Translator: Claire Fielden Reviewer: Denise RQ
So then, "Inception": science fiction or reality?
Is it possible to implant a memory without you knowing it?
Whilst you sleep? Whilst you dream?
But before we can manipulate dreams, we need to understand what they are.
And before we can do that, we need to understand how memory works.
Because your dreams are constructed from the experiences
that you have lived through or even imagined.
To get a better understanding of memory,
I'll need you to go back in time to 1957.
This was the year when Henry Molaison had an operation
to control his epileptic seizures.
At that time, the only possible treatment
was to remove the part of the brain that was causing his seizures.
This part is known as the hippocampus.
This was successful in that it stopped his epileptic seizures.
The only problem was that Henry Molaison developed total amnesia.
He could no longer form new memories of his life.
What have we learned from this tragic experience?
Firstly, that even for such a crucial reason,
this part of the brain should absolutely never be removed.
Secondly, that this tiny part of the brain, your hippocampus
is responsible for your memory.
Not your intelligence or your reasoning skills:
his IQ was perfectly preserved.
No, just your memory.
But to fully understand memory, knowing where it occurs is not enough.
Because, what exactly is the brain?
The brain is a collection of millions, tens of millions of neurons
that communicate with each other.
They communicate using tiny electrical impulses.
A little like, if you were one of these brain neurons,
the only thing you could do is tap your neighbors on the shoulder.
Sometimes, with a telescopic arm, but that's all you could do.
Yet, this very simple, basic way of communicating
is responsible for all your thoughts your memories and your dreams.
How is this possible?
To try and understand this
we need to be able to record the activity of the neurons.
We could implant an electrode into a particular location
and monitor the activity of hundreds of neurons.
Of course, this is highly invasive, you would need a hole in the brain.
We couldn't do this to a human, without a very good reason.
So to overcome this problem, we use mice
to help us to understand, in particular, spatial memory,
so, the memory of how to get to the Chatelet Theater in Paris,
how you got here today, where I am standing on this podium.
We put mice into a maze, where they can run around freely,
going right, going left to find a piece of cheese.
While at the same time,
we record their neural activity, to see how it works.
It has been found that the neurons react to specific places.
There are neurons that fire when I am in a particular place.
And in mice, there is also a neuron,
for example this one here in red,
that will fire when the mouse is at the exit of the maze,
and only when it is there.
If I were to record the activity on a neighboring neuron
it would be active when the mouse was in the same area of the maze, but downstairs.
The neural activity is in fact electrical activity
that can be heard through a loudspeaker.
For example, when the green neuron is active,
when the mouse is in the green area you can hear this.
So, if you close your eyes and listen to the noise,
you could tell the exact location of the mouse.
And if we record from about 50 neurons covering the whole of the space
and use mathematical algorithms called Machine Learning,
we could replicate the exact location of the mouse in space.
In this short film, what you will see is a maze.
The red cross shows the actual location of the animal
and the blue and green dots show the position that we have replicated
using a computer.
You can see the exact path taken by the mouse.
You can tell, simply by looking at the computer screen
where the mouse is.
At times, you can see things are a little more complex
as though the mouse is at several places at once.
But we know that this can't be the case.
So, we think that we are able to replicate not only the actual location of the mouse
but also the path that it is thinking about,
the path that it is deciding to take.
Is this what we are seeing?
Indeed, the mouse goes on to take the path that we had predicted
by calculating its position.
So we are able to read the mouse's thoughts,
or at least where the mouse thinks it is going.
So is it possible to alter what it thinks?
That's where sleep comes into it.
If the mouse is put into this space for example,
and it is given a reward right here.
Later, when it goes to sleep in its little box,
we can see a specific place-cell becoming active
then another, then another,
as though it were dreaming about
the path that it had taken whilst it was awake.
We think that this reproduction of events
is very important for consolidating memories.
You relive the experience during sleep to consolidate it.
So yes, you should learn things before you go to sleep.
Is this really what happens?
To be absolutely sure, we would need to wake up the mouse
and ask it, "Were you just dreaming about walking along that path?"
There's a slight problem in that mice don't talk.
Effectively, it is an imaginary experience.
So, what would happen if, whilst it was sleeping,
whilst this place cell was active.
Could you give the mouse its reward during the time it was asleep?
Would it wake up and go to find its reward?
That's exactly the type of experiment
that we are doing at ESPCI, not far from here,
with our students who are here today:
Marie Lacroix and Gaëtan de Lavilléon.
I can see you all thinking, "He is nice, but he's just a dreamer."
Because how is it possible
to give a reward to a mouse when it is sleeping?
It is possible because, as I told you, brain activity is electrical.
When you give a mouse a big piece of cheese,
you notice a small part of its brain becomes really active.
And so, if you implant an electrode to stimulate that precise region,
you are able to recreate the reward given to the mouse.
So, we recorded the neural activity that occurred
when the mouse was running around,
And we saw that a particular place-cell became active.
So, we designed a machine-brain interface that works during sleep
which, as soon it detects the neural activity
that happens whenever the mouse dreams
that it is in that particular place,
it automatically triggers a sensation of being rewarded.
So when the mouse wakes up, and it is put back into the same place,
it goes directly to the place where it had been rewarded whilst it was sleeping.
This experiment shows us that it is possible to create an association
between receiving a reward and the activity of the neurons.
And even when we are awake,
this association between a physical location and a reward is still there.
So this shows a strong relationship between neural activity.
When a neuron is active, I'm sure that the mouse is at a certain place
or thinks it is at a certain place.
This also shows us that it is possible to take a memory,
and put it back as a more positive one, whilst you sleep.
Or even as a more negative one.
So what about humans?
As I have told you,
recording neural activity is very powerful but very invasive.
You would need to open the brain with the risk of infection.
On the other hand, you could use functional MRI.
Functional MRI is a huge scanner
that allows us to look at the activity of the brain
without having to open up the cranium.
There was a fascinating experiment that took place at Berkeley.
American researchers presented subjects with a series of YouTube videos
over a period of four to five hours.
And whilst the subjects were watching these clips,
a computer program was trying to make the connections
between the video clips
and the brain activity recorded by the MRI.
Next, these subjects were shown a film that they had never seen before.
This film is what you can see on the right of the screen.
And on the left is the image that they were able to recreate,
simply from the activity in the brain.
They managed to largely recreate, what the subjects were watching.
Through MRI, they were able to see what the subjects were thinking.
So, with the experiments on mice, and the experiments on humans,
is "Inception" possible?
In theory, yes. We can't do absolutely everything.
I can't make you learn how to speak English whilst you sleep.
But on the other hand, we can take a memory,
and turn it into something more positive or more negative.
But to do that, we would have to show it to you whilst you were awake.
So we couldn't do it without you knowing.
And we would have to show it to you for about 4 or 5 hours.
And even though the computer program had coded these images,
they would only work for you not for anyone else.
So we are a long way from mass thought manipulation.
If you are afraid that we can alter your thoughts while you sleep,
without your knowledge,
I recommend that you pay closer attention to advertizing.
If we have no reason to fear, do we have any reason to celebrate?
Yes, because with new technology,
we are able to look closely at he neural activity
linked to the thought processes of the mouse.
This gives us great hope for psychiatric disorders
that affect only thought processes.
And the other interesting thing as I have already told you,
we are able to turn a memory into something more positive.
And we hope to be able to use this
to develop new therapies for post-traumatic stress disorder.
What's post-traumatic stress disorder?
It's when patients have made a pathological association
between an experience and a heightened sense of fear.
At present, the only treatment is to ask patients
to put themselves back into the situation.
And by making it a more pleasant, comfortable setting,
try to break the pathological negative association.
The only problem is that even if you use virtual imagery
to make the situation more immersive and realistic,
you still know that it is not real.
And more importantly, your brain knows that it's not real.
The advantage of dreams is that everything is real.
When I am dreaming, I really am Batman.
And it's only when I wake up that I realize that I'm not.
So, if we can identify, during sleep,
the moments when the subjects are reacting to these traumatic experiences,
that would be the ideal opportunity to break the pathological associations.
All these potential applications, and others like them,
exist because we have succeeded in creating a false memory
in a tiny mouse at ESPCI, just next door,
and because we have been able to do it during sleep.
So I can tell you you have no reason to fear.
You can sleep with both your eyes closed.
And have sweet dreams.
(Applause)