Deep Sleep Brain Waves (IMAGE) University of Bern Caption Left panel: In the sleep laboratory, the electrical activity of the brain is recorded using electroencephalography (EEG). Right panel: During deep sleep, slow oscillatory high-amplitude waves emerge in the EEG. These waves are generated by the brain cells' rhythmic alternation between highly active phases (red: "up-states") and passive phases (blue: "down-states"). Credit Simon Ruch/Marc Züst, University of Bern Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.