Tracing infant sleep neurophysiology longitudinally from 3 to 6 months: EEG insights into brain development.

Abstract

Sleep is critical for brain plasticity during early development, yet individual maturation of sleep neurophysiology in infancy remains poorly characterized. Slow wave activity (SWA) is a key marker of cortical maturation and experience-dependent plasticity, making early regional sleep dynamics highly relevant for neurodevelopmental health. We conducted a longitudinal high-density EEG study in 11 healthy infants, of whom 9 contributed analyzable EEG data at both 3 and 6 months. We assessed non-rapid eye movement (NREM) sleep and analyzed the maturation of SWA (0.75-4.25 Hz), theta power (4.5-7.5 Hz), and sigma power (9.75-14.75 Hz) across scalp regions and their associations with behavioral development. From 3 to 6 months, SWA increased maximally in occipital regions, while theta power exhibited a global increase. Sigma power, initially concentrated centrally, dispersed towards frontal regions. Greater frontal power increases correlated with higher motor (theta) and personal-social skill scores (sigma) at 6 months. These findings establish a framework for typical infant sleep EEG maturation, highlighting frequency-specific and regionally distinct developmental patterns. This study provides the first longitudinal evidence that early changes in sleep EEG topography reflect individual developmental trajectories, supporting its utility as a non-invasive and yet precise biomarker for early identification of atypical neurodevelopment at preverbal ages.