and AS adults were examined on their ability to a) identify complex expressions from manipulated photographs of actors expressing these emotions through the eye region and b) discriminate between congruent and incongruent face and voice expressions. Results showed that in comparison to NTs, adults with AS were impaired at identifying complex expressions from the eyes and at discriminating congruent and incongruent expressions in the face and voice. These findings provide further evidence for impaired processing of the eye region in AS and suggest that individuals with AS may be impaired at integrating face and voice expressions. Together, these results provide neurophysiological and behavioural evidence for face processing differences between AS and NT adults. Further research, however is needed to understand these differences.