[RADIOLAB INTRO]

JAD ABUMRAD: This is Radiolab, I'm Jad Abumrad.

ROBERT KRULWICH: And I'm Robert Krulwich.

JAD: And today, our program is about memory.

ROBERT: Oh my God!

JAD: Hey, we're the radio people.

SALES CLERK: Yes. Please, you want to see the furniture?

ROBERT: I think most people think about memory kind of like ...

ROBERT: So we're interested in this filing cabinet.

ROBERT: ... a file cabinet in your brain.

ROBERT: I'm looking for a fairly large capacity.

SALES CLERK: This is traditional style.

ROBERT: Something happens in your life.

ROBERT: This is real wood.

SALES CLERK: Yeah, this is real wooden filing.

ROBERT: You file it away.

ROBERT: Oh, this is pretty good.

ROBERT: And then later when you want to remember something, you flip back through the files, and there's the one.

SALES CLERK: This one?

ROBERT: Yeah.

ROBERT: You pick it up. "Oh, yes. I recall." And there it is, that's the memory.

ROBERT: Can you lock it?

SALES CLERK: Yes. We have the key.

ROBERT: Sure, sometimes you forget where you filed it.

ROBERT: Let me see if I can get ...

ROBERT: But it's there.

ROBERT: Oh, I can't ...

ROBERT: Somewhere. However, when we asked scientists about this analogy, they pretty much all said ...

SCIENTIST: No.

SCIENTIST: No.

SCIENTIST: No.

SCIENTIST: The filing cabinet analogy is just completely wrong.

SCIENTIST: Period

JAD: Well, maybe that's because your metaphor is a little outdated, frankly.

ROBERT: [laughs] I think of memory as more like a—more like a hard drive.

JAD: Here we are, about to go into B&H.

JAD: That you might find at a tech store.

JAD: So much gear! Can you show me your hard drives?

SALES CLERK: Sure.

JAD: Like your brain is basically a biological disc drive.

SALES CLERK: This little one is 320 gigabytes.

JAD: How big is big these days for a hard drive?

JAD: And everything you do ...

SALES CLERK: Up to two terabytes.

JAD: ... everything you see ...

JAD: Could I put all the images I've ever seen in my life, could it go onto this hard drive?

SALES CLERK: Um ...

JAD: ... somehow all that experience gets stored in your head in some kind of neural code.

SALES CLERK: Digital information is stored in zeros and ones.

JAD: Then later when you wanna go back to it, you just find the right file, call it right up and there it is.

SALES CLERK: It's up on your computer screen.

JAD: Your memory. Just as you left it.

SALES CLERK: The way you put it in, the way you take it out, it's all the same.

JAD: Never changes.

SALES CLERK: Never changes. Zeros and ones.

JAD: But again, if you ask scientists about this analogy, they'll tell you ...

SCIENTIST: No.

SCIENTIST: Wrong.

SCIENTIST: Memory isn't like that. Memory is not an inert stack of zeros and ones.

[ARCHIVE CLIP: Malfunction. System is shutting down.]

ROBERT: Well, if neither of those metaphors are an apt description of memory, then what—how should we think about memory?

JAD: Well maybe—and this is what we're gonna look at this hour, maybe it's not as mundane as those metaphors would suggest. Maybe memory is more creative than that.

ROBERT: Creative?

SCIENTIST: Yes.

SCIENTIST: Yeah.

SCIENTIST: On a literal level it's an act of creation.

SCIENTIST: Yeah, exactly.

SCIENTIST: We're reconstructing those memories.

SCIENTIST: Construction.

JAD: Maybe it's more like painting or sculpture.

SCIENTIST: Everyone's constantly their own artist.

SCIENTIST: We take bits and pieces of experience.

SCIENTIST: Some things get sharpened, other things leveled.

SCIENTIST: And infused with imagination and ...

SCIENTIST: Out of that construct ...

SCIENTIST: Construct. Construct.

SCIENTIST: ... what feels like a recollection ...

SCIENTIST: It's a beautiful process.

SCIENTIST: It's—it's unbelievable.

ROBERT: Okay. Well, all that in the next hour coming up.

JAD: Right. This is Radiolab. And later in the show by the way, a truly unbelievable story of amnesia. But let's begin as simply as we can. What is a memory? Like, where do you find a memory? Where do you go to find it? There's a scientist we met, Joe LeDoux who works at NYU, who started looking when he was very young, in the most obvious place.

JOE LEDOUX: As a child I worked in my father's meat market, and the way the cows were slaughtered in those primitive days was with a .22 rifle.

JAD: They'd shoot them in the head?

JOE LEDOUX: They'd shoot them in the head, yeah. And my job was to clean out the—clean the brains.

JAD: This makes a convenient beginning to this story because perhaps ...

JOE LEDOUX: The texture of the brain is very fun to play with.

JAD: ... while the young LeDoux had his fingers in the cow's brain ...

JOE LEDOUX: You stick your fingers in there and have the sense that I was reaching into the cow's soul.

JAD: ... maybe he was also thinking, "Where in that mess are the cow's memories?"

JOE LEDOUX: It had these rough membranes over it and just stripped it.

JAD: "Can I touch a memory? Can I pinch it between my fingers?"

JOE LEDOUX: One bullet.

JAD: One bullet.

JOE LEDOUX: One tiny little bullet. And my job was to go in and find it and remove it, because if you were eating brains, you didn't want to chomp down on lead.

JAD: In any case, LeDoux developed a thing for brains. And many years later in college, he'd get another chance.

JOE LEDOUX: I was taking courses in psychology.

JAD: A professor of his asked him to come into this lab ...

JOE LEDOUX: Studying the brain mechanisms.

JAD: ... and work on rat brains. And no bullets involved. This time he really would be searching for memories.

JOE LEDOUX: And I got hooked on it.

JAD: You with me?

ROBERT: Yeah.

JAD: All right. So it was the '60s, right? LeDoux was in school. And it was an interesting time for the field he was about to enter. Scientists had just discovered this drug. They found that if you give this particular drug to ...

JOE LEDOUX: I think it was probably done in goldfish first.

JAD: ... yeah, give it to a goldfish. Squirt a little in the tank.

JOE LEDOUX: Into the water.

JAD: Suddenly ...

JOE LEDOUX: The goldfish ...

JAD: ... can't make a memory.

JOE LEDOUX: After a goldfish has learned something ...

JAD: ... they'll swim around, have all kinds of experiences, but later remember nothing.

JOE LEDOUX: They won't form a long term memory for it.

ROBERT: What does a goldfish learn then? I mean ...

JAD: Uh, I actually have no idea. But apparently they do learn stuff, except when they have this drug in their system, in which case they'll learn stuff and forget it immediately. And the implications of this were huge.

JONAH LEHRER: Oh, yeah.

JAD: According to science writer Jonah Lehrer ...

JONAH LEHRER: Absolutely.

JAD: Because now for the first time, scientists could say that a memory, well it's a real thing.

JONAH LEHRER: This physical thing. It's not simply an idea, it's a physical trace left in your brain.

JAD: A trace made largely of ...

JONAH LEHRER: Proteins. You know, proteins are the building blocks of memory.

ROBERT: Well, how do they know that?

JAD: Because of that drug.

JOE LEDOUX: It's called anisomycin.

JAD: The amnesia-inducing one.

ROBERT: Mm-hmm.

JAD: What it does is target proteins.

JONAH LEHRER: It prevents new proteins from being formed.

JAD: It busts them up.

ROBERT: And that means what, exactly?

JAD: Well, no proteins, no memory. Well, let me give you an example of how all this works. And this is something LeDoux ended up doing after college.

JAD: The methodology. Can we start there?

JOE LEDOUX: Sure.

JAD: He would take a rat, put it in a box, and then play it a tone.

JOE LEDOUX: Just a five kilohertz pure tone.

JAD: Sort of like, boooop!

JOE LEDOUX: Something like that, yeah.

JAD: Now imagine you're this rat.

ROBERT: Mm-hmm.

JAD: Your entire world is in this box. And suddenly a sound as if from God. And then the sound stops, and you're like, "What? What is—ow! Hey, he shocked me on my feet!"

JOE LEDOUX: The shock is, you know, a mild electric shock.

DAVID BUSH: I mean, it's less than getting static electricity.

JAD: This guy who works in LeDoux's lab ...

DAVID BUSH: I'm David Bush.

JAD: He actually demonstrated it for me.

DAVID BUSH: All right, so what ...

JAD: Or on me.

DAVID BUSH: What I'm gonna do is have you put your fingers on there, okay?

JAD: He made me touch the bottom of the cage.

JAD: Right. I'm putting my fingers on the bottom of the cage. I'm a little scared. Yeah. Yeah. Ah!

JAD: It's really not that bad. It's like static electricity, really.

JAD: Ow!

ROBERT: If you're you, or if you're a rat it might be a whole 'nother thing.

JAD: Even for a rat.

ROBERT: But what's the point? Why are we doing this?

JAD: Oh, well they're trying to make the rat form a memory.

ROBERT: Oh.

JAD: And here's how we now know that that works. So from the rat's perspective, the moment it hears the tone and then feels the shock, inside its head a bunch of neurons start to build a connection.

DAVID BUSH: Whenever you create a memory, it's an act of cellular constructions.

JOE LEDOUX: What we're talking about now is associative memories. Associations between two things in the outside world.

JAD: Between boooop! And bzzzt!

JOE LEDOUX: Those two events have to somehow be connected.

DAVID BUSH: It's as if you're building a bridge over a chasm and that connection ...

JAD: Well, that's basically a memory. A memory is a structure that connects one brain cell to another. So the next time that the rat hears that damn tone, inside its brain tone brain cells are physically connected to shock brain cells. It's gonna know that after this: boooop! Comes this: bzzzt! And so instead of just listening passively, it's gonna freeze.

DAVID BUSH: The back is hunched, and they're just frozen solid.

JAD: Bracing itself for what is about to happen.

DAVID BUSH: Exactly.

JAD: When LeDoux and his team see the rat freeze like that, they know it is in the midst of remembering.

JOE LEDOUX: They'll do that the rest of their life.

JAD: For life.

JOE LEDOUX: Lifetime memory.

JAD: However ...

DAVID BUSH: If you inject a chemical into the brain that prevents these neurons from building this new architecture that a new memory requires, the rat will never form a memory because its neurons are prevented from forming all these new proteins, which a new memory requires.

JAD: And so whatever the rat was doing during the injection, it'll never remember.

DAVID BUSH: Play it the noise and then shock it, and then play it the noise and then shock it, and then play it the noise and then shock it, and the rat never learns.

JAD: It'd be like boooop! "Hey, what's that?" Bzzzt! "Ow! Ooh, what's that?" Bzzzt! "Ow! Ooh, cool. What's that?" Bzzzt!

DAVID BUSH: Perpetually surprised by the shock.

JAD: So the basic rule is that if you get to the memory while it's being made, you can bust it up by inserting this drug

ROBERT: So the memory never is actually formed.

JAD: Right, never committed to memory.

ROBERT: Uh-huh.

JAD: But if the memory gets made and the protein bridge is there in your mind, it's built and built for all time.

ROBERT: So if you have the memory in there then you cannot erase it then.

JAD: Yeah, it's about timing. If you get there first you can erase it, but if you get there after, no.

ROBERT: Okay.

JAD: And that's what everyone thought. Until 2000. One day, LeDoux was in his office and a guy walks in the door.

JOE LEDOUX: The person who walked through the door that day is Karim Nader.

KARIM NADER: Karim Nader. I would often go in Joe's lab and just tell him ideas and stuff.

JAD: This is Karim.

JOE LEDOUX: He was a postdoc in the lab.

KARIM NADER: I went into Joe's office and said "Joe, like, what do you think would happen if ..."

JAD: What do you think would happen if, instead of giving the drug while the rat was making the memory, what if way after the fact, we gave it the drug while it was remembering the memory?

ROBERT: You remembered something.

JAD: Could we mess with the memory then?

KARIM NADER: I thought, wouldn't it be cool if that happened?

JOE LEDOUX: I said, "Well, that'll never work.

KARIM NADER: He said, "That's never gonna work."

JOE LEDOUX: "Don't waste our money."

ROBERT: It was just a very naïve question.

JAD: Yeah. I mean, because the memory's already there.

ROBERT: Right.

JAD: You can't erase a memory that's just already there. I mean have you ever seen that movie Eternal Sunshine of the Spotless Mind?

ROBERT: No.

JAD: No? Well, that's essentially what it was proposing

KARIM NADER: Yeah. I mean, it was crazy.

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: Here at Lacuna, we have perfected a safe, effective technique for the focused erasure of troubling memories.]

KARIM NADER: In this movie, Jim Carrey has all of these memories he wants to get rid of.

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: I'm here to erase Clementine Kruczynski.]

KARIM NADER: And so he goes to this company that ...

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: Good morning, Lacuna.]

KARIM NADER: ... performs this service.

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: How are you today, Mr. Baird?]

KARIM NADER: And so they have him in this room.

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: Comfortable? Please try to focus on the memories.]

KARIM NADER: And he's retrieving all these memories.

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: This is the day we met. Hi there. Hi. I'm Clementine.]

KARIM NADER: And each time he retrieves one ...

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: I'm Joel.]

KARIM NADER: ... they zap his brain.

[ARCHIVE CLIP, Eternal Sunshine of the Spotless Mind: Got it. I love you. Got it.]

JAD: Could we zap a memory that was already there? Could we go in and erase old memories? That was Karim's question.

KARIM NADER: I was just looking to do something conceptually challenging, just kind of fun, right? And just out there.

JAD: Joe thought he was crazy.

JOE LEDOUX: I didn't think the experiment was gonna work. And he said, "Okay." And so he went away and he did the experiment without telling me. And ...

JAD: A couple months later, Nader walks back in the door.

JOE LEDOUX: ... walked in the door and he said ...

KARIM NADER: "Joe, like this is really crazy, but it actually worked."

JOE LEDOUX: It worked.

JAD: Karim said he took a rat, played it the tone.

KARIM NADER: Gave them a tone and then give them a mild shock to the feet.

JAD: So it could form a memory. Tested it just to make sure, and sure enough when it heard the tone, it froze.

KARIM NADER: Yeah.

JAD: Which means it had the memory. Good. Then he waited. A long time.

KARIM NADER: 60 days.

JAD: 60 days?

KARIM NADER: Yeah.

JAD: Two months later, he played the rat the tone, and as it's frozen thinking "Oh no! Oh no, I know what's about to happen," right at that moment, while it was remembering, he gave it the drug.

KARIM NADER: And then the next day we just put them back into the box, and we just gave them some tones to see how afraid they were of the tones. And the ones that got the drug, they behaved as if the tones doesn't mean that they're gonna get zapped anymore.

JAD: All of a sudden the rat had been set back to square one. Now it was like— boooop! "Ooh, what's that?" Bzzzt! "Ow!" Memory was gone.

KARIM NADER: There was no memory.

ROBERT: No memory at all?

JAD: No.

JONAH LEHRER: That was the shocking result of the LeDoux-Nader experiment.

JAD: That's Jonah again.

JONAH LEHRER: The rat is already terrified of the shock, but if you inject the chemical as the rat is remembering what the sound means, the memory disappears. It's as if the memory had never been there in the first place.

ROBERT: Really?

KARIM NADER: Yeah. Joe looked at me, and he just looked very surprised.

JAD: What exactly did you say to him?

JOE LEDOUX: You know, "Holy bleep. Take a look at this because it's so bleep crazy."

ROBERT: [laughs]

KARIM NADER: It took me a while to really kind of believe that it was all true.

JAD: Plus, Joe and others had a concern: maybe this drug isn't erasing a memory, maybe it's just giving the rat brain damage and erasing everything.

JOE LEDOUX: So we designed an experiment that would test the specificity of these effects.

JAD: He wondered, could he pinpoint and extract one single memory of many?

JAD: That's an interesting question.

JOE LEDOUX: Right.

KARIM NADER: The idea was to create a memory network in the rat.

JAD: So in his latest study, what he did was he taught the rat to be scared of two tones, not just one.

KARIM NADER: So one's like a voop! And the other one is a pip. Like, repeating sounds of a pure tone.

JAD: And he teaches the rat to be afraid of both of these tones, each one results in a—bzzzt! Only this time, when he plays the tones 45 days later, he picks just one of them. Maybe for instance this one [tone] to pair with the drug.

KARIM NADER: And then the next day you test both.

JAD: Mm-hmm?

KARIM NADER: And only the one that was paired with the drug is affected.

JAD: So you erased tone one but not tone two?

KARIM NADER: Exactly.

JAD: So do re mi—you can just erase re?

KARIM NADER: That would be the idea.

JAD: Wow. That really is Eternal Sunshine of the Spotless Mind!

KARIM NADER: Well, that movie came out about two years after we published the study that really got all this going.

JAD: Do you think they stole from you?

KARIM NADER: I don't think they stole, but maybe they were thinking along these lines, and they were ...

JAD: They must've read it and been like, "Oh, my God!"

KARIM NADER: There was a write up in the Science Times, and they proposed this would be a treatment for PTSD.

JOE LEDOUX: Post traumatic stress disorder. People who go to war or have been through trauma.

JAD: People haunted by really bad memories.

JOE LEDOUX: They just can't escape the thoughts and memories that they keep reliving.

JAD: How would that work in a therapy situation though?

KARIM NADER: Suppose you have a holocaust victim who's lived for 50 years with these memories and, you know, you would say, "Well, let's talk about what went on in the camp, and the day you saw Mary in the line to go to the chambers."

JOE LEDOUX: You say close your eyes and just imagine.

KARIM NADER: Relive it.

JAD: And right as you're talking about it you swallow a pill?

JOE LEDOUX: Yeah.

KARIM NADER: More or less.

JOE LEDOUX: And so in fact, we've done that.

ROBERT: They've done that?

JAD: They have. Karim Nader now works at McGill University in Montreal, and he has teamed up with a clinical psychologist to try this on people. And it seems that when you give this drug as a person is remembering or reliving a traumatic event, the memory is eroded somewhat. The next time they think about it, it's not quite as painful.

KARIM NADER: One woman, she had been raped as a child by a doctor, and then when she told her mother, her mother said she was making up stories.

JAD: Wow.

KARIM NADER: Apparently she never spoke to anyone about this. And she used to get undressed in the dark in front of her husband.

JAD: Wow.

KARIM NADER: And so she came into the clinic.

JAD: He says she took the drug while thinking about the trauma.

KARIM NADER: And then a week later ...

JAD: She told the story again. And this time it wasn't nearly as hard.

KARIM NADER: She improved dramatically to the point where she was telling the story on TV.

JAD: On TV? Wow! So she went from telling no one about this—including herself—to being so open that she could tell thousands of people?

KARIM NADER: Yeah. She just felt that the emotional part was no longer overwhelming her.

JOE LEDOUX: Some ethicists say that it's wrong to mess with memory but, you know, that's what therapy is too. It's a process of changing your evaluation of situations, learning new things, storing new things.

KARIM NADER: At one point she said, you know, we've given her back herself.

ROBERT: Hmm. I—I know that she feels better, but there's something slightly creepy about this.

JAD: Yeah.

ROBERT: That she feels better because something is now missing in her, something that troubled her. But she's been—in a way, a part of her has been deleted. I mean, look, I think of myself really, I'm Robert Krulwich and I'm a certain age, but really what I am is I'm a string of memories.

JAD: Yeah.

ROBERT: I mean, that is as close to a way of describing the real me as I can find.

JAD: Mm-hmm.

ROBERT: I own those memories, and they define me. But you're saying you can come to me when I'm already formed, when I'm already there, you can give me a shot and you can fundamentally change me.

JAD: There's an assumption in what you're saying which is actually kind of wrong. There really isn't anything like a "real" memory. I mean, think about it: if you can erase a memory while it's being created—that's how we started—and now we learn you can erase a memory while it's being remembered using the same drug?

ROBERT: Yeah?

JAD: What that really means is that every time you are remembering something, you're actually recreating it. That's the only reason the drug works. And so if you're recreating it each time, then each time you're remembering something it's a brand new memory.

ROBERT: Well, no. But I've always kind of assumed that underneath all this remembering, there's some kind of special absolutely original memory locked in a vault somewhere.

JAD: No. No. That is the crazy implication of this experiment.

JONAH LEHRER: That the act of remembering on a literal level, it's an act of creation. Every memory is rebuilt anew every time you remember it.

JAD: And not only is it an act of creation, as Jonah says, Karim would say it's an act of imagination.

KARIM NADER: Every time you remember something you're changing the memory a little bit. We're always changing the memory slightly.

JONAH LEHRER: You think you're remembering something that took place 30 years ago. Actually, what you're remembering is that memory reinterpreted in the light of today, in the light of now.

ROBERT: So does that mean there's no such thing as a memory for all time that hides in a secret vault somewhere? That all you've got is the most recent recollection of the experience?

JONAH LEHRER: Yes.

ROBERT: Well then, how do I know that any memory is verifiably true?

JONAH LEHRER: You don't. You don't. And one of the ironies of this research is that the more you remember something, in a sense the less accurate it becomes.

ROBERT: Hmm.

JONAH LEHRER: The more it becomes about you and the less it becomes about what actually happened.

ROBERT: So let's just do something. Imagine a couple in love and it's their first kiss. He kisses her and she kisses him back. She remembers the kiss of course, and he remembers the kiss of course. As they go through the rest of their romance and the next 36 years together, the kiss will essentially become replaced by two independently re-embroidered and increasingly dishonest kisses?

JONAH LEHRER: Assuming they think about that kiss enough, that's kind of what the theory implies.

ROBERT: But certainly there's gotta be somewhere, between the man and the woman, there's gotta be some true kiss, or is that kiss just gone?

JONAH LEHRER: That true kiss vanished the minute their lips separated.

ROBERT: Huh.

JONAH LEHRER: As soon as reality happens, it begins diverging in all our different brains on a very synaptic level.

ROBERT: Here's where you cue the really sad music.

JONAH LEHRER: They just grow slowly farther and farther apart.

ROBERT: Well, let me do it a different way. Let's suppose that Joan and Bob kiss, and then they part. It's a great kiss.

JONAH LEHRER: Uh-huh.

ROBERT: And then they never think about it again. I mean, it was a great kiss in the moment but they never think about it again.

JONAH LEHRER: Yeah.

ROBERT: 30 years later, Bob is in a railroad station. Joan comes out of a train, their eyes meet, Bob sees Joan, sees her eyes, and remembers suddenly that kiss.

JONAH LEHRER: That memory is more honest than if he'd been thinking about the kiss every day of his life since.

ROBERT: Oh. You know, that's even sadder.

JAD: You know, but it's true. That's what scientists say.

JOE LEDOUX: Absolutely. We had a conference last week, and Yadin Dudai was here, and he proposed that the safest memory, a memory that is uncontaminatable, is one that exists in a patient with amnesia.

YADIN DUDAI: What I meant is that there is a sort of a paradox

ROBERT: This is Yadin?

JAD: This is Yadin.

YADIN DUDAI: And I'm a professor in Israel.

JAD: Reporter Ann Heppermann tracked him down for us.

YADIN DUDAI: Intuitively you think if you use a memory, you know, you know better because you remember it better, you recall it better, you know the details better, and so on and so on. But this is not what science shows. If you have a memory, the more you use it, the more you're likely to change it. So if you never use your memory, it's secured. So taking it a bit farther, the safest memories are the memories which are in the brain of people who cannot remember.

JAD: Okay. Well, I guess we should go to break now.

ROBERT: Oh, yeah. So we should tell you that Jonah Lehrer is the author of a new book called Proust Was a Neuroscientist.

JAD: And Joseph LeDoux from NYU before him, he also wrote a book called The Emotional Brain. And Karim Nader, I don't think he's written a book, but he will.

ROBERT: [laughs] I'm sure he will.

JAD: And also thanks to our producer Ann Heppermann.

ROBERT: And if you need more information, or you want to hear anything again, one word, Radiolab.org.

JAD: Radiolab will continue in a moment.

 

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