Event-Related Potentials During Affective Face Processing and Social-Communicative Development in Infants at Low and High Risk for Autism Spectrum Disorders

Background: Despite the high heritability and pervasive nature of autism spectrum disorders (ASD), recent research suggests that a behaviorally-based diagnosis of ASD may not be accurate until 30 months of age (Turner & Stone, 2007). To identify individuals with ASD at younger ages, prospective studies have examined both behavioral and neural markers in infants from high-risk populations, such as infant siblings of children with ASD (sibs-ASD). In addition to being at increased risk of developing ASD, sibs-ASD often show atypical patterns of social-communicative development regardless of diagnostic outcome. The current study examines the extent to which neural correlates of affective face processing may be related to later measures of social-communicative development.

Objectives: The specific aims of the current study are: 1) To determine whether 6-month-old infants are able to discriminate different degrees of positive affective expression from a neutral expression and to determine if this ability is evident in face-specific (N290 and P400) and non-face-specific novelty (Nc) event-related potential (ERP) components; and 2) To investigate whether individual differences in ERP amplitudes during face processing at 6 months are associated with social-communicative measures at 9 months in sibs-ASD and infant siblings of typically developing children (sibs-TD).

Methods: This study included 10 infants (1 sib-ASD and 9 sibs-TD) recruited from a larger longitudinal study of social emotional development. At 6 months of age, ERP responses were recorded during the presentation of neutral faces and faces with different degrees of positive affect (small and large smiles). At 9 months of age, parents completed the MacArthur-Bates Communicative Development Inventory (CDI) Words and Gestures form. Relations between the amplitudes of ERP components and the CDI Phrases Understood and Early Gestures subscores were examined using Pearson r correlation coefficients.

Results: Infants were able to discriminate both small and large smiles from a neutral expression, as evidenced by larger amplitudes of the P400 and Nc components in response to the positive expressions compared to the neutral. Furthermore, amplitudes of the face-specific N290 and the novelty Nc components at 6 months were related to the infant's inventory of communicative gestures at 9 months. Specifically, a larger inventory of gestures was correlated with a smaller (less negative) N290 amplitude during the neutral face condition (r= .88, p = .02). Greater use of gestures was also correlated with smaller (less negative) Nc amplitudes during both the big smile (r = .95, p = .003) and neutral conditions (r= .85, p = .03).

Conclusions: These findings suggest that 6-month-olds are capable of discriminating between neutral expressions and expressions of positive affect. Furthermore, neural responses during the processing of positive affective expressions may be useful in predicting later social-communicative development. Future research will examine the potential of these ERP responses at 6 months to predict social-communicative development beyond the first year of life as well as explore the possibility that differences in these ERP responses may help to identify individuals who will later be diagnosed with ASD.