When you don't get enough sleep, parts of your brain are going to take catnaps the next day, even while you're ostensibly up and awake, a new study suggests. The results can have real-world consequences, says lead researcher Itzhak Fried of UCLA, who uses the example of a driver slow to pick up on a pedestrian. "The very act of seeing the pedestrian slows down in the driver's overtired brain," he explains in a UCLA release. In fact, it's very much as if the driver has had too much to drink. And while police have standard tests to measure for booze, "no legal or medical standards exist for identifying overtired drivers on the road the same way we target drunk drivers," notes Fried, whose study is in Nature Medicine. The research is based on a small sample—12 people who had to forgo sleep for a whole night because of epilepsy surgery in the morning.
But that still gave Fried's team a unique opportunity to gauge brain function (through memory tests and the like) as the night wore on, per the Telegraph. Electrodes gave them a sense of what was happening in the increasingly tired brain, and the researchers discovered that parts would essentially shut down and try to "sleep," impairing function. While it's well-known that sleep deprivation harms cognitive function, the study is unique in showing what happens on the level of individual cells, notes Forbes. And what happens isn't pretty. Whether such research might lead to new laws or policy is tough to say, but one thing is clear: "When we're dragging after a night of lost sleep, now we know that it may be because our brain cells are feeling groggy and under-performing themselves," writes Alice Walton at Forbes. (Sleep more than 9 hours? Watch out for this.)