Cortical calcium waves in resting newborn mice.

Using a new optical fiber-based approach, we demonstrate the presence of recurrent Ca(2+) transients in cortical neurons of non-anesthetized newborn mice in vivo. These Ca(2+) waves reflect the correlated activity of thousands of cells and were detected only in resting, but not in moving pups. Our results suggest that Ca(2+)-dependent cortical maturation occurs predominantly during the intermittent sleep-like resting periods that are characteristic for the first days of postnatal life.