Radiolab - Sleep

Episode Date: August 2, 2024

We had a question back in 2007, about a thing every creature on the planet does--from giant humpback whales to teeny fruit flies. Why do we all sleep? What does it do for us, and what happens when we go without? We take a peek at iguanas sleeping with one eye open, get in bed with a pair of sleep-deprived new parents, and eavesdrop on the uneasy dreams of rats. We have some exciting news! In the “Zoozve” episode, Radiolab named its first-ever quasi-moon, and now it's your turn! Radiolab has teamed up with The International Astronomical Union to launch a global naming contest for one of Earth’s quasi-moons. This is your chance to make your mark on the heavens. Submit your name ideas now through September, or vote on your favorites starting in November: https://radiolab.org/moonSign up for our newsletter!! It includes short essays, recommendations, and details about other ways to interact with the show. Sign up (https://radiolab.org/newsletter)!Radiolab is supported by listeners like you. Support Radiolab by becoming a member of The Lab (https://members.radiolab.org/) today.Follow our show on Instagram, Twitter and Facebook @radiolab, and share your thoughts with us by emailing [e-mail] support for Radiolab’s science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simons Foundation Initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.

Hey, I'm Lethif Nasser. This is Radiolab. This week I'm re-upping an episode from 2007, you know, which is like very early days of our show, about a fundamental mystery that now, like almost 20 years later, is still just as fundamental and just as mysterious as it was then. it was then. It is a fundamental mystery that takes up about a third of your life and actually probably more considering how much you crave it when you can't get it, but then paradoxically put it off when you can. Anyway, I'm not going to say anymore because I don't want to step on the original episode intro, which is just adorable. So here you are, drift off with our emeritus Radio from WNYC. See? Rewind. I just thought I'd see if I could get the sound of babies sleeping. This is Radiolab. Today's program is about sleep. I don't have to tell you how good sleep is. You do it yourself. Every night.

You try. And how wonderful when it actually works. When you can close your eyes and forget the day and just drift off into oblivion. Like a little baby. But let's suppose that you are a little baby, this little baby, and you grow up to become a scientist, like one of the scientists we'll hear from in this program, and you decide to ask what should be the dumbest question ever. Why do we sleep? And not just us.

Well, pretty much everything sleeps. As far as we know, all mammals do it. All birds. Bees, locusts, cockroaches, crayfish, reptiles, insects, scorpions. Everything that's been studied has something that looks like sleep. It's a mystery. Most things we sort of know what they are for and also how they work. But sleep is really in your face. I mean everybody does it. You do it from the cradle to the grave. You can't help doing it because if you try to stay awake at some point it's irrepressible. And we don't know why.

That's a shameful state of affairs. How can you be a scientist in the 21st century and not know the answer to that? There you go. Okay. That's for shame, okay? It is not for too long. That's a pretty good way to begin, no? With shame? Yeah, yeah. Today on Radiolab we're gonna try to correct this shameful state of affairs when it comes to the subject of sleep. We'll talk with people who can help us understand what it's for.

Why we do it. And what happens when we don't. I'm Robert Kralwicz.'m Chad Abumran stay with us For centuries people thought that sleep was kind of the opposite of being awake It's reasonable one thing sure because you know during the day you're doing all these things, you're having all these thoughts and feelings. At night you just lie there, very very still. Like sometimes a bomb could go off and you wouldn't wake up. I can hardly wake up even in a fire. No, I'm a really heavy sleeper. I'm a very heavy sleeper. The point is, if all you've got are your eyes to go on, sleep can seem like being off. Yeah, like off-ness.

Right. Or worse. Well, both Shakespeare and Cervantes referred to sleep as death. That's Dr. Carlos Schenck. He wrote a great book about sleep called Paradox Lost. We go to bed every night, we die every night, and then we wake up in the morning and we're alive again. And that was a prevailing theory for centuries. For Dr. Schenck, the awakening to just how wrong Shakespeare and Cervantes were about sleep came one day while he was sitting in class from med school.

My first year at medical school. This was back in 1972. We had an emeritus professor who actually was a Nobel Prize winner, Dr. Eccles. Sir John Carew Eccles. Here's what happens. A steamed lecturer walks in the class, pops a cassette into the tape deck, hits play, and out comes this sound. Well, the sound was p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p-p was or let me get it right oh here we go multiply this by a hundred this the professor announced is the sound of a cat's brain while asleep my god shk almost fell out of his seat. This is the brain during sleep? Making these really rapid, high-pitched, multiple sounds.

That just blew us away. It wasn't just- Clearly, while that cat was curled up in his little kitty basket, its brain was very, very alive, much more than anyone expected. And this is still a weird revelation. Like, take my cat Sammy. Sammy. Right? This was the like take my cat Sammy Sammy?

This was the sound of my cat Sammy sleeping. To think that while Sammy is sitting on my lap totally out, there's a circus happening in his brain. What's going on in there? If you can imagine back in the 70s, this was a paradigm shift. People were suddenly like, oh my god, if we're going to figure out anything about sleep, we have to ask the brain. And this is the room where we do all of our surgeries.

And luckily, that's easily done. If you're willing to get your hands dirty. Okay, so the first step is you have to make an incision on top of the animal's head. When you've done that, we drill holes through the animal's skeleton. And then you insert your electrode. Then you've got a little window into their brain. You can see right there on the screen. Wait a second, are you out of your mind? Did you just put a hole into a kitten's head? No, that wasn't my cat. Come on. So what was it we were doing there? What you just heard was a mock surgery to an iguana actually.

Even an iguana, I mean it's not a nice thing to do. Look, look, look, look, the animal was not harmed. Within 20 minutes of coming out of the anesthetic, the animal is moving around, it's eating, it's climbing, and it's basking. It might seem like a rather invasive procedure, but in actuality it's not too bad at all. Yeah, and that by the way is John Leskew. He's a graduate student at the ecology department at Indiana State University, which is where we are. John gave our reporter Kara Oller a tour of the lab. These are our big boys here and they all have nice hats. Showed her the iguanas. These guys are a little frightening to me. They're pretty huge.

They're like four feet long head to tail. Oh, I didn't know that. I mean, they look like baby alligators. Pick that one up. And John measures their brain waves at night to see what happens in their head as they sleep. In a way, it's a continuation of that cat experiment that Dr. Schenck just told us about. Except, what they're looking for is much more peculiar than could ever

happen in a cat or an us. What, what, what is that? Let me put it to you as a puzzle. Okay. And forget iguanas, dolphins, right? Dolphins. Yep. How is it that a dolphin in the ocean, or even say

the dolphins that you might find at six flags in New Jersey, They have two. Cody is our ten-year-old Atlantic bottlenose dolphin. His buddy Avalon, he's twelve years old. And that's our trainer, Megan Tutera. Avia Mitra is holding the mic. Anyhow, here's the puzzle. We asked Megan about this.

How is it that her two dolphins, Cody and Avalon, can successfully sleep given the inherent challenges of being a dolphin. I don't know what even are the challenges of a dolphin. Well, they have significant challenges, my friend. First, they've got to breathe. They're not, they're conscious breathers. They're not unconscious breathers. So they have to think about breathing. Making matters worse, dolphins are not fish.

So they have to breathe air, which means they have to constantly, consciously, come up to the surface to breathe air every few minutes. So you can imagine what would happen if they decided to go unconscious for a while. They would drown. Right. And yet they do manage to sleep. A lot. How long? Eight hours a day. Really?

Yeah, eight hours. But how? That's the puzzle. What happens is they do what we call logging. It's when they rest on the surface of the water. You know, when a log floats down a river, it just floats. That's exactly what they look like. And they rest half their brain at a time. Half their brain is asleep?

Half their brain is asleep at a time. That is nature's solution. To cut the dolphin brain in half. You mean literally? Literally in half so that one half can snooze while the other half keeps the dolphin swimming and surfacing. Just enough to breathe. From the outside you can't really tell what's happening.

It just looks like the dolphin is sort of awake but a little out of it. It's almost like the state of when you're falling asleep but if something happened you'd wake right up. So they're in that state all the time. This sort of guy can be characterized as groggy. That's Steve Lima.

He runs one of the labs back in Indiana. They're sort of awake and they're sort of asleep. It's just a way of staying awake enough. And again, it's easy to miss, but if you look inside that groggy dolphin's brain, what the brain waves are doing? It's exquisitely obvious. It's clear as day.

A six-year-old can figure it out. One half of the brain has these beautiful slow waves, like a sine curve. And the other one's just... Just jagging all over the place. Oh, those are beautiful! Wow, that is amazing! Yeah, it's called uni-hemispheric sleep.

That's what the guys at Indiana State are really interested in because, and here's the next surprise, it seems to go way beyond dolphins. Oh yeah, aquatic mammals like whales, seals, and sea lions. John says that all the marine mammals that have been studied seem to do it too. Recently walruses they're all found to engage in unihemispheric sleep as well. And now the Indiana team led by this guy. I'm Charles Amlanter, chair of the Department of Ecology and Organismal Biology.

They have found this weird split brain behavior in creatures of the air. Let me just back up a little bit and describe this experiment. Charlie and his student had been at the park one day and they noticed something. We observed that ducks sometimes will get together into groups. Like on a log, four ducks will get together and snooze in a neat little line. And the birds that were sitting in the middle of that line tended to be sleeping with both eyes closed. The birds that were sitting on the outside of that row tended to look a little bit more wary. The inevitable question, what's going on here, led to a very simple experiment.

We put four birds in a row, four mallard ducks, this time in the lab, and they watched them sleep. The two birds in the center of this row slept with both eyes closed. The birds on the outer edges, both left and right, slept with one eye closed and one eye opened. One more time. Slept with one eye closed and one eye opened. It's just like in that song. Do you know that Metallica song? No, I missed it. It's a good one. song. Sleep with one eye open Do you know that Metallica song? I missed it. It's a good one. But I knew they were all botanists.

It's true. You know, no one knows this, but that song is really about adaptive sleeping behavior in ducks. Rocked to never, never land The outer eye, the eye that was faced away from the group, the eye that was facing towards where potential predators might come from, that stayed open. At this point, Charlie had a pretty good idea of what was going on because he knew that inside bird brains, each eye is attached to the opposite hemisphere. The left eye is attached to the right hemisphere. The right eye is attached to the left hemisphere. So his team implanted some electrodes to measure what the duck brains were doing and voila! Like the dolphins, the ducks too were sleeping one half of their brain at a time. The bird could simultaneously sleep and be awake.

Not only that, here's the cool part. After a few hours... What happened was that the birds that were on the outer edge then would rotate... Stand up, turn around... 180 degrees... And then sit back down. And the other eye would then get some sleep, and consequently the opposite hemisphere would get some sleep. When we saw that, we said, oh yeah, this is... that's good. Good, because right there in the docks was a perfect illustration of what these guys think it's all about.

You gotta sleep, for whatever reason. Right. But sleep is dangerous. Danger, danger, danger. That's the headline. For dolphins, the main danger is drowning. Danger, danger, danger. You know, for ducks... Getting eaten.

Exactly. Danger, danger, danger. Ducks have to sleep, but how can they? When lurking in the darkness are foxes, and a wolf, and a hundred other eaters of ducks. Do you like snakes? I don't know. Not really. What?

I don't dislike snakes. He's a good man. He's a good man. In another nifty experiment, John took the resident snake, Monty. This is Monty. This is Monty. Hey. Big snake. He is what, about a four foot long python?

And at night? You're so cute. John brought Monty the python into the room where his iguanas sleep. And he terrifies them. Really? Well I mean Monty was in a cage so he couldn't really hurt the iguanas, but as soon as that snake appeared all the lizards popped one eye open. I bet they did. And they trained that open eye right on Monty the snake. Put a big snake in the

room and they'll watch it with one eye all night. That's Steve Lima again. They don't like these snakes that's for sure and they remove the snake from the room the next day and they're still looking for it the next night or two. So they keep one eye, you know, trained on that door for a few more days? About two or three days. They go back to regular sleep. So what does this all mean? Well, think about this. Okay, all the sea mammals, they do it. Right. Uh, well at least the ones that have been studied. All the flying creatures, they do it. The reptiles seem to do it too. Who does that leave?

You mean who's left not sleeping with half a brain on and the other half a brain off? Yeah. Um... Us! Really? We may be the strange ones. Well it is sort of strange in that terrestrial mammals can't do it. Terrestrial mammals just for some reason have lost the ability to do this.

Not all mammals, says John. Terrestrial mammals, the ones that live on land. And here's this theory. Sometime long ago, our scaly ancestor wandered up on the land and thought, I think I'll dig a hole. Yeah, I'm gonna dig a hole. And the hole was dark and it was safe. And for the first time in millions of years of evolution, that little creature closed both eyes.

And so we lost it. Totally speculative theory of course, but the basic idea though is if you are protected and safe, you can afford to close both eyes. Conk out completely. And that simple idea of safety, that explains, well these guys think almost everything. Where you sleep, how you sleep, how long you sleep. It all boils down to two words. Predation risk. Predation risk.

Predation risk. Which is really just a fancy way of saying. Generally speaking, just your risk of being killed. Your risk of being eaten. Now, what does this have to do with us? Here we are, top of the food chain, in our warm beds, nice warm bed, locked door, locked door, covers, maybe a nice neighborhood, a good police force looking after you at nighttime, and you live in a country that has a very secure living environment.

You would think that this whole predation risk idea has nothing to do with us. Well, well, there's a few studies that have looked at say sleep patterns where people are sleeping in novel environments. What's a novel environment? What does he mean? Well like a hotel. Oh. That first night at a hotel? Why is it no one could sleep well that first night at a hotel? On your first night of sleeping in a hotel room you generally have less REM sleep and less deep slow-wave sleep relative to sleeping in your house room, you generally have less REM sleep and less deep slow wave sleep relative to sleeping in your house.

I suffer from that myself. I don't sleep well in hotel rooms, especially if it's just one night per place or something. My sleep is terrible. There are some folk that actually hypothesize there are certain predator relays in the brain. Danger, danger, danger. And that these circuits remain active at all times. relays in the brain. Danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger,

danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger,

danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, danger, Some of us. It's a little too sensitive. Okay, we're in the sleep lab at the Minnesota Regional Sleep Disorder Center, Mission Control we call it. We're viewing the typical sleep terror episode. This little girl who is five years old would engage in these sleep terror episodes every single night. That's Dr. Carlos Schenk who we heard from before. We're in Minnesota now at the Hennepin County Sleep Center

where he works. We're standing in front of a grainy black and white video of a little girl in her PJs screaming. Dr. Schenck discovered an odd category of sleep disorders called parasomnias, which is why we came to talk to him. Para means around. Somnio means sleep, around sleep. This might be the human analog to the ducks,

people whose brains never quite shut off completely during sleep. Well this guy is interesting, he has seizures. No, no, no, he doesn't, wait a second. He showed us tape after tape. We're viewing a man who we very affectionately call Santa Claus. On the screen, a large guy thrashes back and forth. His legs are moving, thrash it back and forth. His legs are moving he's going back and forth with his sides of his back. And then suddenly he starts to...

Is this real? Yeah this guy is in and out of sleep. He has no idea what he's doing. One of the interesting things Dr. Schenck noticed when he first began to diagnose parasomnias in the early 80s is that while they were in that kind of liminal space around sleep, a huge percentage of the patients would have these visceral dreams of being attacked. The common theme is a menace is posed from nowhere, coming out of nowhere. It's an immediate threat that you just can't ignore. Let's put it that way. You have to either fight it or run away from it.

The dreams can be very violent. This is Martin Zabel, age 88. He's another of Dr. Schenck's patients. I remember someone coming up the stairway. In Martin's case, the attackers never had a face. Sometimes it was a bear. And I was going to fight with him. He'd yell at him, get out of here!

That's Martin's wife, Gertrude. Scram! He was always trying to protect me. Yeah, I'd have black and blue breezes on my arms and hands because I was hitting the headboard. Not infrequently the man is dreaming in bed with his wife that he is fighting to defend her from an attacker when in fact he's beating her up. One night I was sleeping and all of a sudden he's got his hands tightly around my throat. I'm petrified. Quit, Mart, you're dreaming, you're hurting me.

She says, Martin you're dreaming. Gertrude and Martin's about are still married believe it or not after 57 years Though she did force him to sell his guns. He has never been happy about that So you're suggesting then that all these people and the iguanas and the ducks and the dolphins people and the iguanas and the ducks and the dolphins all have a portion of their brain which is weary in the night. That's what I'm hinting at. I don't want to go any stronger than hint at, but there seems to be something in us that's always watching out, always weary. Bottom line here though is that sleep for all creatures is a dangerous thing and a few

unfortunate people are still awake to that fact. That's right. Before we go to break, I just want to thank Anne Happerman for her excellent reporting in Minnesota and also before her, Kara Oehler, and to remind you to stay with us because we're going to turn our attention shortly from danger to deprivation. Radiolab will continue in a moment. This is Radio Lab, you are Robert Krawich. Robert Krawich is my name.

And you're? I'm Jad Abumrad. And today our topic on Radio Lab is sleep. Yep. It is something that all of us do. We can't help but do it. It's dangerous to do. It's so good. And it's universal. Think about it, you know, sleep is dangerous. And if sleep could have been circumvented in some way, natural selection probably would have found a way to do it. That's Steve Lima again from Indiana State University. Because it would be such a great idea to not sleep. Don't I know it. But there are times when you just can't sleep. Maybe you're one of

the 35 million Americans I am who has chronic insomnia. You just can't sleep. You don't know why. It just doesn't happen. Or maybe you do it to yourself and you pull all-nighters for school or you have to drive long distances or and here's what we want to turn our attention to next maybe it is done to you. That's the case with producer Hannah Pallin. she kept this audio diary of her own experiment with sleep deprivation. She has an 18-month-old son. It's 2.54 for the record. Today was my first day back at work. We were discussing budgets.

I just, I just, I couldn't even articulate what it was that I was seeing on the computer screen and try to communicate that to the curator that I work for. The words didn't come. Lie down, lie down on me. Instead of saying, well, Nicolette, I believe that that choice was made because, no, no, all that came out was like, honey buckets. I mean, nothing, Nothing would come out.

There's just no brain cells, really. Darn. I almost had him asleep there. So anyway, that was my first day back at work. Dominic will not sleep. I don't know why. I'm trying to get him to sleep. I'm just kind of at my wits end. God, this just sucks.

Totally sucks. Here's the funny thing. Everybody has a theory. And I was talking to my sister-in-law tonight, and her theory is that he's not getting enough milk, because milk has some agent in it that would help him sleep. And he doesn't like milk, it's true. Other people say, oh, if you just would exercise him, if he just gets fresh air and exercise,

he'll sleep all night. If you just let him cry, he would sleep all night. If you just would do whatever it is we're not doing, he would sleep all night. And there's this feeling like... There's a feeling like I am doing it all wrong. And that I'm a failure as a parent. I don't know how to do this. Come here sweetie. Come on, come on, come on.

Just hang on on me. So anyway, I needed to record just one thing really quickly and that is that yesterday and today I've been struck by this. Cute. I'm in struck by these waves of satisfaction and delight with being alive in this amazing landscape with a funny kid. Beautiful mountains and water and I don't know maybe it's just getting a little more sleep in the last couple of days.

But I suddenly feel like wow, I'm so lucky. Okay I've got to take my kid to play now. Here we go! Do you know the muffin man? Okay, that whole I'm loving life. Yeah, that's all gone now. And it's pretty much because Dominic won't take a nap. We came home from the beach, which I thought would wear him out, then we sat down and read some stories, which for some reason...

And I realized that an element to the sleep deprivation, that an element to this whole thing, is that I get angry from having my own needs subverted to the needs of this little tiny person, which when you're not sleep deprived is not a big deal. I'm tired. I tired. I'm tired. I don't want to wish a minute of Dominic's childhood away because it's so precious to me. But damn, I am looking forward to that moment when I'm able to say

honey time to go to sleep. And he does it. Tired? No. Not tired? Just a minute, talk. Close your eyes, buck. Close your eyes. There's my personal take on what it's like to be sleepy. Good night. And to crave sleep as much as you crave water or breath

I crave it Thanks to Hannah Ballant and her son Dominic and her husband Steve I know poor Hannah, but there is a science question lurking in the background Which is when you know when Hannah was so tired Why does she feel that way you know when Hannah was so tired, why does she feel that way? You know what? What because she's she hasn't sat been sleeping. Well, yeah, but but what makes her you know, what is the essence of tiredness? Lack of sleep. Hello Chemically i'm asking you chemically i'm right. What is happening to her if you were way down in her cells

Could you see something tired-like going on? That's a good question. I'm glad you think so because I know a guy who has a theory about this. Did you see Tiger yesterday? Tiger is unbelievable. He's the best round of anybody. I mean the guy is unbelievable. This is Dr. Alan Pack and in addition to being a rabid golf fan, he's also a rabid, but can you be a rabid biologist? Sure. At the University of Pennsylvania, he's been looking at sleep down at the cellular level. And one thing that he's found over and over and over. And that's been shown in mouse, it's been shown in rat, it's been shown in fruit fly.

Is that inside certain cells in all those different animals when they're sleep deprived. Eventually what happens is you don't get proteins properly folded. Excuse me? Proteins properly folded? The phenomenon called the unfolded protein response. What on earth does that mean? Is that a good thing or a bad thing? You're asking why do you need proteins to properly fold? Yeah, I guess that's what I'm asking. Well, you're made of proteins. Proteins are the essence of you.

So if your proteins are misshapen, if they're not folded properly... If you don't fold the proteins properly, they don't have the right three-dimensional structure, and as a result they start accumulating inside the cell, and then these different unfolded proteins can aggregate together and form clumps. Clumps. Clumps. Clumps. Clumps. Clumps. Clumps. Clumps. Clumps.

Clumps. Clumps. Clumps. Clumps. Clumps. Clumps. Clumps. Clumps.

Clumps. Clumps. Clumps. Clumps. Clumps. Clumps. Clumps. Clumps.

Clumps. Clumps. Clumps. Clumps. Clumps. Clumps. And because she hasn't slept much, inside her cells, lots of these valuable little proteins have not folded properly. That he thinks is the consequence of not having enough sleep. So maybe what's going on is the cells can't do their business quite as well and things start to break down. And that adds up across the whole of your body to a feeling of... But when she gets to sleep, remember when she was so happy? Yeah.

I suddenly feel like, wow. Because of the sleep, a group of cleaner uppers have gone through her cells, removed the toxic and misshapen proteins so that, in effect, sleep is the best housemaid you've ever had in the hotel of you. And this idea, the idea of sleep as a cleaner-upper, might even explain one of the most basic things about us as humans. How we learn. That's the notion of Dr. Giulio Tononi.

My producer, Ellen Horn, and I went to visit him at his offices in Madison, Wisconsin. What are we expecting? What does he look like? A football player. A football player. I went to visit him at his offices in Madison, Wisconsin. What are we expecting? What does he look like? A football player. A football player. But like a quarterback or tight end, not like a linebacker. Not like a linebacker.

So big but not overwhelming. Yes. How do you even know that? On the website. See, but I was totally wrong. Now, to be fair, he is a very attractive guy. He has sandy blonde hair and glasses. He's actually more of the sensitive guy intellectual than a linebacker. Introduce yourself.

I'm Giulio Tononi. I am a professor of psychiatry here at the University of Wisconsin, Madison. But when it comes to the subject of sleep, which is his specialty, he takes sleep very seriously. What got you in sleep? Sleep is the annihilation of consciousness. So it's a terrible time in which everything disappears, the universe and yourself with it. I think if people didn't sleep and didn't have the unconsciousness of sleep, they possibly wouldn't even realize that consciousness is an enormous gift.

So being awake then is wonderful, but it's what happens when you're asleep, he says. That's what allows you to make very important connections in your life. And he noticed this first when he was connecting with, I believe it was a guitar, playing music. I used to play, for instance, I played classical guitar. I'm sure many people who play musical instruments know that you may train and train and train on a piece during the day and you get better for sure but you're never perfect and then you sleep over it the next day you wake up you play it again and now it's smooth and you know it flows beautiful.

That happen to you? It happen to me, it happens to lots of people. That happen to me all the time. I discovered that sometimes if I worked on a piece and put it away, went to bed and got some rust, I had it better learned than if I stayed up all night cramming. Yeah, definitely. There's one story, and I hadn't thought about this for a long time, but, well, first of all, Rob and I play in a band together. The band is called the Sisterhood of Convoluted Thinkers.

And we switch instruments a lot. She's usually the bass player. I was gonna play drums. That's why she had to learn how to play drums. So we rented a cabin. We went somewhere to rehearse, and at night she was really just kind of practicing and practicing and trying to get this rhythm.

This one particular beat, like I worked on it like a lot. I just keep going and going. I remember playing that one thing again and again and again. Yeah. Stop! And I finally just gave up and went to sleep. And the next morning I got up and went like straight to the kit and I just played it like immediately. The butt hit the stool, and she was going... Ba-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da- and the notes that you were using to propel your fingers, all those things somehow got into, got more, got better learned.

So you learned overnight or you, I mean what does that have to do with, are you remember better in the morning? Well what happens is that the next day you're a bit better off. What happens during the night to make you better off, this is up for contention. Tononi's contention is that sleep helps you remember

by forgetting. I don't know what that means. Let me explain to you what he's saying. He says there's a limited amount of space in your brain. The real estate in the brain is a limited amount. That makes sense. It's a small little guy up there. And yet every experience you have during the day... Is going to take away some space.

Uses up a little of what you got. When you are awake, inevitably you learn whether you want it or not. You are going around talking to me, having breakfast, going to work, then yacking on the phone with your friends, talking to your mom, very different from the friends, then going home, taking a bath, I take a bath, yeah I get it, I get it. Everything you do during the day, every thought you think, no matter how small, it all causes your brain to form new connections. This conversation, as we're having it,

is reshaping my brain. Yeah. A little pathways are forming that weren't there before I sat down. Exactly. Whether we recognize it or not, lots of things are going to change your brain by the end of the waking day So if in the middle of the afternoon you sit down with your guitar, and you practice the guitar intently

Those two hours you're also making connections Because you're concentrating maybe you're making more connections than usual These are guitar connections and all those synaptic connections made during the day one other other by the time you're ready for sleep up in your head it's a really mess and that is where we think sleep kicks in. Well I'm gonna guess here but I think you think that sleep is a garbage detail that comes in says okay you're done you're done you're done. It's actually even simpler than that. According to Tononi there's not really a janitor who comes in and decides okay

you have to leave you get to stay nothing like that. Instead he says what happens. We think that during sleep waves of electrical activity, kind of like a late evening bath, wash over your head. They start at the back of your head and they move to the front. These waves are called slow oscillations. And over the course of the night, one thousand times a night, those waves wash through all the experiences of your day, all the little synaptic connections that you made all day long, and every one of those connections, all of them, gets just a little bit softer. They get weaker, progressively, gracefully, they get weaker. Even, he says, the things you want to hold on to, like the guitar. Wait a second, wait a second, you were the one who said

you learned how to play the instrument in the afternoon, you went to sleep and you play the instrument better in the morning. Yeah. Why would you wake up the next morning playing better? You should play more weekly with less confidence and less memory because after all you've just given the whole place a bath. It's all relative sir. What he means by relative is this. That mess of new connections in your head, some of those connections are softer, some of those connections were louder. The random things you ordered for lunch, they're softer.

Okay. But the guitar, because you spend so much time thinking about guitar technique, you spend so much energy on it, that's louder. So we're just measuring connections here. Now imagine that sleep is a big volume knob. So listen to what happens when you lower the volume on the whole day. Lower and lower and lower.

Now you hear how the softer stuff just falls away? You can't hear it anymore? Yeah. But the guitar, while it's getting softer too, because it was so loud to begin with, now it stands out a bit more clearly no Yeah, the signal the scene of that have survived reasonably well are heard better because the background has become more silent So your ability to play the guitar better the next morning is not because you've learned Skills overnight that you didn't have before is because all the other stuff taken up your brain has gone down in volume and you're left with relatively speaking a better guitar fingering technique. You put your finger on it. So Mr. Ternoni feels that sleep is a little bit like wind and rain, like the process of

erosion. At the end of the day, or rather at the beginning of the morning, the things left standing are the things you need to know. This is Radiolab. I'm Chad. And I'm Robert. And today's program is about sleep. As in the kind of sleep where you perchance to dream. Exactly. Do you know that story about the benzene molecule? No. Speaking of dreams. No.

Well, here, okay. The benzene molecule? 1865. German chemist is trying to figure out the shape of this molecule benzene. He knows that has a certain amount of one kind of atom and a certain amount of another, but he can't figure out how they all link up.

Right. And he's tortured by this problem. Ghost Sleep has a dream of a snake biting its tail, wakes up, bolts right up, and says, it's a ring. It's a ring! Do you believe that? I want to. Well, yeah. I mean, don't get me wrong. I hate it when people tell me their dreams. Hate it. I want to stab my eye with a fork, frankly, when people tell me their dreams. I don't know why.

I'm never going to tell you about my dreams again. I'm good. But you know, you're not alone because for a long time, scientists have avoided studying dreams because they think they're so random and meaningless and unstudyable. But we did meet a guy. I'm Bob Stickgold, S-T-I-C-K, G-O-L-D. I'm an associate professor of psychiatry at Harvard Medical School.

Who found an interesting way to ask the question, Why do we dream? Simple question, very hard answer. Robert Stickgold was one of the first modern scientists to take dreams seriously. And for him, it actually began kind of by accident. I had been up in Vermont with my family. We had gone and climbed Camel's Hump, one of the higher, easy to climb mountains in Vermont. We'd gone at eight in the morning. We were

back at two in the afternoon. And for that whole day, he'd been up climbing on the rocks, gripping them with his hands, really climbing. Later that night... I lie down. I close my eyes. his hands really climbing. Later that night... I lie down, I close my eyes. I can feel the rocks under my hands. And I sort of startle up and I say, well, that's really bizarre.

It wasn't like I was thinking about it. I was there. I could feel the rock. I'd been off the mountain for eight hours. Nothing like that had happened. I lied down in bed for three minutes starting to go to sleep and boom it's there and I tried again and I fell asleep. Two hours later I wake up, have to go to the bathroom, go to the bathroom, I come back and I say, that was way cool, I have to try that again. And I cannot get it back.

try that again. And I cannot get it back. What happened in those two hours to those memories that they won't intrude anymore? And then I started talking to friends and they said, oh, try canoeing. Or someone else says, try white water rafting if you want to get that. And someone else says, oh, hello, take organic chemistry. And you go to bed at night and all you see are these bloody molecules rotating in front of your eyes. Those daytime activities are affecting your dreams. And that got him thinking. What exactly is the connection

between what you do during the day and what you dream at night? What are the rules of that? He figured, all right, well, this replay is kind of interesting, maybe I'll test it. But how? If I get some subjects together, what could I have them do during the day that would reliably end up in their dreams? Well, you can't have them all go for a hike. And I'm probably not going to get permission to take them whitewater rafting.

Too expensive. So what could he do? Sort of sat fallow for a year. And I was moaning to some of my students about how I can't think of how to do this. And someone says, Tetris. And somebody else says, absolutely. And I'm saying, what? What?

They say, well, don't you play Tetris? And I say, yes. Well, when you start playing Tetris, Turns out when you start playing Tetris... You go to bed at night, you lie down in bed, and you see Tetris pieces falling down in front of your eyes. Sure. Sure? Oh yeah. You knew that?

Absolutely. Your eyeballs. You guys both know that? Oh yeah. I got a cover of a science magazine for the first published paper on dreaming in 40 years because I discovered that and everybody already knew it. It was that simple. He got a bunch of people, put them in a room, had them play Tetris.

Later that night they woke up and 60% of them were dreaming of Tetris. 60%. How do you know that? I mean just from their report? 60% of them. We're dreaming of Tetris. 60%! How do you know that? I mean just from their reports? They report as they're falling asleep, we're monitoring them electrophysiologically, and as they start to drift off to sleep, please report now. Filming.

Yeah. The first day. This Tetris observation was a pretty good start in terms of getting at that question. Why do we dream? Why do we dream? Why do we dream? How does it work? What if, as a next step, instead of having the people report their own dreams, waken them up from doing that whole thing, what if instead you could cut the person out of

the equation entirely and go right to the source, to the dream directly? Matt Wilson. I'm a researcher here at MIT and I'm a neuroscientist studying learning and memory. That's what Matt Wilson does. He takes us to the dream lab. So when we first come in, what we see is this bank of monitors. Thirteen monitors all in a row. Each monitor displaying ongoing activity in the brain.

Little panels, each panel showing these... It's like the Kennedy Space Center really. All the monitors have data just flashing all over them. Graphs and squiggly lines and numbers. It's not immediately clear where all this information is coming from. But if you peek around the back, you'll see that all the computer wires go to one box, which then connects to a cable, which then goes up to the ceiling, over to a wall, and down into the head, into the head of one tiny rat. He's just kind of hanging out in his own little basket.

Is that the little guy himself? Yeah, that's him. He looks pretty normal except for this cable coming out of his skull, and the cable is basically a microphone, or a bunch of them, which Matt uses to eavesdrop on the brain cells inside the rat's head as they chit chat. And this is what that sounds like. You can hear this kind of snap crackle pop sound. These are individual cells that are firing. Like a rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr Right there. One of those. That kind of whooshing sound. I can tell this animal is sitting, resting, quietly.

Amazingly, he says this while he has his back to the animal. He is so fluent with the Morris Code language of the rat's brain cells, he doesn't even have to actually look at the animal to know what it's doing. He can just instantly decode all of that snapping. Kind of like that guy in The Matrix, the bald guy. I don't even see the code. All I see is blonde, brunette, redhead. Just by listening, Matt knows when the animal is sitting, he knows when it is sleeping,

he knows when it's running around in a maze, he even can tell which direction it's running. Just happened that as we were studying these patterns while the animal ran around, after the experiments, the animals would, they would get tired, they would go to sleep. I would be there in the room, but I would continue to listen to the activity. Notice how it's gotten silent? And I began to notice that when the animals were asleep, the brain cells weren't just firing randomly. In fact, when animals would go into REM sleep, so now he is in, going into REM right now. The pattern of activity here, notice it's not these whooshes anymore, sounded very much like the pattern

that the animal had just been running through. In fact, if you weren't watching the animal, you would think, oh, animal has gotten up and is running around again. But then you turn and you look and you see the animal is asleep. He checked the data and it wasn't simply that the rat was running around in its mind while its body was asleep. It seemed to be running a specific route. The same route, in fact, that it had run earlier in the day. Same sequence, same order, same everything?

Yes. It was rerunning its maze, step for step. So then he asked the next question. Are they seeing the things that they saw while they were awake? We can actually look into these questions as a rat. And? So the answer is we see evidence of replay in basically all of the parts of the brain that we have looked in.

They see the maze that they ran through? The very same maze? Yes. So that is dreaming in a sense. Well, how do we define dreaming? Sounds like dreaming to me. I don't know. But the question remains, why would the rat or any creature do this? And so Matt came up with a simple next experiment. He decided to give the rat two mazes.

What would that do to its dreams in the night, or whatever you want to call them? If they run on maze number one, and then on maze number two, we see them running maze one and maze two together in a way that they did not experience when they were awake. So it's like a remix, a new pattern that includes part of maze one and part of maze two. It turns out that when the rat had more than one maze in its memory, it began to invent completely new mazes. This gives us the thought that sleep is this unique opportunity to basically run through events to put them together in ways that may not have occurred while the animals were awake. And that's what learning really is. Learning is about synthesis,

about taking things that were apparently unrelated, figuring out the connection, figuring out the rules, the hidden rules, the undiscovered rules that will allow us to create something new. I think dreaming is a time when we try out possibilities that in waking we might not feel were worth trying. And when it really works, it can be profoundly important. If Robert Stickgold is right, then how does this solving the problem thing,

how does it work? How does the brain decide what to put into a dream and what to leave out of a dream? One of the interesting things about dreams is that people don't have dreams where they're word processing, where they're surfing the net. These things that they spend huge amounts

of their day doing don't get into their dreams. But somehow Tetris gets in there every time. Every time. Why would that be? Well, he has a hunch. Which he's actually exploring with a completely different video game. We've moved to a game called Alpine Racer, which we bought out of an arcade.

She showed us. Took us down the hall to the game room. And there in the corner it stood. Market place. Oh wow, it's a full body game. Please step up. I stepped up to the game. It's trying to lock itself.

Got out of the platform. It's still warming up. And then I set off down a virtual mountain. Alright, I'm going down the hill. I'm also a girl. I'm also avoiding the skis. Oh, I'm going to the hill. I'm also a girl. I'm also avoiding the skeet. Oh, I'm doing a nice little turn there. Be careful of the little wall. Straight down ahead. And down we go.

Oh no, no, that tree! Wait, wait, I got down... Ah, ah! We're now going to go through the tunnel. This is a... Ow! Oh, that hurts! As you can hear, this game was really stressful, which is by design. Robert Stickel has the theory that as you go through your day, your brain is constantly keeping track of emotions.

That's the thing. Emotional content. Like when you run into a virtual tree, for example. Your brain is going to flag that stuff. It's going to flag that as important. It says, oh, I need to remember this so I can work on it later. I'm going to put a sticky on this one. So if it puts a sticky on everything that's hard during the day, then all the brain has to do when it's creating a dream is go and grab

stickies. Oh, then I died. But I like, and it's over. Could you say that again? So you have people play Alpine Racer for 45 minute bursts throughout the day. What happens next? You wake them up? We monitor their brain activity and just as they're falling asleep within the first two minutes after they fall asleep, we'll wake them up. Please report now. There's a microphone right next to them in their bed, and they just report what was going through their minds. I was just thinking about skiing. Skiing. And we get, on the first night, up to 40% of all the reports

being about skiing. And the game that I've been playing. I'll play at ski race circuit. 40 percent. Almost half of them. And that's right up there what I would expect to see after trauma. Where something has been labeled so intensely that the brain says, okay, it's obvious

what's on the agenda for tonight. Stickgold thinks he's seeing the outline of the dream making process here. It starts, really simply, at the very beginning of sleep, like right after you fall asleep, with the replay. This, he suspects, is just the brain emptying out its stickies. Things that really intrigued me during the day, that I felt during the day.

Yeah, but... What happens if we let the people go to sleep, sleep two hours, like I did in that very first time after climbing the mountain. Wake them up after two hours of sleep. Because remember, he couldn't get back the memory of the rocks after he'd spent two hours asleep. That's right, and what he's found is that if you fast forward two hours into the dream.

Get almost no reports of skiing at all. The replay seems to dissolve into a remix. We start getting reports like, oh, I dreamt I was sliding down a hill. Like I'm going downhill. Just rolling down a hill. Downward motion. I was thinking about, I was about to say a downhill banana.

I was thinking about skateboarding. I was thinking about Thinking about a bunch of bananas. Doing yoga on a ski slope. Someone else had a dream that they were rushing through a forest with their body incredibly stiff and their legs not moving at all as if they were on a conveyor belt. It's like as the dream goes on the brain is starting to free associate. What do I have in my past that has anything to do with mountains, anything to do with

crashing or skiing, anything at all that can help me. What do I have in all my memories, in my case from the last 60 years, that fits associatively, thematically? And the result? Well, it might seem random, it is, but every so often, he says, you come up with the right answer. So now we get to your dreams of people discovering the structure of benzene.

Kuchel was his name. Kekul actually was his name. August Kekul. He was the German guy I talked about earlier who had a dream of a snake eating its tail and realized from that dream that the shape of the benzene molecule is a ring. I don't know if that dream is true, but maybe that is in fact the point of dreaming. It's this time when you shut off the outside, turn inside, take the problems that you've got and start to really work on them, pull them apart, make connections that you wouldn't

normally make during the day. However, have you ever wondered why it would be necessary when solving problems like this to dream so vividly. Are you at all puzzled by the super duper technicolor extraordinarily cinematic quality of some of these things? Because if it were just an everyday brain function to sort of make sense of the world and allow you to make new connections, you really wouldn't need quite the movie quality. So when we talk about dreams, what seems to come into dreams are memories, concepts, relationships, associations that have a strong emotional flavor. And I'm guessing from the data need a full blown orchestration to be properly processed.

And it is. It's technicolor. The colors are overwhelming almost. So if I hear you write what you're saying to Robert's question about why are the dreams so vivid, is that I don't know, but maybe the vividness helps. That whole long answer is what a Harvard professor says instead of saying I don't know. So.

So. Harvard professor says instead of saying, I don't know. All right. That's all we got for today. If you'd like to learn anything more about what you heard in today's show, please visit radiolab.org. Hi, I'm Samin and I'm from Oakland, California. And here are the staff credits. Radio Lab was created by Jad Abumrad and is edited by Sorin Wheeler. Lulu Miller and Latif Nasser are our co-hosts. Dylan Keefe is our Director of Sound Design. Our staff includes Simon Adler, Jeremy Bloom, Becca Bresler, W. Harry Fortuna, David Gable,

Maria Paz Gutierrez, Sindhu Yenum Sambandham, Matt Kielty, Annie McEwen, Alex Neeson, Valentina Powers, Sarah Carey, Sarah Sandbach, Ariane Wath, Pat Walters, and Molly Webster. Our fact checkers are Diane Kelly, Emily Krieger, and Natalie Middleton. Hi, I'm Erica Inyongers. Leadership support for Radiolab Science Programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simon's Foundation initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.