LATIF NASSER: Hey, I'm Latif Nasser. This is Radiolab. This week, I'm reupping an episode from 2007, you know, which was like the 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, 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 gonna 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.

[RADIOLAB INTRO]

HANNAH PALIN: I just thought I'd see if I could get the sound of babies sleeping.

JAD ABUMRAD: 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—or 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 grew 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.

SCIENTIST: Well, pretty much everything sleeps.

SCIENTIST: As far as we know, all mammals do it. All birds.

SCIENTIST: Bees, locusts, cockroaches, crayfish ...

SCIENTIST: Reptiles, insects.

SCIENTIST: Scorpions.

SCIENTIST: Everything that's been studied has something that looks like sleep.

SCIENTIST: 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?

ROBERT KRULWICH: There you go. Okay. [laughs]

ROBERT: That's a pretty good way to begin, you know?

JAD: With shame?

ROBERT: Yeah, yeah. Today on Radiolab, we're gonna try to correct this shameful state of affairs when it comes to the subject of sleep.

JAD: We'll talk with people who can help us understand what it's for.

ROBERT: Why we do it.

JAD: And what happens when we don't.

ROBERT: I'm Robert Krulwich.

JAD: I'm Jad Abumrad.

ROBERT: Stay with us.

JAD: For centuries, people thought that sleep was kind of the opposite of being awake.

ROBERT: It's reasonable, one would think.

JAD: Sure. Because 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.

ROBERT: I can hardly wake up even in a fire. [laughs] I don't know why! No, I'm a really heavy sleeper. I'm a very, very heavy sleeper.

JAD: The point is, if all you've got are your eyes to go on, sleep can seem like being—well ...

ROBERT: Like being off.

JAD: Yeah, like off-ness.

ROBERT: Right.

JAD: Or worse.

CARLOS SCHENCK: Well, both Shakespeare and Cervantes referred to sleep as 'death.'

JAD: That's Dr. Carlos Schenck. He wrote a great book about sleep called Paradox Lost.

CARLOS SCHENCK: 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 the prevailing theory for centuries.

JAD: 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.

CARLOS SCHENCK: My first year at medical school ...

JAD: This was back in 1972.

CARLOS SCHENCK: ... we had an emeritus professor who actually was a Nobel Prize winner, Dr. Eccles. Sir John Carew Eccles from Australia.

JAD: Here's what happened. This esteemed lecturer walks into class.

ROBERT: Uh-huh.

JAD: Pops a cassette into the tape deck, hits play, and out comes this sound.

CARLOS SCHENCK: Well, the sound was puh puh puh puh puh puh. Or—wait a second, let me get it right. Oh, here we go. [sound of a pen striking a glass]. And multiply this by a hundred.

JAD: This, the professor announced, is the sound of a cat's brain while asleep.

ROBERT: My God!

JAD: Schenck almost fell out of his seat.

CARLOS SCHENCK: This is the brain during sleep? Making these really rapid, high-pitched, multiple sounds. That just blew us away. It wasn't just ...

JAD: Clearly, while that cat was curled up in its 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.

JAD: Sammy.

JAD: All right? [cat purring] 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, if we're gonna figure out anything about sleep, we have to ask the brain."

JOHN LESKU: And this is the room where we do all of our surgeries.

JAD: And luckily, that's easily done—if you're willing to get your hands dirty.

JOHN LESKU: 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 electrodes.

JAD: Then you've got ...

JOHN LESKU: And that's simply it.

JAD: ... a little window into their brain. You could see right there on the screen, you could see the brain waves.

ROBERT: Wait a second. Are you out of your mind? Did you just put a hole into a kitten's head?

JAD: No, that wasn't my cat! C'mon!

ROBERT: So what was it we were doing there?

JAD: What you just heard was a mock surgery to an iguana, actually.

ROBERT: [laughs] Even an iguana. I mean, it's not a nice thing to do.

JAD: Look, look, look. The animal was not harmed.

JOHN LESKU: 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.

JAD: Yeah. And that, by the way, is John Lesku. He's a graduate student at the Ecology Department ...

JOHN LESKU: At Indiana State University.

JAD: Which is where we are. John gave our reporter, Kara Oehler ...

KARA OEHLER: Testing.

JAD: ... a tour of the lab.

JOHN LESKU: There are big boys here, and they all have nice hats.

JAD: Showed her the iguanas.

KARA: These guys are a little frightening to me. They're pretty huge.

JAD: They're like four feet long, head to tail.

ROBERT: Oh, I didn't know that.

JAD: I mean, they look like baby alligators.

JOHN LESKU: Pick that one up.

JAD: 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 in us.

ROBERT: What is that?

JAD: Well, let me put it to you as a puzzle, okay?

ROBERT: Mm-hmm.

JAD: Forget iguanas. Dolphins, right? Dolphins.

ROBERT: Yep.

JAD: 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.

MEGAN TUTERA: Cody is our 10-year-old Atlantic bottlenose dolphin. His buddy Avalon, is 12 years old.

JAD: And that's their trainer, Megan Tutera. Avir Mitra is holding the mic. Anyhow, here's the puzzle—and we asked Megan about this. How is that her two dolphins, Cody and Avalon, can successfully sleep given the inherent challenges of being a dolphin?

ROBERT: I don't—what are the challenges of a dolphin?

JAD: Well, they have significant challenges, my friend. First, they've gotta breathe.

MEGAN TUTERA: They're not—they're conscious breathers. They're not unconscious breathers. So they have to think about breathing.

JAD: Making matters worse, dolphins are not fish, so they have to breathe air. Which means they have to constantly, consciously, come up to the service to breathe air every few minutes. So you can imagine what would happen if they decided to go unconscious for a while.

ROBERT: They would drown.

JAD: Right. And yet they do manage to sleep. A lot.

ROBERT: How long?

JAD: Eight hours a day. Like us.

ROBERT: Really?

JAD: Yeah, eight hours.

ROBERT: But how?

JAD: That's the puzzle.

MEGAN TUTERA: 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?

AVIR MITRA: Uh-huh.

MEGAN TUTERA: That's exactly what they look like. And they rest half their brain at a time.

AVIR: Half their brain is asleep?

MEGAN TUTERA: Half their brain is asleep at a time.

JAD: That is nature's solution: to cut the dolphin brain in half.

ROBERT: You mean literally in half?

JAD: Literally in half, so that one half can snooze while the other half keeps the dolphin swimming and surfacing.

ROBERT: Wow!

JAD: 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.

MEGAN TUTERA: Well, 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.

STEVEN LIMA: This little guy can be characterized as groggy.

JAD: That's Steve Lima. He runs one of the labs back in Indiana.

STEVEN LIMA: They're sort of awake and they're sort of asleep, and it's just a way of staying awake enough.

JAD: And again, it's easy to miss, but if you look inside that groggy dolphin's brain at what the brainwaves are doing ...

STEVEN LIMA: It's exquisitely obvious.

JAD: It's clear as day.

STEVEN LIMA: 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 jagging all over the place.

AVIR: Awesome! Oh, those are beautiful!

ROBERT: Wow, that is amazing!

JAD: 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.

JOHN LESKU: Oh yeah. The aquatic mammals like whales, seals and sea lions.

JAD: John says that all of the marine mammals that have been studied seem to do it too.

JOHN LESKU: Recently walruses, they all are found to engage in unihemispheric sleep as well.

JAD: And now the Indiana team led by this guy ...

CHARLES AMLANER: I'm Charles Amlaner, chair of the Department of Ecology and Organismal Biology.

JAD: ... they have found this weird split-brain behavior in creatures of the air.

ROBERT: Oh!

CHARLES AMLANER: Okay, let me just back up a little bit and describe this experiment.

JAD: Charlie and his student had been at the park one day and they noticed something.

CHARLES AMLANER: We observed that ducks ...

JAD: Ducks.

CHARLES AMLANER: ... sometimes will get together into groups.

JAD: Like, on a log. Four ducks will get together and snooze in a neat little line.

CHARLES AMLANER: 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.

JAD: The inevitable question ...

CHARLES AMLANER: What's going on here?

JAD: ... led to a very simple experiment.

CHARLES AMLANER: We put four birds in a row.

JAD: Four mallard ducks, this time in a lab. And they watched them sleep.

CHARLES AMLANER: 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.

JAD: One more time.

CHARLES AMLANER: Slept with one eye closed and one eye opened.

JAD: It's just like in that song. You know that Metallica song?

ROBERT: [laughs] I missed it.

JAD: It's a good one.

ROBERT: But I knew they were all botanists.

JAD: It's true! You know, no one knows this, but that song is really about adaptive sleeping behavior in ducks.

CHARLES AMLANER: 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.

JAD: 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.

CHARLES AMLANER: The left eye is attached to the right hemisphere, the right eye is attached to the left hemisphere.

JAD: 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.

CHARLES AMLANER: The bird could simultaneously sleep and be awake.

JAD: Not only that—here's the cool part—after a few hours ...

CHARLES AMLANER: What happened was is that the birds that were on the outer edge, then would rotate.

JAD: Stand up, turn around.

CHARLES AMLANER: 180 degrees.

JAD: And then sit back down.

CHARLES AMLANER: And the other eye would then get some sleep, and consequently the opposite hemisphere would get some sleep.

JOHN LESKU: When we saw that we said "Oh yeah, that's good!"

JAD: Good, because right there in the ducks was a perfect illustration of what these guys think it's all about: you gotta sleep, for whatever reason.

ROBERT: Right.

JAD: But sleep is dangerous. That's the headline. For dolphins, the main danger is drowning, you know?

ROBERT: Yeah.

JAD: For ducks ...

ROBERT: Getting eaten.

JAD: 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?

JOHN LESKU: Do you like snakes?

KARA: I don't know. Not really.

JOHN LESKU: What?

KARA: I don't dislike snakes.

JOHN LESKU: He's a good man. He's a good man.

KARA: Mm-hmm.

JAD: In another nifty experiment, John took the resident snake, Monty ...

JOHN LESKU: This is Monty.

KARA: Hi.

JAD: Big snake.

JOHN LESKU: He is, what, about a four-foot-long python.

JAD: And at night ...

JOHN LESKU: You're so cute!

KARA: [laughs]

JAD: ... John brought Monty the python into the room where his iguanas sleep.

JOHN LESKU: And he terrifies them.

ROBERT: Really?

JAD: 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.

ROBERT: [laughs] I bet they did!

JAD: Pop, pop, pop, pop! And they trained that open eye right on Monty the snake.

STEVEN LIMA: Put a big snake in the room, and they'll watch it with one eye all night.

JAD: That's Steve Lima again.

STEVEN LIMA: They don't like these snakes, that's for sure. And I mean, we moved the snake from the room the next day and they're still looking for it the next night or two.

JAD: So they keep one eye trained on that door for a few more days?

STEVEN LIMA: About two or three days, then they go back to regular sleep.

ROBERT: So what does this all mean?

JAD: Well, think about this. Okay, all the sea mammals, they do it.

ROBERT: Right.

JAD: 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?

ROBERT: You mean who's left not sleeping with half a brain on and the other half a brain off?

JAD: Yeah.

ROBERT: Um ...

JAD: Us!

ROBERT: Really?

JAD: We may be the strange ones.

JOHN LESKU: 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.

JAD: Not all mammals, says John. The terrestrial mammals. The ones that live on land.

ROBERT: Ah.

JAD: And here's his 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. Ahh! And so we lost it.

ROBERT: [laughs]

JAD: 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.

STEVEN LIMA: Predation risk.

JOHN LESKU: Predation risk.

CHARLES AMLANER: Predation risk.

JAD: Which is really just a fancy way of saying ...

CHARLES AMLANER: Generally speaking, just your risk of being killed.

JAD: 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.

CARLOS SCHENCK: Nice warm bed.

JAD: A locked door.

CARLOS SCHENCK: A locked door. Covers.

JAD: Maybe a nice neighborhood.

CARLOS SCHENCK: A good police force looking after you at night time. And you live in a country that has a very secure living environment.

JAD: You would think that this whole predation risk idea has nothing to do with us. Well?

CARLOS SCHENCK: Well, there's a few studies that have looked at, say, sleep patterns where people are sleeping in novel environments.

ROBERT: What's a novel environment? What does he mean?

JAD: Well, like a hotel.

ROBERT: Oh.

JAD: That first night at a hotel, why is it no one can sleep well that first night at a hotel?

CARLOS SCHENCK: 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.

JAD: I suffer from that myself, I don't sleep well in hotel rooms. Especially if it was just one night per place or something, my sleep is terrible.

CARLOS SCHENCK: There are some folk that actually hypothesize there are certain predator relays in the brain, and that these circuits remain active at all times.

JAD: Now what if that's true that 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.

CARLOS SCHENCK: 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.

JAD: That's Dr. Carlos Schenck, who we heard from before. We're in Minnesota now at the Hennepin County Sleep Center ...

CARLOS SCHENCK: Here in the sleep lab ...

JAD: Where he works. We're standing in front of a grainy, black-and-white video of a little girl in her PJs, screaming.

CARLOS SCHENCK: So look at the time.

JAD: Dr. Schenck discovered an odd category of sleep disorders called 'parasomnias,' which is why we came to talk to him. 'Para' means around, 'somnia' means sleep. Around sleep. This might be the human analog to the ducks: people whose brains never quite shut off completely during sleep.

CARLOS SCHENCK: Well, this guy is interesting. He has seizures. No, no, no, he doesn't. Wait a second.

JAD: He showed us tape after tape.

CARLOS SCHENCK: We're viewing a man who we very affectionately call Santa Claus.

JAD: On the screen, a large guy thrashes back and forth.

CARLOS SCHENCK: His legs are moving. He's going back and forth from his side to his back.

JAD: And then suddenly, he starts to ...

[ARCHIVE CLIP: Ho, ho, ho, ho, ho. Ho, ho, ho, ho, ho, ho, ho. Ho, ho, ho.]

ROBERT: Is this real?

JAD: 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.

CARLOS SCHENCK: 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.

MARTIN SABELLE: The dreams can be very violent.

JAD: This is Martin Sabelle, age 88. He's another of Dr. Schenck's patients.

MARTIN SABELLE: I remember someone coming up the stairway.

JAD: In Martin's case, the attackers never had a face. Sometimes it was a bear.

MARTIN SABELLE: And I was gonna fight with him.

GERTRUDE SABELLE: He'd yell at them, "Get out of here!"

JAD: That's Martin's wife, Gertrude.

GERTRUDE SABELLE: "Scram!" He was always trying to protect me.

MARTIN SABELLE: Yeah, I would have black and blue bruises on my arms and hands because I was hitting the headboard.

CARLOS SCHENCK: 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.

GERTRUDE SABELLE: 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."

MARTIN SABELLE: She says, "Martin, you're dreaming."

JAD: Gertrude and Martin Sabelle are still married, believe it or not, after 57 years. Though she did force him to sell his guns.

GERTRUDE SABELLE: He has never been happy about that.

MARTIN SABELLE: Well, they were quite valuable.

ROBERT: 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 wary in the night?

JAD: 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.

ROBERT: 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.

JAD: That's right. Before we go to break, I just wanna thank Ann Hepperman for her excellent reporting in Minnesota, and also before her, Kara Oehler. And to remind you to stay with us because we're gonna turn our attention shortly from danger to deprivation. Radiolab will continue in a moment.

JAD: This is Radiolab. You are Robert Krulwich.

ROBERT: Robert Krulwich. It's my name. And you're ...

JAD: Jad Abumrad. And today, our topic on Radiolab is sleep.

ROBERT: Yep. It is something that all of us do. We can't help but do it. It's dangerous to do.

JAD: It's so good!

ROBERT: It's so good. and it's universal.

STEVEN LIMA: 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.

JAD: That's Steve Lima again from Indiana State University.

STEVEN LIMA: Because it would be such a great idea to not sleep.

JAD: Don't I know it.

ROBERT: [laughs]

JAD: 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.

ROBERT: Yeah.

JAD: 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.

ROBERT: Hmm.

JAD: That's the case with producer Hannah Palin. She kept this audio diary of her own experiment with sleep deprivation.

[baby crying]

JAD: She has an 18-month-old son.

HANNAH: 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 my computer screen and try to communicate that to the curator that I work for. The words didn't come. [whispers] 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.

[baby screaming]

HANNAH: 2:47. Dominic will not sleep. I don't know why. And I'm trying to get him to sleep and kind of at my wits end. Oh 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."

[baby crying]

HANNAH: 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. Come on. Come on. Come on.

HANNAH: So anyway, I needed to record just one thing really quickly, and that is that yesterday and today, I've been struck by—I've been struck by these waves of satisfaction and delight with being alive in this amazing landscape with a funny kid. 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 gotta take my kid to play now. Here we go! [singing] Do you know the muffin man? The muffin man.

HANNAH: 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. Well, he 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 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.

DOMINIC: I tired.

HANNAH: I'm tired.

DOMINIC: I'm tired.

HANNAH: 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? Not tired?

DOMINIC: Just talk.

HANNAH: Close your eyes, bug. 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!

JAD: [whispers] Thanks to Hannah Palin. And her son Dominic, and her husband Steve. I know. Poor Hannah.

ROBERT: 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 ...

JAD: Because she's—she hasn't been sleeping.

ROBERT: Well yeah, but what makes her—you know, what is the essence of tiredness?

JAD: Lack of sleep. Hello?

ROBERT: 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 what I mean.

JAD: That's a good question, actually.

ROBERT: Good. I'm glad you think so. Because I know a guy who has a theory about this.

ALLAN PACK: Did you see Tiger yesterday?

ROBERT: Tiger Woods?

ALLAN PACK: He's just unbelievable. He had the best round of anybody. I mean, the guy is unbelievable!

ROBERT: This is Dr. Allan Pack, and in addition to being a rabid golf fan, he's also a rabid—can you be a rabid biologist?

JAD: [laughs] Sure.

ROBERT: 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 ...

ALLAN PACK: And that's been shown in mouse, it's been shown in rat, it's been shown in fruit fly.

ROBERT: ... is that inside certain cells in all those different animals, when they're sleep-deprived ...

ALLAN PACK: Eventually what happens is you don't get proteins properly folded.

JAD: Excuse me?

ROBERT: [laughs]

JAD: Proteins properly folded?

ROBERT: Mm-hmm.

ALLAN PACK: A phenomenon called the unfolded protein response.

JAD: What on Earth does that mean? Is that a good thing or a bad thing?

ROBERT: You're asking why do you need proteins to properly fold?

JAD: Yeah, I guess that's what I'm asking.

ROBERT: Well, you're made of proteins. Proteins are the essence of you, so if your proteins are misshapen, if they're not folded properly ...

ALLAN PACK: 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 inside the cell and essentially clog it up. And it's really quite toxic to cells.

ROBERT: Clumpiness equals tiredness would be his formula. But remember when Hannah was so exhausted?

JAD: Yeah.

HANNAH: God, this just sucks.

ROBERT: Well, because she hasn't slept much ...

HANNAH: Totally sucks.

ROBERT: ... 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 [yawns]. But when she gets the sleep, remember when she's so happy?

JAD: Yeah.

HANNAH: I suddenly feel like, wow!

ROBERT: Because of the sleep ...

HANNAH: I'm so lucky.

ROBERT: ... 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 Doctor Giulio Tononi.

ELLEN HORNE: Testing, testing, testing.

ROBERT: And my producer Ellen Horne and I went to visit him at his offices in Madison, Wisconsin.

ROBERT: What are we expecting? What does he look like? We don't know what he looks like.

ELLEN: A football player.

ROBERT: A football player.

ELLEN: But like a quarterback or a tight end. Not like a linebacker.

ROBERT: Not like a linebacker. So big, but not overwhelming?

ELLEN: Yeah.

ROBERT: Yeah. How do you even know that?

ELLEN: Website. See, but I was totally wrong.

ROBERT: [laughs]

ROBERT: Now to be fair, he is a very attractive guy. He has sandy blond hair and glasses. He's actually more the sensitive guy intellectual than a linebacker.

ROBERT: Yeah, introduce yourself.

GIULIO TONONI: I'm Giulio Tononi. I am a professor of psychiatry here at the University of Wisconsin-Madison.

ROBERT: But when it comes to the subject of sleep, which is his specialty, he takes sleep very seriously.

ROBERT: What got you interested in sleep?

GIULIO TONONI: 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.

ROBERT: 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, just playing music.

GIULIO TONONI: 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.

ROBERT: That happened to you?

GIULIO TONONI: It happened to me. It happens to lots of people.

ROB CHRISTIANSEN: That happened 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 rest, I had it better learned than if I stayed up all night cramming.

JAD: Yeah.

JEANNINE DUFREE: 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.

ROB CHRISTIANSEN: The band is called the Sisterhood of Convoluted Thinkers.

JEANNINE DUFREE: And we switch instruments, like, a lot.

ROB CHRISTIANSEN: She's usually the bass player.

JEANNINE DUFREE: I was gonna play drums.

ROB CHRISTIANSEN: So she had to learn how to play drums.

JEANNINE DUFREE: So we rented a cabin.

ROB CHRISTIANSEN: We went somewhere to rehearse. And at night, she was really just kind of practicing and practicing and trying to get this rhythm.

JEANNINE DUFREE: This one particular beat. Like, I worked on it, like, a lot. I just keep going and going.

ROB CHRISTIANSEN: I remember playing that one thing again and again and again.

JEANNINE DUFREE: Yeah. 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.

ROB CHRISTIANSEN: The butt hit the stool and she was gone.

JEANNINE DUFREE: Ba-da-da-da-da-da.

ROB CHRISTIANSEN: She could just do it.

JEANNINE DUFREE: I thought it was magic. You could just learn stuff in your sleep.

ROBERT: So wait, 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 into—got more—got better learned. So you learned overnight, or you—I mean, what does that have to do with—you remember better in the morning?

GIULIO TONONI: What happens is that the next day you're a bit better off. What happened during the night to make you better off? This is up for contention.

ROBERT: Tononi's contention is that sleep helps you remember by forgetting.

JAD: Uh, I don't know what that means.

ROBERT: [laughs] Let me explain to you what he's saying. He says there's a limited amount of space in your brain.

GIULIO TONONI: The real estate in the brain is pretty limited.

ROBERT: Limited amount.

JAD: That makes sense. It's a small little guy up there.

ROBERT: Yep. And yet every experience you have during the day ...

GIULIO TONONI: Is gonna take away some space.

ROBERT: ... uses up a little of what you got.

GIULIO TONONI: 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.

ROBERT: Then yakking on the phone with your friends, talking to your mom.

JAD: Very different from the friends.

ROBERT: Then going home, taking a bath.

JAD: Gotta take a bath? Yeah, I get it. I get it.

ROBERT: Everything you do during the day, every thought you think, no matter how small, it all causes your brain to form new connections.

ROBERT: This conversation as we're having it, is reshaping my brain.

GIULIO TONONI: Yeah.

ROBERT: Little pathways are forming that weren't there before I sat down.

GIULIO TONONI: Exactly. Whether we recognize it or not, lots of things are going to change your brain by the end of the waking day.

ROBERT: 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 and 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.

GIULIO TONONI: And that is where we think sleep kicks in.

ROBERT: Well, I'm gonna guess here, but I think you think that sleep is a garbage detail? It comes in and says, "Okay, you're done. You're done. You're done."

GIULIO TONONI: It's actually even simpler than that.

ROBERT: 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 ...

GIULIO TONONI: We think that during sleep, waves ...

ROBERT: 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.

GIULIO TONONI: These waves are called slow oscillations.

ROBERT: And over the course of the night ...

GIULIO TONONI: One thousand times a night.

ROBERT: ... 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 ...

GIULIO TONONI: All of them.

ROBERT: ... gets just a little bit softer.

GIULIO TONONI: They get weaker. Progressively, gracefully, they get weaker.

ROBERT: Even, he says, the things you want to hold onto, like the guitar.

ROBERT: 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 played the instrument better in the morning.

GIULIO TONONI: Yeah.

ROBERT: 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.

GIULIO TONONI: It's all relative, sir.

ROBERT: What he means by relative is this. That mess of new connections in your head?

JAD: Yeah?

ROBERT: Some of those connections are softer, some of those connections were louder. The random things you ordered for lunch, they're softer.

JAD: Okay.

ROBERT: But the guitar, because you spent so much time thinking about guitar technique, you spent 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?

JAD: Yeah.

ROBERT: 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?

JAD: Yeah!

GIULIO TONONI: The signal, the synapses that have survived reasonably well are heard better because the background has become more silent.

ROBERT: 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 taking up your brain has gone down in volume, and you're left with, relatively speaking, a better guitar fingering technique.

GIULIO TONONI: You put your finger on it.

ROBERT: [laughs]

ROBERT: So Mr. Tononi 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.

JAD: This is Radiolab. I'm Jad.

ROBERT: And I'm Robert.

JAD: And today's program is about sleep.

ROBERT: As in the kind of sleep where you perchance to dream.

JAD: Exactly. Did you know that story about the benzene molecule?

ROBERT: No.

JAD: Speaking of dreams.

ROBERT: No.

JAD: Well, here ...

ROBERT: The benzene mol ...

JAD: 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 it can't figure out how they all link up.

ROBERT: Right?

JAD: And he's tortured by this problem. Goes to sleep.

ROBERT: Yeah?

JAD: Has a dream of a snake biting its tail. Wakes up. Bolts right up, and says, "It's a ring. It's a ring!"

ROBERT: [laughs] Do you believe that?

JAD: I want to.

ROBERT: Well, yeah.

JAD: 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. It just drives me ...

ROBERT: Well, I'm never gonna tell you about my dreams again.

JAD: Good.

ROBERT: [laughs] 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.

JAD: Right.

ROBERT: But we did meet a guy ...

BOB STICKGOLD: I'm Bob Stickgold. S-T-I-C-K-G-O-L-D. I'm an associate professor of psychiatry at Harvard Medical School.

ROBERT: ... who found an interesting way to ask the question ...

BOB STICKGOLD: Why do we dream? Simple question, very hard answer.

ROBERT: Robert Stickgold was one of the first modern scientists to take dreams seriously. And for him, it actually began kind of by accident.

BOB STICKGOLD: 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.

ROBERT: And for that whole day, he'd been up climbing on the rocks, gripping them with his hands, really climbing. Later that night ...

BOB STICKGOLD: I lie down. I close my eyes. 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, 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?

BOB STICKGOLD: And then I started talking to friends, and they say, "Oh, try canoeing." Or someone else says "Try—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.

ROBERT: And that got him thinking: what exactly is the connection between what you do during the day, and what you dream at night?

JAD: 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 dream?

ROBERT: Well, you can't have them all go for a hike.

JAD: Mm-mm.

BOB STICKGOLD: And I'm probably not gonna get permission to take them whitewater rafting.

JAD: Too expensive.

ROBERT: So what could he do?

BOB STICKGOLD: 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 said, "What? What?" They said, "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.

ROBERT: Sure.

JAD: Oh, yeah.

BOB STICKGOLD: You knew that?

JAD: Absolutely.

ROBERT: In front of your eyeballs.

BOB STICKGOLD: You guys both know that?

JAD: Oh, yeah.

BOB STICKGOLD: I got a cover of Science magazine for the first published paper on dreaming in 40 years because I discovered that, and everybody already knew it!

ROBERT: [laughs]

ROBERT: 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 percent of them were dreaming of Tetris. 60 percent!

JAD: How do you know that? I mean, just from their reports?

BOB STICKGOLD: They report. As they're falling asleep, we're monitoring them, electrophysiologically. And as they start to drift off to sleep, "Please report now."

JAD: This Tetris observation was a pretty good start in terms of getting at that question.

BOB STICKGOLD: Why do we dream?

JAD: 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: Matt Wilson. I'm a researcher here at MIT, and I'm a neuroscientist studying learning and memory.

JAD: That's what Matt Wilson does. He takes us to the Dream Lab.

MATT WILSON: So when we first come in, what we see is this bank of monitors.

JAD: 13 monitors, all in a row.

MATT WILSON: Each monitor displaying ongoing activity in the brain, with little panels, each panel showing these ...

JAD: 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.

MATT WILSON: Here he is.

JAD: He's just kind of hanging out in his own little basket.

MATT WILSON: You see him just resting.

JAD: Is that the little guy himself?

MATT WILSON: Yeah, that's him.

JAD: 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 chitchat. And this is what that sounds like ...

[scratching, popping sounds]

MATT WILSON: You can hear this kind of snap-crackle-pop sound. These are individual cells that are firing.

JAD: Like right there. One of those.

MATT WILSON: And that kind of whooshing sound ...

JAD: Uh-huh?

MATT WILSON: I can tell this animal's sitting, resting quietly.

JAD: 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.

ROBERT: Hmm.

JAD: Kind of like that guy in The Matrix, the bald guy.

[ARCHIVE CLIP, The Matrix: I don't even see the code. All I see is blonde, brunette, redhead.]

JAD: 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.

MATT WILSON: It 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.

[ARCHIVE CLIP, Matt Wilson: Notice how it's gotten silent?]

[ARCHIVE CLIP, Jad: Yeah.]

MATT WILSON: 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 ...

[ARCHIVE CLIP, Matt Wilson: So now he is, in fact, going into REM right now.]

MATT WILSON: ... the pattern of activity that you could hear ...

[ARCHIVE CLIP, Matt Wilson: Notice that it's not these whooshes anymore.]

MATT WILSON: ... 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.

JAD: 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.

ROBERT: The same sequence, same order, same everything?

MATT WILSON: Yes.

JAD: It was rerunning its maze step for step. So then he asked the next question.

MATT WILSON: Are they seeing the things that they saw while they were awake? We can actually look into these questions as a rat.

ROBERT: And? [laughs]

MATT WILSON: So the answer is we see evidence of replay in basically all of the parts of the brain that we have looked in.

JAD: They see the maze that they ran through? The very same maze?

MATT WILSON: Yes, they see the maze.

JAD: So that is dreaming, in a sense.

MATT WILSON: Well ...

JAD: They are ...

MATT WILSON: ... how do we define dreaming? So ...

JAD: 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.

ROBERT: What would that do to its dreams of the night, or whatever you want to call them?

MATT WILSON: 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.

ROBERT: Oh!

JAD: Oh, so it's like a remix.

MATT WILSON: Exactly.

JAD: A new pattern that includes part of maze one and part of maze two.

MATT WILSON: Precisely.

JAD: Turns out that when the rat had more than one maze in its memory, it began to invent completely new mazes.

MATT WILSON: 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 connection, that is figuring out the rules, the hidden rule, the undiscovered rules that will allow us to create something new.

BOB STICKGOLD: 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.

ROBERT: 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 the dream?

BOB STICKGOLD: 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 spent huge amounts of their day doing don't get into their dreams.

JAD: But somehow Tetris gets in there every time.

ROBERT: Every time!

JAD: And why would that be?

ROBERT: Well, he has a hunch.

JAD: Which he's actually exploring with a completely different video game.

BOB STICKGOLD: We've moved to a game called Alpine Racer, which we bought out of an arcade.

JAD: Which he showed us. Took us down the hall to the game room.

BOB STICKGOLD: Here we are.

ROBERT: And there in the corner, it stood.

JAD: Mockingly!

JAD: Oh, wow! It's a full-body game.

BOB STICKGOLD: Please step up.

ROBERT: I stepped up to the game. Got on the platform.

BOB STICKGOLD: It's still warming up.

ROBERT: And then I set off down a virtual mountain.

ROBERT: All right, I'm going downhill. I'm also a girl. I'm also avoiding the skis. Make a nice little turn there. Careful of the wall. Straight down ahead, and down we go. Oh, no the tree! [yells] We're not gonna go through the tunnel. This is a—ow! Oh, that hurt! [laughs]

ROBERT: As you can hear, this game was really stressful.

JAD: Yes.

ROBERT: Which is by design. Robert Stickgold 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 gonna flag that stuff.

BOB STICKGOLD: It's gonna flag that it's important.

ROBERT: It says, "Ooh, I need to remember this so I can work on it later. I'm gonna put a sticky on this one."

BOB STICKGOLD: 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.

ROBERT: Oh, and then I died! But I died nice.

BOB STICKGOLD: Just for the record, you got further than Jad on your first try.

JAD: Wow! Wow! It's like "Aaaah" and it's over. [laughs]

ROBERT: [laughs] Could you say that again?

JAD: Well, so you have people play Alpine Racer for 45-minute bursts throughout the day. What happens next? You wake them up?

BOB STICKGOLD: 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.

[ARCHIVE CLIP, loudspeaker voice: Please report now.]

BOB STICKGOLD: There's a microphone right next to them on their bed, and they just report what was going through their minds.

[ARCHIVE CLIP, woman: I was just thinking about skiing.]

[ARCHIVE CLIP, woman: Skiing.]

[ARCHIVE CLIP, man: Skiing.]

BOB STICKGOLD: And we get on the first night up to 40 percent of all the reports being about skiing.

[ARCHIVE CLIP, woman: And the game that I've been playing.]

[ARCHIVE CLIP, man: Alpine Ski Racer, I guess.]

BOB STICKGOLD: 40 percent. Almost half of them. And that's right up there with 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."

JAD: 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?

ROBERT: Hmm.

JAD: With the replay. This, he suspects, is just the brain emptying out its stickies.

ROBERT: Things that really intrigued me during the day, that I felt during the day.

JAD: Yeah. But ...

BOB STICKGOLD: 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?

ROBERT: Because remember, he couldn't get back the memory of the rocks after he'd spent two hours asleep.

JAD: That's right. And what he's found is that if you fast-forward two hours into the dream ...

BOB STICKGOLD: Get almost no reports of skiing at all.

JAD: ... the replay seems to dissolve into a remix.

BOB STICKGOLD: We start getting reports like, "Oh, I dreamt I was sliding down a hill."

[ARCHIVE CLIP, woman: Like I'm going downhill.]

BOB STICKGOLD: "Just rolling down a hill."

[ARCHIVE CLIP, woman: Downward motion.]

[ARCHIVE CLIP, man: I was thinking about—I was about to say downhill banana.]

[ARCHIVE CLIP, woman: I was thinking about skateboarding.]

[ARCHIVE CLIP, woman: I was thinking about ...]

[ARCHIVE CLIP, man: I was thinking about a bunch of bananas.]

[ARCHIVE CLIP, woman: Doing yoga on a ski slope.]

BOB STICKGOLD: 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.

JAD: 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?"

BOB STICKGOLD: What do I have in all my memories—in my case from the last 60 years—that fits associatively, thematically?

JAD: And the result? Well, it might seem random—it is—but every so often, he says, you come up with the right answer.

BOB STICKGOLD: So now we get to your dreams of people discovering the structure of benzene. Kekulé was his name.

JAD: Kekulé, actually, was his name.

ROBERT: [laughs]

JAD: August Kekulé.

ROBERT: That's close.

JAD: He was a 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.

ROBERT: However, have you ever wondered why it would be necessary when solving problems like this to dream so vividly?

JAD: Hmm.

ROBERT: 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.

BOB STICKGOLD: 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.

JAD: So if I hear you right, 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?

BOB STICKGOLD: That whole long answer is what a Harvard professor says instead of saying "I don't know."

JAD: [laughs]

ROBERT: [laughs]

LATIF: 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.

[LISTENER: Hi, I'm Suneen, and I'm from Oakland, California. And here are the staff credits. Radiolab was created by Jad Abumrad, and is edited by Soren 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 Gebel, Maria Paz Gutiérrez, Sindhu Gnanasambandan, Matt Kielty, Annie McEwen, Alex Neason, Valentina Powers, Sarah Qari, Sarah Sandbach, Arianne Wack, Pat Walters and Molly Webster. Our fact-checkers are Diane Kelly, Emily Krieger and Natalie Middleton.]

[LISTENER: Hi, I'm Erica in Yonkers. Leadership 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.]

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