My name is Uri Hasson.
I'm a Professor at Princeton University,
and this is the second part of the talk,
in which we're going to see
how we transfer memories from one brain to the other
and make my brain linked to other brains
in the society.
So, in the first part, we saw
how brain patterns during memory
are related to what happened before.
And we saw that by speaking,
I'm making your brain responses similar to mine.
And now we can combine these two together
and ask, can I take my brain patterns
that are related to my memories
and, by speaking, plant my memories in your brains?
So, how did we do this experiment?
Think about it that I have a brain pattern in my brain
that is related to what I'm thinking.
And now I'm articulating this --
invoking my memories and articulating them.
So, you are listening.
And my task is to take the memories from my brain
and to make it... the construct...
reconstruct it and appear it in your brain.
So, how did we do it in the lab?
We took the movie of Sherlock from the series... from the BBC series.
We took the first episode.
We took the first 50 minutes.
And we showed it to people in the scanner, people that never saw it before.
So, basically, now, they have to encode a new memory into their brains.
And to give you a feeling of the stimulus,
I'm going to play you, now,
20 seconds from the middle of the episode for your enjoyment.
"What about these suicides, then, Sherlock?
I thought that'd be right up your street.
Three exactly the same.
Four. There's been a fourth. There's something different this time.
A fourth?
Where?
Brixton. Lauriston Gardens.
What's new about this one? You wouldn't have come to get me if there wasn't something different.
You know how they never leave notes?
Yeah. This one did. Will you come?"
Okay. So, after people watch the movie in the scanner,
we did the opposite condition.
What is the opposite from watching a movie in the scanner?
It's when you are lying... dark in the scanner.
There is no input going to your brain.
We give a microphone,
and your task is to retell the story to another person.
So, now you need to use words
to invoke your memories and transmit it to another brain.
And I'm going, now, to play you, again,
a 20 second recording of a subject describing the scene
that he had just seen in the scanner to another person.
The recording is going to be a bit noisy,
because it was recorded in the scanner.
And we do a lot of noise cancelling in the scanner
to have a clean recording,
so we also have the transcript of the recording.
"So, they have this exchange
where Ms. Hudson comes in,
asks if everything looks okay,
and she picks up the newspaper
and she's asking Sherlock about the...
the murders that have happened.
Sherlock briefly looks outside
and he sees that there are cop cars,
and he says that there's been a fourth murder,
and something must have been different,
so that's why they're there.
And just moments later, the police... the chief walks in."
So, as you can see, it's a very detailed recording.
And now we can take this recording
of the memories of the storytelling of the movie
and play it to another group of listeners
that have never watched the movie,
and record their brain responses while they're listening.
And then we can take the brain responses
and compare them to the brain responses of the people
that actually watched the movie.
And this is how, experimentally in the lab,
we can look at this transmission of memories
from the moment you encode it
to the moment you tell it
to the moment other people are listening to it.
This is the behavioral responses
of one of the storytellers... the listeners.
As you can see, we divided...
the movie is 50 minutes...
we divided it into 50 segments.
Each is about, like, 50 seconds to a minute.
And as you can see,
it took her 22 minutes to tell the 50-minute story,
so there is some compression.
She's compressing the event, right?
But she's mostly telling the events in order,
from scene to scene, in order.
Sometimes the remembering is out of order.
And sometimes, rarely,
they forget a scene, but they're remembering most of it.
And this is all 17 subjects that watched the movie
and recalled it in the scanner.
As you can see, we have, really,
one subject, over here,
that it took her 45 minutes to describe a 50-minute movie --
she is very detailed.
But even the subjects that are not as detailed,
and more compressing...
they don't skip events, and they tell all of them in the order
and in a precise way.
And all the ones that are telling it in a very short way
might be even better storytellers,
because they can really compress the movie
and tell you only what's important in the movie.
And now that we have this, like,
very detailed behavior,
we can start to look... okay, what happened in the brain?
So, how do we do it?
We take a given brain area,
and because there is a difference in the timing
-- right? --
it might take you 40 seconds to see and only 20 seconds to describe an event,
we can't use the temporal correlation anymore,
so we use spatial correlation.
We take the activity in this brain area,
and we average it over time within this short event.
And now we have a brain pattern,
in this particular episode in the movie,
and we see whether this brain pattern
correlates with the brain pattern of another subject
in another condition
while they are seeing the same scene.
Okay?
So, for example, we can look on
subject encoding with the subject recalling in the dark scanner.
So, when you're seeing the movie,
this is on the left.
And in the right is when you're remembering the...
when you're recording the movie.
And we can see whether the brain pattern in scene 1
are correlated.
And we can do it for all the scenes --
we have 50 of them.
And this correlation has to be stronger than the correlation
between different non-matching scenes.
So, I want to have a particular activation,
that's particular to this moment in the movie,
in your brain area when you're watching it and encoding it.
And we can do this analysis across the entire brain.
And what we see...
we see areas in which the activation
when you're remembering reinstates the activation
when you were watching.
And you can see that there are many brain areas
that you reinstate.
First, you can see that the responses are not similar in the visual cortex.
So, it's not that you reinstate the images of the movie.
But then, if you look at the other areas...
remember, the areas that have long timescales
and integrate the meaning...
this are the areas in which you really reinstate your memories
and the narrative.
So, these are the areas that really accumulate
the story over time.
And now we can see what's happening
between the story teller, when he remembers the events,
and the listeners, when they are listening.
And remember, the listeners never watched the movie.
And again, what we see...
only now it's spatial patterns instead of temporal patterns...
we see that by speaking,
the brain responses of the listeners
become similar to the brain responses of the speaker
that is remembering the movie
in these higher-order areas that integrate information
over long timescales.
And now we can really close the circuit
and ask, are the listeners,
while they're listening to the story teller in the scanner...
are their brain responses similar to the speaker
when he actually watched the movie for the first time
and encoded it to memory?
And to our surprise, this is exactly what we see.
It's as if the listeners were in the cinema with the speaker
when he watched the movie and encoded it to memory.
So, this is now a nice demonstration...
how we can see that memories...
I can really transmit my memories
and bring you with me to my past,
to my experiences, using language.
And what is amazing about this is,
if you think about it,
I can reinstate my memories.
I remember, always, the detective, always the murderer,
and what was the context in which they meet,
for example in a taxi cab.
But you didn't see the movie.
So, when I'm saying, "London, cab driver, taxi, detective,"
you have to combine everything in your brain
and you have to imagine, right?,
because you didn't see the movie.
You don't have the memory.
And that tells us something very deep about the memory system.
You can see that imagination and remembering
are the same,
and this is another demonstration of how the past and the future
merge together,
because for the brain it's the same to remember stuff
and to imagine new stories.
And this is perhaps the most interesting result from this study...
is the following.
If I'm seeing how much you understood the story of the movie
-- right? this is on the y axis --
and how much you're similar...
your brain responses as a listener
to my brain responses while I was watching the movie,
you can see that the more similar you are to me
the better you understand the movie, right?
But we had, like, 17 people that watched the movie,
and we used to take only one version of the movie,
of one subject,
to play to the listener.
And you can see that there are...
you can see all these, like, 17 subjects over here.
And here they were most similar to the person
that you listened to.
And this means that you don't get an objective description of the movie.
You get my viewpoint of the movie.
You get the way I understood the movie, right?
So, it's very efficient.
You don't need to spend 50 minutes in the movie.
Now I can... you can get the movie in 20 minutes,
right?, but you don't get the actual movie --
you get my perspective of the movie.
And now we can ask, wait... if this is the case,
what if you have a very strange perspective of the movie?
Alright, so now you can see that
the way you're remembering
depends on the way I'm viewing the world.
Right?
And now we have to complicate a bit our model for communication, right?,
because I want to be coupled to your brain, right?,
and I want to make yours similar to mine.
But actually, between you and I,
there are different memories and different perspectives,
so it's not as easy to make your brain similar to mine.
In early areas, it's easier.
I can... you know, I can produce sound,
and your auditory cortex is going to go up and down.
It's very easy to be coupled to your sensory system.
But if I want you to get me
in these higher-order areas that integrate information
over many, many minutes
and really depend on all your memories over time,
I need to align the way we understand the world.
So, there is a filter between you and I.
And how can we experimentally
test these filters?
This is the experiment we did.
We took a story of J.D. Salinger,
"Pretty Mouth and Green My Eyes".
And in this story, Salinger is very smart to keep it ambiguous.
The background is as follows.
A husband lost track of his wife in a party.
He's coming home by himself -- very, very anxious.
Where is my wife?
Take a phone, pick up the phone
and call to his best friend,
and ask him, "Did you see my wife?"
Next to the best friend,
there is a woman that is lying naked in the bed.
And Salinger is very smart not to tell...
not to reveal her identity.
So, you're not really so [unknown].
And as good scientists, we decided...
let's ruin the ambiguity and simply tell you her identity.
We're going to give you a memory, or a filter,
on reality.
For one of the groups,
we were saying the woman that is lying naked,
this is the wife.
She's having an affair with the best friend.
Now, in this context, when the husband is asking,
"Can I come over? I really feel lonely and anxious."
And the best friend says,
"No, please don't come. I'm very tired."
You know why he's saying, "please don't come."
He probably doesn't want to be caught.
But in the second context, we give for other subjects...
we told, the wife is loyal,
the husband the jealous,
the naked woman is the girlfriend of the best friend.
And in this context, when the husband wants to come
and the friend says no,
you say, oh, this is an annoying friend.
It's the middle of the night.
You want to go to bed.
So, you have a very different interpretation.
And now, after we tell this context,
everyone is listening to the exact same story.
There is no difference between them.
The other difference is their memory of the context,
what happened before the story started.
And you can see that this memory
is going to change the way they process the story.
And now, I can see...
I can train a classifier
and say, these are the responses from these particular brain areas
in all the people that believe in the first context,
that the wife is having an affair.
These are the responses in this brain area
in all the people that believed
that the husband is a jealous partner.
And after you learn the similarity patterns across people,
I'm giving you a leave-out subject.
This is his brain responses.
And now you need to guess.
And if you are guessing,
50% you are going to say the right answer, right?
But once we learn the similarity across people,
we can predict with 90% accuracy
whether you believe that the wife is having an affair
or that the husband is crazy jealous,
only based on your similarity to other people in the group.
So, this means that this memory
is going to make you more similar
to people that think like you, right?
And now, basically... so, this is like a summary of the results, right?
You're going to be more similar to people in your group.
And now you can ask, wait...
if these memories are so effective in changing my brain...
if someone telling me the wife is having an affair
is going to change the way I perceive reality,
then it's really important from where I am gathering my information,
because it's going, really, to change how I'm thinking.
I have a different perspective on reality.
And now we can ask, from where do we get our stories?
Right?
Because now we can see that your memories are shaped by other people
-- the way that they are thinking --
so it's really important to ask from where do we get our information.
And I think the...
the most of the information we get from other brains,
from our friends.
So, tell me who your friends are,
and I will tell you who are you.
So, look at your family, look at your friend,
the group of people that you're connected to.
They're going to shape how you think.
And then, of course,
you have to see who else is influencing your brain,
for example, which TV news you are listening to, right?,
which newspaper you are reading.
And you have to realize by reading one source of information
you get some perspective on the world,
and it's going to be very different from another person's, right?
So, now it's really important, now, also to think about...
what is the common input for us as a society?
And in a way, to summarize this
is to say that my memories are your stories,
and your stories are my memories,
and we are all connected together to a big web.
So, now, if you really want to understand human cognition,
you cannot study individuals in a box.
We need to understand how we connect to other people.
And how this, like, way of connection constantly shapes who we are,
and moves us from who we are now in the present to the future.
So, there's a constant dynamic between our past and our future,
and our current future is connected to other people,
and this is how we're all like a big web.
And in a way, what we're doing in our lab
is to study this connection across people,
and how one person influences another person.
But that will be another story,
and for that you need to go and read our other papers
that are coming out from the lab.
Thank you so much.