Figure 1 (IMAGE) Tohoku University Caption Estimating brain environmental changes from optical signals detected during REM sleep. Credit Yoko Ikoma & Ko Matsui Usage Restrictions Reporters may use freely these materials in news coverage with appropriate credit information. License Original 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.