Face/Object Perception in Infant Siblings of Children with Autism Spectrum Disorders (ASD)

Background: Previous behavioral and neural studies have revealed face processing atypicalities in individuals with Autism Spectrum Disorders (ASD) and their first-degree relatives. Because these atypicalities are seen in both affected and unaffected family members, they may be considered an “endophenotype” of ASD, reflecting a genetically-mediated risk factor for the disorder. Objectives: To study the development of this potential endophenotypic marker, we investigated Face vs. Object perception in 8-month-old infant siblings of children with ASD (“High-Risk” infants) in comparison to infants from families without autism history (“Low-Risk” infants), using stimuli identical to those employed in our event-related potentials (ERP) study measuring neural responses to Faces vs. Objects at 10 months of age. Methods: Forced-Choice Preferential Looking was used to measure infants' preferences in three different Face/Object studies: 1) “Faces vs. Objects”: This measured infants' preferences for pictures of Faces vs. Objects (the objects being Toys), with values greater than 50% indicating a significant face preference. 2) “Faces vs. Objects: Inversion Effects”: This study compared infants' preferences for Upright vs. Inverted Faces to their preferences for Upright vs. Inverted Objects (the objects being Strollers), with “Difference Scores” [Upright Pref(faces)-Upright Pref(objects)] greater than 0% indicating a greater inversion effect for Faces. 3) “Emotional Faces”: This measured infants' preferences for different emotional valences (Happy vs. Disgusted vs. Neutral), with values greater than 50% indicating a preference for one emotion over another. Pictures of Faces and Objects were manipulated in Matlab so that they were matched in luminance, contrast and spatial frequency content. Results: In Study 1, both subject groups showed a significant preference for Faces over Objects, although the effect was larger in Low-Risk (67%) than High-Risk (60%) infants. In Study 2, both subject groups exhibited a significantly larger inversion effect for Faces than for Objects (Difference Score ~12%), with no difference between groups. Preliminary data from Study 3 suggest that while Low-Risk infants preferred Disgusted over Neutral Faces, High-Risk infants exhibited the opposite preference. Conclusions: These preliminary behavioral data suggest differences in Face/Object perception between High-Risk and Low-Risk infants, although group differences appear smaller than those observed in our ERP measures. Together, our behavioral and ERP measures of Face/Object processing provide a potential endophenotypic marker associated with ASD.