Greater Increase in Hippocampal Activity During the Early Postnatal Period After Preterm Birth Is Associated With Better Cognitive and Motor Outcomes at 18 Months.

Establishing a proper balance between neuronal excitation (E) and inhibition (I) is essential for healthy brain development, with alterations in this dynamic linked to neurodevelopmental disorders. Animal models suggest that hippocampal activity rapidly increases in the early postnatal period, believed to support the development and stabilization of E/I neural circuitry. This process has not yet been examined in humans, however. Utilizing longitudinal data from the Developing Human Connectome Project, the present study evaluated the impact of early hippocampal activity and gestational age at birth on later outcomes in a cohort of preterm infants (N = 58). Hippocampal activity was assessed using the amplitude of low-frequency fluctuations (ALFF) derived from resting-state functional magnetic resonance imaging collected at two timepoints in the early postnatal period (prior to 20 weeks following birth). Increases in hippocampal activity during this early postnatal period predicted better cognitive and motor function at 18 months of age. Greater gestational age was associated with greater hippocampal activity increase between timepoints. Interestingly, no significant relationships were found between baseline hippocampal activity and 18-month outcomes, suggesting that dynamic changes rather than static measures may be especially sensitive to preterm birth and subsequent alterations in neurodevelopmental processes. These findings underscore the importance of changes in early hippocampal function and gestational age as key risk factors for future neurodevelopmental concerns.