Frontal lead in preterm functional brain maturation.

Understanding how brain maturation unfolds in preterm neonates is critical for both neuroscience and clinical care. Structural MRI suggests that the frontal cortex develop late, yet EEG offers a direct window into functional activity that follows a different trajectory. We analysed 211 EEG recordings from 62 preterm neonates (25-40 weeks postmenstrual age, PMA) using convolutional neural networks trained on single channels to estimate functional brain age (FBA). We introduced the spatial difference in FBA (sd_FBA) metric, which quantifies the relative maturity of each channel compared with all others within a recording. sd_FBA revealed a consistent maturation gradient, frontal regions exhibited the highest sd_FBA, followed by central regions, whereas occipital and temporal regions showed lower values. With increasing PMA, central maturation converged with frontal values, while occipital regions remained significantly lower. Functional maturation in preterm infants follows a clear frontal-occipital gradient, in contrast to structural MRI findings. The sd_FBA metric provides a novel, normalized index for tracking regional maturation, offering a new tool to understand functional brain development and potentially improve neurodevelopmental risk stratification.