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Hey, I'm Latif 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 is a fundamental mystery that takes up about a third of your life and actually probably more. Okay,
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 any more 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 hosts, Jad and Robert. Wait, you're listening? Okay. All right. Okay. Okay.
You're listening to Radiolab from WNYC. Rewind. I just thought I'd see if I could get the sound of baby 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 it is.
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, you know, 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 a pretty good way to begin, huh? With shame? Yeah, yeah. Today on Radiolab, we're going to 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 Krolwich. I'm Jad Abumrad. Stay with us.
For centuries, people thought that sleep was kind of the opposite of being awake. It's reasonable, one would think. 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. In fact, like, sometimes a bomb could go off and you wouldn't wake up. I can hardly wake up even in a fire.
I don't know why. No, I'm a really heavy sleeper. I'm a very, very heavy sleeper. The point is, if all you've got are your eyes to go on, sleep can seem like being off. 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 for 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 happened. This esteemed lecturer walks in the class, pops a cassette into the tape deck, hits play, and out comes this sound. Well, the sound was... Or... Wait a second. Let me get it right. Oh, here we go.
and multiply this by a hundred. This, the professor announced, is the sound of a cat's brain while asleep. My God! Schenck 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 on his little kitty basket its brain was very very alive much more than anyone expected and it's this is still a weird revelation like take my cat Sammy Sammy all right this is 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, we're going to figure out anything about sleep. We have to ask the brain. And then 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 skull.
And then you insert your electrode. Then you've got a little window into their brain. You could see right there on the screen. 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 in iguana, it's not a nice thing to do. 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 Oler. Testing. Testing.
These are our big boys here, and they all have nice hats. These guys are a little frightening to me. They're pretty huge. Oh, I didn't know that. Pick that one up. What is that?
Let me put it to you as a puzzle. Forget iguanas. Dolphins, right? Dolphins. 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 10-year-old Atlantic bottlenose dolphin. His buddy Avalon is 12 years old. And that's our trainer, Megan Tutera. Avira 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 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.
It would drown. Right. And yet they do manage to sleep. A lot. How long? Eight hours a day. Like us. 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? Uh-huh. 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 could 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.
Those are beautiful. Wow, that is amazing. Yeah, it's called unihemispheric 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...
By this guy. I'm Charles Amlaner, 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 a student had been at the park one day and they noticed something. We observed that ducks... Ducks. Ah, ah.
Sometimes we'll 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? 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.
Rock the 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've got to sleep for whatever reason. Right. But sleep is dangerous. Danger. Danger.
That's the headline. For dolphins, the main danger is drowning. You know? For ducks... Getting eaten. Exactly. Ducks have to sleep. But how can they? When lurking in the darkness are foxes and wolves and a hundred other eaters of ducks. Do you like snakes? I don't know. 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. Hi. Big snake. He is what, about a four foot long python? Mm-hmm. 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. 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! Us!
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 his theory. Sometime long ago, our scaly ancestor wandered up onto land and thought, I think I'll dig a hole. Yeah, I'm going to 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 safety.
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. A 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. 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. Now what if that's true? We all have buried deep in our reptile brain a sort of predator alert system. Perhaps in 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 Schenck, 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. So look at the time.
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, large guys thrashing 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.
This is Martin Zabel, age 88. He's another of Dr. Schenck's patients. In Martin's case, the attackers never had a face. Sometimes it was a bear. That's Martin's wife, Gertrude. Scram! 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.
Gertrude and Martin Zabel are still married, believe it or not, after 57 years, though she did force him to sell his guns. So you're suggesting then that all these 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 wary. 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, Cara Oler. 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.
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This is Radiolab. You are Robert Krolwich. Robert Krolwich is my name. And you're? I'm Jad Abumrad. And today our topic on Radiolab is sleep. 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. 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 Palin. 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 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. So anyway, that was my first day back at work. Dominic will not sleep.
I don't know why. And I'm trying to get him to sleep. I'm kind of at my wit's 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 and I don't know how to do this. Come here, sweetie. Come on, come on, come on. Just hang out 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. I have to do this. I've been struck by these waves of...
satisfaction and delight with being alive in this amazing landscape with a funny kid. These 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 just suddenly feel like, wow, I'm so lucky. Okay, I've got to take my kid to play now. Here we go.
Did 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 and an element to this whole thing is that I get angry sometimes.
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'm 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
To that moment when I'm able to say, honey, time to go to sleep. And he does it. Tired. No. Not tired. Just in my cup. Close your eyes, Buck. Close your eyes. There's my personal take on what it's like to be sleepy and to crave sleep as much as you crave water or breath. I crave it. Thanks to Hannah Palin.
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, what... Because she's...
She hasn't been sleeping. Well, yeah, but what makes her, you know, what is the essence of tiredness? Lack of sleep. Hello. No, chemically, I'm asking you, chemically. 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, actually. I'm glad you think so, because I know a guy who has a theory about this. Did you see Tiger yesterday night?
He's unbelievable. He had 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 mice, it's been shown in rats, it's been shown in fruit flies.
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? A 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.
inside the cell and essentially clog up. And it's really quite toxic to cells. Clumpiness equals tiredness. That would be his formula. Remember when Hannah was so exhausted? Yeah. God, this just sucks. Well, 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's so happy? I suddenly feel like, wow. Because of the sleep... I'm so lucky. 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. Testing, testing, testing, testing. 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. But like a quarterback or tight end, not like a linebacker. So big but not overwhelming. Yes. How do you even know that?
Yeah, 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 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 into 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. He was 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 beautifully.
That happened to you? It happened to me. It happens to lots of people. That happened to me all the time. I discovered that sometimes if I worked on a piece and put it away and 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 going to play drums. So 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, I worked on it a lot. I just keep going and going. I remember playing that one thing again and again and again. And I finally just gave up and went to sleep.
And the next morning, I got up and went straight to the kit, and I just played it immediately. The butt hit the stool, and she was gone. She could just do it. I thought it was magic. You could just learn stuff in your sleep. So in the middle of the night, somehow, the things that your fingers did repeatedly, and the notes that you were using to propel your fingers, all those things somehow got more...
got better learned. So you learned overnight or you... What does that have to do with... Do 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. Yep. And yet every experience you have during the day is going to take away some space. It uses up a little of what you've got. When you are awake, inevitably, you learn whether you want it or not. You are going around talking to me, having breakfast. I'll just have a medium coffee. Going to work.
Then yakking 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. 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 a 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. And 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 upon the other upon the other
By the time you're ready for sleep at the end of the day, up in your head, it's a giant, unruly mess. And that is where we think sleep kicks in.
Well, I'm going to guess here, but I think you think that sleep is a garbage detail that comes in and 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... 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, 1,000 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. Why would you wake up the next morning playing better? You should play more weakly, 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. I'll have a turkey on rice.
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, lower, and lower. Lower.
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 synapses 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. It's 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. LAUGHTER
So Mr. Chinoni 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.
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This is Radiolab. I'm Jad. 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. The benzene? 1865. German chemist is trying to figure out the shape of this molecule, benzene. He knows it 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. Yeah. 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. 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. Yeah.
and unstudiable. Right. 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 8 in the morning. We were back at 2 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, and I can feel the rocks under my hands. And I sort of startle up, and I say, Whoa!
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 lie 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. I have to go to the bathroom. I 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. 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 whitewater 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
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? It 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...
It 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? Oh, yeah. You knew that? Absolutely. 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. Ha, ha, ha. Ha, ha, ha.
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 reports? They report them. As they're falling asleep, we're monitoring them electrophysiologically, and as they start to drift off to sleep, please report now. Filming. Yeah.
This Tetris observation was a pretty good start in terms of getting at that question. 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, waking them up and 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.
It 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 with 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. There he is. He's just kind of hanging out in his own little basket. See him just resting. 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... right there, like one of those. That kind of whooshing sound. I can tell this animal's sitting, resting, quietly.
Amazingly, he says this while he has his back to the animal. He is so fluent with the Morse 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, even can tell which direction it's running. It just happened that as we were studying these patterns while the animal ran around, after the experiments, the animals 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, in fact, going into REM right now, the pattern of activity you could hear, notice if 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, the 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, they see the maze. So that is dreaming in a sense. Well, how do we define dreaming? Sounds like dreaming to me. I mean, 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 of 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 and figuring out the connections, 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. This way. Took us down the hall to the game room. Here we are. And there in the corner it stood...
Mockingly. Oh, wow, it's a full-body game. Please step up. I stepped up to the game. Wait, it's trying to lock itself in. Got on the platform. It's still warming up. And then I set off down a virtual mountain. All right, I'm going down the hill. I'm also a girl. I'm also avoiding the skis. Oh, I'm going to take a nice little turn there. Be careful of the wall. Straight down ahead. And down we go. Oh, no, no, that tree. Wait, I got down...
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 Stickle has the theory that as you go through your day, your brain is constantly keeping track of emotions, of
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 it's 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 I died but I died nice
Just for the record, you got further than Jad on your first try. Wow. Wow. It's 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 down.
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 it. It's a key race. 40%. Almost half of them. And that's right up there of 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...
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... The replay seems to dissolve into a remix. Like a...
Going downhill. Just rolling downhill. Downward motion. I was thinking about... I was about to say a downhill banana.
I was thinking about skateboarding. I was 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.
Kekul 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 right, what you're saying to Robert's question about why are the dreams so...
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. 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. Radiolab 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 Bressler, W. Harry Fortuna, David Gable, Maria Paz Gutierrez, Cindy Yenumsambandam, Matt Kielty, Annie McEwen, Alex Neeson, Valentina Powers, Sarah Carey, Sarah Sandbach, Arianne Wack, Pat Walters, and Molly Webster. Our fact checkers are Diane Kelly, Emily Krieger, and Natalie Middleton.
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