20103
Preserved Configural Processing in High-Functioning Adults with Autism: An EEG/ERP Study
Typical developing adults are experts in the recognition of human faces and their expressions because they are capable of facial configural processing. Individuals with autism spectrum disorders (ASD) are impaired in face perception. This impairment has been associated in some studies to deficits in facial configural processing. Configural processing encompasses analysis of the generic position of the facial features (first-order relations), analysis of the spacing among them (second-order relations), as well as the ability to glue them in a unified face gestalt (also known as holistic processing).
Objectives:
To study the neural correlates of configural processing in adult ASD, by using a set of stimuli with distinct processing requirements (from first to second order configural and holistic processing) and to investigate behavioural and neurophysiological indicators of configural processing. Differentiation between these levels of face processing is possible by using face stimuli that lack some of the information available in photographic images, for example schematic faces lack second-order information, whereas Mooney faces lack first-order and second-order information.
Methods:
The sample consisted of 25 participants: we measured using electrode arrays of 40 channels event-related potentials (ERPs) in 9 high-functioning adults with ASD and 16 healthy controls, during a face decision task, using a comprehensive set of photographic, schematic and Mooney upright and inverted faces, and as control scrambled images. These heterogeneous set of stimuli involve differentially the various levels of configural processing (first-order, second-order and holistic). Subjects with ASD were recruited from the Neurodevelopment and Autism Unit from Child Center of Hospital Pediátrico, Centro Hospitalar Universitário de Coimbra and the Coimbra and Viseu Autism Associations (APPDA). ASD subjects were male (mean age = 23.1 years; SD = 7.04). The diagnosis was based on the results of gold standard instruments such as parental or caregiver interview (Autism Diagnostic Interview– Revised, ADI-R) and direct structured proband assessment (Autism Diagnostic Observation Schedule, ADOS). The clinical criteria for autistic disorder were based on DSM-V. The 16 healthy controls were men (mean age = 23.4 years; SD = 5.06). Control subjects were screened for ASD with the Social Communication Questionnaire. Electrophysiological data were recorded using a NuAmps 40 Channel Quick-Cap (Compumedics, NeuroScan, USA). Analysis of variance (ANOVA) with within subjects factors face type (upright, inverted and scrambled) and hemisphere (left and right) and between subjects factor group (ASD, Controls). Significance level was set at (α)=0.05(p<0.05).
Results:
Behaviorally, there were no differences in performance between ASD and healthy controls. Both groups found it easier to recognize photographic and schematic faces than Mooney faces. We were able to detect that at the electrophysiological level that subjects with ASD displayed a normal configural processing related N170 inversion effect (being significant bilaterally).
Conclusions:
We conclude that the adult ASD subjects show positive electrophysiological evidence for sparing of facial configural processing, using an extended set of faces. Given that when their attention is oriented to the faces they are able to perform facial configural processing, the results do not seem to support reports of local processing biases in the ASD population.