Translator: Elisabeth Buffard Reviewer: Ms Buffard's students
Hello everyone.
The brain.
It is central to our reasoning,
our actions;
and yet,
we have no sensitive perception of it.
I work at the INRIA
where researchers in mathematics and computer science
develop methods
to better observe,
better understand the brain
and interact with it.
So we already know a lot about the brain.
But in fact, each brain
is very distinctive,
has its own specificities.
First, its shape.
Just like our bodies are all different,
with different morphologies,
our brains are different too:
a brain has furrows
that are characteristic to each person.
Then, its functional organization.
There are general principles
common to all the brains,
for instance, visual areas located at the rear,
sensorimotor areas in the center,
auditory areas in the temporal areas.
But the precise contours of these areas,
their size too,
depend on our history,
how the brain developed
during our growth,
and activities that we may have had
which are unique to each of us.
So each of our brains
is worthy exploring
as terra incognita.
To conduct this exploration,
we will map the brain.
That is to say,
know precisely in an individual brain,
which are the areas that correspond
to very specific actions.
And when these areas are identified,
we can even go watch the activity
that takes place in these areas, establish its characterization
or even detect it.
To go on this exploration, we need some luggage.
Our luggage is a measuring device
which is nearly a century old
but continues to reveal to us every day
the secrets of this organ, and it is the EEG,
which consists of electrodes are placed on the scalp
that measures the electrical activity
of neurons at the brain surface,
that they emit when they communicate.
This area of the brain ...
imagine it like a globe, okay?
The activity of the inhabitants would be represented by areas
more or less luminous depending on their degree of communication,
of activity.
And our electrodes,
are like satellites around the Earth
observing the activity of its inhabitants,
here, the neurons,
but at a rough scale.
So how can we,
from such measurements
provided by the electroencephalogramme
get to map zones
corresponding to specific activities?
As we get measurements that, after all, are removed
and add to the superimposition
of all these hourly activities in fact,
because they are emitted
by all the tissues which separate the brain from the scalp.
To solve such a seemingly hard problem,
mathematics offers a solution,
they offer solutions
when we have equations and unknowns,
and unknowns are the distribution of the electrical activity
on the brain surface,
equations are the physical principles that link
this electrical activity, these activities, with each other,
and link the activity to the measurements.
Let's take a much simpler example:
Imagine I give you a wallet
and I tell you the total amount of money in it.
Can you can deduce
the exact distribution of notes and coins?
No. But if I tell you
it contains the minimum number of coins and notes
to reach that sum, then, yes,
there is one solution:
that used by the teller or cashier
when he gives you the change.
So with principles such as this,
that is to say parts of simplicity principles
or a priori knowledge,
we add to the problem, we can find a solution for mapping,
that is to say identify which areas are activated in a brain
from measurements made on the electroencephalogramme.
But this mapping is individualized
for a particular brain.
This type of work
can help a surgeon, in the case of a patient,
to locate in a brain
pathological areas
communicating poorly,
that need operating,
and locate around these areas
eloquent areas, which themselves communicate well
and must be preserved.
From a mapping,
we may also want
to analyze the activity taking place, that is to say
through the electroencephalogram
we get signals, so a good time resolution.
we can observe the activity on the brain surface
like a film
While these areas we see activating contain many neurons
that are not necessarily specific to a single action
but if you ask a person
to repeat a single action many times,
such as moving their right arm,
we will be able to filter in the measurements
what always corresponds to the movement of the right arm,
and filter all the other brain activities
that have no relation to the action.
So, we can identify in the brain areas
what is the type of dynamics
specific to a certain activity.
Once you can
determine the nature of the activity corresponding to certain actions,
it becomes possible
to detect it at the very time it is being performed,
in real time.
It brings the possibility
to open new communication channels
between the brain and its environment.
If we translate this detection in another command language,
and this new way of communication
does not necessarily pass through the muscles.
So, we've been talking about brain activity.
Let's take an example
of what can trigger brain activity.
For example, you are at a red light in your car
and you're waiting for the green light.
Well, when the green light is displayed,
it triggers a very specific activity in your brain.
It is an activity that says, "Ah! that's what I expecting. "
It comes 300 milliseconds after the light signal
and is called the P 300 wave.
Well this type of signal,
this type of activity in response to an expected signal,
we've used it in an experiment
with patients at the University Hospital in Nice last year,
to enable them to communicate.
For this, we proposed an interface that was
composed of a keyboard
whose letters would flash on the screen.
In fact, at each flash of the letter,
the flash was represented by a small smiley,
whenever the letter that the person wants to spell flashes,
it triggers the green light activity.
"Ah! This is the letter I wanted to type. "
So, we tested this interface
with patients suffering from Lou Gehrig's disease,
which is a neurodegenerative motor neuron disease,
the neurons that connect the brain to the muscles
and sometimes gradually make patients
unable to enonciate or move their limbs,
and sometimes even both.
Our hospital partners at the University Hospital in Nice
seek alternative means of communication
for those people whose brain
is prevented from operating in emission.
However, their brain
is fully operational as regards
cognitive tasks and reception.
So here you see the patient
has the word "dream" in mind
d- r - e - a - m,
and focuses sequentially on each of the letters
of the word she wants to type.
And she counts in her head
how many times the letter she wants to spell
is being flashed.
At each of these signals,
for the right letter,
the p300 wave is detected in her brain.
Look at the letter E which is the third from the top.
1, 2, 3,
4 ... This patient, after four or five flashes of the letter,
sees that the system was able to decode the letter
she was focusing her visual attention on.
Patients or their families have asked us:
"But do you work on telepathy, actually? "
What do you think?
Is it telepathy?
No, we're actually trying to decode something
in the patients' brains,
this information that tells us:
she has just perceived the signal she expected.
She has just perceived the correct letter.
But we are not trying to decode, in the patients' brain
the exact letter that they were thinking about.
This would be possible if we had records at a scale
finer than that offered by the electroencephalogram.
For this, we should place electrodes
directly into the brain.
So to conclude this exploration,
I will digress a little into the world of imagination.
When we want to perform complex movements,
it is useful to think of them mentally in advance.
It is a technique that has been used by great sportsmen,
for example Jean-Claude Killy
to improve their performance.
But it's not just sportsmen
who may want to increase their performance.
Take the example of a patient who has sufferred a stroke
and would be unable to move their arm,
their right arm.
In fact, if this person imagines moving their right arm,
it triggers a brain activity which is very similar
to the one obtained if they actually moved their arm.
With the techniques I just mentioned,
if we are able to characterize this activity
which is produced by the motor imagination,
we are able to detect it at the very moment
the person is imagining.
So we can use that information
and turn it into real action.
We equip their arm with a motorized orthosis
which will trigger the movement
that the person can no longer trigger themselves,
whenever they imagine move it.
Seeing this, the patient's brain
will need to develop new connections
that will gradually allow it to recover movement.
Gradually, we can decrease the electric assistance
and the patent will teake back the control of their own arm.
So this is a new form of physiotherapy
which uses the brain, brain activity,
which is under consideration --there are clinical studies being made now--
of transforming imagination into action.
So we have seen in this brief exploration
that mapping
allows characterizing areas that are activated in the brain
individually, customized,
and can even go look at
the dynamics of brain activity
to better understand, interpret and even translate it into real action.
So I invite you to keep imagining
what you want to do.
Because imagining things
puts them within your reach.
Thank you. (Applause)