It’s no secret that our brains don’t function as well when we’re sleep deprived. But new research has shed light on why that’s the case.
After a bad night’s sleep, it’s common to experience brain fog and find yourself daydreaming during important moments. Researchers at MIT have found that it isn’t simply because you’re tired.
Cerebrospinal fluid (CSF) usually flows out of the brain while a person sleeps. That process washes away waste that builds up during waking hours. The flushing is needed for the brain to function normally. When a person is sleep deprived, pulses of CSF flow happen while they are awake, causing a loss of attention.
“If you don’t sleep, the CSF waves start to intrude into wakefulness where normally you wouldn’t see them. However, they come with an attentional tradeoff, where attention fails during the moments that you have this wave of fluid flow,” said Prof. Laura Lewis.
While we know sleep is essential, scientists have never been sure why that is. In 2019, Prof. Lewis and her team found that CSF flow happened in a rhythmic pattern during sleep and was linked to changes in brain waves. That made them wonder what happened to CSF when people were sleep deprived.
For the study, they used 26 volunteers who were tested after a good night’s sleep and again after they were kept awake in a lab. They monitored how people’s brains and bodies functioned during normal tasks the next morning.
As expected, sleep-deprived people did worse at the tasks. And memory lapses coincided with fluxes in CSF. This suggests that the CSF flows have to happen at some point; if you miss sleep — the optimal time — it will happen at the cost of your attention span when you should be focused.
In addition to the CSF flows, they saw that the body also had physical reactions. About 12 seconds before the CSF flows out of the brain, people’s pupils would constrict. They would dilate again when people regained focus. That underscores how interconnected the body’s functions are.
Prof. Bill Wisden, the director of the UK Dementia Research Institute at Imperial College London, said that there is still a lot that needs to be learned. “It is not clear if these changes in brain fluid flow with sleep deprivation are good and protective in some way or bad and pathological.” The stressed that the study shows how much sleep impacts our function.
Dr. Ria Kodosaki, a neuroscientist at Univ. College London said that, “Paradoxical as it may be, these dangerous lapses may be the brain’s way of protecting itself. Think of them as forced pit stops: the brain temporarily drops its external focus to perform essential housekeeping.”
This study doesn’t explain why sleep is essential. However, it is a step forward in explaining why we feel so terrible when we miss sleep. As the clocks fell back this weekend, we hope you take care of yourself and get a good night’s sleep!
