Scientists have new insight into why we have trouble focusing after a bad night of sleep .

Attention lapses when we’re sleep-deprived result from our brain’s efforts to clean itself up, a process that usually happens during sleep, recent research found. Typically at night, a fluid that surrounds our brain flushes out toxins, cell debris and junk proteins that build up during the day. This cleansing helps curb inflammation and keeps the brain working properly.

If we don’t sleep well, our brain tries to compensate while we’re awake—triggering pulses of fluid that coincide with sharp reductions in attention lasting a few seconds, according to a recent study published in Nature Neuroscience.

“It’s this kind of very sleeplike moment,” said Laura Lewis , an associate professor of electrical and medical engineering at the Massachusetts Institute of Technology and co-author of the study. “The person is awake, but at the same time, there’s clearly this brief breakdown of ability to focus on the outside world.”

The research indicates the brain has two different modes: One is housekeeping, and the other is being awake, and they’re not compatible, according to Dr. Maiken Nedergaard , a professor of neuroscience at the University of Rochester medical school who wasn’t involved in the work.

Getting enough sleep is linked to many health benefits, including better metabolism and lower risks of heart disease , high blood pressure, stroke and Type 2 diabetes.

The Centers for Disease Control and Prevention recommends adults get at least seven hours of sleep. But about one in three U.S. adults reports not getting enough .

While some can handle a disrupted sleep schedule better than others, all sleep-deprived people who participated in the study experienced this effect, Lewis said.

The risks associated with these failures to focus—like car crashes—can be high, she said. “This suggests that there’s really some very urgent function of sleep the brain is trying to get to that’s worth this cost,” she added.

Lewis’s group examined 26 people between the ages of 19 and 40 who had no history of sleep disorders. The participants were each tested twice—once when well-rested and once after staying awake all night. During each experiment, they received a functional MRI scan to help the researchers track the movement of fluid out of the brain. Participants also wore a cap that monitored their brain activity while they completed attention tasks.

Sleep-deprived participants had slower reactions, or missed visual and auditory cues. During those misses, the scientists observed a surge of cerebrospinal fluid through and out of the brain. Participants’ heart rates and their breathing slowed.

“Something is happening not just in the brain, but kind of in the whole body,” Lewis said. This suggests there is likely one unified circuit that switches us between high-attention and low-attention states.

These fluid surges while we are awake aren’t identical to those that would happen during sleep, she added. They’re shorter, and start and stop rather than constantly flow. Other studies have shown the waste products in the fluid are absorbed into the bloodstream surrounding the brain, which eventually takes them to the kidneys and liver—where they’re removed from the body.

Insufficient sleep is linked to not only disrupted cognitive function, but also a higher risk of injury, obesity, depression and neurodegenerative diseases such as Parkinson’s and Alzheimer’s.

Monitoring the brain’s self-regulation and maintenance functions, like this fluid flushing, are opportunities for new diagnostic tools and avenues for treatment, Nedergaard said.

“Sleep disturbances precede most neurodegenerative diseases by up to decades,” she added. “We really start to look at sleep as an opportunity to prevent many of the diseases of aging.”