Electrophysiological Correlates of Face Processing In Simplex and Multiplex ASD Families

Background: Broader autism phenotype (BAP) is the expression of mild autism-like traits in relatives of individuals with autism spectrum disorder (ASD). Dawson and colleagues (2005) demonstrated that parents of two or more individuals with ASD may exhibit atypical early ERPs to faces, suggesting that basic face processing may be an endophenotype for the disorder. Previous research suggests that a number of BAP traits, including social deficits, are more strongly expressed in parents of multiple children with autism than in parents of only a single child with autism, indicating that a greater number of variants in autism-related genes may be present in multiplex families (Losh et. al 2008). Face processing deficits may also differ in simplex vs multiplex families.  

Objectives: ERP investigations have provided information about timing and specification of brain functioning related to early stage processing of faces; these processes occur < 200 ms after stimulus onset. The objective of this project is to extend the work of Dawson et al. (2005) to address the P1 attention component and the specialized face-processing N170 component in simplex parents, multiplex parents, and parents without a family history of ASD

Methods: Simplex parents were recruited from the UW Simons Simplex Collection; multiplex parents were recruited from the UW CPEA Family Study of Autism. EEG data was collected to upright and inverted faces and houses. The P1 and N170 ERP components were analyzed from occipital and posterior temporal regions. Preliminary data were available from 20 parents from simplex families and 24 parents from multiplex families; data collection is ongoing.

Results: Parents of children with ASD showed characteristic ERP responses that are similar to those found in neurotypical adults. Specifically the P1 and N170 was greater in amplitude to faces than houses and N170 latency was faster to faces than houses. The N170 was also faster but of lower amplitude to upright than inverted faces. In preliminary group analyses, multiplex families had significantly greater P1 amplitude and faster N170 latencies; group did not interact with stimulus type or orientation.

Conclusions: ERPs allow one to disentangle these early stage processing steps and assess whether there are basic level perceptual and attention impairments. Preliminary data suggest that multiplex and simplex families show ERP responses to faces and houses that are similar to neurotypical adults and ASD multiplex and simplex families do not differ in face processing. However, there may be subtle group differences in brain processes underlying attention and category processing as assessed by the P1 and N170. Additional analyses will examine behavioral face memory tasks and their relation to these ERP components. Further, data collection is ongoing and as the sample size increases, we will be able to examine heterogeneity in face processing.