A mouse. A laser beam. A manipulated memory | Steve Ramirez and Xu Liu | TEDxBoston
-
0:08 - 0:10Steve Ramirez:
My first year of grad school, -
0:10 - 0:12I found myself in my bedroom
-
0:12 - 0:14eating lots of Ben & Jerry's
-
0:14 - 0:16watching some trashy TV
-
0:16 - 0:19and maybe, maybe listening
to Taylor Swift. -
0:19 - 0:21I had just gone through a breakup.
-
0:21 - 0:22(Laughter)
-
0:22 - 0:25So for the longest time, all I would do
-
0:25 - 0:28is recall the memory of this
person over and over again, -
0:28 - 0:31wishing that I could get
rid of that gut-wrenching, -
0:31 - 0:33visceral "blah" feeling.
-
0:33 - 0:36Now, as it turns out,
I'm a neuroscientist, -
0:36 - 0:38so I knew that the memory of that person
-
0:38 - 0:41and the awful, emotional undertones
that color in that memory, -
0:41 - 0:44are largely mediated
by separate brain systems. -
0:44 - 0:46And so I thought, what if we could
go into the brain -
0:46 - 0:48and edit out that nauseating feeling
-
0:48 - 0:51but while keeping the memory
of that person intact? -
0:51 - 0:54Then I realized, maybe
that's a little bit lofty for now. -
0:54 - 0:56So what if we could start off
by going into the brain -
0:56 - 0:59and just finding a single
memory to begin with? -
0:59 - 1:02Could we jump-start
that memory back to life, -
1:02 - 1:05maybe even play with the contents
of that memory? -
1:05 - 1:08All that said, there is one person
in the entire world right now -
1:09 - 1:11that I really hope is not
watching this talk. -
1:11 - 1:14(Laughter)
-
1:14 - 1:17So, there is a catch.
There is a catch. -
1:17 - 1:20These ideas probably remind
you of "Total Recall," -
1:20 - 1:22"Eternal Sunshine of the Spotless Mind,"
-
1:22 - 1:23or of "Inception."
-
1:23 - 1:25But the movie stars that we work with
-
1:25 - 1:27are the celebrities of the lab.
-
1:27 - 1:28Xu Liu: Test mice.
-
1:28 - 1:30(Laughter)
-
1:30 - 1:33As neuroscientists,
we work in the lab with mice -
1:33 - 1:36trying to understand how memory works.
-
1:36 - 1:39And today, we hope
to convince you that now -
1:39 - 1:42we are actually able to activate
a memory in the brain -
1:42 - 1:44at the speed of light.
-
1:44 - 1:47To do this, there's only two simple
steps to follow. -
1:47 - 1:51First, you find and label
a memory in the brain, -
1:51 - 1:54and then you activate it with a switch.
-
1:54 - 1:56As simple as that.
-
1:56 - 1:58(Laughter)
-
1:58 - 1:59SR: Are you convinced?
-
1:59 - 2:03So, turns out finding a memory
in the brain isn't all that easy. -
2:03 - 2:06XL: Indeed. This is way more
difficult than, let's say, -
2:06 - 2:08finding a needle in a haystack,
-
2:08 - 2:11because at least, you know,
the needle is still something -
2:11 - 2:13you can physically put your fingers on.
-
2:13 - 2:15But memory is not.
-
2:15 - 2:18And also, there's way
more cells in your brain -
2:19 - 2:24than the number of straws
in a typical haystack. -
2:24 - 2:26So yeah, this task does
seem to be daunting. -
2:26 - 2:30But luckily, we got help
from the brain itself. -
2:30 - 2:33It turned out that all we need
to do is basically -
2:33 - 2:35to let the brain form a memory,
-
2:35 - 2:38and then the brain will tell us
which cells are involved -
2:38 - 2:40in that particular memory.
-
2:40 - 2:43SR: So what was going on in my brain
-
2:43 - 2:45while I was recalling the memory of an ex?
-
2:45 - 2:48If you were to just completely
ignore human ethics for a second -
2:48 - 2:49and slice up my brain right now,
-
2:49 - 2:51you would see that there
was an amazing number -
2:51 - 2:54of brain regions that were active
while recalling that memory. -
2:54 - 2:57Now one brain region
that would be robustly active -
2:57 - 2:59in particular is called the hippocampus,
-
2:59 - 3:01which for decades
has been implicated in processing -
3:01 - 3:04the kinds of memories
that we hold near and dear, -
3:04 - 3:06which also makes it
an ideal target to go into -
3:06 - 3:09and to try and find and maybe
reactivate a memory. -
3:09 - 3:11XL: When you zoom in into the hippocampus,
-
3:11 - 3:14of course you will see lots of cells,
-
3:14 - 3:17but we are able to find
which cells are involved -
3:17 - 3:18in a particular memory,
-
3:18 - 3:21because whenever a cell is active,
-
3:21 - 3:22like when it's forming a memory,
-
3:22 - 3:26it will also leave a footprint
that will later allow us to know -
3:26 - 3:29these cells are recently active.
-
3:29 - 3:31SR: So the same way
that building lights at night -
3:31 - 3:35let you know that somebody's probably
working there at any given moment, -
3:35 - 3:37in a very real sense, there
are biological sensors -
3:37 - 3:39within a cell that are turned on
-
3:39 - 3:41only when that cell was just working.
-
3:41 - 3:44They're sort of biological
windows that light up -
3:44 - 3:46to let us know that that cell
was just active. -
3:46 - 3:48XL: So we clipped part of this sensor,
-
3:48 - 3:51and attached that to a switch
to control the cells, -
3:51 - 3:55and we packed this switch
into an engineered virus -
3:55 - 3:58and injected that into the brain
of the mice. -
3:58 - 4:00So whenever a memory is being formed,
-
4:00 - 4:03any active cells for that memory
-
4:03 - 4:05will also have this switch installed.
-
4:05 - 4:08SR: So here is what the hippocampus
looks like -
4:08 - 4:10after forming a fear memory, for example.
-
4:10 - 4:12The sea of blue that you see here
-
4:12 - 4:14are densely packed brain cells,
-
4:14 - 4:15but the green brain cells,
-
4:15 - 4:18the green brain cells
are the ones that are holding on -
4:18 - 4:19to a specific fear memory.
-
4:19 - 4:21So you are looking at the crystallization
-
4:21 - 4:24of the fleeting formation of fear.
-
4:24 - 4:26You're actually looking
at the cross-section -
4:26 - 4:27of a memory right now.
-
4:27 - 4:30XL: Now, for the switch
we have been talking about, -
4:30 - 4:33ideally, the switch
has to act really fast. -
4:33 - 4:35It shouldn't take minutes
or hours to work. -
4:35 - 4:39It should act at the speed
of the brain, in milliseconds. -
4:39 - 4:41SR: So what do you think, Xu?
-
4:41 - 4:43Could we use, let's say,
pharmacological drugs -
4:44 - 4:45to activate or inactivate brain cells?
-
4:45 - 4:49XL: Nah. Drugs are pretty messy.
They spread everywhere. -
4:49 - 4:52And also it takes them
forever to act on cells. -
4:52 - 4:56So it will not allow us
to control a memory in real time. -
4:56 - 5:00So Steve, how about let's zap
the brain with electricity? -
5:00 - 5:03SR: So electricity is pretty fast,
-
5:03 - 5:05but we probably wouldn't
be able to target it -
5:05 - 5:07to just the specific cells
that hold onto a memory, -
5:07 - 5:09and we'd probably fry the brain.
-
5:09 - 5:12XL: Oh. That's true.
So it looks like, hmm, -
5:12 - 5:14indeed we need to find a better way
-
5:14 - 5:18to impact the brain at the speed of light.
-
5:18 - 5:23SR: So it just so happens that light
travels at the speed of light. -
5:23 - 5:26So maybe we could activate
or inactivate memories -
5:26 - 5:28by just using light -
-
5:28 - 5:29XL: That's pretty fast.
-
5:29 - 5:31SR: - and because normally brain cells
-
5:31 - 5:33don't respond to pulses of light,
-
5:33 - 5:35so those that would respond
to pulses of light -
5:35 - 5:37are those that contain
a light-sensitive switch. -
5:37 - 5:39Now to do that, first we need
to trick brain cells -
5:39 - 5:41to respond to laser beams.
-
5:41 - 5:42XL: Yep. You heard it right.
-
5:42 - 5:44We are trying to shoot lasers
into the brain. -
5:44 - 5:45(Laughter)
-
5:45 - 5:49SR: And the technique that lets us do that
is optogenetics. -
5:49 - 5:52Optogenetics gave us this
light switch that we can use -
5:52 - 5:54to turn brain cells on or off,
-
5:54 - 5:56and the name of that switch
is channelrhodopsin, -
5:56 - 5:59seen here as these green dots
attached to this brain cell. -
5:59 - 6:02You can think of channelrhodopsin
as a sort of light-sensitive switch -
6:02 - 6:04that can be artificially
installed in brain cells -
6:05 - 6:06so that now we can use that switch
-
6:06 - 6:09to activate or inactivate the brain
cell simply by clicking it, -
6:09 - 6:12and in this case we click it on
with pulses of light. -
6:12 - 6:16XL: So we attach this light-sensitive
switch of channelrhodopsin -
6:16 - 6:18to the sensor we've been talking about
-
6:18 - 6:20and inject this into the brain.
-
6:20 - 6:24So whenever a memory is being formed,
-
6:24 - 6:26any active cell for that particular memory
-
6:26 - 6:29will also have this light-sensitive switch
installed in it -
6:29 - 6:32so that we can control these cells
-
6:32 - 6:36by the flipping of a laser
just like this one you see. -
6:36 - 6:39SR: So let's put all of this
to the test now. -
6:39 - 6:41What we can do is we can take our mice
-
6:41 - 6:44and then we can put them in a box
that looks exactly like this one, -
6:44 - 6:46and then we can give them
a very mild foot shock -
6:46 - 6:49so that they form a fear
memory of this box. -
6:49 - 6:51They learn that something
bad happened here. -
6:51 - 6:53Now with our system,
the cells that are active -
6:53 - 6:55in the hippocampus
in the making of this memory, -
6:55 - 6:58only those cells will now
contain channelrhodopsin. -
6:58 - 7:01XL: When you are as small as a mouse,
-
7:01 - 7:05it feels as if the whole
world is trying to get you. -
7:05 - 7:07So your best response of defense
-
7:07 - 7:09is trying to be undetected.
-
7:09 - 7:11Whenever a mouse is in fear,
-
7:11 - 7:13it will show this very typical behavior
-
7:13 - 7:15by staying at one corner of the box,
-
7:15 - 7:18trying to not move any part of its body,
-
7:18 - 7:21and this posture is called freezing.
-
7:21 - 7:25So if a mouse remembers that something
bad happened in this box, -
7:25 - 7:28and when we put them
back into the same box, -
7:28 - 7:30it will basically show freezing
-
7:30 - 7:32because it doesn't want to be detected
-
7:32 - 7:35by any potential threats in this box.
-
7:35 - 7:36SR: So you can think of freezing as,
-
7:36 - 7:39you're walking down the street
minding your own business, -
7:39 - 7:41and then out of nowhere
you almost run into -
7:41 - 7:43an ex-girlfriend or ex-boyfriend,
-
7:43 - 7:44and now those terrifying two seconds
-
7:44 - 7:47where you start thinking,
"What do I do? Do I say hi? -
7:47 - 7:49Do I shake their hand?
Do I turn around and run away? -
7:49 - 7:51Do I sit here and pretend
like I don't exist?" -
7:51 - 7:55Those kinds of fleeting thoughts
that physically incapacitate you, -
7:55 - 7:57that temporarily give you
that deer-in-headlights look. -
7:57 - 8:00XL: However, if you put the mouse
in a completely different new box, -
8:00 - 8:02like the next one,
-
8:02 - 8:04it will not be afraid of this box
-
8:04 - 8:09because there's no reason that it
will be afraid of this new environment. -
8:09 - 8:12But what if we put
the mouse in this new box -
8:12 - 8:16but at the same time,
we activate the fear memory -
8:16 - 8:18using lasers just like we did before?
-
8:18 - 8:21Are we going to bring back the fear memory
-
8:21 - 8:25for the first box into this
completely new environment? -
8:25 - 8:28SR: All right,
and here's the million-dollar experiment. -
8:28 - 8:31Now to bring back to life
the memory of that day, -
8:31 - 8:33I remember that the Red Sox had just won,
-
8:33 - 8:35it was a green spring day,
-
8:35 - 8:37perfect for going up and down the river
-
8:37 - 8:39and then maybe going to the North End
-
8:39 - 8:41to get some cannolis, #justsaying.
-
8:41 - 8:44Now Xu and I, on the other hand,
-
8:44 - 8:47were in a completely windowless black room
-
8:47 - 8:51not making any ocular movement
that even remotely resembles an eye blink -
8:51 - 8:53because our eyes were fixed
onto a computer screen. -
8:53 - 8:56We were looking at this mouse
here trying to activate a memory -
8:56 - 8:58for the first time using our technique.
-
8:58 - 9:00XL: And this is what we saw.
-
9:00 - 9:03When we first put the mouse into this box,
-
9:03 - 9:06it's exploring, sniffing
around, walking around, -
9:06 - 9:07minding its own business,
-
9:07 - 9:09because actually by nature,
-
9:09 - 9:11mice are pretty curious animals.
-
9:11 - 9:14They want to know,
what's going on in this new box? -
9:14 - 9:15It's interesting.
-
9:15 - 9:19But the moment we turned on the laser,
like you see now, -
9:19 - 9:22all of a sudden the mouse
entered this freezing mode. -
9:22 - 9:26It stayed here and tried not to move
any part of its body. -
9:26 - 9:28Clearly it's freezing.
-
9:28 - 9:30So indeed, it looks like
we are able to bring back -
9:30 - 9:32the fear memory for the first box
-
9:32 - 9:36in this completely new environment.
-
9:36 - 9:38While watching this, Steve and I
-
9:38 - 9:40are as shocked as the mouse itself.
-
9:40 - 9:41(Laughter)
-
9:41 - 9:45So after the experiment,
the two of us just left the room -
9:45 - 9:46without saying anything.
-
9:46 - 9:50After a kind of long,
awkward period of time, -
9:50 - 9:52Steve broke the silence.
-
9:52 - 9:54SR: "Did that just work?"
-
9:54 - 9:57XL: "Yes," I said. "Indeed it worked!"
-
9:57 - 9:59We're really excited about this.
-
9:59 - 10:02And then we published our findings
-
10:02 - 10:04in the journal Nature.
-
10:04 - 10:06Ever since the publication of our work,
-
10:06 - 10:09we've been receiving numerous comments
-
10:09 - 10:11from all over the Internet.
-
10:11 - 10:14Maybe we can take a look at some of those.
-
10:17 - 10:20SR: So the first thing
that you'll notice is that people have -
10:20 - 10:22really strong opinions
about this kind of work. -
10:22 - 10:24Now I happen to completely
agree with the optimism -
10:24 - 10:25of this first quote,
-
10:25 - 10:28because on a scale
of zero to Morgan Freeman's voice, -
10:28 - 10:30it happens to be
one of the most evocative accolades -
10:30 - 10:32that I've heard come our way.
-
10:32 - 10:34(Laughter)
-
10:34 - 10:37But as you'll see, it's not
the only opinion that's out there. -
10:37 - 10:40XL: Indeed, if we take
a look at the second one, -
10:40 - 10:42I think we can all agree that it's, meh,
-
10:42 - 10:44probably not as positive.
-
10:44 - 10:46But this also reminds us that,
-
10:46 - 10:48although we are still working with mice,
-
10:48 - 10:52it's probably a good idea
to start thinking and discussing -
10:52 - 10:55about the possible ethical ramifications
-
10:55 - 10:57of memory control.
-
10:57 - 10:59SR: Now, in the spirit of the third quote,
-
10:59 - 11:01we want to tell you about a recent project
-
11:01 - 11:04that we've been working on in lab
that we've called Project Inception. -
11:07 - 11:10So we reasoned that
now that we can reactivate a memory, -
11:10 - 11:13what if we do so but then
begin to tinker with that memory? -
11:13 - 11:16Could we possibly even
turn it into a false memory? -
11:16 - 11:20XL: So all memory
is sophisticated and dynamic, -
11:20 - 11:23but if just for simplicity,
let's imagine memory -
11:23 - 11:25as a movie clip.
-
11:25 - 11:27So far what we've told you
is basically we can control -
11:27 - 11:29this "play" button of the clip
-
11:29 - 11:34so that we can play this video clip
any time, anywhere. -
11:34 - 11:36But is there a possibility
that we can actually get -
11:36 - 11:39inside the brain and edit this movie clip
-
11:39 - 11:42so that we can make it
different from the original? -
11:42 - 11:44Yes we can.
-
11:44 - 11:46Turned out that all we need
to do is basically -
11:47 - 11:51reactivate a memory
using lasers just like we did before, -
11:51 - 11:54but at the same time,
if we present new information -
11:54 - 11:58and allow this new information
to incorporate into this old memory, -
11:58 - 12:01this will change the memory.
-
12:01 - 12:04It's sort of like making a remix tape.
-
12:04 - 12:07SR: So how do we do this?
-
12:07 - 12:09Rather than finding
a fear memory in the brain, -
12:09 - 12:11we can start by taking our animals,
-
12:11 - 12:14and let's say we put them in a blue box
like this blue box here -
12:14 - 12:17and we find the brain cells
that represent that blue box -
12:17 - 12:19and we trick them to respond
to pulses of light -
12:19 - 12:20exactly like we had said before.
-
12:20 - 12:23Now the next day, we can take
our animals and place them -
12:23 - 12:26in a red box that they've never
experienced before. -
12:26 - 12:28We can shoot light
into the brain to reactivate -
12:28 - 12:29the memory of the blue box.
-
12:29 - 12:31So what would happen here if,
-
12:31 - 12:33while the animal is recalling
the memory of the blue box, -
12:33 - 12:36we gave it a couple of mild foot shocks?
-
12:36 - 12:38So here we're trying to artificially
make an association -
12:38 - 12:40between the memory of the blue box
-
12:40 - 12:42and the foot shocks themselves.
-
12:42 - 12:43We're just trying to connect the two.
-
12:43 - 12:45So to test if we had done so,
-
12:45 - 12:47we can take our animals once again
-
12:47 - 12:48and place them back in the blue box.
-
12:48 - 12:51Again, we had just reactivated
the memory of the blue box -
12:51 - 12:54while the animal got a couple
of mild foot shocks, -
12:54 - 12:56and now the animal suddenly freezes.
-
12:56 - 12:59It's as though it's recalling being
mildly shocked in this environment -
12:59 - 13:02even though that never actually happened.
-
13:02 - 13:04So it formed a false memory,
-
13:04 - 13:06because it's falsely
fearing an environment -
13:06 - 13:07where, technically speaking,
-
13:07 - 13:09nothing bad actually happened to it.
-
13:09 - 13:12XL: So, so far we are only talking about
-
13:12 - 13:14this light-controlled "on" switch.
-
13:14 - 13:17In fact, we also have
a light-controlled "off" switch, -
13:17 - 13:19and it's very easy to imagine
-
13:19 - 13:22that by installing this
light-controlled "off" switch, -
13:22 - 13:26we can also turn off a memory,
any time, anywhere. -
13:28 - 13:30So everything
we've been talking about today -
13:30 - 13:34is based on this philosophically
charged principle of neuroscience -
13:34 - 13:39that the mind, with its seemingly
mysterious properties, -
13:39 - 13:42is actually made of physical stuff
that we can tinker with. -
13:42 - 13:44SR: And for me personally,
-
13:44 - 13:45I see a world where we can reactivate
-
13:45 - 13:47any kind of memory that we'd like.
-
13:47 - 13:51I also see a world where we can
erase unwanted memories. -
13:51 - 13:53Now, I even see a world
where editing memories -
13:53 - 13:54is something of a reality,
-
13:54 - 13:56because we're living in a time
where it's possible -
13:56 - 13:59to pluck questions from the tree
of science fiction -
13:59 - 14:01and to ground them
in experimental reality. -
14:01 - 14:02XL: Nowadays, people in the lab
-
14:02 - 14:05and people in other groups
all over the world -
14:05 - 14:09are using similar methods
to activate or edit memories, -
14:09 - 14:12whether that's old or new,
positive or negative, -
14:12 - 14:15all sorts of memories
so that we can understand -
14:15 - 14:17how memory works.
-
14:17 - 14:19SR: For example, one group in our lab
-
14:19 - 14:21was able to find the brain cells
that make up a fear memory -
14:22 - 14:24and converted them into
a pleasurable memory, just like that. -
14:24 - 14:28That's exactly what I mean about editing
these kinds of processes. -
14:28 - 14:30Now one dude in lab
was even able to reactivate -
14:30 - 14:32memories of female mice in male mice,
-
14:32 - 14:34which rumor has it
is a pleasurable experience. -
14:34 - 14:39XL: Indeed, we are living
in a very exciting moment -
14:39 - 14:42where science doesn't have
any arbitrary speed limits -
14:42 - 14:46but is only bound by our own imagination.
-
14:46 - 14:48SR: And finally,
what do we make of all this? -
14:48 - 14:50How do we push this technology forward?
-
14:50 - 14:52These are the questions
that should not remain -
14:52 - 14:53just inside the lab,
-
14:53 - 14:56and so one goal of today's talk
was to bring everybody -
14:56 - 14:58up to speed with the kind
of stuff that's possible -
14:58 - 14:59in modern neuroscience,
-
15:00 - 15:01but now, just as importantly,
-
15:01 - 15:04to actively engage everybody
in this conversation. -
15:04 - 15:07So let's think together as a team
about what this all means -
15:07 - 15:09and where we can and should go from here,
-
15:09 - 15:11because Xu and I think we all have
-
15:11 - 15:14some really big decisions ahead of us.
-
15:14 - 15:15Thank you.
XL: Thank you. -
15:15 - 15:17(Applause)
- Title:
- A mouse. A laser beam. A manipulated memory | Steve Ramirez and Xu Liu | TEDxBoston
- Description:
-
Can we edit the content of our memories? It’s a sci-fi-tinged question that Steve Ramirez and Xu Liu are asking in their lab at MIT. Essentially, the pair shoot a laser beam into the brain of a living mouse to activate and manipulate its memory. In this unexpectedly amusing talk they share not only how, but -- more importantly -- why they do this.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDxTalks
- Duration:
- 15:25