Lateralized neonatal EEG coherence during sleep predicts language outcome

Background Enriched language exposure may benefit infants in the neonatal intensive care unit. We hypothesized that changes in neonatal electroencephalogram (EEG) coherence during sleep, in response to maternal voice exposure, predict language development. Methods Convalescent neonates underwent 12-h polysomnography. A recording of the mother’s voice was randomized to continuous playback in the first or second 6 h. We calculated the imaginary coherence (ICOH—a measure of functional connectivity) between EEG leads. Spearman correlations were computed between ICOH and 18-month Bayley-III language scores. Results Thirty-five neonates were included ( N = 18 33-to-<35 weeks gestation; N = 17 ≥ 35 weeks). Predictive value of ICOH during neonatal non-rapid eye movement (NREM) sleep was left lateralized, and varied with gestational age and voice playback. ICOH in the left-hemispheric (C3-Cz; T3-Cz) channels across multiple EEG frequency bands was associated with 18-month language scores (rho = −0.34 to −0.48). The association was driven by neonates born at 33–34 weeks gestation, and a trend suggested a possible effect of maternal voice at some EEG frequencies. Right hemisphere ICOH (C4-Cz; T4-Cz) was not associated with language outcome. Conclusions Left-hemispheric EEG functional connectivity during neonatal NREM sleep shows early signs of physiologic asymmetry that may predict language development. We speculate that sleep analyses could have unique prognostic value. Impact During neonatal NREM sleep, EEG functional connectivity predicts future language development. Left temporal and central EEG coherence—specifically the imaginary component of coherence—is predictive, whereas the same analysis from the right hemisphere is not. These results appear to vary according to the infant’s gestational age, and a trend suggests they may be enhanced by measuring functional connectivity during exposure to the mother’s voice. These findings identify early evidence of physiologic differentiation within the cerebral hemispheres and raise the possibility that neonatal NREM sleep has a role to play in language development.