Patterns of Hemisphere Asymmetry in EEG Activity in Infants at High Risk for Autism

Background: A current direction of research in autism examines the correlations between early biomarkers and the development of the disorder’s phenotype. One biomarker that has returned promising results is the brain’s electrical activity. Frontal EEG asymmetry has been related to behavioral measures of temperament (Fox et al., 2001). In particular, asymmetry patterns in the alpha band have been shown to correlate strongly with temperament classification, and individuals with autism demonstrate a trend opposite to the expected correlation for this bandwidth (Fox et al., 2003; Sutton et al., 2005). This work has largely been done in older children with autism, and questions remain about the extent to which early asymmetry patterns in EEG activity, for all frequency ranges, serve as early risk factors of autism and how well they predict later behavioral phenotypes.

Objectives: This study examines developmental patterns of asymmetry in EEG activity in infants who are at high risk for developing autism and compares them to the patterns of low risk infants. EEG asymmetry is also examined in relation to temperament in this sample.

Methods: As part of a larger comprehensive study of infant siblings of children with autism, infants are being studied at 6, 9, 12, and 18 months. At each of these time points, EEG data are collected under an eyes-open condition while the researcher blows bubbles to keep the infant quiet and alert. Additionally, at each of these visits, parents complete the Infant Behavior Questionnaire (IBQ). We calculate power spectra for frequency bands that collectively span the 1-50 Hz range and compare them between infants at high risk for autism (by virtue of having an affected sibling) and infants at low risk (having only typically developing siblings). Data are first examined for developmental patterns in asymmetry levels in various frequencies bands across all time points. Subsequently, in order to examine relations between early brain activity and later behavior measures, patterns of asymmetry at 6 months are compared with the IBQ temperament scores recorded at 12 months for a subset of infants.

Results: We have obtained usable data from 65 infants: 27 low risk and 38 high risk. Preliminary analysis indicates that the alpha bandwidth EEG asymmetry scores for the high risk infant group differ significantly from those of the low risk group across all time points. Infants displaying early clinical symptoms of autism represent outliers following a different asymmetry trend. For the high risk group, six-month EEG asymmetries appear to predict twelve-month temperament scores in accordance with low risk trends.

Conclusions: This analysis indicates that infants at high risk for autism demonstrate developmental patterns of EEG asymmetry that are distinct from those with low risk but also from those with clinical symptoms of autism. These early EEG patterns predict later temperament measures and may predict future scores on autism diagnostic measures.