Snoozing rodents provide clues to how a sleeping brain bolsters memories of recently learned material. Cells in two brain areas–the somatosensory cortex, which handles sensory information, and the hippocampus, which contributes to learning and memory–emit distinctive electrical waves in a timed pattern as mice and rats sleep, say György Buzski of Rutgers University in Newark, N.J., and his coworkers. This activity reflects a collaborative neural process that reinforces memories initiated during the day, the scientists suggest in an upcoming Proceedings of the National Academy of Sciences.
Buzski's team implanted electrodes in the brains of 10 mice and four rats. During a sleep phase known as slow-wave sleep, unique bursts of electrical activity in the somatosensory cortex were immediately preceded by characteristic electrical discharges in the hippocampus. This synchronized cell activity supports the notion that communication between the somatosensor