Can Memories Be Erased?

"Life without memory is no life at all," so said Luis Buñuel, the surrealist filmmaker. But do we really want every memory? Joel Barish didn't. Remember the guy played by Jim Carrey in Michel Gondry's 2004 film, Eternal Sunshine of the Spotless Mind? He wanted the memory of Clementine Kruczynski (Kate Winslet) extracted, traces of her wiped clean. But surely this was a film fantasy and is not possible in real life. Or is it?

In 2000 my lab published a paper that jump-started a wave of research and speculation about memory erasure. The studies were done in rats, not people, and were focused on a very specific kind of memory. But the work generated heated discussions in the scientific and lay press about the broad implications of memory erasure in humans, including questions about the ethics of memory manipulation. Bush's panel on bioethics weighed in with a scathing comment, but its views were based on their emotional reaction to the very idea of memory manipulation rather than a careful analysis of the scientific discoveries and their implications.

Within the last couple of years, there have in fact been significant scientific advances. Announcements in the press of successful "memory erasure" have given those who suffer from traumatic memory hope that they may one day be able to lead normal lives again. Each such announcement leads to a flooding of my inbox with requests by people who want various memories erased, ranging from memories of annoying ex-spouses to debilitating memories of rape, torture or horrible accidents. So can human memory really be erased? And, if so, should we do this?

A little background. My lab has studied emotional, especially fear, functions of the brain for the past 25 years. We do this mostly in rats using Pavlovian fear conditioning, a procedure in which a sound is paired with a mild foot shock, and the next time the rat hears the sound it acts scared (it freezes) and has highly aroused physiological responses (blood pressure, heart rate, and respiration increase and stress hormones flow). These are automatic (involuntary) responses elicited by the stimulus and help the body defend against the danger that the stimulus warns about. The sound is able to elicit these responses days, weeks, moths and even years later because an association is learned between the sound and the shock and this is stored in the brain as a memory. The association is formed in a region of the brain called the amygdala which receives sensory inputs from nerve pathways that process the sound and the shock. Neurons there integrate the tone with the shock to form an association between the neutral and the harmful events. When the neutral stimulus occurs later, it activates this association, which in turn activates output connections of the amygdala then control behavioral and physiological responses.

Long ago it was discovered that the formation of a long-lasting memory requires the synthesis of new proteins in the brain. The proteins allow the conversion of a temporary or short-term memory into a persistently stored long-term memory. So well established was this idea that it was considered a dogma in neuroscience. It was thus only natural that we would ask whether protein synthesis in the amygdala is necessary for the creation of long-lasting fear memories. It surprised no one that it was. This is just the beginning of the story.

Part of the memory consolidation dogma was that a memory is consolidated only once. Thus, each time the memory is retrieved, it is the original memory that is activated and remembered. But in spite of this strongly held assumption, other research, largely ignored for decades, suggested that memories become labile when retrieved and have to be restored, or re-consolidated, via protein synthesis in order to remain available for later retrieval. If something is done to them during the time when they are labile and before they are reconsolidated they are subject to disruption -- that is, the memories might be erased, or made permanently inaccessible, during this time.

This takes us to the experiment we did in 2000. Karim Nader, a postdoctoral researcher, carried out this study. He created a fear memory in rats, and allowed enough time for it to be fully consolidated into a long-term persistent memory. He then had the rats retrieve the memory by exposing them to the sound. Right after that, he injected the protein synthesis inhibitor into the amygdala. The rats had short-term memory for a few hours but no long-term memory the next day, or any other day after that.

Four years later, Joel Barish had his memory of Clementine erased by using pictures to elicit memories of her and then having his brain zapped as each memory was retrieved. This is very similar to what we did in the rat studies. But can this be done in people?

Nader's study led to a massive tide of research. Some scientists tried to dismiss it (since it went against the idea [dogma] that a memory is only consolidated once). But the data poured in from around the world. Hundreds and hundreds of studies were performed in many different animals (worms, bugs, rats, mice and even people) showing that memory could be interfered with after retrieval. Not all the studies used protein synthesis inhibitors. Drugs that interfere with the process of protein synthesis indirectly also seem to do the trick. We have a long way to go before we fully understand what is going on mechanistically, but it seems clear that memory, or at least some kinds and aspects of memory, can be altered after they are retrieved (reactivated).

So where does that leave us? Can we erase memories in people? To answer this question we need to make a distinction -- fear memories created through associative conditioning are not the same as conscious recollections of the frightening experience. When you form an association between a neutral stimulus and danger (a street corner where you were hit by a car), later exposure to the neutral stimulus not only automatically elicits behavioral and physiological fear responses, it also retrieves a conscious memory of the experience. In contrast to conditioned fear memories created in the amygdala, conscious memories crucially involved the hippocampus and other areas of the cerebral cortex (the wrinkled out layers of the brain).

Most research showing that fear memory can be disrupted after retrieval in animals has involved the automatic kinds of memory rather than the conscious kind. However, in recent studies of humans, where effects on conscious memory can be easily assessed, the physiological responses to the tone but not the conscious memory of having been conditioned to the tone were blunted. This suggests that even if it is possible to "erase" conditioned fear memories, conscious fear memories may not be altered significantly. This is very promising for therapeutic purposes since it might allow a reduction in the emotional upheaval elicited by trauma-related stimuli without interfering with the conscious memory of the trauma. With emotional arousal to the traumatic memory weakened, it might be easier to engage in successful therapy about the traumatic experience.

Above I just said the emotional memory is weakened. Why didn't I say "erased"? It is very hard to scientifically prove that something doesn't exist. All we know is that memory is weaker after treatments that block reconsolidation. It might be erased from the brain or it might still be in the brain but inaccessible. Some studies suggest that fear memory is erased since it doesn't recover after the treatment but whether erasure occurred is an interpretation.

Memory erasure remains a possible but unproven hypothesis. But the blunting of unwanted emotional responses elicited by stimuli from the past is definitely possible and has broad implications. We are nothing without our memories, but sometimes they also make us less than we could be. The job of the scientist is to push the frontiers of knowledge. Society then has to decide what to do with that information. Although some ethicists argue that memory should not be tampered with, every special date and anniversary, every advertisement, every therapy session, every day in school is an effort to create or modify memory. Tampering with memory is a part of daily life. If we take a more realistic view of just how much we mess with memory, the dampening of memories that produce emotional responses in traumatized individuals might seem less malevolent.

Now the disclaimer. I am not a physician or therapist, and I can't blunt your memory of past emotions. Even if I were qualified, there would still be roadblocks. The drugs that are used in animals have for the most part not been proven safe for use in humans. The one drug that is safe, propranalol, may have only weak effects. My lab published a paper in the magazine Science a few months ago revealing a new approach that doesn't depend on drugs, but this idea in the early stages of exploration. New discoveries will likely take us to the point where it will be possible to blunt some forms of memory. When that happens, physicians and therapists will have to make difficult decisions about how the treatment should be used. In the meantime, everyone involved should welcome the broadest possible debate on this challenging but promising possibility.

 

 

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Comments

[mulegino]

This memory erasure seems to work quite well for "journalists" of the MSM, who have had all memories of 2003, WMD's, Saddam Hussein and imminent threats wiped so clean from their minds that they are having to create new such memories about Iran.

[wietog]

"He shot who in the what now?" - Homer Simpson's aging dad

[MerrieWay]

Erase memory? The Pharma's are doing so. Their sales reps are the doctor's advisors, as to prescribing and determining the drugs efficacy.
Brain-altering drugs are dangerous: impossible to measure appropriate dosage: a cocktail gunshot, a toss at the dart board, and long-term effects are not a consideration
The Pharma's are doing an excellent job in giving chemical lobotomies to minimize psychiatric symptoms. Young patients (under 21) on Zyprexa, Cloxaril, Lamictal, have short term memory loss and longer informational processing time. On higher dosages, sleeping 14 to 16 hours is acceptable.

Medicating 2-year-olds, for potential symptoms of bi-polar, ADD, ADHD is publicized when a child OD's from drug concoctions.
.I interviewed a researcher at a major Pharma corp, he admitted trial drug tests were unreported if a placebo tested better or the same as the new drug. Tests were repeated until the reports were drug favorable.

There are known alternatives for deactivating severe emotional memories. Hypnosis, NLP, energy work, neuro-feedback, acupuncture, meditation, tai-chi, qui-gong, yoga, nutrients,­supplement­s have proven to have positive effects on Post Traumatic Stress, and other traumatic incidences
.
In China, doctors and energy masters can remove blocks of trauma, not by erasing the memory, but by neutralizing the thoughts and feelings associated with it, lessening the response. (same thought different perception. We know cell memory can be anywhere in the body...the heart is made of the same material as the brain. And who said we aren't body, mind, and spirit?

[Joseph LeDoux - Huffpost Blogger]

Thanks for the important comment. Treating children (and adults) with psychoactive drugs is definitely something to be concerned about. As you said, there are non-drug approaches that can help. Some anxiety disorders, like some phobias, are best treated behaviorally. For other conditions, though, behavioral treatments can be less effective, and can also depend on who administers them. But they are important and should be used more as a first line of attack. As I wrote, we recently published a study showing how powerful non-drug behavioral manipulations can be. That said, the drug used so far in studies attempting to dampen the emotional impact of memories, propranolol, is off patent and available as a generic product. So its use is being driven by research rather than drug companies. Thanks again.

[ThermoChemist]

Can Memories Be Erased...?

Yes..!

You need to contact someone named Noah Bennett. He knows of a big Haitian who specializes in this.!

: )

[DAE]

I've forgotten 99.9% more than I've remembered. Of the 0.1% memories I've remembered I figure the vast have been altered to fit my psychic need. Haven't had PTSD so I'm lucky

[LMPE]

I would like all memories of celebrity scandals/mishaps erased from my memory.

[seawolf77]

Jim Morrison had a line in Soul Kitchen "Learn to forget" . What we have to realize as humans is that going over the memories that make our hearts beat faster versus going over the memories we can;t stand to think about evn in our worst nightmares are inversely proportional to their effect on our health and well being. Learn to remember with impunity. That is the secret. Life with impunity.

[Joseph LeDoux - Huffpost Blogger]

I used to have a postcard announcing an art show on my wall. It said: from the things we can't remember to the things we can't forget. This echos your statement perfectly. Thanks for the comment.

[TheBlackCat]

Fascinating article. Thanks!

[Mnemanth]

A bottle of bourbon...­and all my memories seem to just fade away....

[Joseph LeDoux - Huffpost Blogger]

Glad you like the band name. Check out the band. Our music is based on research, mostly my own work, on emotion and memory. The songs are rock/blues/country type songs with traditional rock themes of love, heartache, and life, but with lyrics that relate to how the brain works. Our first CD is available on itunes or from our website www.amygdaloids.com We have a new one coming out later in the fall that features Rosanne Cash doing duets with me on 2 songs.
Thanks for the comment.

[Joseph LeDoux - Huffpost Blogger]

Sorry bout that. I responded to the wrong comment when I responded to you. Alcohol does indeed disrupt memory. It goes right to the part of the brain I said is involevd in conscious memory (the hippocampus) and increases the actvity of inhibitory neurons. So the active processes that would normally form and store a memory are weakened, and you can't remeber what you did while you were drinking.

[Idytme]

"a member of the rock band The Amygdaloids"
Love the name of your band..... haha

[Joseph LeDoux - Huffpost Blogger]

Glad you like the band name. Check out the band. Our music is based on research, mostly my own work, on emotion and memory. The songs are rock/blues/country type songs with traditional rock themes of love, heartache, and life, but with lyrics that relate to how the brain works. Our first CD is available on itunes or from our website www.amygdaloids.com We have a new one coming out later in the fall that features Rosanne Cash doing duets with me on 2 songs.
Thanks for the comment.

l

[Idytme]

Great article. My mother went to a seminar about memory a few years ago and was told about one study that has always fascinated me. I haven't been able to find it on the web, so this is my (bad? LOL) memory of what she relayed to me: After the Columbia Space Shuttle disaster, they asked people where they were when they found out the news. They ahad them write it down and put the info in a sealed envelope. They went back 5 years later and asked the same question. A huge percentage of them said something other than they did originally, and of these people a lot of them ( I wish I had the stats) believed their new memory over *their own account put in their own writing in a sealed envelope!*
So we do constantly re-write our memories, which brings up a heck of a lot of questions about a lot of topics.
Her latest seminar was about why we retain negative memories over positive ones, and they talked about the amygdala with negative memories and a frontal lobe area (errr... don't remember) for positive ones, and to re-enforce this area, you.......­wait for it..... review three positive things that happened in your day before you fall asleep.
So what about adrenalin's role in laying down strong negative memories, and why doesn't propanolol work as well as others, and would that change if given immediately after the trauma, in the ER for instance.

[Joseph LeDoux - Huffpost Blogger]

Lots of good questions. The Challenger is a good example. Another is eye witness testimony. People often will testify about what they read in the paper rather than what they witnessed. Each retrieval of a memory is an opportunity for change. Hormones like adrenalin do make emo memories stronger but not necessarily more accurate. You really remember the experience, but the not the details. That's why the Challenger example is so good. The viewers had really vivid memories years later but these were quite different from what they reported at the time. Thanks for commenting.

[Idytme]

Dr LeDoux, thank-you for your comments, but you did not answer my final question. Maybe you cannot do that yet for what-ever reason, but it seems to me that if a rape victim comes into the hospital, and a doctor could say to them, "I'm gonna give this propanalol to you which has the possibility, but not promise of reducing PTSD, that the woman should be given the option. Rape survivors will tell you by experience that anything to reduce PTSD would be worth it. I doesn't alter memories as much as it takes away the trauma. Anything that gives that option should be offered in my opinion.
There is a huge difference between "erasing" memories (what propanolol has been portrayed on some TV programs) and getting rid of the trauma of those events so they do not cripple you for life.
I think our responses are cave-man-like. If you need a deep set memory to avoid lions, for example, that is a great adaptation, but there is nothing in modern day society saying that if you have all your windows and doors locked and an intruder breaks in and brutalizes you, that it will help you in the future, except to always be afraid sleeping in your bed even when all the windows and doors are locked, for example.

[Becklyy]

This is so interesting. I've noticed that if I write down my early memories, as in a memoir, the original memory disappears and is replaced by what I wrote. I can no longer recall the event in the sensual way I used to, but only the words and a more shallow image.

[Joseph LeDoux - Huffpost Blogger]

Memory is very tricky. Can't live without it. But the question is, how much should we live with it. It's pretty sloppy. Changes over time, sometimes very significantly. Thanks for the comment.

[blisster]

The three pound universe, this incredible organ that is the absolute definition of who, why and what we are. I would love to be able to visit the earth far into the future to see what advances we've made in understanding the complexities of how the human brain functions. My guess is there will be many who will not like some of the answers, conclusions or applications of these scientific discoveries.
It will make the theory of evolution debate seem like a stroll in the park.
When my son was six, he asked me, "Daddy , do you know what is even bigger than the universe?"
"I don't know, what ?" His reply still blows me away today, "Our imagination", he said.

[ignorantwillyharper]

My imagination tells me, we may not be her very much longer.

[blisster]

Nothing lasts forever, including your,,, imagination. But as Lennon so aptly put, "When you dream alone it's only a dream but when we dream together that's reality."

[Joseph LeDoux - Huffpost Blogger]

I agree with your son. In many ways the universe is a product of our imagination since we don't know its extent and limits, if any. And yes, there are major ethical issues raised, but as I hope I got across in the piece, some come from a misunderstanding of how much we manipulate memory already. Thanks.

[Joseph LeDoux - Huffpost Blogger]

meant to reply to you but may have hit the button below and replied to someone who commented on you. see below.
JL

[PlaceboStudman]

very cool stuff

Even if it doesn't mean anything for humans, yet, that doesn't mean it wont have meaning for humans in the future.

My only bummer is that I guess this means that the infamous mythological Star Trek "Memory N-Gram" doesnt exist

Oh well.....L­OL

[Joseph LeDoux - Huffpost Blogger]

I'm not a Trekie so I don't know if the spelling you used "N-gram" is your written version of what they said or whether you saw it written that way. However, there is a scientific concept "the engram" that has been around for a long time that traditionally refers to the idea of a memory being stored as an item or thing. For a while it was thought that each memory might be a protein. Today, we are more likely to think of memory as being stored as part a neural circuit with lots of synaptic connections involved in each memory. When we retrieve a memory we thus reconstruct a lot of neural activity. This may account for some, but not all, of the messiness of memory. My song "A Trace" from The Amygdadoids first CD, Heavy Mental, was about the synaptic storage of the memory of an ex lover. Check it out on itunes.

[Danlantic]

The spelling is "engram". I remember that Star Trek episode when it originally aired. It raised suspicions in me about the show.

It is a term coined by L. Ron Hubbard for Scientology. I knew about Scientology from Martin Gardner's Fads and Fallacies in the Name of Science (1957). I looked for further Scientology in the series and fortunately found none. It's just that one scifi author had merely picked up a term from another.

Now I come to another item in fantasy literature and it was something I dismissed.

In the Odyssey Telemachus starts wandering to other Greek cities to find out if any other vets of the Trojan Wars may have heard anything about Ulysses. He visits Sparta and finds that Helen and Menelaus have reconciled. Helen explains she was driven mad by Aphrodite so her adultery with Paris was beyond her control. After dinner Telemachus and Menelaus start mourning over the loss of his father and all the friends who died in the war. They start crying. They can't stop. Helen, however, has (somewhere, sometime) had expert training in Egyptian potions and herbs. She spikes 2 cups of wine and serves them. Not only does it put Telemachus and Menelaus to sleep but in the morning they wake refreshed with no intense emotional memory of the sorrows.

Now, that you have described much the same thing being done with rats, I have started to wonder if Homer was describing a real drug developed by the Egyptians.