Fruit Flies (IMAGE) Johns Hopkins Medicine Caption When the sleep-drive neurons turn on, it puts the fruit flies to sleep. And when the sleep-drive neurons are turned off in well-rested flies, the flies awaken. Credit Johns Hopkins Medicine 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.