May 24, 2007


Birds do it, bees do it...yet science still can't answer the basic question: why do we sleep?

Every creature on the planet sleeps--from giant humpback whales to teeny fruit flies. What does it do for us, and what happens when we go without? We take a peek at iguanas sleeping with one eye open, get in bed with a pair of sleep-deprived new parents, and eavesdrop on the uneasy dreams of rats.

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Intro: 00:51 You're ... listening ... to ... to ... You're ... listening ... to ... to Radiolab.

Speaker 4: 00:58 I just thought I'd see if I could get the sound of babies sleeping.

Jad Abumrad: 01:09 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. Well, 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. Well, pretty much everything sleeps.

Speaker 6: 01:53 As far as we know, all mammals do it. All birds.

Speaker 7: 01:56 Bees, locusts, cockroaches, crayfish ...

Speaker 6: 01:59 Reptiles, insects.

Speaker 7: 02:00 Scorpions.

Jad Abumrad: 02:01 Anything that's been studied has something that looks like sleep.

Robert Krulwich: 02:04 It's a mystery. Most things we sort of know what they are for, and also how they work. But sleep is really in your face. I mean, everybody does it. You do it from the cradle to the grave. You can't help doing it, because if you try to stay awake, at some point it's irrepressible. And we don't know why. That's a shameful state of affairs. How can you be a scientist in the 21st century and not know the answer to that? There you go. Okay.

Jad Abumrad: 02:37 Yeah, nice word, shame. Okay. [inaudible 00:02:37]

Robert Krulwich: 02:37 That's a pretty good way to begin. You know?

Jad Abumrad: 02:39 With shame?

Robert Krulwich: 02:40 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 Abumrad: 02:46 We'll talk with people who can help us understand what it's for ...

Robert Krulwich: 02:49 Why we do it.

Jad Abumrad: 02:50 ... and what happens when we don't.

Robert Krulwich: 02:53 I'm Robert Krulwich.

Jad Abumrad: 02:54 I'm Jad Abumrad.

Robert Krulwich: 02:55 Stay with us.

Jad Abumrad: 03:05 For centuries, people thought that sleep was kind of the opposite of being awake.

Robert Krulwich: 03:10 It's reasonable, one would think.

Jad Abumrad: 03:12 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 Krulwich: 03:23 I can hardly wake up even in a fire.

Jad Abumrad: 03:26 I don't know why ...

Robert Krulwich: 03:30 No, I'm a really heavy sleepy. I'm a very, very heavy sleeper.

Jad Abumrad: 03:33 The point is, if all you've got are your eyes to go on, sleep can seem like being ... Well-

Robert Krulwich: 03:39 Like being off.

Jad Abumrad: 03:40 Yeah, like off-ness.

Robert Krulwich: 03:42 Right. Or worse.

Dr. Carlos Shan: 03:44 Well, both Shakespeare and Cervantes referred to sleep as death.

Jad Abumrad: 03:49 That's Dr. Carlos Shank. He wrote a great book about sleep called Paradox Lost.

Dr. Carlos Shan: 03:53 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 Abumrad: 04:01 For Dr. Shank, the awakening to just how wrong Shakespeare and Cervantes were about sleep came one day while he was sitting in class for med school.

Dr. Carlos Shan: 04:09 My first year at medical school ...

Jad Abumrad: 04:11 This was back in 1972.

Dr. Carlos Shan: 04:12 ... we have an emeritus professor who actually was a Nobel Prize winner, Dr. Eccles, Sir John Carew Eccles from Australia and ...

Jad Abumrad: 04:20 Here's what happened. This esteemed lecturer walks into class, pops a cassette into the tape deck, hits play, and out comes this sound.

Dr. Carlos Shan: 04:27 Well, the sound was ... or ... wait a second, let me get it right. Oh, here we go ... and multiply this by a hundred ...

Jad Abumrad: 04:45 This, the professor announced is the sound of a cat's brain while asleep.

Dr. Carlos Shan: 04:51 My God.

Jad Abumrad: 04:53 Shank almost fell out of his seat.

Dr. Carlos Shan: 04:55 This is the brain during sleep? Making these really rapid, high=pitched, multiple sounds. That just blew us away. It was just ...

Jad Abumrad: 05:03 Clearly, while that cat was curled up in it's 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. All right. That's just 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 paradime shift. People were suddenly like, "oh my God, if we're gonna figure out anything about sleep, we have to ask the brain".

John Lescue: 05:42 And then this is the room where we do all of our surgeries.

Jad Abumrad: 05:45 And luckily, that's easily done, if you're willing to get your hands dirty.

John Lescue: 05:51 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 Abumrad: 06:05 Then you've got a little window into their brain. You could see right there on the screen, you could see the brain waves ...

Robert Krulwich: 06:12 Now, are you out of your mind? Did you just put a hole into a kitten's head?

Jad Abumrad: 06:15 No, that wasn't my cat. C'mon.

Robert Krulwich: 06:17 So what was it we were doing there?

Jad Abumrad: 06:18 What you just heard was a mock surgery to an iguana, actually.

Robert Krulwich: 06:22 Even an iguana, man. It's not a nice thing to do.

John Lescue: 06:27 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.

Robert Krulwich: 06:37 Uh-huh.

Jad Abumrad: 06:38 Yeah. And that, by the way, is John Lescue. He's a graduate student at the Ecology Department-

John Lescue: 06:42 At Indiana State University.

Jad Abumrad: 06:44 Which is where we are. John gave our reporter, Carol Oller-

Carol Oller: 06:47 Testing.

Jad Abumrad: 06:49 -a tour of the lab.

John Lescue: 06:50 There are big boys here and they all have nice hats.

Jad Abumrad: 06:52 Showed her the iguanas.

Carol Oller: 06:54 These guys are a little frightening to me. They're pretty huge.

Jad Abumrad: 06:57 They're like four feet long, head to tail.

Robert Krulwich: 07:00 Oh, I didn't know that.

Jad Abumrad: 07:00 I mean, they look like baby alligators.

John Lescue: 07:02 Pick that one up.

Jad Abumrad: 07:02 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. Shank 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 Krulwich: 07:17 What is that?

Jad Abumrad: 07:20 Let me put it to you as a puzzle, okay?

Robert Krulwich: 07:20 Mm-hmm (affirmative)

Jad Abumrad: 07:21 Forget iguanas. Dolphins. Right? Dolphins.

Robert Krulwich: 07:24 Yup.

Jad Abumrad: 07:25 How is it that a dolphin, in the ocean, or even say the dolphins that you might find at Six Flags in New Jersey, I think they have two.

Megan Tuterra: 07:34 Cody is our 10 year old, Atlantic Bottlenose dolphin. His buddy, Avalon, is 12 years old ...

Jad Abumrad: 07:40 And that's their trainer, Megan Tuterra. Avera Metra 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 Krulwich: 07:40 I don't know. What are the challenges of a dolphin?

Jad Abumrad: 07:58 Well, they have significant challenges, my friend. First, they've gotta breathe.

Megan Tuterra: 08:02 They're conscious breathers. They're not unconscious breathers. So they have to think about breathing.

Jad Abumrad: 08:07 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 unconscious for a wile.

Robert Krulwich: 08:22 They would drown.

Jad Abumrad: 08:23 Right. And yet they do manage to sleep. A lot.

Robert Krulwich: 08:27 How long?

Jad Abumrad: 08:29 Eight hours a day. Like us.

Robert Krulwich: 08:30 Really?

Jad Abumrad: 08:31 Yeah, eight hours.

Robert Krulwich: 08:32 But how?

Jad Abumrad: 08:33 That's the puzzle.

Megan Tuterra: 08:33 What happens is they do what we call's when they rest on the surface of the water. You know when a log floats down a river, it just floats? That's exactly what they look like. And they rest half their brain at a time.

Jad Abumrad: 08:47 Half their brain is asleep?

Megan Tuterra: 08:49 Half their brain is asleep at a time.

Jad Abumrad: 08:51 That is nature's solution. To cut the dolphin brain in half.

Robert Krulwich: 08:55 You mean literally in half?

Jad Abumrad: 08:56 Literally in half. So that one half can snooze while the other half keeps the dolphin swimming and surfacing-

Robert Krulwich: 09:02 Wow.

Jad Abumrad: 09:02 -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 Tuterra: 09:09 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.

Steve Lema: 09:17 This little guy can be characterized as groggy.

Jad Abumrad: 09:19 That's Steve Lema. He runs one of the labs back in Indiana.

Steve Lema: 09:22 They're sort of awake and they're sort of asleep then. It's just a way of staying awake enough.

Jad Abumrad: 09:27 And again, it's easy to miss, but if you look inside that groggy dolphin's brain at what the brainwaves are doing ...

Steve Lema: 09:33 It's exquisitely obvious ...

Jad Abumrad: 09:35 It's clear as day.

Steve Lema: 09:36 A six year old could figure it out. When half the brain has these beautiful slow waves like a sign curve and the other one's just jagging all over the place.

Speaker 15: 09:53 Awesome.

Speaker 16: 09:53 Wow, those are beautiful.

Robert Krulwich: 09:54 Wow, that is amazing.

Jad Abumrad: 09:56 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 Lescue: 10:06 Oh yeah. They're aquatic mammals like whales, seals and sea lions.

Jad Abumrad: 10:10 John says that all of the marine mammals that have been studied seem to do it too.

John Lescue: 10:13 Recently, walruses, they're all are found to engage in unihemispheric sleep as well.

Jad Abumrad: 10:18 And now the Indiana team led by ... by this guy.

Charles Amlanne: 10:22 I'm Charles Amlanner, Chair of the Department of Ecology and Organismal Biology.

Jad Abumrad: 10:27 They have found this weird split-brain behavior in creatures of the air.

Robert Krulwich: 10:31 Oh?

Charles Amlanne: 10:31 Okay, let me just back up a little bit and describe this experiment.

Jad Abumrad: 10:37 Charlie and his student had been at the park one day and they noticed something.

Charles Amlanne: 10:39 We observed that ducks ...

Jad Abumrad: 10:41 Ducks.

Charles Amlanne: 10:43 ... sometimes will get together into groups.

Jad Abumrad: 10:45 Like, on a log. Four ducks will get together and snooze in a neat little line.

Charles Amlanne: 10:49 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 Abumrad: 11:04 The inevitable question ...

Charles Amlanne: 11:05 What's going on here?

Jad Abumrad: 11:07 ... led to a very simple experiment.

Charles Amlanne: 11:08 We put four birds in a row.

Jad Abumrad: 11:09 Four mallard ducks, this time in the lab and they watched them sleep.

Charles Amlanne: 11:13 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 Abumrad: 11:24 One more time.

Charles Amlanne: 11:25 Slept with one eye closed and one eye opened.

Jad Abumrad: 11:28 It's just like in that song. Do you know that Metallica song?

Robert Krulwich: 11:36 I missed it.

Jad Abumrad: 11:36 It's a good one.

Robert Krulwich: 11:38 But I knew they were all botanists.

Jad Abumrad: 11:39 It's true. You know, no one knows this, but that song is really about adaptive sleeping behavior in ducks.

Charles Amlanne: 11:48 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 Abumrad: 11:57 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 Amlanne: 12:06 The left eye is attached to the right hemisphere, the right eye is attached to the left hemisphere.

Jad Abumrad: 12:12 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 Amlanne: 12:24 The bird could simultaneously sleep and be awake.

Jad Abumrad: 12:29 Not only that, here's the cool part, after a few hours ...

Charles Amlanne: 12:31 What happened was is that the birds that were on the outer edge, then would rotate-

Jad Abumrad: 12:36 Stand up, turn around.

Charles Amlanne: 12:37 -180 degrees.

Jad Abumrad: 12:38 And then sit back down.

Charles Amlanne: 12:40 And the other eye would then get some sleep and consequently the opposite hemisphere would get some sleep.

Speaker 18: 12:45 When we saw that we said "oh yeah, that's good."

Jad Abumrad: 12:50 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 Krulwich: 12:58 Right.

Jad Abumrad: 12:58 But sleep is dangerous. That's the headline. For dolphins, the main danger is drowning. You know? For ducks ...

Robert Krulwich: 13:08 Getting eaten.

Jad Abumrad: 13:08 Exactly. Ducks have to sleep, but how can they when lurking in the darkness are foxes, wolves and a hundred other eaters of ducks.

Speaker 19: 13:19 Hey you guys.

John Lescue: 13:19 Do you like snakes?

Speaker 19: 13:20 I don't know. Not really.

John Lescue: 13:24 What?

Speaker 19: 13:24 I mean, I don't dislike snakes.

John Lescue: 13:26 He's a good man, he's a good man.

Jad Abumrad: 13:28 In another nifty experiment, John took the resident snake, Monty ...

John Lescue: 13:32 This is Monty.

Speaker 19: 13:35 Hi.

Jad Abumrad: 13:35 Big snake.

John Lescue: 13:36 He is, what, about a four foot long python.

Jad Abumrad: 13:40 And at night ...

John Lescue: 13:40 You're so cute.

Jad Abumrad: 13:41 ... John brought Monty, the python into the room where his iguanas sleep.

John Lescue: 13:45 And he terrifies them.

Robert Krulwich: 13:45 Really?

Jad Abumrad: 13:47 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 Krulwich: 13:54 I bet they did.

Jad Abumrad: 13:56 Pop, pop, pop, pop, pop. And they trained that open eye right on Monty the snake.

Steve Lema: 13:59 Put a big snake in the room and they'll watch it with one eye all night.

Jad Abumrad: 14:03 That's Steve Lema again.

Steve Lema: 14:04 They don't like these snakes, that's for sure. And we moved the snake from the room the next day and they're still looking for it the next night or two.

Jad Abumrad: 14:10 So they keep one eye trained on that door for a few more days?

Steve Lema: 14:13 About two or three days, then they go back to regular sleep.

Jad Abumrad: 14:29 So what does this all mean? Well, think about this. Okay, all the sea mammals, they do it.

Robert Krulwich: 14:33 Right.

Jad Abumrad: 14:34 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 Krulwich: 14:42 You mean who's left not sleeping with half a brain on and the other half a brain off?

Jad Abumrad: 14:45 Yeah. Us!

Robert Krulwich: 14:50 Really?

Jad Abumrad: 14:51 We may be the strange ones.

John Lescue: 14:53 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 Abumrad: 14:59 Not all mammals, says John, the terrestrial mammals. The ones that live on land. 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. And so we lost it. Totally speculative theory of course, but the basic idea, though, is if you are protected and safe, you can afford to close both eyes. Conk out completely. And that simple idea of safety, that explains ... well these guys think, almost everything. Where you sleep, how you sleep, how long you sleep, it all boils down to two words.

Steve Lema: 15:55 Predation risk.

John Lescue: 15:56 Predation risk.

Charles Amlanne: 15:57 Predation risk.

Jad Abumrad: 15:58 Which is really just fancy way of saying ...

Charles Amlanne: 16:00 Generally speaking, just your risk of being killed.

Jad Abumrad: 16:02 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.

Dr. Carlos Shan: 16:13 Nice warm bed.

Jad Abumrad: 16:14 A locked door.

Dr. Carlos Shan: 16:15 A locked door. Covers.

Jad Abumrad: 16:17 Maybe a nice neighborhood.

Dr. Carlos Shan: 16:18 A good police force looking after you at nighttime and you live in a country that has a very secure living environment.

Jad Abumrad: 16:27 You would think that this whole predation risk idea has nothing to do with us. Well?

Dr. Carlos Shan: 16:33 Well, there's a few studies that have looked at say sleep patterns where people are sleeping in novel environments.

Robert Krulwich: 16:40 What's a novel environment? What does he mean?

Jad Abumrad: 16:41 Well, like a hotel.

Robert Krulwich: 16:43 Oh.

Jad Abumrad: 16:43 That first night at hotel, why is it no one can sleep well that first night at a hotel?

John Lescue: 16:47 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.

Robert Krulwich: 16:57 I suffer from that myself, I don't sleep we hotel rooms. Especially if it was just one night per place or something, my sleep is terrible.

John Lescue: 17:04 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 Abumrad: 17:20 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.

Dr. Carlos Shan: 17:33 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 Abumrad: 17:49 That's Dr. Carlos Shank, who we heard from before. We're in Minnesota now at the Hennipin County Sleep Center, where he works.

Dr. Carlos Shan: 17:49 Here in the sleep lab-

Jad Abumrad: 17:56 We're standing in front of a grainy, black and white video of a little girl in her pj's, screaming. Dr. Shank 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 who's brains never quite shut off completely during sleep.

Dr. Carlos Shan: 18:20 Well this guy is interesting. He has seizures. No, no, no, he doesn't. Wait a second.

Jad Abumrad: 18:25 He showed us tape after tape.

Dr. Carlos Shan: 18:26 We're viewing a man who we very affectionately call Santa Claus.

Jad Abumrad: 18:30 On the screen, a large guy thrashes back and forth.

Dr. Carlos Shan: 18:34 His legs are moving, he's going back and forth from his side to his back.

Jad Abumrad: 18:38 And then, suddenly he starts to ...

Speaker 20: 18:39 Ho, ho, ho, ho, ho. Ho, ho, ho, ho, ho, ho, ho. Ho, ho, ho.

Robert Krulwich: 18:39 Is this real?

Jad Abumrad: 18:53 Yeah, this guy is in and out of sleep. He has no idea what he's doing. One of the interesting things Dr. Shank 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.

Dr. Carlos Shan: 19:10 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: 19:21 The dreams can be very violent.

Jad Abumrad: 19:25 This is Martin Sabelle, age 88. He's another of Dr. Shanks' patients.

Martin Sabelle: 19:29 I remember someone coming up the stairway.

Jad Abumrad: 19:33 In Martin's case, the attackers never had a face. Sometimes it was a bear.

Martin Sabelle: 19:37 And I was gonna fight with him.

Gertrude Sabell: 19:40 He'd yell at them, "Get out of here."

Jad Abumrad: 19:42 That's Martin's wife, Gertrude.

Gertrude Sabell: 19:44 "Scram!" It was always trying to protect me.

Martin Sabelle: 19:47 Yeah, I would have black and blue bruises on my arms and hands because I was hitting the headboard.

Dr. Carlos Shan: 19:54 Not infrequently, the man is dreaming, in be with his wife, that he is fighting to defend her from an attacker, when in fact, he's beating her up.

Gertrude Sabell: 20:01 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: 20:12 She says, "Martin, you're dreaming."

Jad Abumrad: 20:14 Gertrude and Martin Sabelle are still married, believe it or not, after 57 years. Though she did force him to sell his guns.

Gertrude Sabell: 20:22 He has never been happy about that.

Martin Sabelle: 20:24 Well, they were quite valuable.

Robert Krulwich: 20:26 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?

Jad Abumrad: 20:37 That's what I'm hinting at. I don't wanna go any stronger than hint at, but there seems to be something in us that's always watching out, always wary.

Robert Krulwich: 20:47 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 Abumrad: 20:56 That's right. Before we go to break, I just wanna thank Ann Hepperman for excellent reporting in Minnesota and also before her, Cara [Oller 00:21:03]. 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.

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Jad Abumrad: 22:53 This is Radiolab, you are Robert Krullwich.

Robert Krulwich: 22:55 Robert Krullwich, that's my name. And you're-

Jad Abumrad: 22:57 I'm Jad Abumrad. And today our topic on Radiolab is sleep.

Robert Krulwich: 23:00 Yup. It is something that all of us do, we can't help but do it.

Jad Abumrad: 23:04 It's so good.

Robert Krulwich: 23:04 It's dangerous to do. It's so good. And it's universal.

Steve Lema: 23:07 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.

Jad Abumrad: 23:14 That's Steve Lema again from Indiana State University.

Steve Lema: 23:18 Because it would just be such a great idea to not sleep.

Jad Abumrad: 23:21 Don't I know it. But there are times when you just can't sleep.

Robert Krulwich: 23:25 Right.

Jad Abumrad: 23:25 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. You pull all nighters for school or you have to drive long distances or ... and here's what we wanna 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.

Hannah Palin: 23:59 It's 2:54, for the record. Today was my first day back at work. We were discussing budgets. 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.

Lie down. Lie down on me.

Instead of saying, "well, Nicolette, I believe that that choice was made because ... " no, no, all that came out was, "honey buckets" I mean nothing, nothing would come out. There was just no brain cells, really. So anyway, that was my first day back at work. 2:47. Dominic will not sleep. I don't know why. I'm trying to get him to sleep and I'm kind of at my wit's end. God, this just sucks. Totally sucks. Here's the funny thing. Everybody has a theory. When I was talking to my sister-in-law tonight and her theory is that he's not 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 this is feeling like I am doing it all wrong and that I'm a failure as a parent. I don't know how to do this.

C'mere Sweetie. C'mon, c'mon, c'mon. Just lay down 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 these waves of satisfaction and delight with being alive and this amazing landscape with a funny kid. And 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 suddenly feel like, wow. I'm so lucky. Okay, I've gotta take my kid to play now. Here we go. Do you know the muffin man? 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 realize that an element to the sleep depravation 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: 28:01 I'm tired.

Hannah Palin: 28:02 I'm tired.

Dominic: 28:04 I'm tired. I sleep.

Hannah Palin: 28:09 I don't wanna 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.

Are you tired?

Dominic: 28:09 No.

Hannah Palin: 28:31 You're not tired? 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 thanks to [inaudible 00:28:57]

Jad Abumrad: 28:57 And her son, Dominic and her husband Steve. I know, poor Hannah.

Robert Krulwich: 29:03 But there is a science question lurking in the background, which is when Hannah was so tired, why does she feel that way?

Jad Abumrad: 29:14 Because she hasn't been sleeping.

Robert Krulwich: 29:17 Well, yeah. But what is the essence of tiredness?

Jad Abumrad: 29:22 Lack of sleep. Hello?

Robert Krulwich: 29:24 Chemically, I'm asking.

Jad Abumrad: 29:25 Oh, got it.

Robert Krulwich: 29:27 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 wanna know.

Jad Abumrad: 29:33 That's a good question, actually.

Robert Krulwich: 29:34 Good. I'm glad you think so because I know a guy who has a theory about this.

Dr. Alan Pack: 29:38 Did you see Tiger yesterday, huh? Tiger Woods is just, he's unbelievable. He's the best of anybody. I mean the guy is unbelievable.

Robert Krulwich: 29:45 This is Dr. Alan Pack and in addition to being a rabid golf fan, he's also a rabid ... can you be a rabid biologist?

Jad Abumrad: 29:52 Sure.

Robert Krulwich: 29:52 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 ...

Dr. Alan Pack: 30:00 And that's been showing in mouse, it's been showing in rat, it's been showing in fruit fly.

Robert Krulwich: 30:04 ... is that inside certain cells, in all those different animals, when they're sleep deprived ...

Dr. Alan Pack: 30:08 Eventually what happens is you don't get proteins properly folded.

Jad Abumrad: 30:14 Excuse me? Proteins properly folded?

Robert Krulwich: 30:17 A phenomenon called the unfolded protein response.

Jad Abumrad: 30:20 What on earth does that mean? Is that a good thing or a bad thing?

Robert Krulwich: 30:23 Are you asking why do you need proteins to properly fold?

Jad Abumrad: 30:25 Yeah, I guess that's what I'm asking.

Robert Krulwich: 30:26 Well, you're made from proteins. Proteins are the essence of you. So if your proteins are misshapen, if they're not folded properly ...

Dr. Alan Pack: 30:35 If you don't fold the proteins properly, then don't have the right three dimensional structure and as a result they start accumulating I the cell and then these different unfolded proteins can aggregata together and form clumps. Clumps. Clumps. In say, the cell and essentially clog up and it's really quite toxic to cells.

Robert Krulwich: 30:58 Clumpiness equals tiredness is what his formula ... remember when Hannah was so exhausted?

Jad Abumrad: 31:04 Yeah.

Hannah Palin: 31:05 God, this just sucks.

Robert Krulwich: 31:06 Well, because she hasn't slept much ...

Hannah Palin: 31:08 Totally sucks.

Robert Krulwich: 31:09 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 the sleep ... remember when she's so happy?

Jad Abumrad: 31:31 Yeah.

Hannah Palin: 31:31 I suddenly feel like, wow.

Robert Krulwich: 31:33 Because of the sleep ...

Hannah Palin: 31:34 I'm so lucky.

Robert Krulwich: 31:35 ... a group of cleaner uppers have gone through her cells, removed the toxic and misshapen proteins so that ... and in fact 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. Julio [Tenonie 00:32:02].

Ellen Horn: 32:02 Testing, testing. Testing, testing.

Robert Krulwich: 32:05 And 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? We don't know what he looks like.

Ellen Horn: 32:05 A football player.

Robert Krulwich: 32:14 A football player?

Ellen Horn: 32:17 But like a quarterback or tightend, not like a linebacker.

Robert Krulwich: 32:19 Not like a linebacker. So big, but not overwhelming?

Ellen Horn: 32:26 Yes.

Robert Krulwich: 32:28 How do you even know that?

Ellen Horn: 32:30 Website. See, but I was totally wrong.

Robert Krulwich: 32:34 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.

Dr. Julio tenon: 32:43 I'm Julio Tenonie, I am a professor of psychiatry here at the University of Wisconsin, Madison.

Robert Krulwich: 32:48 But when it comes to the subject of sleep, which is his specialty, he takes sleep very seriously. What go you into sleep?

Dr. Julio tenon: 32:56 Sleep is the annihilation of conscious. 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 Krulwich: 33:12 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.

Dr. Julio tenon: 33:26 I used to play first. 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 it flows beautifully.

Robert Krulwich: 33:53 That happened to you?

Dr. Julio tenon: 33:54 It happened to me. It happens to lots of people.

Speaker 31: 33:55 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.

rob: 34:08 Yeah.

Speaker 31: 34:09 Definitely. There's one story, and I haven't thought about this for a long time. But first of all, Rob and I play in a band together.

rob: 34:16 The band is called the Sisterhood of Convoluted Thinkers.

Speaker 31: 34:19 And we switch instruments like a lot.

rob: 34:21 She's usually the bass player.

Speaker 31: 34:22 I was gonna play drums.

rob: 34:22 So she had to learn how to play drums.

Speaker 31: 34:24 So we rented a cabin.

rob: 34:25 We went somewhere to rehearse and at night she was really just kind of practicing and practicing and trying to get this rhythm.

Speaker 31: 34:31 This one particular beat, I worked on it a lot. I just keep going and going and-

rob: 34:36 I remember playing that one thing again and again and again.

Speaker 31: 34:40 Yeah. 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.

rob: 34:50 The butt hit the stool and she was going. She could just do it.

Speaker 31: 34:57 I thought it was magic. That you can just learn stuff in your sleep.

Robert Krulwich: 35:02 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 better learned. So you learned overnight or you ... you remember better in the morning?

Dr. Julio tenon: 35:20 What happens is that the next day you're a bit better off. What happens during the night to make you better off is [inaudible 00:35:27]

Robert Krulwich: 35:27 Tenonie's contention is that sleep helps you remember by forgetting.

Jad Abumrad: 35:35 I don't know what that means.

Robert Krulwich: 35:35 Let me explain to you what he's saying. He says there's a limited amount of space in your brain.

Dr. Julio tenon: 35:40 The real estate in the brain is pretty limited.

Robert Krulwich: 35:42 A limited amount.

Jad Abumrad: 35:43 That makes sense. It's a small little guy up there.

Robert Krulwich: 35:45 Yup. And yet every experience you have during the day-

Dr. Julio tenon: 35:48 Is going to take away some space.

Robert Krulwich: 35:49 -uses up a little of what you got. When you are awake, inevitably, you learn. Whether you want it or not. You are going around talking to me, having breakfast, going to work and yakking on the phone with your friends, talking to your mom, very different from the friends, then going home, taking a bath. Gotta take a bath.

Jad Abumrad: 36:10 Yeah, I get it.

Robert Krulwich: 36:11 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. Little pathways are forming that weren't there before I sat down.

Dr. Julio tenon: 36:25 Exactly. Whether we recognize it or not, lots of things are going to change your brain by the end of the waking day.

Robert Krulwich: 36:32 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 gonna 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 ... "

Dr. Julio tenon: 37:20 It's actually even simpler than that.

Robert Krulwich: 37:21 According to Tenonie, 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 ...

Dr. Julio tenon: 37:29 We think that during sleep ...

Robert Krulwich: 37:32 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.

Dr. Julio tenon: 37:41 These waves are called slow oscillations.

Robert Krulwich: 37:44 And over the course of the night ...

Dr. Julio tenon: 37:46 One thousand times a night ...

Robert Krulwich: 37:47 Those waves wash through all the experiences of your day, all the little synaptic connections that you made all day long and everyone of those connections, all of them, gets just a little bit softer.

Dr. Julio tenon: 38:00 They get weaker, progressively, gracefully, they get weaker.

Robert Krulwich: 38:02 Even, he says, the things you wanna hold onto, 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.

Dr. Julio tenon: 38:26 It's all relative, Sir.

Robert Krulwich: 38:28 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. 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 the whole day. Lower and lower and lower. Now you hear how the softer stuff just falls away, you can't hear it anymore? 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 Abumrad: 39:14 Yeah.

Dr. Julio tenon: 39:15 The signal. The signals that have survived reasonably well are heard better because his background has become more silent.

Robert Krulwich: 39:21 So your ability to play the guitar better the next morning is not because you've learned these 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.

Dr. Julio tenon: 39:39 You put your finger on it.

Robert Krulwich: 39:42 So Mr Tenonie 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 Abumrad: 40:11 We should go to break.

Robert Krulwich: 40:11 Okay, so coming up next, for those of us who can get to sleep, next, our chance to dream.

Jad Abumrad: 40:17 This is Radiolab. I'm Jad Abumrad.

Robert Krulwich: 40:19 And I'm Robert Krulwich.

Jad Abumrad: 40:20 We'll continue in a moment.

Cheryl Ing: 40:22 This is Cheryl Ing, calling from San Francisco. Radiolab is supported in part by the National Science Foundation and by the Alfred P, Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at

Jad Abumrad: 40:47 This is Radiolab, I'm Jad.

Robert Krulwich: 40:48 And I'm Robert.

Jad Abumrad: 40:48 And today's program is about sleep.

Robert Krulwich: 40:50 As in the kind of sleep where you perchance to dream.

Jad Abumrad: 40:53 Exactly. Do you know that story about the benzene molecule?

Robert Krulwich: 40:58 No.

Jad Abumrad: 40:58 Speaking of dreams. Well, here-

Robert Krulwich: 41:01 The benzene molecule?

Jad Abumrad: 41:01 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. And he's tortured by this problem. Goes to sleep, has a dream of a snake biting its tail. Wakes up, bolts right up and says, "it's a ring. It's a ring."

Robert Krulwich: 41:25 Do you believe that?

Jad Abumrad: 41:26 I want to.

Robert Krulwich: 41:27 Well, yeah.

Jad Abumrad: 41:28 I mean, don't get me wrong. I hate it when people tell me their dreams. Hate it. I wanna stab my eye with a fork when people tell me their dreams. I don't know why-

Robert Krulwich: 41:35 Well, I'm never gonna tell you about my dreams again.

Jad Abumrad: 41:37 Good.

Robert Krulwich: 41:38 But, no, you're not alone. Because for a long time, scientists have avoided studying dreams because they think they're so random and meaningless and study-able. But we did meet a guy ...

Bob Stickgold.: 41:50 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 Krulwich: 41:57 Who found an interesting way to ask the question ...

Bob Stickgold.: 41:59 Why do we dream?

Robert Krulwich: 42:01 Simple question. Very hard answer.

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

Bob Stickgold.: 42:12 I'd 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 8:00 in the morning, we were back at 2:00 in the afternoon.

Robert Krulwich: 42:24 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.: 42:31 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 on the bed for three minutes, starting to go to sleep and boom it's there. And I try it 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? And then I started talking to friends and they said, "Oh try canoeing." Or someone else says, "Try white water rafting if you wanna get that." And someone else says, "Oh, hello. Take organic chemistry."

And you go to bed at night and all you see are these spreading molecules rotating in front of your eyes. Those daytime activities are affecting your dreams.

Robert Krulwich: 43:41 And that got him thinking. What exactly is the connection between what you do during the day and what you dream at night?

Jad Abumrad: 43:48 What are the rules of that? He figured, all right, this replay is kind of interesting. Maybe I'll test it. But how? If I get some subjects together, what could I have them do during the day that would reliably end up in their dreams?

Robert Krulwich: 44:02 Well he can't have them all go for hike. And they're probably not gonna get permission to take them white water rafting.

Jad Abumrad: 44:08 Too expensive.

Robert Krulwich: 44:08 So what could he do?

Bob Stickgold.: 44:09 Sort of sat fallow for a year. And I was moaning to some of my students about how can't think of how to do this and someone says, "Tetris". And somebody else says, "Absolutely". And I'm saying, "What? What?" He said, "Well, don't you play Tetris?" And I say, "Yes" "Well, when you start playing Tetris ... " It turns out when you start playing Tetris and you go to bed at night, you lie down in bed, and you see Tetris pieces falling down in front of your eyes.

Jad Abumrad: 44:47 Sure.

Robert Krulwich: 44:47 Sure?

Jad Abumrad: 44:48 Oh, yeah.

Bob Stickgold.: 44:48 You knew that?

Jad Abumrad: 44:49 Absolutely. [crosstalk 00:44:51]

Bob Stickgold.: 44:50 You guys both know that?

Jad Abumrad: 44:51 Oh yeah.

Bob Stickgold.: 44:54 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.

Robert Krulwich: 45:07 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%.

Jad Abumrad: 45:18 How do you know that, just from their reports?

Bob Stickgold.: 45:20 As they were falling asleep, we're monitoring them electrophysiologically and as they start to drift off to sleep, please report now.

Jad Abumrad: 45:33 This Tetris observation was a pretty good start in terms of getting at that question.

Bob Stickgold.: 45:37 Why do we dream?

Jad Abumrad: 45:38 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: 45:53 I'm Matt Wilson. I'm a researcher here at MIT and I'm a neuro scientist studying learning and memory.

Jad Abumrad: 45:59 That's what Matt Wilson does. He takes us to the dream lab.

Matt Wilson: 46:04 So when we first come in, what we see is this bank on monitors.

Jad Abumrad: 46:08 13 monitors, all in a row.

Matt Wilson: 46:09 Each monitor displaying ongoing activity in the brain. Little panels, each panel showing these ...

Jad Abumrad: 46:16 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, who's just kinda hanging out in his own little basket.

Matt Wilson: 46:44 See him just resting.

Jad Abumrad: 46:45 Is that the little guy, himself?

Matt Wilson: 46:46 Yeah, that's him.

Jad Abumrad: 46:48 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.

Matt Wilson: 47:06 You can hear this kinda snap, crackle, pop sound. These are individual cells that are firing.

Jad Abumrad: 47:12 Like ... right there. One does.

Matt Wilson: 47:15 That kind of whooshing sound. I can tell this animal's sitting, resting quietly.

Jad Abumrad: 47:23 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.

Matt Wilson: 47:39 I don't even see the code. All I see is blonde, brunette, redhead.

Jad Abumrad: 47:43 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: 47:52 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?

Jad Abumrad: 48:06 Yeah.

Matt Wilson: 48:06 I began to notice that when the animals were asleep, the brain cells weren't just firing randomly. In fact, when the animals would go into REM sleep ...

So now he is going into REM right now.

The pattern of activity we'd hear ...

Notice that it's not these whooshes anymore.

It sounded very much like the pattern that the animal had just been running through. Like 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 Abumrad: 48:35 He checked the data and it wasn't simply that the rat was running around in it's mind while it's 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 Krulwich: 48:45 The same sequence, same order, same everything?

Matt Wilson: 48:48 Yes.

Jad Abumrad: 48:49 It was re-running its maze. Step for step. So then he asked the next question.

Matt Wilson: 48:55 Are they seeing the things that they saw while they were awake? We actually look into these questions as a rat.

Jad Abumrad: 49:01 And?

Matt Wilson: 49:02 So the answer we see evidence of replay in basically all of the parts of the brain that we have looked in.

Jad Abumrad: 49:08 They see the maze that they ran through? The very same maze?

Matt Wilson: 49:10 Yes, they see the maze.

Jad Abumrad: 49:11 Because that is dreaming, in a sense.

Matt Wilson: 49:12 Well, how do we define dreaming?

Jad Abumrad: 49:15 Sounds like dreaming to me. I don't know. But the question remains, why would the rat or any creature do this? And so Matt came up with a simple next experiment. He decided to give the rat two mazes.

Robert Krulwich: 49:27 What would that do to it's dreams of the night? Or whatever you wanna call them.

Matt Wilson: 49:30 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.

Jad Abumrad: 49:41 So it's like a remix, a new pattern that includes part of maze one and part of maze two.

Matt Wilson: 49:46 Precisely.

Jad Abumrad: 49:47 It turns out that when the rat had more than one maze in its memory, it began to invent completely new mazes.

Robert Krulwich: 49:53 Oh, wow.

Matt Wilson: 49:54 This gives us the thought that sleep has 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 in those, figuring out the rules, the hidden rules, the undiscovered rules that will allow us to create something new.

Bob Stickgold.: 50:23 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 Krulwich: 50:36 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.: 50:48 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.

Jad Abumrad: 51:00 But somehow Tetris gets in there every time.

Bob Stickgold.: 51:03 Every time.

Jad Abumrad: 51:03 And why would that be?

Robert Krulwich: 51:05 Well, he has a hunch.

Jad Abumrad: 51:06 Which he's actually exploring with a completely different video game.

Bob Stickgold.: 51:08 We've moved to a game called Alpine Racer, which we bought out of an arcade.

Jad Abumrad: 51:13 Which he showed us. Took us down the hall to the game room.

Bob Stickgold.: 51:17 Here we are.

Robert Krulwich: 51:18 And there, in the corner it stood.

Jad Abumrad: 51:21 Mockingly. Oh wow, it's a full body game.

Bob Stickgold.: 51:24 Please step up.

Robert Krulwich: 51:25 I stepped up to the game, got on the platform.

Bob Stickgold.: 51:28 It's still warming up.

Robert Krulwich: 51:29 And then I set off down a virtual mountain. All right, I'm going down the hill. I am also a girl. I am also avoiding the ... oh, I'm doing a nice little turn there. Be careful of the wall. Straight down ahead. And down we go. Ahhh! Oh no! A tree! Ahhh! We're now gonna go through the tunnel. This is ... Ow! Oh, that hurt!

As you can hear, this game was really stressful, which is by design. Robert Stickgold has the theory that as you go through your day, your brain's constantly keeping track of emotion, that's the thing, emotional content, like when you run into a virtual tree, for example. Your brain is gonna flag that stuff. It's gonna flag that it's important. 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.: 52:19 So if it puts a sticky on everything that's heard during the day, then all the brain has to do when it's creating a dream is go and grab stickies.

Robert Krulwich: 52:28 Oh, I died. But I died nice.

Bob Stickgold.: 52:32 Just for the record, you got further than Jad on your first try.

Robert Krulwich: 52:36 Wow. Wow, it's like ...

Jad Abumrad: 52:39 Then it's over. You know?

Bob Stickgold.: 52:41 Could you say that again?

Jad Abumrad: 52:42 So you have people play Alpine Racer for 45 minute bursts throughout the day, what happens next? Do you wake them up?

Bob Stickgold.: 52:48 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. There's a microphone right next to them on their bed. And they just report what was going through their minds.

Speaker 36: 53:05 I was just thinking about skiing.

Bob Stickgold.: 53:08 And we get on the first night, up to 40% of all the reports being about skiing.

Speaker 36: 53:14 And the game that I've been playing.

Bob Stickgold.: 53:19 40%. Almost half of them. And that's right up there, what I would expect to see after trauma with something that's been labeled so intensely that the brain says, "Okay, it's obvious what's on the agenda for tonight."

Jad Abumrad: 53:33 Stickgold thinks he's seeing the outline of the dream making process here. It starts really simply, the very beginning of sleep, like right after you fall asleep, with the replay. This, he suspects. Is just the brain emptying out it's stickies.

Bob Stickgold.: 53:46 Things that really intrigued me during the day, that I felt during the day.

Jad Abumrad: 53:49 Yeah. But-

Bob Stickgold.: 53:50 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 Krulwich: 54:01 Because remember, he couldn't get back the memory of the rocks after he'd spent two hours asleep.

Jad Abumrad: 54:06 That's right. And what he's found is that if you fast forward two hours into the dream.

Bob Stickgold.: 54:09 Got almost no reports of skiing at all.

Jad Abumrad: 54:12 The replay seems to dissolve into a remix.

Bob Stickgold.: 54:16 We start getting reports like "Oh, I dreamt I was sliding down a hill."

Speaker 36: 54:20 It's like I'm going downhill.

Bob Stickgold.: 54:23 Just rolling down a hill.

Speaker 36: 54:29 Downward motion.

Speaker 37: 54:31 I was thinking about ... I was about to say a downhill banana.

Speaker 38: 54:32 I was thinking about skateboarding. I was thinking about doing-

Speaker 37: 54:34 I was thinking about a bunch of bananas.

Speaker 39: 54:36 Doing yoga on a ski slope.

Bob Stickgold.: 54:37 Somebody 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 Abumrad: 54:48 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 and anything to do with crashing or skiing, anything at all that can help me?

Bob Stickgold.: 55:00 What do I have in all my memories, in my case, for the last 60 years that fits associatively, thematically?

Jad Abumrad: 55:08 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.: 55:14 So now we get to your dreams of people discovering the structure of benzene. Kekule was his name.

Jad Abumrad: 55:22 Kekule actually was his name. I'll guess Kekule.

Robert Krulwich: 55:25 That's close.

Jad Abumrad: 55:25 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.

Robert Krulwich: 55:52 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 qualities of some of these things? Because if it were just an everyday brain function to sort of make sense of the world and that would allow you to make new connections, you really wouldn't need quite the movie quality.

Matt Wilson: 56:18 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 Abumrad: 56:42 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.

Matt Wilson: 56:51 That whole long answer is what a Harvard Professor says instead of saying I don't know.

Jad Abumrad: 57:00 I guess we should wrap up. If you want anymore information on anything that you've heard this hour, visit our website, is the address.

Robert Krulwich: 57:07 There will be more information about sleep on there, won't there?

Jad Abumrad: 57:09 Yes. There will be more information on sleep. And you can sign up for our podcasts, Also, while you're at it, send us an email, is the address.

Robert Krulwich: 57:20 Remember also that sleep spelled backwards is peels, which is what you would do to an orange, grapefruit and to a pear.

Jad Abumrad: 57:26 I'm Jad Abumrad.

Robert Krulwich: 57:27 I'm Robert Krulwich.

Jad Abumrad: 57:28 We'll see you later.

Recording: 57:30 First message.

Hannah Palin: 57:31 Radiolab is produced by Jad Abumrad, Ellen Horn, Senior Producer, Lulu Miller, Assistant Producer, Production Executive, Steve Copello.

Recording: 57:42 Next message.

Hannah Palin: 57:44 For additional reporting by Producers Ed Hepperman and Cara Oller. Production support by Sarah Palagrini, Scott Goldberg, Alaska Keville, Sam Lavender, Avra Metra, Ryan Scammel and Jacob Wineburg. Thanks to the musicians we interviewed, Brad Creswell, Jeanine Durfey, Rob Christianson, George Preston and Karen Havelick. And special thanks to me, Hannah Palin. You're welcome.

Robert Krulwich: 58:13 Hi, I'm Robert Krulwich, Radiolab is supported by IBM. By 2050, the world population will reach nearly 10 billion and food production will need to grow by 70%. So what if artificial intelligence could help? Farmers are already using it to help increase crop fields. Watson and the IBM cloud provide access to weather data and analyze satellite imagery to help them monitor soil moisture levels and reduce water waste. So as the population grows, more food can be put on tables. So let's put smart to work and find out how at