Sexual Dimorphism of Social-Emotional Development in Toddlers

Background: The increasing prevalence of developmental disorders such as autism spectrum disorder (ASD) and the effectiveness of early intervention services in improving long-term outcomes for affected individuals highlights the necessity in identifying early risk factors and biological markers for atypical neurodevelopment. In children without neurodevelopmental concerns, there is a developmental increase in high-frequency neural oscillations (Beta and Gamma) and a developmental decrease in low-frequency neural oscillations (Delta and Theta). Although there is significant heterogeneity in prior studies, relative to neurotypical populations, infants at-risk for developmental disorders often exhibit lower levels of high-frequency oscillations and higher levels of low-frequency oscillations. Specifically, EEG studies of awake infants at-risk for autism have found: reduced frontal power and higher alpha power at 3 months and lower spectral power across all frequencies at 6 months whereas other studies suggest high-risk infants demonstrate different developmental trajectories in neural oscillations than their low-risk peers.

Objectives: To identify associations between electrocortical spectral power during infant natural sleep and subsequent social-emotional development in toddlers.

Methods: Participants included in the present analysis consisted of infants initially enrolled in the Safe Passage Study with follow-up assessments currently underway. The sample consisted of 203 infants (116 males/87 females; gestational age at birth M: 39.4 weeks, SD: 1.1 weeks) from the Western Cape Province of South Africa who had both neonatal EEG and developmental assessments at ~3 years of age. Neonatal EEG was recorded during sleep in the supine position using EGI’s (GEM) 28-lead net for approximately thirty minutes. Average electrocortical power was computed in 10 frequency bands (Delta 1-3 Hz; Theta 4-6 & 7-9 Hz; Alpha: 10-12 Hz, Beta: 13-15, 16-18, & 19-21 Hz, Low-Gamma: 22-24 & 25-36 Hz, Gamma: 37-48 Hz) and 12 brain regions (left and right: frontal-polar, frontal, central, parietal, temporal, & occipital) separately within active (REM) and quiet (slow wave) sleep. The Brief Infant-Toddler Social and Emotional Assessment (BITSEA) was administered at 3 years of age (M: 37.0 months, SD: 2.6 months). Multiple regressions were run to predict social-emotional development from neonatal EEG power with prenatal exposures, gestational age at birth, and hours of life as covariates. Secondary sex specific analyses were also computed.

Results: In active sleep, increased Alpha, Beta, and Low-Gamma EEG power in the left temporal, right temporal, and left-frontal regions were associated with increased socioemotional problems on the BITSEA, (F(1, 196) = 2.33 - 2.92, p’s = .000 - .01. Sex specific analyses revealed increased Delta, Theta, and Alpha EEG power during quiet sleep in the left temporal, frontal, and frontal polar regions were associated with increased socioemotional problems in males only, (F(1, 111) = 4.49 – 6.37, p’s = .000 - .01. Conversely for females, increased Delta, Theta, and Alpha EEG power in the right frontal and central regions were associated with increased socioemotional competence scores, (F(1, 82) = 1.18, p’s = .000 - .01 (Figure 1).

Conclusions: Our results demonstrate sexual dimorphism of EEG brain markers at birth associated with subsequent socioemotional development in toddlers.