Can we edit memories?
-
0:01 - 0:05Memory is such an everyday thing
that we almost take it for granted. -
0:06 - 0:08We all remember what we had
for breakfast this morning -
0:08 - 0:10or what we did last weekend.
-
0:10 - 0:12It's only when memory starts to fail
-
0:12 - 0:15that we appreciate just how amazing it is
-
0:15 - 0:18and how much we allow
our past experiences to define us. -
0:20 - 0:22But memory is not always a good thing.
-
0:23 - 0:27As the American poet and clergyman
John Lancaster Spalding once said, -
0:27 - 0:30"As memory may be a paradise
from which we cannot be driven, -
0:30 - 0:33it may also be a hell
from which we cannot escape." -
0:35 - 0:37Many of us experience
chapters of our lives -
0:38 - 0:40that we would prefer
to never have happened. -
0:40 - 0:43It is estimated that
nearly 90 percent of us -
0:43 - 0:47will experience some sort of
traumatic event during our lifetimes. -
0:48 - 0:53Many of us will suffer acutely
following these events and then recover, -
0:53 - 0:56maybe even become better people
because of those experiences. -
0:57 - 1:01But some events
are so extreme that many -- -
1:01 - 1:05up to half of those who survive
sexual violence, for example -- -
1:05 - 1:08will go on to develop
post-traumatic stress disorder, -
1:08 - 1:09or PTSD.
-
1:11 - 1:14PTSD is a debilitating
mental health condition -
1:14 - 1:18characterized by symptoms
such as intense fear and anxiety -
1:18 - 1:21and flashbacks of the traumatic event.
-
1:22 - 1:26These symptoms have a huge impact
on a person's quality of life -
1:26 - 1:29and are often triggered
by particular situations -
1:29 - 1:32or cues in that person's environment.
-
1:33 - 1:38The responses to those cues may have been
adaptive when they were first learned -- -
1:38 - 1:41fear and diving for cover
in a war zone, for example -- -
1:41 - 1:42but in PTSD,
-
1:42 - 1:46they continue to control behavior
when it's no longer appropriate. -
1:47 - 1:50If a combat veteran returns home
and is diving for cover -
1:50 - 1:52when he or she hears a car backfiring
-
1:52 - 1:56or can't leave their own home
because of intense anxiety, -
1:56 - 2:00then the responses
to those cues, those memories, -
2:00 - 2:04have become what we would
refer to as maladaptive. -
2:05 - 2:11In this way, we can think of PTSD
as being a disorder of maladaptive memory. -
2:13 - 2:14Now, I should stop myself here,
-
2:14 - 2:17because I'm talking about memory
as if it's a single thing. -
2:17 - 2:19It isn't.
-
2:19 - 2:21There are many different types of memory,
-
2:21 - 2:25and these depend upon different circuits
and regions within the brain. -
2:26 - 2:31As you can see, there are two
major distinctions in our types of memory. -
2:32 - 2:34There are those memories
that we're consciously aware of, -
2:34 - 2:36where we know we know
-
2:36 - 2:37and that we can pass on in words.
-
2:38 - 2:40This would include memories
for facts and events. -
2:41 - 2:43Because we can declare these memories,
-
2:43 - 2:46we refer to these as declarative memories.
-
2:47 - 2:50The other type of memory
is non-declarative. -
2:50 - 2:54These are memories where we often
don't have conscious access -
2:54 - 2:56to the content of those memories
-
2:56 - 2:58and that we can't pass on in words.
-
2:59 - 3:01The classic example
of a non-declarative memory -
3:01 - 3:04is the motor skill for riding a bike.
-
3:04 - 3:08Now, this being Cambridge,
the odds are that you can ride a bike. -
3:08 - 3:10You know what you're doing on two wheels.
-
3:10 - 3:13But if I asked you to write me
a list of instructions -
3:13 - 3:16that would teach me how to ride a bike,
-
3:16 - 3:18as my four-year-old son did
when we bought him a bike -
3:18 - 3:20for his last birthday,
-
3:20 - 3:22you would really struggle to do that.
-
3:23 - 3:26How should you sit on the bike
so you're balanced? -
3:26 - 3:28How fast do you need to pedal
so you're stable? -
3:29 - 3:31If a gust of wind comes at you,
-
3:31 - 3:33which muscles should you tense
and by how much -
3:33 - 3:35so that you don't get blown off?
-
3:36 - 3:40I'll be staggered if you can give
the answers to those questions. -
3:40 - 3:43But if you can ride a bike,
you do have the answers, -
3:43 - 3:46you're just not consciously aware of them.
-
3:49 - 3:50Getting back to PTSD,
-
3:50 - 3:53another type of non-declarative memory
-
3:53 - 3:55is emotional memory.
-
3:55 - 3:58Now, this has a specific
meaning in psychology -
3:58 - 4:01and refers to our ability
to learn about cues in our environment -
4:01 - 4:04and their emotional
and motivational significance. -
4:05 - 4:06What do I mean by that?
-
4:06 - 4:11Well, think of a cue
like the smell of baking bread, -
4:11 - 4:13or a more abstract cue
like a 20-pound note. -
4:14 - 4:17Because these cues have been pegged
with good things in the past, -
4:17 - 4:19we like them and we approach them.
-
4:20 - 4:25Other cues, like the buzzing of a wasp,
elicit very negative emotions -
4:25 - 4:29and quite dramatic
avoidance behavior in some people. -
4:30 - 4:32Now, I hate wasps.
-
4:32 - 4:34I can tell you that fact.
-
4:34 - 4:37But what I can't give you
are the non-declarative emotional memories -
4:37 - 4:40for how I react
when there's a wasp nearby. -
4:40 - 4:42I can't give you the racing heart,
-
4:42 - 4:46the sweaty palms,
that sense of rising panic. -
4:46 - 4:48I can describe them to you,
-
4:48 - 4:50but I can't give them to you.
-
4:52 - 4:55Now, importantly,
from the perspective of PTSD, -
4:55 - 5:00stress has very different effects on
declarative and non-declarative memories -
5:00 - 5:03and the brain circuits
and regions supporting them. -
5:03 - 5:07Emotional memory is supported
by a small almond-shaped structure -
5:07 - 5:08called the amygdala
-
5:08 - 5:09and its connections.
-
5:10 - 5:14Declarative memory, especially the what,
where and when of event memory, -
5:14 - 5:17is supported by a seahorse-shaped
region of the brain -
5:17 - 5:18called the hippocampus.
-
5:19 - 5:22The extreme levels of stress
experienced during trauma -
5:23 - 5:26have very different effects
on these two structures. -
5:27 - 5:30As you can see, as you increase
a person's level of stress -
5:30 - 5:32from not stressful to slightly stressful,
-
5:32 - 5:33the hippocampus,
-
5:33 - 5:36acting to support the event memory,
-
5:36 - 5:37increases in its activity
-
5:37 - 5:41and works better to support
the storage of that declarative memory. -
5:41 - 5:45But as you increase to moderately
stressful, intensely stressful -
5:45 - 5:49and then extremely stressful,
as would be found in trauma, -
5:49 - 5:52the hippocampus
effectively shuts down. -
5:53 - 5:56This means that under
the high levels of stress hormones -
5:56 - 5:58that are experienced
during trauma, -
5:58 - 6:00we are not storing the details,
-
6:00 - 6:04the specific details
of what, where and when. -
6:05 - 6:08Now, while stress is doing that
to the hippocampus, -
6:08 - 6:10look at what it does to the amygdala,
-
6:10 - 6:13that structure important
for the emotional, non-declarative memory. -
6:13 - 6:16Its activity gets stronger and stronger.
-
6:18 - 6:20So what this leaves
us with in PTSD -
6:20 - 6:24is an overly strong emotional --
in this case fear -- memory -
6:24 - 6:27that is not tied
to a specific time or place, -
6:27 - 6:32because the hippocampus
is not storing what, where and when. -
6:32 - 6:36In this way, these cues
can control behavior -
6:36 - 6:38when it's no longer appropriate,
-
6:38 - 6:40and that's how
they become maladaptive. -
6:41 - 6:47So if we know that PTSD
is due to maladaptive memories, -
6:47 - 6:50can we use that knowledge
to improve treatment outcomes -
6:50 - 6:52for patients with PTSD?
-
6:54 - 6:58A radical new approach being developed
to treat post-traumatic stress disorder -
6:58 - 7:02aims to destroy those maladaptive
emotional memories -
7:02 - 7:04that underlie the disorder.
-
7:04 - 7:07This approach has only
been considered a possibility -
7:07 - 7:10because of the profound changes
in our understanding of memory -
7:10 - 7:12in recent years.
-
7:13 - 7:15Traditionally, it was thought
that making a memory -
7:15 - 7:18was like writing in a notebook in pen:
-
7:18 - 7:21once the ink had dried,
you couldn't change the information. -
7:22 - 7:24It was thought that all
those structural changes -
7:24 - 7:27that happen in the brain
to support the storage of memory -
7:27 - 7:29were finished within about six hours,
-
7:29 - 7:31and after that, they were permanent.
-
7:31 - 7:34This is known as the consolidation view.
-
7:35 - 7:38However, more recent research suggests
that making a memory -
7:38 - 7:41is actually more like writing
in a word processor. -
7:42 - 7:46We initially make the memory
and then we save it or store it. -
7:46 - 7:49But under the right conditions,
we can edit that memory. -
7:50 - 7:54This reconsolidation view suggests
that those structural changes -
7:54 - 7:56that happen in the brain to support memory
-
7:56 - 7:58can be undone,
-
7:58 - 8:00even for old memories.
-
8:02 - 8:06Now, this editing process
isn't happening all the time. -
8:06 - 8:09It only happens under
very specific conditions -
8:09 - 8:10of memory retrieval.
-
8:11 - 8:15So let's consider memory retrieval
as being recalling the memory -
8:15 - 8:17or, like, opening the file.
-
8:18 - 8:21Quite often, we are simply
retrieving the memory. -
8:21 - 8:23We're opening the file as read-only.
-
8:24 - 8:26But under the right conditions,
-
8:26 - 8:28we can open that file in edit mode,
-
8:28 - 8:30and then we can change the information.
-
8:30 - 8:34In theory, we could delete
the content of that file, -
8:34 - 8:36and when we press save,
-
8:36 - 8:40that is how the file -- the memory --
-
8:40 - 8:41persists.
-
8:43 - 8:45Not only does this reconsolidation view
-
8:45 - 8:49allow us to account for some
of the quirks of memory, -
8:49 - 8:52like how we all sometimes
misremember the past, -
8:52 - 8:56it also gives us a way to destroy
those maladaptive fear memories -
8:56 - 8:58that underlie PTSD.
-
8:58 - 9:01All we would need would be two things:
-
9:01 - 9:06a way of making the memory unstable --
opening that file in edit mode -- -
9:06 - 9:09and a way to delete the information.
-
9:09 - 9:11We've made the most progress
-
9:11 - 9:13with working out
how to delete the information. -
9:14 - 9:16It was found fairly early on
-
9:16 - 9:20that a drug widely prescribed
to control blood pressure in humans -- -
9:20 - 9:22a beta-blocker
called Propranolol -- -
9:22 - 9:24could be used to prevent
the reconsolidation -
9:24 - 9:26of fear memories in rats.
-
9:27 - 9:31If Propranolol was given
while the memory was in edit mode, -
9:31 - 9:35rats behaved as if they were no longer
afraid of a frightening trigger cue. -
9:36 - 9:40It was as if they had never learned
to be afraid of that cue. -
9:40 - 9:44And this was with a drug
that was safe for use in humans. -
9:45 - 9:46Now, not long after that,
-
9:46 - 9:50it was shown that Propranolol could
destroy fear memories in humans as well, -
9:50 - 9:55but critically, it only works
if the memory is in edit mode. -
9:56 - 9:59Now, that study was with
healthy human volunteers, -
9:59 - 10:02but it's important because it shows
that the rat findings -
10:02 - 10:06can be extended to humans
and ultimately, to human patients. -
10:07 - 10:09And with humans,
-
10:09 - 10:14you can test whether destroying
the non-declarative emotional memory -
10:14 - 10:17does anything to
the declarative event memory. -
10:18 - 10:20And this is really interesting.
-
10:20 - 10:23Even though people
who were given Propranolol -
10:23 - 10:24while the memory was in edit mode
-
10:24 - 10:28were no longer afraid
of that frightening trigger cue, -
10:28 - 10:30they could still describe the relationship
-
10:30 - 10:34between the cue
and the frightening outcome. -
10:35 - 10:39It was as if they knew
they should be afraid, -
10:40 - 10:41and yet they weren't.
-
10:42 - 10:45This suggests that Propranolol
can selectively target -
10:45 - 10:48the non-declarative emotional memory
-
10:48 - 10:52but leave the declarative
event memory intact. -
10:52 - 10:56But critically, Propranolol can only have
any effect on the memory -
10:56 - 10:58if it's in edit mode.
-
10:59 - 11:01So how do we make a memory unstable?
-
11:01 - 11:03How do we get it into edit mode?
-
11:04 - 11:06Well, my own lab has done
quite a lot of work on this. -
11:06 - 11:11We know that it depends on introducing
some but not too much new information -
11:11 - 11:14to be incorporated into the memory.
-
11:14 - 11:16We know about the different
chemicals the brain uses -
11:16 - 11:19to signal that a memory
should be updated -
11:19 - 11:21and the file edited.
-
11:21 - 11:24Now, our work is mostly in rats,
-
11:24 - 11:28but other labs have found the same factors
allow memories to be edited in humans, -
11:28 - 11:33even maladaptive memories
like those underlying PTSD. -
11:33 - 11:36In fact, a number of labs
in several different countries -
11:36 - 11:41have begun small-scale clinical trials
of these memory-destroying treatments -
11:41 - 11:42for PTSD
-
11:42 - 11:45and have found really promising results.
-
11:46 - 11:49Now, these studies need replication
on a larger scale, -
11:49 - 11:53but they show the promise
of these memory-destroying treatments -
11:53 - 11:55for PTSD.
-
11:55 - 12:00Maybe trauma memories do not need to be
the hell from which we cannot escape. -
12:03 - 12:06Now, although this memory-destroying
approach holds great promise, -
12:06 - 12:08that's not to say
that it's straightforward -
12:08 - 12:11or without controversy.
-
12:11 - 12:13Is it ethical to destroy memories?
-
12:13 - 12:15What about things
like eyewitness testimony? -
12:15 - 12:18What if you can't give someone Propranolol
-
12:18 - 12:21because it would interfere
with other medicines that they're taking? -
12:22 - 12:24Well, with respect to ethics
and eyewitness testimony, -
12:24 - 12:26I would say the important
point to remember -
12:26 - 12:29is the finding from that human study.
-
12:30 - 12:34Because Propranolol is only acting
on the non-declarative emotional memory, -
12:34 - 12:38it seems unlikely that it would affect
eyewitness testimony, -
12:38 - 12:40which is based on declarative memory.
-
12:41 - 12:43Essentially, what these
memory-destroying treatments -
12:43 - 12:45are aiming to do
-
12:45 - 12:47is to reduce the emotional memory,
-
12:47 - 12:50not get rid of the trauma
memory altogether. -
12:50 - 12:54This should make the responses
of those with PTSD -
12:54 - 12:56more like those who have
been through trauma -
12:56 - 12:58and not developed PTSD
-
12:58 - 13:02than people who have never
experienced trauma in the first place. -
13:02 - 13:06I think that most people would find that
more ethically acceptable -
13:06 - 13:10than a treatment that aimed
to create some sort of spotless mind. -
13:12 - 13:13What about Propranolol?
-
13:13 - 13:15You can't give Propranolol to everyone,
-
13:15 - 13:19and not everyone wants to take drugs
to treat mental health conditions. -
13:19 - 13:22Well, here Tetris could be useful.
-
13:23 - 13:24Yes, Tetris.
-
13:25 - 13:27Working with clinical collaborators,
-
13:27 - 13:30we've been looking at whether
behavioral interventions -
13:30 - 13:34can also interfere with
the reconsolidation of memories. -
13:34 - 13:36Now, how would that work?
-
13:36 - 13:38Well, we know that
it's basically impossible -
13:38 - 13:40to do two tasks at the same time
-
13:40 - 13:43if they both depend on
the same brain region for processing. -
13:44 - 13:46Think trying to sing along to the radio
-
13:46 - 13:48while you're trying to compose an email.
-
13:48 - 13:52The processing for one
interferes with the other. -
13:52 - 13:55Well, it's the same when
you retrieve a memory, -
13:55 - 13:56especially in edit mode.
-
13:56 - 14:00If we take a highly visual symptom
like flashbacks in PTSD -
14:00 - 14:03and get people to recall
the memory in edit mode -
14:03 - 14:06and then get them to do
a highly engaging visual task -
14:06 - 14:08like playing Tetris,
-
14:08 - 14:12it should be possible to introduce
so much interfering information -
14:12 - 14:14into that memory
-
14:14 - 14:16that it essentially becomes meaningless.
-
14:18 - 14:19That's the theory,
-
14:19 - 14:22and it's supported by data
from healthy human volunteers. -
14:23 - 14:27Now, our volunteers watched
highly unpleasant films -- -
14:27 - 14:30so, think eye surgery,
road traffic safety adverts, -
14:30 - 14:32Scorsese's "The Big Shave."
-
14:33 - 14:37These trauma films produce
something like flashbacks -
14:37 - 14:41in healthy volunteers
for about a week after viewing them. -
14:42 - 14:45We found that getting people
to recall those memories, -
14:45 - 14:48the worst moments
of those unpleasant films, -
14:48 - 14:51and playing Tetris at the same time,
-
14:51 - 14:54massively reduced the frequency
of the flashbacks. -
14:54 - 14:59And again: the memory had to be
in edit mode for that to work. -
15:00 - 15:04Now, my collaborators have since
taken this to clinical populations. -
15:04 - 15:07They've tested this in survivors
of road traffic accidents -
15:07 - 15:10and mothers who've had
emergency Caesarean sections, -
15:10 - 15:14both types of trauma
that frequently lead to PTSD, -
15:14 - 15:17and they found really promising
reductions in symptoms -
15:17 - 15:19in both of those clinical cases.
-
15:21 - 15:26So although there is still much to learn
and procedures to optimize, -
15:26 - 15:29these memory-destroying treatments
hold great promise -
15:29 - 15:31for the treatment
of mental health disorders -
15:31 - 15:33like PTSD.
-
15:33 - 15:38Maybe trauma memories do not need
to be a hell from which we cannot escape. -
15:39 - 15:41I believe that this approach
-
15:41 - 15:43should allow those who want to
-
15:43 - 15:45to turn the page
on chapters of their lives -
15:45 - 15:48that they would prefer
to never have experienced, -
15:48 - 15:50and so improve our mental health.
-
15:51 - 15:52Thank you.
-
15:52 - 15:53(Applause)
- Title:
- Can we edit memories?
- Speaker:
- Amy Milton
- Description:
-
Trauma and PTSD rewire your brain -- especially your memory -- and can unearth destructive emotional responses when stirred. Could we eliminate these triggers without erasing the memories themselves? Enter neurologist Amy Milton's mind-blowing, memory-editing clinical research poised to defuse the damaging effects of painful remembered experiences and offer a potential path toward better mental health.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 16:06
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