How does the brain know when it's time to wake up' Researchers have identified1 a chemical signal that serves as a timer in the mouse brain, logging both the length of a single sleep session and the number of interruptions and predicting exactly how likely an animal is to wake up at any given moment. This signal could offer a new way to measure 'sleep debt', or accumulated sleep loss. Such a biomarker could one day lead to methods for checking whether someone is sleep-deprived, says Ketema Paul, a neuroscientist at the University of California, Los Angeles, who was not involved in the research. 'We really don't have what a lot of people call the sobriety test for sleep,' Paul says, adding that such a test could be useful to ensure that people in high-stakes occupations, such as driving trucks or working in a hospital emergency room, are able to remain alert. 'The negative effects of sleep loss can have serious negative consequences.' Previous sleep research has focused mostly on the...
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