BrainStuff Classics: Why Do We Sleep?

from our cave days. Well, like Edison, we hear a brain Stuff hate sleep. That's why we wanted to do this episode to figure out why we have to do it. Normal people spend thirty of their lives asleep, and most are either like us and wish that they didn't have to sleep so they could get more done, or they just want to get a RESTful, uninterrupted night without waking up. Studies actually show that six percent of adults claim to have problems sleeping at least a few nights a week.

And here's the thing. Everyone's got to sleep. Yet we still don't know exactly why, but we're going to try to do our best to crack that case. Today that's right. Let's review some theories for why we sleep, what happens when we sleep, and what happens when we don't. Even though we don't know why we sleep, there's all kinds of educated speculation. The most prevalent is that sleep gives our brain a chance to organize and process information, possibly

through dreams. Basically, our brain takes all the sensory stimuli we received while we're awake and decides what to keep in where to file it. Everything else gets trashed. It's even possible that our ability to learn tasks actually benefits from quote sleeping on it as a process is better understood after our brain reviews and catalogs it. While most agree with this memory consolidation theory, it's tough to pin down since we all sleep oh differently. And here's another theory.

Sleep gives our bodies time to rest and repair. Or how about sleep lowers our energy consumption so we conserve the meals we eat. Other theories delve into the biochemical mechanism of the brain. In a series of experiments on mice, showed that cerebral spinal fluid was pumped around their brains while they slept, expelling waste like molecular detritus and toxic proteins into their livers for breaking down. So do we

sleep just to flush the toilet on our cerebral commodes? Well, other sleep researchers were skeptical of the study that I just mentioned, pointing out that there are some big differences between a mouse's brain and humans. So while the answer to why we sleep isn't written in stone, we all know that when we sleep, both our mind and our body feel refreshed. We at least know what's happening when we sleep, right Well, most of us need between seven to nine hours of sleep at night, but that changes

during different periods of life. For example, a newborn baby might sleep twenty hours a day, but by the time they're three months old, they recognize the circadian rhythm of sleeping at night and waking up in the morning. And when you're older, like senior citizen older, you can probably get by on only six or seven hours a night. Regardless of how long you're asleep, you must experience both R E M and non R e M stages to sleep. Well.

That's rapid eye movement, not the band R E M. From Athens, Georgia, A normal person spends of their sleep in R E M, with each session lasting between five and thirty minutes, and during this time our brain speeds up, our eyes and face might twitch in R e M because we're dreaming. We need around ninety minutes to fulfill a complete cycle of R e M N non r EM sleep, and researchers think this cycle ties sleep back

to our ability to process tasks and memories. Recording show that many of the same neurons that fire when we're learning are reactivated during our E M, consolidating the patterns into permanently wired connections. But don't sleep too much more than eight hours can lead to depression or even Parkinson's and heart disease. Of course, if we don't sleep, that's a whole other mess of problems. Rats will actually drop dead if they go more than three weeks without sleep.

Us humans, we get lethargic, cranky, and foggy headed at first, almost like we're intoxicated. We might even nod off into micro sleep for a few seconds, and this is what happens after one or two nights without sleep. By day three, we start hallucinating and lose the ability to recognize reality and that's if you're really pushing the boundaries of sleep. Simply failing to get enough sleep is connected to obesity, high blood pressure, a weakened immune system, heart disease, cancer,

and diabetes. And it's no big re elation that lots of us don't get enough sleep. We might try to get by on caffeine or nicotine, and alcohol is a good sedative, but it doesn't actually provide the sleep we need for neural processing. So, in the words of the immortal poet Chris Ludicrous bridges, if you're tired, be quiet and go to sleep. Today's episode was written by Ben

Bolan and produced by Tyler Clang. To hear more from Ben, tune into his podcast Prediculous History, which is what it says on the tip, but in a really fun way. And of course, for more on this and lots of other answers to annoyingly persistent questions, visit our home planet, how Stuff Works dot com.