Neurovascular coupling develops alongside neural circuits in the postnatal brain.

In the adult brain, increases in local neural activity are accompanied by increases in regional blood flow. This relationship between neural activity and hemodynamics is termed neurovascular coupling and provides the blood flow-dependent contrast detected in functional magnetic resonance imaging (fMRI). Neurovascular coupling is commonly assumed to be consistent and reliable from birth; however, numerous studies have demonstrated markedly different hemodynamics in the early postnatal brain. Our recent study in J. Neuroscience examined whether different hemodynamics in the immature brain are driven by differences in the underlying spatiotemporal properties of neural activity during this period of robust neural circuit expansion. Using a novel wide-field optical imaging technique to visualize both neural activity and hemodynamics in the mouse brain, we observed longer duration and increasingly complex patterns of neural responses to stimulus as cortical connectivity developed over time. However, imaging of brain blood flow, oxygenation, and metabolism in the same mice demonstrated an absence of coupled blood flow responses in the newborn brain. This lack of blood flow coupling was shown to lead to oxygen depletions following neural activations - depletions that may affect the duration of sustained neural responses and could be important to the vascular patterning of the rapidly developing brain. These results are a step toward understanding the unique neurovascular and neurometabolic environment of the newborn brain, and provide new insights for interpretation of fMRI BOLD studies of early brain development.