Objectives: The objective was to determine whether children at risk for ASD show the anticipated age-related pattern of neural response to faces. The expected pattern was characterized by a shift from a larger response to familiar (i.e, mother’s) face at younger ages, followed by a larger response to unfamiliar (i.e., stranger’s) face at older ages.
Methods: Data were collected from infants at high risk for ASD (HRA) and low risk control (LRC) infants at 6, 9 and 12 months of age. ERPs were recorded using a 64- or 128-channel Hydrocel Geodesic Sensor Net. All signals were referenced to a single vertex electrode, sampled at 250 Hz, and filtered using a bandpass of 0.1 to 100 Hz. Stimuli included images of the infant’s mother and an unfamiliar stranger. The component of interest was the Nc, a negative-going fronto-central deflection occurring 400-850 milliseconds after stimulus onset. Mean amplitude was calculated from a region of interest that included 14 electrodes.
Results: A 3 (age: 6, 9, 12) X 3 (hemisphere: left, midline, right) X 2 (condition: mother, stranger) mixed model examined effects on mean amplitude of the Nc. There was a main effect of hemisphere F(2, 174) = 5.75, p < .01, such that the neural response was smaller over the right hemisphere than over the left hemisphere (p<.01) and midline leads (p=.01). In addition, an age X condition X group interaction was found. Follow-up tests revealed no within- or between- subject differences at 6 months of age. By 9 months of age, the LRC group demonstrated the anticipated effect of condition (i.e., larger response to mother’s face than stranger’s face, t = 2.00, p=.04), where the HRA group did not show a difference across conditions. Analyses at 12 months indicated that the LRC revealed the expected age-related shift, with a larger response to stranger than mother (t=2.87, p<.01), while the HRA group again showed no difference across conditions.
Conclusions: In the present investigation, the control infants at low risk for ASD showed the anticipated age-related changes in response to familiar and unfamiliar faces, showing differential responses starting at 9 months of age. However, the infants at high risk for ASD did not show a differential response between their mother’s face and a stranger’s face at any age, suggesting that the processing of important social stimuli may be atypical in children with a family history of ASD.
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See more of: Brain Structure & Function