‘Timer’ in the brain tracks sleep — and predicts awakening - Nature

What the report says

Nature reports that researchers have identified a molecular signal in mice that appears to track how long an animal has been asleep, how often that sleep is disrupted and how ready the animal is to wake. The finding, described in a bioRxiv preprint that has not yet undergone peer review, points to chemical tags on brain-cell proteins as a possible biomarker for sleep loss.

According to Nature, the study was led by neuroscientist Yao Chen at Washington University in St. Louis. Her team monitored protein kinase A, or PKA, an enzyme also found in humans and previously associated with wakefulness. Using a fluorescent sensor in mouse brains, the researchers observed that PKA-related protein tagging remained elevated during wakefulness, then gradually declined after sleep began. Brief sleep interruptions caused the signal to rise again before resuming its decline.

The researchers reported that this pattern captured both total sleep duration and microarousals, allowing the signal to better estimate a mouse’s moment-to-moment likelihood of waking than elapsed sleep time alone. Chen told Nature the marker does not function like an alarm that determines the exact instant of waking, but instead reflects increasing physiological readiness.

Nature frames the work as potentially important because sleep deprivation is difficult to measure objectively. Ketema Paul, a University of California, Los Angeles neuroscientist not involved in the work, said a reliable test for sleep deprivation could be useful in safety-sensitive fields such as trucking or emergency medicine. Any application to people remains uncertain, and the evidence so far comes from mouse studies.