Spatiotemporal dynamics of EEG microstate networks over the first two years of life: A multi-cohort longitudinal study.

Microstates, brief instances of distinct spatial topographies measured with electroencephalography (EEG), offer a novel approach to studying whole-brain network dynamics at a sub-second scale. While emerging literature is leveraging microstate dynamics in adults and children to understand mature largescale network function, the developmental trajectories of these networks during their rapid construction in infancy remain poorly understood. Magnetic resonance approaches have revealed much about largescale networks in sleep, but very little is known about functional network dynamics in awake, behaving infants. Using longitudinal resting-state EEG from 854 infants across 2 diverse cohorts, we identified conserved emergence of various network configurations (classes A-G) during the first 2 years of life via data-driven clustering analyses. Significant longitudinal changes included more frequent and rapid transitions between microstate classes, particularly in early infancy. Sensory microstates showed consistent development across cohorts, while higher-order cognitive microstates demonstrated context-specific trends. These findings reveal novel insights into the functional development and organization of largescale brain networks during this period of substantial development.