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<nettime> can memories be selectively erased...
. __ . on Thu, 25 Dec 2003 18:28:55 +0100 (CET)


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<nettime> can memories be selectively erased...


So no computer will ever help us, even with the best and most complete
storage of information, if we let scientists play around with our
memories.... great, really great...

####

Scientific American, December 22, 2003   
 
Unmaking Memories: Interview with James McGaugh   
 
In the sci-fi thriller Paycheck, an engineer has his memory erased after
completing a sensitive job. Scientific American.com spoke with a leading
neurobiologist to find out just how close scientists are to controlling
recall.   

By JR Minkel    
 
In the movie Paycheck, opening Christmas Day, a crack reverse engineer
helps companies steal and improve upon the technology of their rivals, then
has his memory of the time he spent working for them erased. The story,
based on Philip K. Dick’s sci-fi thriller of the same name, is set in the
near future, but such selective memory erasure is still highly speculative
at best. ScientificAmerican.com asked neurobiologist James McGaugh of the
University of California at Irvine, who studies learning and memory, to
explain what kinds of memory erasure are currently possible. For more
information, see his book Memory and Emotion: The Making of Lasting
Memories, released in 2003. 

Scientific American.com: Early in Paycheck we see the main character get
several months' worth of his memories erased by having individual neurons
zapped. Is that possible?  JM: No. First of all there is no evidence of
memories being stored individually. And even if they were stored in
individual neurons, no one would know where they were. What we know an
awful lot about are the brain systems that are involved in storing
memories. Your memories of this conversation, for example, are stored
rather diffusely in the brain. They're not going to be stored in a couple
of neurons someplace that anybody could easily identify. 

SA: But haven't surgeons poked people's brains in certain spots and made
them recall specific things? 

JM: [In the 1950s] Wilder Penfield up at the Montreal Neurological
Institute was doing surgery for people who had brain seizures, and he had
to stimulate the brain and have people talk to make sure that he wouldn't
eliminate speech areas, for example. He found that he could evoke some
things that appeared to be like memories, but it's more likely that he was
just evoking [an impression of] something, not a specific memory. 

SA: Are there any ways to erase memories by stimulating the brain? 

JM: The dominant evidence that goes back over 50 years is that one can
block or certainly reduce memories formed within the past several hours by
treating human or animal subjects with electro-convulsive shock. But it's
nonselective; whatever happened in that past several hours will be gone.
And that's rather gross stimulation applied to the skull. What Larry Squire
at UC San Diego has shown is that if human subjects are repeatedly given
electro-convulsive shocks (several times a week for several weeks), they
will have impaired global memory that goes back many months, but that
memory will gradually recover. He did this in the late 1980s. 

SA: Are there any more selective ways to erase memory? 

JM: If one work with the hippocampus, one can selectively remove animals'
memories of places where they have received training. In the Morris water
maze, for example, animals are trained to swim from a variety of regions
[in] a six-foot tank to an invisible platform located about two centimeters
below the surface of the water. That kind of learning requires the
hippocampus. If the hippocampus is blocked electrically or chemically
within a few hours after animals have been trained to go that spot, they
will not remember it the next day. So that would be an example of a place
memory that could be influenced by discrete stimulation of a specific
region of the brain. This doesn't mean the memory is permanently stored
there. It means that the hippocampus is involved in the processing of that
information, which is ultimately stored someplace else. And it's not
something that could be done by electrical stimulation applied outside of
the brain except for electro-convulsive shock, which activates the entire
brain. 

SA: How do we know memories aren't stored in the hippocampus? 

JM: If subjects are taught something and then the hippocampus is removed
several weeks later (in an extreme case), the information is retained. Take
the very famous case of HM. He has anterograde amnesia--he is unable to
learn new knowledge about the world--because he doesn't have his anterior
hippocampus. He has retrograde amnesia that goes back for maybe a year, but
for earlier times--a year longer and back to childhood--the memories are
pretty much intact. So that says that these regions cannot be the
repositories of a long-term memory. [For more on the milder sorts of memory
problems we all face, click here.] 

SA: Doesn't some research indicate that every time a memory is recalled,
there is a window of a few hours in which it can be erased? 

JM: That's highly controversial. This issue was first studied in the 1970s,
and the idea was that if you recall a memory it becomes vulnerable to
destruction, just as it was during the original learning. Additional
studies showed that the effect is temporary. When you apply some amnesic
treatment after animal subjects recall something, the memory impairment
goes away within a few days. So it's not as though the treatment destroyed
the memory. That hypothesis, called the reconsolidation hypothesis, was
revived a couple of years ago, and evidence supporting it is mixed at best.
It is on very shaky grounds. 

SA: You discovered that a drug called propranolol could reduce recall of
emotionally charged memories. How did that come about? 

JM: My colleague Larry Cahill [of the University of California at Irvine]
and I discovered that, based on about 20 years of prior animal research.
(My work is primarily with laboratory animals.) We learned that strong
emotions make for strong memories. The people who were around at 9/11 are
going to remember that forever. And I'm sure the people who win the lottery
remember where they were and what they were doing when they won the
lottery. Over the course of several decades we traced out how this happens.
Adrenaline is released from the adrenal medulla and then activates the
brain by what are called beta-receptors. These are protein receptors on
neurons that receive adrenaline and its first cousin noradrenaline. Their
activation enables strong emotions to make strong memories. 

We reasoned then that we should be able to block the formation of strong
emotionally evoked memories by giving human subjects a beta-blocker, which
would prevent the action of adrenaline and noradrenaline. The experiment
was as follows. Subjects were shown a series of 12 slides depicting one of
two stories. The subjects believe they are just rating emotionality of the
pictures. In the boring story, a mother and boy leave home, see a damaged
car, and go to visit father, who works in a hospital. The other group gets
the same slides, but as mother and boy cross the street, the boy is hit by
the car, his legs are severed, and they rush him to the hospital where
surgeons work frantically to reconnect his legs. Now the important thing is
that only the middle part of the story is emotional and, as it turns out,
the subjects that got the emotional story remembered more of the middle
part. 

The next experiment was very simple: we presented only the emotional story,
but before it started we gave the subjects a beta-blocker, propranolol. We
measured their memory three weeks later and it was as if we had given them
the boring story. We had eliminated the effect of emotional arousal on
memory. This paper was published in the mid-90s, and that has been
replicated many times now. 

SA: Is anyone using this therapeutically? 

JM: Yes, two clinical trials have been published recently, one by Roger
Pitman at Harvard University in which subjects are put on beta-blockers as
soon as possible after they have had a traumatic injury such as an
automobile accident. People are at risk of post-traumatic stress disorder
when they have such injuries. The idea is to blunt the intensity of those
memories so that they won't take over the lives of those people. And the
answer in both of the clinical trials, one in the U.S. and the other in
France, is yes: several months after the incident or injury there are
significantly decreased signs of post-traumatic stress disorder. 

SA: Aside from electric shock and propranolol are there any other examples
of drugs or methods that have memory dulling or erasing effects? 

JM: Benzodiazepines such as Valium create anterograde amnesia. As a matter
of fact, one of the drugs, Halcion, was removed from the market in Great
Britain because it has very potent anterograde amnesic affects. Human
subjects can take these drugs to reduce anxiety and go through the day and
think that everything is fine. But the next day they remember very little
of the previous day. 

SA: Do we know how that happens? 

JM: Yes, to a large degree. I've done an awful lot of work investigating
that in my own laboratory and we know that when receptors in the
basolateral region of the amygdala are hit by benzodiazepines, memories are
not formed. 

SA: What is the amygdala doing? 

JM: What is now widely accepted is that when the basolateral amygdala gets
activated, it instructs other regions of the brain to make stronger
memories of what has just happened. We've done countless experiments in
which we've trained animals and then tickled the basolateral amygdala with
various chemical agents either immediately afterwards or several hours
afterwards. We found that if we tickled it immediately afterwards we could
either enhance or impair the formation of memory of all kinds. So when it
is put out of commission by benzodiazepine there can be no modulation of
the storage of recent events. Now there are several studies using brain
imaging pioneered, once again, by my colleague Larry Cahill that show the
degree of activation of the amygdala at the time subjects learn emotionally
arousing material is a highly reliable predictor of how well that material
will be remembered several weeks later. 

SA: Is it conceivable that we could ever have control of memory erasure or
do you believe it will always be a global thing? 

JM: Ever is a long time. It is conceivable that things might get more
precise. You never know what technology is going to provide. I never
thought 20 years ago that we would be able to peer into the brain using
brain imaging and watch it at work. So it's conceivable that technology in
the future will allow us to do some things to the brain from outside that
we cannot now do, and there could be some greater selectivity. 

Let me give a caveat to that. Let's suppose I said I am going to say a word
to you and then I am going to use a new magical technique that technology
has provided to eliminate that memory. So now I say "bicycle" and I go zap.
Now think about bicycle. I said the word bicycle, but you know the general
meaning of bicycle, you know what a bicycle looks like, you may remember a
specific bicycle, you may remember having done something on a specific
bicycle, and you remember how to ride a bicycle. Did I get rid of all of
those? Not very likely, because those are all very deeply embedded in all
kinds of memories that you have. Let's suppose that I did get rid of all of
those; then you'd lose a huge portion of your life. Everything you knew
about riding a bicycle would go, which would mean everything connected to
that would also go. Your home, your family would be gone, and it can't work
that way. There is an interconnectedness to the knowledge we have.
Information does not exist in the abstract. 

SA: Do movies ever treat memory problems accurately? Memento (in which a
man who can't form new memories tries to avenge his wife's murder) is a
personal favorite. 

JM: I've seen a number of movies in which memories are not supposed to be
working properly and I have not yet seen one that is faithful to what we
know about how memories work. Memento was very unfaithful. An amnesic
cannot learn new information and this guy was randomly learning sometimes
and not others. I was making note of it while watching the movie. He was
doing things that he couldn't possibly do if he were amnesic because he
wouldn't be able to remember to. Then there were other times in which they
showed him as a classic amnesic in which he would repeatedly introduce
himself to someone even though he had introduced himself many times. That's
what the amnesic would do, but also he has this plan to do something; well,
amnesiacs don't have the plan to do anything, because they can't even
remember if they had breakfast. A true amnesic's life wouldn't be
interesting because they have to be taken places--because they don't know
where they are supposed to go. We forget that memories are required in
order to make plans. You have to have an idea of what you intend to do. And
what you intend to do is a memory. 

If you lose the ability to recall your old memories then you have no life.
You might as well be a rutabaga or a cabbage. And you see that when you see
memories disappear in people who have severe brain diseases. You see the
memories wilting away. They can't remember words, they can't remember the
names of their family, then they can't remember to do anything, and then
they become comatose and they die. Memory--there can be no doubt about
it--is our most important set of abilities. 

----------------------------------------------------------------------------
JR Minkel is a freelance writer based in New York City.  

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