Differences in EEG Power at 3 Months Distinguish Infants at High-Versus Low Risk for ASD
In the context of increasing evidence for the efficacy of early intervention in improving developmental outcomes, there is both significant interest and a need to delineate early risk markers of atypical development that may facilitate earlier intervention. An emerging body of evidence from prospective studies of infants at high familial risk for ASD suggests that alterations in brain development are present from 6 months of age, prior to the emergence of the first behavioral signs of ASD (Jones et al., 2014). To date, early neural markers within the first six months of life have been scarcely explored.
In an effort to guide the identification of early risk markers in ASD, we aimed to (1) identify whether infants at high-risk for ASD show altered intrinsic oscillatory patterns by 3 months of age compared to infants at low-risk and (2) explore whether early neural activity is associated with behavioral, cognitive, and social communicative outcomes across early development.
Participants in the current study were part of an ongoing, prospective study examining infant siblings at high (HRA) versus low (LRC) familial risk for ASD. At 3 months of age, we collected continuous, high-density baseline electroencephalographic (EEG) recordings (HRA n = 25; LRC n = 14). Average frontal EEG power was calculated within the delta, theta, alpha, beta and gamma bands (as defined previously by Tierney et al., 2012). Cognitive development was assessed at 6 and 12 months using the Mullen Scales of Early Learning (MSEL) and early ASD markers were assessed at 9 and 12 months using the Autism Observation Scale for Infants (AOSI).
The HRA group had significantly lower power in the high-alpha (U = 78.00, z = -2.840, p = .004) and beta (U = 67.00, z = -3.162, p = .001) bands, with a trend in the low-alpha (U = 93.00, z = -2.401, p = .016) and gamma bands (U = 88.00, z = -2.547, p = .010). A Kruskal-Wallis H test revealed significant differences in frontal power between outcome groups (LRC no-ASD [n = 8], HRA-ASD [n = 7], HRA no-ASD [n = 15]) in the beta band (H(2) = 6.31, p = .043) and a trend in the gamma band (H(2) = 5.60, p = .061). This effect was driven by significant differences between the LRC no-ASD and HRA-ASD groups. Frontal EEG power at 3-months, for all infants, was positively correlated with gross motor and expressive language skills across the first year of life (ps < .05) and inversely correlated with AOSI total score at 9 months (i.e., higher 3mo EEG power was associated with fewer ASD risk markers).
Our findings suggest that frontal EEG power, as early as 3 months of age, offers potential to predict ASD risk as well as the development of gross motor and expressive language skills. On a broader scale, this finding is consistent with the well-established concept that across neurologic disorders brain-based changes may be detectable on imaging well before behavioral changes become manifest.