WPI-IIIS Logo (IMAGE) University of Tsukuba Caption New insights into REM sleep crack an enduring mystery. Credit University of Tsukuba Usage Restrictions This image may be used with appropriate caption and credit. 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.