Cortical bursts provide spatio-temporal frames for the large-scale phase synchrony emerging across the birth transition

Structural corticocortical connectivity grows rapidly around birth, but how it establishes the large-scale neuronal interactions needed for lifelong neurocognitive performance remains unclear. Using repeated high-density EEG from 233 preterm-born infants recorded at 33-45 weeks postmenstrual age, we characterized the development of three phase-based interaction modes with distinct temporal relationships to cortical bursts: burst-based, burst-framed, and general phase-based connectivity. Burst-framed connectivity was quantified with a novel metric, nested phase-phase correlation. All three modes declined globally with age but differed spatially: burst-based connectivity became more confined, burst-framed connectivity reorganized towards sensorimotor-association connectivity, whereas general phase-based connectivity retained a stable modular organization. General phase-based connectivity was initially concentrated along burst-framed connections, but this coupling weakened with age. Its greater persistence around term age was associated with poorer neurocognitive outcomes, suggesting delayed network maturation. These findings suggest that bursting may transiently scaffold the maturation of large-scale corticocortical phase synchrony across the birth transition.