NOVA

NARRATOR

Memory-- it's the key to our identity. Without memory, we're nothing. It's who we are. But how does it actually work? It's a huge mystery. Today, scientists are probing our brains like never before. We're seeing a memory being formed in front of your eyes. Finding clues that lead us to shocking new places. Your memory's not as accurate as you think it is. We can tinker with a specific memory at will. Perhaps Mother Nature needs a little bit of tweaking on the dial. From editing memories... We can implant a false memory....to deleting our worst fears. It was unbelievable. I was standing there like, "How can this be possible? I used to be terrified of spiders." We target and even erase the fear memory itself. Are we approaching the day where at the flick of a switch, we can rewrite our past? Being able to use new technologies to edit memories is frightening. I think that it's a matter of when this happens, not a matter of if it'll happen. "Memory Hackers," right now on NOVA. I remember... I remember... I remember... I remember... Hmm... Memory.

We know it as a record of our lives

how to find our keys or recite facts from school. But stop and think about it. It's so much more. From your earliest memory... Falling off of a horse at about five years old. When I walked into kindergarten and I met my best friend. About 1925, we moved to 513 Spring Avenue.

NARRATOR

Your happiest... When my daughter was born. When she, like, came out. Seeing a real life human being breathe that first breath of fresh air. Or saddest... The death of my father. We are little but the sum of our memories.

DANIELA SCHILLER

It's who we are. That's how we understand ourselves and our lives.

NARRATOR

Consider for a moment just how vivid a memory can be. The smells, the sounds... I know the shoes, the socks, the pants and shirt I wore. It was like it happened yesterday. I do have a picture in my head. I can see it! That is a remarkably complex computational process that memory achieved within milliseconds. What an incredible, powerful gift. How is this gift possible? How does the world get into our heads and turn into a memory? How does memory actually work? Wow. Turns out that's one of the biggest mysteries in science today. If you go and ask most people, they would say they understand memory, but the truth is really rather far from that. We sort of understand the tip of the iceberg.

RODDY ROEDIGER

We're just kind of nibbling around

the big central mystery of memory

how do I bring back in time now something that happened to me long ago? It's a very difficult problem that we haven't solved.

SCHILLER

Memory is the biggest mystery. It's as big as the question of, "What is the universe? Why are we here?"

NARRATOR

Could this 11-year-old boy hold one of the keys to unlocking the mystery? On first glance, Jake Hausler looks like a normal fifth grader, but as Washington University's Roddy Roediger is discovering, he seems to be anything but.

ROEDIGER

What happened Friday, October 28, 2011? World Series game seven. Cardinals won 6-2. Who were the pitchers for the teams? Chris Carpenter for St. Louis, Matt Harrison for the Rangers.

ANNOUNCER

The World Champs in 2011! We're just getting to know Jake and just starting to study him. He's obviously a very bright kid with a different kind of very powerful memory. Let's try a different day here. How about May 4, 2013? That was a Saturday, and I saw Iron Man 3. He appears to have a pretty unique ability. So he can tell you what he did years ago to this date, and that's very, very unusual, in and of itself, and to find it in a child is particularly unusual. When was Osama bin Laden killed? May 2, 2011 in Pakistan, May 1, 2011 in U.S.A.

ROEDIGER

I mean, it's amazing. I've never felt like my memory was particularly bad, but compared to Jake's, clearly it is. It's just a mystery as to what's going on here.

NARRATOR

Jake can remember details from almost every day of his life since age seven. Once he started speaking, really, we noticed he was different.

MOM

What are the 13 colonies? Georgia, Connecticut, Massachusetts, Maryland...

DAD

I remember taking him to the grocery store one time and he knew where all the items were by aisle. It's a little bit like having a computer living with you.

NARRATOR

We'd all remember getting a pet, but the exact date?

DAD

What day did I pick up Gracie in Wisconsin? March 31. Where did I fly into? Minneapolis/St. Paul. What did I eat for dinner the night I was in Wisconsin? Cheese curds? That is correct. (laughing) There's no doubt that there's something different going on there.

What's different about Jake is that he has HSAM

Highly Superior Autobiographical Memory. Highly Superior, you can remember days from your life in lots of detail, like what day of the week was it, and you can't forget. What about 2004?

NARRATOR

Jim McGaugh is a pioneer in the science of memory. He discovered HSAM 15 years ago.

McGAUGH

And when did you meet with me? June 28, 2008.

NARRATOR

So far, out of the several thousand tested, he's discovered 55 adults who have this amazing ability. A Saturday at Panera Bread in Newport Beach.

McGAUGH

I can give them any date, say ten years ago, five years ago, 20 years ago, and so on. Do you know when Elvis Presley died? August 16, '77. And their performance will be at least 80% correct, and maybe 100% correct, depending upon the particular individual.

NARRATOR

One of the best memories McGaugh has ever tested

belongs to someone you might recognize

actress Marilu Henner from the hit show Taxi. I knew as a very young child that I had a very unusual memory. They called me Miss Memory, Miss UNIVAC, The Memory Kid, things like that.

NARRATOR

Name-calling aside, they're not geniuses. In fact, on average, they have normal IQs. They are not superior in other forms of learning, like book learning, standard laboratory learning tasks, and so on. I think a misconception, as you probably know, that people have, they think it's some type of autistic savant thing, that we're using some type of mathematical calculation like in Rain Man. Yeah, defitely not Rain Man. So what gives them this amazing ability? McGaugh has scanned over a dozen HSAMs and found some intriguing hints. For example, an area in the brain associated with memory-- the uncinate fasciculus-- is more active in HSAMs. There are some differences in the brain. They're statistically significant, but they have not given us a pattern such that we can say, "This is the neurobiological basis of HSAM." What is it about their brains that enables this ability? That's the open question. And that's where Jake comes in. He is the youngest person ever discovered with HSAM, and here at Washington University, scientists are mapping his brain with new imagingechnologies. Over the next year, they'll test his memory while doing hundreds of scans. All right, Jake, so what happened on April 8, 2013? I went to the St. Louis Zoo. When they are finished, they will have perhaps the most comprehensive picture ever of a child's brain.

McDERMOTT

We're getting loads and loads of data on him. It's very, very exciting. I mean, to do this in a normal person in this comprehensive a way would be really exciting, and to be able to do it on a child who has particularly unique abilities is extra special.

NARRATOR

Then, they'll compare Jake's scans to other children's to see if they can unlock the secret of wt makes his memory so extraordinary.

MAN

It's a chance of a lifetime. You can't write a grant saying we're gonna go look for someone like him because you'll never find him, right?

NARRATOR

The hope is that this little boy's brain can help answer some big questions about how our memory works. Jake clearly is able to extract remarkable amounts of information from his brain, but we don't know if you or I have that information in us, but we just can't remember it, or if it just doesn't get encoded into our brain function in the first place. The mystery with Jake and the other HSAMs is, do they actually keep more memories than the rest of us, or do we all have this wealth of detail buried deep inside our brains-- we just can't get at it? If we can understand how he harnesses that, to be able to generate that within ourselves could be a very powerful tool.

McGAUGH

There is potential there that we will learn something truly new and important about the functioning of the most complicated and interesting known structure in the universe, and that's our brain. And the most important thing it does is learn and remember.

NARRATOR

But what exactly is a memory? Amazingly, this simple question has stumped thinkers for ages. Until the 1950s, few clues emerged, and then came a single patient who would change everything. When I was a young researcher, learning was learning and memory was memory, and it was just, you know, a thing that happens. And then along came the findings of Brenda Milner and her subject, HM. HM stands for Henry Molaison, patient zero in the study of memory. After a childhood bicycle accident, Molaison began to suffer severe epileptic seizures. To try and quell those seizures, neurosurgeons performed an operation where they removed the parts of his brain that they thought were creating those seizures. Much of what they removed came from a part of the brain called the hippocampus. After the surgery, his seizures were gone, but there was an alarming side effect.

WALKER

From that point forward, he could no longer make any new memories. He was what we call "densely amnesic."

It could only mean one thing

the hippocampus must be the part of the brain responsible for creating new long-term memories. This in itself was a breakthrough, but that was just the start.

BRENDA MILNER (recording)

Do you know what you did yesterday?

HM (recording)

No, I don't.

MILNER (recording)

How about this morning?

NARRATOR

Brenda Milner wanted to know, despite his amnesia, could he still have some form of memory?

BRENDA MILNER

He was a very nice person. He was very cooperative. Fortunately for us, he liked doing tests, he liked puzzles.

NARRATOR

So she came up with a puzzle to trace a star shape using only a mirror to see his hand.

MILNER

If you try this, it's jolly difficult, but normal subjects, with practice, a few trials, learn to do this thing.

NARRATOR

Because HM appeared to have zero ability to make new long-term memories, he should be hopeless. He shouldn't be able to learn anything. How's he going to do? I didn't know, I didn't know, I had no idea. And in fact, every time Milner asked him to train, he claimed he'd never done the task before. But his performance betrayed him. He got better and better, until... I was so excited, because this was a breakthrough. He can't remember the events of his life, but it seems that he can possibly learn motor skills. The fact that HM could remember motor skills but not new events in his life meant that memory couldn't be just one thing. We had to leave behind the notion there was just one kind of memory. We now knew that there are different kinds of memory, and those different kinds of memories depend on different parts of the brain. Knowing where memories are in the brain is one thing, but how do they get there? How does a long-term memory get written in the brain in the first place? These are the questions that have driven Nobel Prize-winner Eric Kandel for over 60 years. It all started back in Vienna on his ninth birthday.

ERIC KANDEL

I received a marvelous little toy car that I drove with great pleasure through our small apartment.

NARRATOR

Two days later was Kristallnacht, the infamous Night of Broken Glass. In that violent prelude to the Holocaust, thousands of Nazi soldiers stormed the Jewish neighborhoods in Vienna.

KANDEL

November 9, there was a knock on the door, and two Nazi policemen came in and said, "Pack all your things." When we came back a week later, everything of value is gone, including my little toy car. That was a very painful experience.

NARRATOR

A painful experience that would define his life's work.

KANDEL

Everyone who went through the Holocaust, there are memories that you can never forget.

Kandel wanted to know

how did that experience become a memory he would carry with him for life? That got me interested in psychology and psychoanalysis. And when I got interested in that, I said, "What's the central question in psychoanalysis?" It's memory, how we recall things.

NARRATOR

But where to start? His biggest lead was Milner's early work with HM. The hippocampus is crucial for forming new memories. But how do they get there? Could there be a physical mechanism on the cellular level?

KANDEL

So I thought I would record from single cells in the hippocampus, and those cells would be so unique, they would speak to me of memory storage.

NARRATOR

Within months, he was able to record the sound of hippocampal neurons firing.

KANDEL

Our colleagues were euphoric. But we didn't learn a darn thing about learning and memory. So I realized one needed to take a reductionist approach, and I thought I would use a simple animal with a simple nervous system, simple behavior, and try to study that.

NARRATOR

Enter Aplysia Californica, a giant sea slug with one of the simplest nervous systems in the animal kingdom.

KANDEL

One of the great giants in the field thought I was throwing my career away. In my naivet, I was confident that this would be right.

NARRATOR

He thought if he could just isolate the cellular changes that occurred when Aplysia learns simple tasks, it would be the key to understanding our memory. Humans have neurons. Sea slugs have neurons. They're not that different, right? Even at the level of DNA, our DNA's not so terribly different. The same fundamental kinds of changes should underlie memory. To test his hypothesis, Kandel's first step was to create a memory in the sea slug. To do that, he trained it to fear a light touch.

KANDEL

If you touch it in the siphon, it'll withdraw the siphon.

NARRATOR

The siphon is the slug's water spout. When it is touched, it also withdraws its gill slightly as a protective reflex. But pair that touch...

KANDEL

Touch, shock.

NARRATOR

...with a mild shock, you get a much stronger reaction. And do it repeatedly... Now when you touch the animal's siphon again, even weeks later, without a shock, it reacts as if it got shocked. Somehow, it remembers that that light touch means shock. It has formed a long-lasting memory. The question is, how? Kandel had a hunch. If he could just replicate that touch experiment with single cells, he could see exactly what was going on to make a memory.

KANDEL

We could take the cells out of the animal and put it into the cell culture and reconstruct the neural circuit. We could look at each level and see what happens with long-term memory.

MARTIN

That was this huge breakthrough. What Eric Kandel really did was he took this sort of phenomenon of memory and turned it into a biological question. "What are the changes that are happening that give rise to memory?"

NARRATOR

To find out, Kandel's team extracted two neurons from the sea slug. This is a sensory neuron from its siphon, and that's a motor neuron from the tail. They are connected by a single synapse.

KANDEL

The synapse is the point of contact where one neuron talks to another.

NARRATOR

Then, to simulate a long-term memory just like with the live animal, Kandel repeatedly stimulated the sensory neuron. And when he did, suddenly something magical happened. New synaptic connections started to grow.

KANDEL

This made us realize for the first time that long-term memory actually involves an anatomical change in the brain whereby new connections are being formed. And that just really blew us away the first time we saw it.

JOE LEDOUX

That was a phenomenal discovery because it showed us for the first time that memory involves a structural physical change in the brain. That became the foundation for our whole conceptual basis for understanding memory.

NARRATOR

Using today's technology, you can witness this process first-hand. This shows you the nucleus in the cell. After repeated stimulation, the neuron's nucleus starts to pump out these tiny glowing specks called mRNA, recipes for building proteins. They're about to travel down to the synapse with instructions to build new connections. And you see this magnificent voyage that this particle, which is carrying messenger RNA to the synapses. When it gets there, the instructions are released and the new connections grow, seen here in green. We're seeing a memory being formed in front of your eyes. These anatomical changes occur in your brain when you learn and remember something. From sea slugs to humans, these physical changes are considered the biological basis of memory. It's an article of faith at this point that the mechanisms that he has uncovered are fundamental ones to learning and memory for all of us. Kandel's work launched a new way of probing memory,

grounded in biology and built around a simple premise

the growth of new connections is what allows a memory to persist for days, months, even years. But that was just a piece of the picture, a basic mechanism for how memory works at the level of single cells. Even in a sea slug, a memory is made up of about 50 neurons out of 20,000. In a human, it's more like tens of thousands out of 100 billion. Somehow, it's this network that stores a memory.

Which begs the question

where exactly does a particular memory live in us? To this day, that remains a mystery, but we aren't without clues. In the last 25 years, new imaging tools have allowed a generation of explorers to chart memory in the human brain. And today, we can finally begin to draw a rough map of where some of our most treasured memories live. Take something like a first kiss. Most people remember their first kiss. Do I remember my first kiss? (laughing) I do. When did I kiss that girl? There was this Italian, this dashing Italian.

MAN

She was like, "This is something people do who like each other," and I was, "Okay, I like you." I remember, you know, sort of planning this kiss for, like, a week! Her friend whispered to me, "Make a move and walk faster." And all of a sudden, Lauren and I were alone in kind of a grove of trees. He takes my face like this and plants one on me! It was like the universe exploded or something like that. It just felt like suddenly, everything was different.

MATT WALKER

The question becomes then, where is the memory? And what we started to understand is that there isn't a nicely sort of packaged memory that's sort of folded up like a letter and placed inside of an envelope in one specific area of the brain. Different parts of memories are coded in different locations of the brain. Think about your first kiss. The visual elements are coded at the back of the brain in the visual cortex. The smell components are coded in the olfactory cortex just above the nose. The motoric, the kinesthetic elements, they're coded up here in the motor cortex. The emotional elements are coded in deep brain structures like the amygdala. And together, it is the hippocampus that is going to grab ahold of those individual brain anatomical areas, those balloons of information, and it is going to bind them together and produces a memory that you're capable of remembering.

NARRATOR

So if different parts of a memory live in different parts of the brain, and we know that the growth of new connections is important for storing them, that would suggest that every memory is physically tattooed onto our brains. So how come we don't remember them all? The question is, if there are these structural changes that give rise to memory, but memories are changeable and dynamic, how can that be? Perhaps the answer can be found in the act of remembering itself.

Think about it

a memory only comes alive when you recall it. What happens in your brain each time you recollect a past experience? That's what Karim Nader wondered. His quest for answers started when he was a grad student at one of Kandel's lectures. Eric Kandel came and gave this brilliant talk. You know, there are examples for this...

NADER

He had beautiful pictures showing that synapses could grow over time. The work is very elegant. It took everyone's breath away.

NARRATOR

Looking at those pictures gave Nader an idea.

NADER

"Hey, why would all of this have happened just once? "Wouldn't it be cool if all of this happened again when you recall the memory?"

NARRATOR

If Kandel's work helped establish that memories can't form without new proteins that build new connections, what happens to those connections when you remember something? At the time, memory was pictured kind of like a library. The underlying dogma was that when you formed a memory, it was filed away in your brain, and that's it. It was there now forever. It's called consolidation.

RAMIREZ

You can't modify it, it just is. It's just in the brain.

NARRATOR

So when you remember your first kiss, you pull out that book, look at it, and put it back. Though it may fade over time or get lost in the stacks, the original story, or memory, is always still there. Nader wondered, "Could this really be true? "Or is it possible that just the act of recalling the memory could rewrite the story?" To find out, Nader designed an experiment.

JOE LEDOUX

When Karim told me he wanted to do that experiment, I probably said something like, "Don't do it, don't waste your time." But being a smart guy, he went off and did it.

NARRATOR

So Nader decided to put his idea to the test. He started by training rats to fear the sound of a tone... (ringing) Okay, so there's the tone....by pairing it with a mild shock. Now there's the shock. So right now he's really scared, he doesn't like this at all. Just like Kandel's sea slugs, the rats quickly learn to fear the tone alone. They have formed a long-term memory that the tone predicts shock. So every time it hears the tone... (ringing)

NADER

So you see, even though there's no shock, the animal's freezing, it's afraid.

NARRATOR

We know the rats' brains have built new connections to store the memory. But what happens to those connections when the rat recalls the memory? (ringing) To find out, Nader first plays the tone to remind the rat of his fear, and when he freezes... The next part is gonna be giving him a compound directly. The compound is anisomycin, a drug known to block the proteins needed to build the connections that store new memories. But Nader's rats have already formed the memory; they're just recalling it. If memory consolidation really is like a book in a library, the drug should have no effect. The rats' brains should have built a permanent memory and they should still freeze when they hear the tone.

NADER

So if the memory is wired in the brain, this drug should have absolutely no effect.

NARRATOR

But now when Nader plays the tone... (ringing)

NADER

Oh my God, so now you see.

NARRATOR

He keeps moving. You would think that the animal should be freezing if it still had the memory there, but now it's acting as if the memory has been erased from its mind. As if it never learned to fear the tone in the first place. The memory appears to be gone. My jaw just dropped. I just couldn't believe it. So I ran into my supervisor's office going, "Holy (bleep) (bleep) (bleep), I can't (bleep) believe this happened." I mean the probability of this happening is like zero, right? Because a drug known to block the formation of new memories also blocked them during recall, it means the act of remembering must make memories vulnerable to change.

In other words

It's not this you have a memory, you encode it, and it's stuck there. But instead what it means is that every time that memory is recalled, it is vulnerable to alteration. Nader's discovery that any time you recall the memory you essentially disrupt it was a significant advance. It changes everything we think about memory. It turns out memory is not at all actually like putting a book away in the library of the brain, but it's more like bringing up a file on your computer, constantly modifying that file.

NARRATOR

The theory is, every time you recall something, you have to pull it up off the hard drive to view it. To return it to long-term memory, you have to hit "save" and reconsolidate the memory by creating new proteins to essentially rewire the memory into your brain. Imagine something precious in a box. And then each time you take it out, it changes a little bit. And then you put it back. Then take it out, changes a little bit. That's how your memory works. The idea that the simple act of remembering could make your memories vulnerable to change transformed our understanding of memory. Within a few years, Nader's findings were replicated in dozens of species and led to over a thousand experiments, even reportedly inspired the movie Eternal Sunshine of the Spotless Mind.

MARK RUFFALO

Just focus on the memories. Here at Lacuna, we have a safe technique for the focused erasure of troubling memories.

NARRATOR

But what if this isn't just the stuff of movies? What if it's possible to use reconsolidation in humans? Perhaps to erase certain memories, like the ones that keep you up at night.

MAN

Heights-- I'm terrified of heights.

WOMAN

I don't want to be on a ladder. I don't want to be on the second floor. I don't like to be looking down. I can't tell you the last time I've been in a pool, I can't tell you the last time I've owned a bathing suit. But, I mean, the water gets like probably right here, and it's like the... (hyperventilating) Elevators. (chuckles) Snakes are the worst. I don't know what it is about bees, but I just can't... I can't be around them. Spiders. I'm petrified of spiders. Even the smallest ones. Terrified. If I see a spider I don't want to come near it. I'm really scared of spiders. Or at least I used to be. But now I'm just completely relaxed sitting here with a tarantula. And it's really crazy.

NARRATOR

Ever since she was a little girl, Sasha de Waal has been plagued by her fear of spiders. But thanks to a new therapy using reconsolidation, that fear seems to have been erased. Yeah. (laughing): I'm petting a poisonous spider indeed. The scientist who cured Sasha is Merel Kindt from the University of Amsterdam. When she heard about Karim Nader's work, she immediately saw the potential.

MEREL KINDT

So I was really thrilled. I realized if this is going to work for humans, this is, yeah, very important news. So can you tell me a bit more about your fear of spiders?

NARRATOR

Using reconsolidation, she has developed a treatment to erase patients' life-long fears. They just scare me. Just fear. When I sleep I dream about it, I'm just very scared. For the treatment we will walk to the other side of the room, and there is a terrarium tank with a tarantula in it. I'm going to ask you to touch the tarantula. Okay? They're not poisonous, right? Yeah, well, all tarantulas are poisonous. Walk to the yellow line. Very good, you are doing very good. Just like with Nader's rats, the first step is to get Jeroen to draw up the memory of his fear. (breathing heavily)

KINDT

You're doing very good. We ask our participants to approach the tarantula, which triggers the original fear memory. How much distress do you feel right now? Dry mouth. I feel shaking. You are doing very, very well. Try to look here. Don't avoid it. Stay here, it's important that you see it. Yeah? Just put your hand here. And then stop, yeah? What do you think that will happen? Approaching the spider makes the fear memory unstable. Yeah. Okay, very good, we go to the other side of the room. Such that if we give propranolol after the exposure to the tarantula, the drug can interfere with the restabilization of the original fear memory.

NARRATOR

Propranolol is a blood-pressure medication that blocks the release of noradrenaline in the amygdala, the fear center of the brain. Since noradrenaline is part of the brain's anxiety signal during a fearful event, blocking it after recall seems to disrupt the reconsolidation of the fear part of the memory. What is very important is that it is not a forget pill. If we do not trigger the memory reactivation, the drug will not work. The next day Jeroen returns. What we are going to do is again, walking to the other side of the room and I'm going to ask you again to touch the spider. You can touch it here at the backside. (chuckles) Very good. Did you touch it, did you feel it? Yeah, yeah. Okay, try it again. It felt like rubber. Yeah, try it again. Oh, man. Okay. It takes a few tries, but after just minutes... Do it again. Very good, yes, yes. Yes. How does it feel to touch a tarantula? Like touching a hamster. Yeah. Maybe he likes it. So far Kindt's repeated this work in over 30 people with spider phobia and other anxiety disorders, and... The effects were so overwhelming that I did not believe them initially. But in fact, the therapy worked in every spider phobe she tested, even a year later. It was unbelievable, and I was standing there, like, how can this be possible? (chuckles) It's my new friend. It's really confusing. It's like a contradiction... Yeah, yeah, contradiction....with how I used to feel and how I feel now. It's so strange, like I am someone else now. We of course cannot prove that we delete or even erase the original fear memory, because we can only observe the new behavior, but given that the fear does not come back, we hypothesize that the previously formed memory are in fact deleted. Treating people with spider phobia is only the first step. Kindt is now among a handful of scientists using reconsolidation to treat a variety of disorders from drug addiction to PTSD, and though the research is in its infancy, early results have been promising. I am very hopeful that the reconsolidation intervention will be further developed for people with post-traumatic stress disorder. But reconsolidation is more than just a therapeutic tool. If the act of recalling a memory makes it vulnerable to change, this may also explain something we've known all along... That our memory is often an unreliable narrator. I could swear by anyone, pass every lie detector test that... I had met Mother Teresa, but I hadn't. Something that I wanted to happen, but it never did happen. I believe that my earliest memory was a very happy memory of going to a movie called The Greatest Show on Earth. And it wasn't until much later I found out that the movie was released when I was eight years old. So it couldn't have been my earliest memory. This comes as no surprise to Elizabeth Loftus. She's spent the last 40 years exploring exactly how unreliable our memory is. I think people ought to pay more attention to the fact that there are memory errors all around them. Her work has inspired a generation of researchers, including psychologist Julia Shaw. The question isn't, do we have false memories? It's, how false are our memories? There are so many things that can and do go wrong along the way. To find out how wrong, Shaw has designed perhaps the most comprehensive study ever on false memory. She starts by recruiting over a hundred people for what they think is a study about their childhood memories. So this is my first meeting with the participant. The first event which we'll be talking about was a time when you were 12 and you moved from Trinidad to Kelowna with your family. I hated the move. Actually the study is to see if it's possible to implant a false memory about committing a crime. I had colleagues saying, "This isn't going to work. "There's no way you will get individuals to think that they committed a crime that never happened." She begins with a true event gathered from their parents-- in this case a family move. We moved around like every year kinda thing. But this was just a trick to gain trust.

The next step is to introduce the false memory

a fight so severe that the police were called. So the other event which your parents report happening was when you were 14 years old you initiated a physical fight and the police called your parents. They said it happened in Kelowna, in the fall and you were with Ryan when it happened.

Only two of the details are real

the name of the best friend and the place she lived at the time. The rest is made up. Honestly, I don't remember. Like I don't know what you're talking about. I don't.. I feel like... I don't think I've ever been in a fight. I'm so confused.

NARRATOR

Shaw then turns to a series of cognitive techniques known to induce false memories, starting with an imagination exercise. I'd like you to relax, close your eyes and focus your attention on trying to retrieve this memory. Okay. Bolstered with a little social pressure... This might seem a bit strange, but it does work for most people. Okay. Subtly introducing this notion that "it works for most people if they try hard enough," which is a subtle form of social manipulation. And ask the participant to visualize certain details of the stories. Introducing things that are easy to picture first. Picture yourself at the age of 14. "Picture yourself at the age of 14." That's an easy thing to picture. In Kelowna. In Kelowna, the place that she lived at the age. Also easy to picture. And it's fall. It's fall, everybody can picture fall. And you were with Ryan when it happened. When people imagine events that might have occurred in their past, we know that that's a potent way of creating a false memory. After giving the memory a week to set, she brings the participant back. Okay, so, welcome back. And so by the time we get to interview number two, we're seeing a different story. I remember, like, a verbal fight and maybe I... It seems so unlike... but maybe I pushed or something? Good, okay. So this is where she's first fully buying into this idea that she's actually had a fight. I feel like she pushed me first. Okay.

SHAW

And this person is starting to picture how it could have happened. And "what could have been" turns into "what would have been" turns into "what was."

NARRATOR

So by the third interview, the memory has taken hold. I think the cops showed up, and we were kind of having a... maybe like a verbal kind of fight and then it kind of maybe got into a push. And it wasn't just this once. Shaw was able to convince over 70% of participants that they committed a crime. I think I just lost it. Couldn't take it anymore. I was incredibly surprised at the rate that I had in terms of successfully implanting these false memories. You physically feel things about it? (quietly): Yes. And yet there we were, and they just kept coming and coming and coming. So much so, Shaw's team cut the study short. So this is a false memory study. (laughing): I'm so embarrassed. And the ramifications go way beyond fooling college students. False memory studies like this question one of the cornerstones of the criminal justice system.

LOFTUS

In those hundreds of cases where DNA testing has proven that these individuals were wrongly convicted, about three-quarters of the time the convictions were based on faulty eye witness testimony.

NARRATOR

So if our memories are more malleable than we think, and we can change them, even erase some of them, what's next? Will there ever be a day when at just the push of a button, we can implant or edit specific memories at will? Is this your first trip? Like in the movies? The seed that we plant in this man's mind will grow into an idea. This idea will define him. It may come to change... well, it may come to change everything about him. Movies like Inception, Total Recall, Eternal Sunshine, of course they're possible. If mice had Hollywood, then it's possible in practice right now. In fact, here at Columbia University, Christine Denny is one of a handful of neuroscientists who can do just that.

CHRISTINE DENNY

It does seem like science fiction. But we are really doing Inception in our lab with turning on and off memories.

NARRATOR

It's called optogenetics, a technique so revolutionary it allows us not only to map a specific memory, but manipulate it with lasers. At least in these little guys. These mice might not look so special. You could not tell my mice apart from a mouse on the street or wherever you would go to a pet store and buy a mouse. They don't look any different. But they are. These are genetically modified mice that allow Denny to record specific memories and turn them on and off at will. To demonstrate, she starts by putting a mouse in a new environment.

DENNY

You can see that the mouse is just sitting here in the corner, freezing. Basically scared of the environment.

NARRATOR

That's because it's bright. There's no place to hide. But the goal isn't to frighten mice. She wants to see if she can override this fear by playing back a happy memory she recorded yesterday. What we did is labeled a positive memory in the brains of these mice. Yesterday this same mouse got to explore the kind of place

it naturally likes

dimly lit, full of soft bedding, with a nice place to hide. And while he was scurrying around, Denny recorded the exact neurons that fired when he made a memory of that pleasant place.

DENNY

The cells that are labeled here in green, when I turn on the laser, those cells will turn on the memory.

NARRATOR

But how? How do you record a specific memory? And how do you get brain cells to respond to light? Here's where the sci-fi wizardry comes in. We genetically engineered mice so that we can permanently label an individual memory. The key is this mouse's special genome. It's bred to carry a piece of DNA from algae that has the code for a light-sensitive protein. In nature, that protein allows the algae to respond to light. In Denny's mice, it just sits there quietly in the mouse's genome, not doing anything until... When you inject a drug right before you expose them to this positive experience. The drug switches that gene on, telling any brain cells that fire within the hour to install this light-sensitive protein on their surfaces. As the mouse is exploring a pleasant environment, any neurons that fire will leave a footprint of the memory in the mouse's brain. After the drug wears off, only those cells will respond to light.

Meaning

It's basically like a switch. So what you can then do is use a laser to control these cells.

NARRATOR

These tiny fiber optics can shine light directly into the mouse's brain. And what we're going to try to do now is to turn on these cells that we've labeled with a positive memory. Right now the mouse is scared, but if Denny is right, the laser should activate the exact same neurons that fired when the mouse was making a happy memory, effectively causing it to relive that positive experience. Okay, so watch now what happens when I'm going to turn this laser on. You can see that the animal's actually smelling, grooming himself, which is a sign that he feels safe. But turn the laser off...

DENNY

And you can see that the animal is resuming its behavior of freezing in the corner.

NARRATOR

Denny can now trigger this memory at will. On. Off. I think the first time we did it, we didn't believe it. But when you see inside of the brains of these mice and then to think that you're only manipulating those cells and changing the behavioral output of the animal, that's... yeah, science fiction.

SCHACTER

This is potentially one of the most important new developments in memory research because it suggests a level and precision of control over memory that we've really never seen before.

NARRATOR

A degree of precision many scientists think we might have over our memories some day.

RAMIREZ

I think that it's a matter of when this happens, not a matter of if it'll happen in people.

NARRATOR

Which raises the question, if by a flick of a switch we could edit that first kiss or erase that argument with a spouse, would we want to? What scientists now are starting to realize is that we can modify memories in some remarkable ways. How do we think about that? By starting to manipulate those memories, are we suggesting that evolution got it wrong? Could it be possible that our memories are built the way they are for a reason? Why would we be constructed with a memory system that is so potentially open to suggestion and change? Perhaps Jake, the 11-year-old boy with the amazing memory, can help answer that question one day. After months of scans, scientists are still searching for something to explain his extraordinary ability. But even if they don't find anything, that's an important clue.

DOSENBACH

Jake's already telling us something about our memories, namely that the human brain has the capability to remember your entire life in great detail. It's a fascinating question of, why don't we?

NARRATOR

Consider Jake. Though he and other HSAMs love having their special memories, even at his young age, he is aware that it comes at a price.

JAKE

Just like to everything, there's an upside and there's a downside. The downside is you can remember every bad thing that happens to you.

McCAUGH

They live in different worlds than the worlds that you and I live in. And you have to wonder, would you like to live in that world?

NARRATOR

A world where you can't forget. Forgetting is probably one of the most important things that brains will do. Perhaps evolution was smart enough to design a system that stores only stuff that's important. Could it be that what we think of as memory's flaws are actually part of its strength?

MARTIN

Maybe we have a misconception of what the purpose of memory is. That we think of it more as an accurate recording of past experiences as opposed to a creative process of combining our experiences over time.

WALKER

Perhaps the ultimate goal of memory is not to retain every single fact that you've learned. If you had just this picture- perfect back catalogue of 30, 40, 50, 60 years of experience, imagine how hard it would be to pick out the individual specific experiences that you need at any one moment against the backdrop of that sea of noise.

NARRATOR

Somehow this complex choreography of single cells adds up to our memory, a mysterious system that allows us to time-travel to the past and imagine our future. But perhaps memory's ultimate gift is a way to navigate that sea of noise so we can pick out the experiences that each of us weave together to tell the story of our lives. Captioned by Media Access Group at WGBH access.wgbh.org This NOVA program is available on DVD. To order, visit shopPBS.org, or call 1-800-PLAY-PBS. NOVA is also available for download on iTunes.