WEBVTT

99:59:59.999 --> 99:59:59.999
Can we, as adults, grow new nerve cells?

99:59:59.999 --> 99:59:59.999
There's still some confusion 
about that question,

99:59:59.999 --> 99:59:59.999
as this is a fairly new field of research.

99:59:59.999 --> 99:59:59.999
For example, I was talking
to one of my colleagues, Robert --

99:59:59.999 --> 99:59:59.999
who is an oncologist --

99:59:59.999 --> 99:59:59.999
and he was telling me,

99:59:59.999 --> 99:59:59.999
"Sandrine, this is puzzling,


99:59:59.999 --> 99:59:59.999
some of my patients that have been told
they are cured of their cancer,

99:59:59.999 --> 99:59:59.999
still develop symptoms of depression."

99:59:59.999 --> 99:59:59.999
And I responded to him,

99:59:59.999 --> 99:59:59.999
"Well, from my point of view 
that makes sense.

99:59:59.999 --> 99:59:59.999
The drug you give to your patients
that stops the cancer cells multiplying,

99:59:59.999 --> 99:59:59.999
also stops the newborn neurons
being generated in their brain."

99:59:59.999 --> 99:59:59.999
And then Robert looked at me 
like I was crazy and said,

99:59:59.999 --> 99:59:59.999
"But Sandrine, these are adult patients,
adults do not grow new nerve cells."

99:59:59.999 --> 99:59:59.999
And much to his surprise, I said,
"Well actually, we do."

99:59:59.999 --> 99:59:59.999
And this is a phenomenon 
that we call Neurogenesis.

99:59:59.999 --> 99:59:59.999
[Neurogenesis]

99:59:59.999 --> 99:59:59.999
Now, Robert is not a neuroscientist,
so when he went to medical school,

99:59:59.999 --> 99:59:59.999
so when he went to medical school
he was not taught what we know now --

99:59:59.999 --> 99:59:59.999
that the adult brain 
can generate new nerve cells.

99:59:59.999 --> 99:59:59.999
So, Robert, you know, 
being a good doctor that he is,

99:59:59.999 --> 99:59:59.999
wanted to come to my lab to understand
the topic a little bit better.

99:59:59.999 --> 99:59:59.999
And I took him for a tour

99:59:59.999 --> 99:59:59.999
of one the of most exciting
parts of the brain,

99:59:59.999 --> 99:59:59.999
when it comes to Neurogenesis --

99:59:59.999 --> 99:59:59.999
and this is the Hippocampus.

99:59:59.999 --> 99:59:59.999
So this is this gray structure
in the center of the brain.

99:59:59.999 --> 99:59:59.999
And what we've known for what
seems like already for very long,

99:59:59.999 --> 99:59:59.999
is that this is important for learning,
memory, mood and emotion.

99:59:59.999 --> 99:59:59.999
However, what we have learned
more recently,

99:59:59.999 --> 99:59:59.999
is that this is one of the unique
structures of the adult brain

99:59:59.999 --> 99:59:59.999
where new neurons can be generated.

99:59:59.999 --> 99:59:59.999
And if we slide 
through the Hippocampus

99:59:59.999 --> 99:59:59.999
and zoom in,

99:59:59.999 --> 99:59:59.999
what you actually see here in blue

99:59:59.999 --> 99:59:59.999
is a newborn neuron
in an adult mouse brain.

99:59:59.999 --> 99:59:59.999
So when it comes to the human brain,

99:59:59.999 --> 99:59:59.999
my colleague Dr. Jonas Frisén
from the Karolinska Institute,

99:59:59.999 --> 99:59:59.999
has estimated that we produce

99:59:59.999 --> 99:59:59.999
700 new neurons per day
in the Hippocampus.

99:59:59.999 --> 99:59:59.999
So you might think this is not much

99:59:59.999 --> 99:59:59.999
according to the billions
of neurons we have,

99:59:59.999 --> 99:59:59.999
but by the time we will turn 50,

99:59:59.999 --> 99:59:59.999
we will have all exchanged the neurons
we were born with in that structure

99:59:59.999 --> 99:59:59.999
with adult-born neurons.

99:59:59.999 --> 99:59:59.999
So, why are these neurons important
and what are their functions?

99:59:59.999 --> 99:59:59.999
So first, we know that they're important
for learning and memory.

99:59:59.999 --> 99:59:59.999
And in the lab we have shown

99:59:59.999 --> 99:59:59.999
that if we block the ability
of the adult brain

99:59:59.999 --> 99:59:59.999
to produce new neurons
in the Hippocampus,

99:59:59.999 --> 99:59:59.999
then we block certain memory abilities.

99:59:59.999 --> 99:59:59.999
And this is especially new and true
for spacial recognition.

99:59:59.999 --> 99:59:59.999
So like, how you navigate
your way in the city.

99:59:59.999 --> 99:59:59.999
So we are still learning a lot,

99:59:59.999 --> 99:59:59.999
and we are not only important
for memory capacity,

99:59:59.999 --> 99:59:59.999
but also for the quality of the memory.

99:59:59.999 --> 99:59:59.999
And we will be helpful to add time
to our memory

99:59:59.999 --> 99:59:59.999
and we will help differentiate
very similar memories.

99:59:59.999 --> 99:59:59.999
Like, how do you find your bike


99:59:59.999 --> 99:59:59.999
but you park at this station
everyday in the same area

99:59:59.999 --> 99:59:59.999
but in a slightly different position?

99:59:59.999 --> 99:59:59.999
And more interesting 
to my colleague Robert,

99:59:59.999 --> 99:59:59.999
is the research we have been doing
on Neurogenesis and Depression.

99:59:59.999 --> 99:59:59.999
So in an animal model of depression,

99:59:59.999 --> 99:59:59.999
we see that we have
a lower level of neurogenesis,

99:59:59.999 --> 99:59:59.999
and if we give antidepressants,

99:59:59.999 --> 99:59:59.999
then we increase the production
of these newborn neurons.

99:59:59.999 --> 99:59:59.999
and we decrease
the symptoms of depression.

99:59:59.999 --> 99:59:59.999
establishing a clear link 
between neurogenesis

99:59:59.999 --> 99:59:59.999
and depression.

99:59:59.999 --> 99:59:59.999
But moreover, if you 
just block neurogenesis,

99:59:59.999 --> 99:59:59.999
then you block the efficiency
of the antidepressant.

99:59:59.999 --> 99:59:59.999
So by then, Robert had understood
that very likely,

99:59:59.999 --> 99:59:59.999
his patients were suffering
from depression

99:59:59.999 --> 99:59:59.999
even after being cured of their cancer

99:59:59.999 --> 99:59:59.999
because the cancer drug had stopped
the newborn neuron to be generated.

99:59:59.999 --> 99:59:59.999
And it will take time 
to generate new neurons

99:59:59.999 --> 99:59:59.999
that reach their normal functions.

99:59:59.999 --> 99:59:59.999
So, collectively, now,

99:59:59.999 --> 99:59:59.999
we think we have enough evidence to say
that Neurogenesis is a target of choice

99:59:59.999 --> 99:59:59.999
if we want to improve
memory information or mood,

99:59:59.999 --> 99:59:59.999
or even prevent their decline
associated with aging,

99:59:59.999 --> 99:59:59.999
or associated with stress.

99:59:59.999 --> 99:59:59.999
So the next question is,

99:59:59.999 --> 99:59:59.999
can we control Neurogenesis?

99:59:59.999 --> 99:59:59.999
The answer is yes.

99:59:59.999 --> 99:59:59.999
And we are now going to do a little quiz.

99:59:59.999 --> 99:59:59.999
So I'm going to give you a set
of behavior and acitivity

99:59:59.999 --> 99:59:59.999
and you tell me if you think
it will increase Neurogenesis

99:59:59.999 --> 99:59:59.999
or if it will decrease neurogenesis.

99:59:59.999 --> 99:59:59.999
Are we ready?

99:59:59.999 --> 99:59:59.999
Okay, let's go.

99:59:59.999 --> 99:59:59.999
So what about learning?
Increasing?

99:59:59.999 --> 99:59:59.999
Yes.

99:59:59.999 --> 99:59:59.999
So learning will increase the production
of these new neurons.

99:59:59.999 --> 99:59:59.999
How about stress?

99:59:59.999 --> 99:59:59.999
Yes, stress will decrease the production
of new neurons in the Hippocampus.

99:59:59.999 --> 99:59:59.999
How about sleep deprivation?

99:59:59.999 --> 99:59:59.999
Indeed, it will decrease Neurogenesis.

99:59:59.999 --> 99:59:59.999
How about sex?

99:59:59.999 --> 99:59:59.999
Oh wow!

99:59:59.999 --> 99:59:59.999
(Laughter)

99:59:59.999 --> 99:59:59.999
Yes, you are right, it will increase
the production of new neurons.

99:59:59.999 --> 99:59:59.999
However, it's all about balance here.

99:59:59.999 --> 99:59:59.999
We don't want to fall in a situation


99:59:59.999 --> 99:59:59.999
about too much sex 
leading to sleep deprivation.

99:59:59.999 --> 99:59:59.999
(Laughter)

99:59:59.999 --> 99:59:59.999
So how about getting older?

99:59:59.999 --> 99:59:59.999
So, neurogenesis' rate will decrease
as we get older,

99:59:59.999 --> 99:59:59.999
but this is still occuring.

99:59:59.999 --> 99:59:59.999
And then finally, how about running?

99:59:59.999 --> 99:59:59.999
So, I will let you judge
that one by yourself.

99:59:59.999 --> 99:59:59.999
So this is one of the first studies
that was carried out by one of my mentors,

99:59:59.999 --> 99:59:59.999
Prof. Rusty Gage for the Salk Institute,

99:59:59.999 --> 99:59:59.999
showing that the environment
can have an impact

99:59:59.999 --> 99:59:59.999
on the production of new neurons.

99:59:59.999 --> 99:59:59.999
And here you see a section
of the hippocampus of a mouse

99:59:59.999 --> 99:59:59.999
that had no running wheel in its cage.

99:59:59.999 --> 99:59:59.999
And the little black dots you see
are actually newborn neurons-to-be.

99:59:59.999 --> 99:59:59.999
And now, you see a section
of the hippocampus of a mouse

99:59:59.999 --> 99:59:59.999
that did have a running wheel in its cage.


99:59:59.999 --> 99:59:59.999
So you see the massive increase
in the black dots

99:59:59.999 --> 99:59:59.999
representing the new neurons-to-be.

99:59:59.999 --> 99:59:59.999
So activity impacts neurogenesis
but that's not all.

99:59:59.999 --> 99:59:59.999
What you eat will have an effect

99:59:59.999 --> 99:59:59.999
on the production of new neurons
in the hippocampus.

99:59:59.999 --> 99:59:59.999
So here we have a sample of diet --

99:59:59.999 --> 99:59:59.999
of nutrients that have been shown
to have efficacy.

99:59:59.999 --> 99:59:59.999
And I'm just going
to point a few out for you.

99:59:59.999 --> 99:59:59.999
So calorie restriction of 20%-30%
will increase neurogenesis.

99:59:59.999 --> 99:59:59.999
Intermittent fasting --

99:59:59.999 --> 99:59:59.999
so spaces of time between your meal --

99:59:59.999 --> 99:59:59.999
will increase neurogenesis.

99:59:59.999 --> 99:59:59.999
Intake of Flavonoids, which is contained
in dark chocolate or blueberries,

99:59:59.999 --> 99:59:59.999
which are contained
in dark chocolate or blueberries,

99:59:59.999 --> 99:59:59.999
will increase neurogenesis.

99:59:59.999 --> 99:59:59.999
Omega-3 fatty acids,

99:59:59.999 --> 99:59:59.999
present in fatty fish, like salmon,

99:59:59.999 --> 99:59:59.999
will increase the production
of these new neurons.

99:59:59.999 --> 99:59:59.999
Conversely, a diet rich
in High Saturated Fat,

99:59:59.999 --> 99:59:59.999
will have a negative impact
on neurogenesis.

99:59:59.999 --> 99:59:59.999
Ethanol --

99:59:59.999 --> 99:59:59.999
intake of alcohol --

99:59:59.999 --> 99:59:59.999
will decrease neurogenesis.

99:59:59.999 --> 99:59:59.999
However, not everything is lost --

99:59:59.999 --> 99:59:59.999
Resveratrol, which is
contained in red wine,

99:59:59.999 --> 99:59:59.999
has been shown to promote the survival
of these new neurons.

99:59:59.999 --> 99:59:59.999
So next time you are at a dinner party,

99:59:59.999 --> 99:59:59.999
you might want to reach for this possibly
"Neurogenesis-neutral" drink.

99:59:59.999 --> 99:59:59.999
(Laughter)

99:59:59.999 --> 99:59:59.999
And then finally, 
let me point out the last one --

99:59:59.999 --> 99:59:59.999
a quick one.

99:59:59.999 --> 99:59:59.999
So Japanese groups
are fascinated with food textures,

99:59:59.999 --> 99:59:59.999
and they have shown that actually
soft diet impairs neurogenesis,

99:59:59.999 --> 99:59:59.999
as opposed to food
that requires mastication,

99:59:59.999 --> 99:59:59.999
chewing, or crunchy food.

99:59:59.999 --> 99:59:59.999
So all of this data, where we need to look
at the cellular level,

99:59:59.999 --> 99:59:59.999
have been generated using animal models.

99:59:59.999 --> 99:59:59.999
But this diet has also been given
to human participants,

99:59:59.999 --> 99:59:59.999
and what we could see

99:59:59.999 --> 99:59:59.999
is that the diet modulates memory and mood
in the same way it modulates neurogenesis.

99:59:59.999 --> 99:59:59.999
Such as, calorie restriction will improve
memory capacity,

99:59:59.999 --> 99:59:59.999
whereas a high-fat diet will exacerbate
symptoms of depression.

99:59:59.999 --> 99:59:59.999
As opposed to Omega-3 fatty acids,
which increase neurogenesis,

99:59:59.999 --> 99:59:59.999
and also help to decrease
the symptoms of depression.

99:59:59.999 --> 99:59:59.999
So we think that the effect of diet
on mental health,

99:59:59.999 --> 99:59:59.999
on memory and mood,

99:59:59.999 --> 99:59:59.999
is actually mediated by the production
of the new neurons in the hippocampus.

99:59:59.999 --> 99:59:59.999
And it is not only what you eat,
but it's also the texture

99:59:59.999 --> 99:59:59.999
but it's also the texture
of the food when you eat it,

99:59:59.999 --> 99:59:59.999
and the amount you eat.

99:59:59.999 --> 99:59:59.999
On our side --

99:59:59.999 --> 99:59:59.999
neuroscientists interested
in neurogenesis --

99:59:59.999 --> 99:59:59.999
we need to understand better the function
of these new neurons,

99:59:59.999 --> 99:59:59.999
and how we can control their survival
and their production.

99:59:59.999 --> 99:59:59.999
We also need to find how to protect
the neurogenesis of Robert's patients.


99:59:59.999 --> 99:59:59.999
And on your side --

99:59:59.999 --> 99:59:59.999
I leave you in charge
of your Neurogenesis.

99:59:59.999 --> 99:59:59.999
Thank you.

99:59:59.999 --> 99:59:59.999
(Applause)

99:59:59.999 --> 99:59:59.999
Margaret Heffernan: 
Fantastic research, Sandrine!

99:59:59.999 --> 99:59:59.999
Now, I told you you changed my life --

99:59:59.999 --> 99:59:59.999
I now eat a lot of blueberries.

99:59:59.999 --> 99:59:59.999
I'm really interested
in the running thing --

99:59:59.999 --> 99:59:59.999
Do I have to run?

99:59:59.999 --> 99:59:59.999
Or is it really just about


99:59:59.999 --> 99:59:59.999
aerobic exercise
getting oxygen to the brain?

99:59:59.999 --> 99:59:59.999
Could it be any kind of vigorous exercise?

99:59:59.999 --> 99:59:59.999
Sandrine Thuret: So for the moment,

99:59:59.999 --> 99:59:59.999
we can't really say 
if it's just the running itself,

99:59:59.999 --> 99:59:59.999
but we think that anything that indeed
will increase the production --

99:59:59.999 --> 99:59:59.999
of moving the blood flow to the brain --

99:59:59.999 --> 99:59:59.999
should be beneficial.

99:59:59.999 --> 99:59:59.999
MH: Right, so I don't have
to get a running wheel in my office?

99:59:59.999 --> 99:59:59.999
ST: No, you don't!

99:59:59.999 --> 99:59:59.999
(Laughter)

99:59:59.999 --> 99:59:59.999
MH: Oh, what a relief!

99:59:59.999 --> 99:59:59.999
Okay, that's wonderful.

99:59:59.999 --> 99:59:59.999
Thank you so much.

99:59:59.999 --> 99:59:59.999
ST: Thank you, thank you.

99:59:59.999 --> 99:59:59.999
(Applause)