0:00:01.936,0:00:06.317
Can we, as adults, grow new nerve cells?

0:00:07.150,0:00:10.237
There's still some confusion[br]about that question,

0:00:10.261,0:00:12.871
as this is a fairly new field of research.

0:00:13.569,0:00:16.928
For example, I was talking[br]to one of my colleagues, Robert,

0:00:16.952,0:00:18.260
who is an oncologist,

0:00:18.284,0:00:19.585
and he was telling me,

0:00:20.014,0:00:21.769
"Sandrine, this is puzzling.

0:00:21.793,0:00:26.107
Some of my patients that have been told[br]they are cured of their cancer

0:00:26.131,0:00:28.528
still develop symptoms of depression."

0:00:29.520,0:00:30.815
And I responded to him,

0:00:30.839,0:00:33.179
"Well, from my point of view[br]that makes sense.

0:00:33.203,0:00:37.741
The drug you give to your patients[br]that stops the cancer cells multiplying

0:00:37.765,0:00:42.868
also stops the newborn neurons[br]being generated in their brain."

0:00:43.820,0:00:46.606
And then Robert looked at me[br]like I was crazy and said,

0:00:46.630,0:00:48.812
"But Sandrine, these are adult patients --

0:00:48.836,0:00:51.408
adults do not grow new nerve cells."

0:00:52.543,0:00:56.209
And much to his surprise, I said,[br]"Well actually, we do."

0:00:57.098,0:01:01.924
And this is a phenomenon[br]that we call neurogenesis.

0:01:01.948,0:01:03.138
[Neurogenesis]

0:01:03.162,0:01:06.932
Now Robert is not a neuroscientist,

0:01:06.956,0:01:11.581
and when he went to medical school[br]he was not taught what we know now --

0:01:11.605,0:01:15.344
that the adult brain[br]can generate new nerve cells.

0:01:17.217,0:01:21.587
So Robert, you know,[br]being the good doctor that he is,

0:01:21.611,0:01:23.310
wanted to come to my lab

0:01:23.334,0:01:26.158
to understand the topic[br]a little bit better.

0:01:26.881,0:01:29.136
And I took him for a tour

0:01:29.160,0:01:32.073
of one of the most exciting[br]parts of the brain

0:01:32.097,0:01:34.270
when it comes to neurogenesis --

0:01:34.294,0:01:36.382
and this is the hippocampus.

0:01:37.080,0:01:40.932
So this is this gray structure[br]in the center of the brain.

0:01:41.613,0:01:44.035
And what we've known already[br]for very long,

0:01:44.059,0:01:48.824
is that this is important for learning,[br]memory, mood and emotion.

0:01:49.343,0:01:52.390
However, what we[br]have learned more recently

0:01:52.414,0:01:57.072
is that this is one of the unique[br]structures of the adult brain

0:01:57.096,0:01:59.746
where new neurons can be generated.

0:02:00.405,0:02:02.716
And if we slice through the hippocampus

0:02:02.740,0:02:04.008
and zoom in,

0:02:04.032,0:02:06.833
what you actually see here in blue

0:02:06.857,0:02:11.430
is a newborn neuron[br]in an adult mouse brain.

0:02:12.769,0:02:15.824
So when it comes to the human brain --

0:02:15.848,0:02:19.380
my colleague Jonas Frisén[br]from the Karolinska Institutet,

0:02:19.404,0:02:25.144
has estimated that we produce[br]700 new neurons per day

0:02:25.168,0:02:26.366
in the hippocampus.

0:02:27.183,0:02:28.858
You might think this is not much,

0:02:28.882,0:02:31.271
compared to the billions[br]of neurons we have.

0:02:31.644,0:02:34.715
But by the time we turn 50,

0:02:34.739,0:02:39.415
we will have all exchanged the neurons[br]we were born with in that structure

0:02:39.439,0:02:41.654
with adult-born neurons.

0:02:43.248,0:02:48.284
So why are these new neurons important[br]and what are their functions?

0:02:49.324,0:02:53.022
First, we know that they're important[br]for learning and memory.

0:02:53.046,0:02:54.563
And in the lab we have shown

0:02:54.587,0:02:57.823
that if we block the ability[br]of the adult brain

0:02:57.847,0:03:00.407
to produce new neurons in the hippocampus,

0:03:00.431,0:03:02.947
then we block certain memory abilities.

0:03:03.721,0:03:10.633
And this is especially new and true[br]for spatial recognition --

0:03:10.657,0:03:13.455
so like, how you navigate[br]your way in the city.

0:03:14.181,0:03:15.659
We are still learning a lot,

0:03:15.683,0:03:18.746
and neurons are not only important[br]for memory capacity,

0:03:18.770,0:03:21.673
but also for the quality of the memory.

0:03:21.697,0:03:25.742
And they will have been helpful[br]to add time to our memory

0:03:25.766,0:03:30.448
and they will help differentiate[br]very similar memories, like:

0:03:30.472,0:03:32.552
how do you find your bike

0:03:32.576,0:03:36.092
that you park at the station[br]every day in the same area,

0:03:36.116,0:03:38.258
but in a slightly different position?

0:03:40.068,0:03:42.552
And more interesting[br]to my colleague Robert

0:03:42.576,0:03:47.438
is the research we have been doing[br]on neurogenesis and depression.

0:03:48.010,0:03:49.948
So in an animal model of depression,

0:03:49.972,0:03:53.976
we have seen that we have[br]a lower level of neurogenesis.

0:03:54.500,0:03:56.743
And if we give antidepressants,

0:03:56.767,0:04:00.221
then we increase the production[br]of these newborn neurons,

0:04:00.245,0:04:03.388
and we decrease[br]the symptoms of depression,

0:04:03.412,0:04:08.872
establishing a clear link[br]between neurogenesis and depression.

0:04:09.191,0:04:13.500
But moreover, if you[br]just block neurogenesis,

0:04:13.524,0:04:16.357
then you block the efficacy[br]of the antidepressant.

0:04:17.714,0:04:19.477
So by then, Robert had understood

0:04:19.501,0:04:23.199
that very likely his patients[br]were suffering from depression

0:04:23.223,0:04:25.818
even after being cured of their cancer,

0:04:25.842,0:04:30.223
because the cancer drug had stopped[br]newborn neurons from being generated.

0:04:30.247,0:04:33.875
And it will take time[br]to generate new neurons

0:04:33.899,0:04:36.105
that reach normal functions.

0:04:37.780,0:04:42.189
So, collectively, now we think[br]we have enough evidence

0:04:42.213,0:04:45.928
to say that neurogenesis[br]is a target of choice

0:04:45.952,0:04:49.566
if we want to improve[br]memory formation or mood,

0:04:49.590,0:04:53.153
or even prevent the decline[br]associated with aging,

0:04:53.177,0:04:55.311
or associated with stress.

0:04:56.288,0:04:58.019
So the next question is:

0:04:58.043,0:05:00.217
can we control neurogenesis?

0:05:01.066,0:05:02.257
The answer is yes.

0:05:02.860,0:05:05.423
And we are now going to do a little quiz.

0:05:06.201,0:05:09.382
I'm going to give you a set[br]of behaviors and activities,

0:05:09.406,0:05:14.090
and you tell me if you think[br]they will increase neurogenesis

0:05:14.114,0:05:16.280
or if they will decrease neurogenesis.

0:05:16.804,0:05:17.963
Are we ready?

0:05:18.550,0:05:19.709
OK, let's go.

0:05:20.034,0:05:21.621
So what about learning?

0:05:22.521,0:05:23.701
Increasing?

0:05:23.725,0:05:24.884
Yes.

0:05:24.908,0:05:28.694
Learning will increase the production[br]of these new neurons.

0:05:28.718,0:05:30.034
How about stress?

0:05:31.431,0:05:36.168
Yes, stress will decrease the production[br]of new neurons in the hippocampus.

0:05:36.192,0:05:37.804
How about sleep deprivation?

0:05:39.375,0:05:42.074
Indeed, it will decrease neurogenesis.

0:05:42.098,0:05:43.319
How about sex?

0:05:44.414,0:05:45.566
Oh, wow!

0:05:45.590,0:05:46.857
(Laughter)

0:05:46.881,0:05:50.634
Yes, you are right, it will increase[br]the production of new neurons.

0:05:50.658,0:05:52.810
However, it's all about balance here.

0:05:52.834,0:05:55.047
We don't want to fall in a situation --

0:05:55.071,0:05:56.999
(Laughter)

0:05:57.023,0:05:59.857
about too much sex[br]leading to sleep deprivation.

0:05:59.881,0:06:02.110
(Laughter)

0:06:02.753,0:06:04.944
How about getting older?

0:06:07.645,0:06:11.328
So the neurogenesis rate[br]will decrease as we get older,

0:06:11.352,0:06:13.098
but it is still occurring.

0:06:14.042,0:06:16.233
And then finally, how about running?

0:06:17.912,0:06:20.721
I will let you judge that one by yourself.

0:06:21.563,0:06:23.359
So this is one of the first studies

0:06:23.383,0:06:27.786
that was carried out by one of my mentors,[br]Rusty Gage from the Salk Institute,

0:06:27.810,0:06:30.084
showing that the environment[br]can have an impact

0:06:30.108,0:06:31.997
on the production of new neurons.

0:06:32.021,0:06:36.275
And here you see a section[br]of the hippocampus of a mouse

0:06:36.299,0:06:38.544
that had no running wheel in its cage.

0:06:38.568,0:06:42.603
And the little black dots you see[br]are actually newborn neurons-to-be.

0:06:43.246,0:06:48.384
And now, you see a section[br]of the hippocampus of a mouse

0:06:48.408,0:06:51.004
that had a running wheel in its cage.

0:06:51.028,0:06:52.551
So you see the massive increase

0:06:52.575,0:06:55.388
of the black dots representing[br]the new neurons-to-be.

0:06:56.819,0:07:00.612
So activity impacts neurogenesis,[br]but that's not all.

0:07:01.639,0:07:04.286
What you eat will have an effect

0:07:04.310,0:07:07.224
on the production of new neurons[br]in the hippocampus.

0:07:07.248,0:07:10.208
So here we have a sample of diet --

0:07:10.232,0:07:13.509
of nutrients that have been shown[br]to have efficacy.

0:07:13.973,0:07:16.568
And I'm just going[br]to point a few out to you:

0:07:16.592,0:07:21.686
Calorie restriction of 20 to 30 percent[br]will increase neurogenesis.

0:07:22.128,0:07:25.610
Intermittent fasting --[br]spacing the time between your meals --

0:07:25.634,0:07:27.773
will increase neurogenesis.

0:07:27.797,0:07:29.120
Intake of flavonoids,

0:07:29.144,0:07:32.147
which are contained[br]in dark chocolate or blueberries,

0:07:32.171,0:07:33.994
will increase neurogenesis.

0:07:34.355,0:07:35.861
Omega-3 fatty acids,

0:07:35.885,0:07:38.096
present in fatty fish, like salmon,

0:07:38.120,0:07:40.558
will increase the production[br]of these new neurons.

0:07:41.502,0:07:45.603
Conversely, a diet rich[br]in high saturated fat

0:07:45.627,0:07:48.367
will have a negative impact[br]on neurogenesis.

0:07:49.232,0:07:53.414
Ethanol -- intake of alcohol --[br]will decrease neurogenesis.

0:07:53.981,0:07:56.703
However, not everything is lost;

0:07:56.727,0:07:59.779
resveratrol, which is[br]contained in red wine,

0:07:59.803,0:08:03.294
has been shown to promote[br]the survival of these new neurons.

0:08:03.708,0:08:05.574
So next time you are at a dinner party,

0:08:05.598,0:08:09.602
you might want to reach for this possibly[br]"neurogenesis-neutral" drink.

0:08:09.909,0:08:12.042
(Laughter)

0:08:12.066,0:08:14.567
And then finally,[br]let me point out the last one --

0:08:14.591,0:08:15.749
a quirky one.

0:08:15.773,0:08:19.668
So Japanese groups are fascinated[br]with food textures,

0:08:19.692,0:08:24.995
and they have shown that actually[br]soft diet impairs neurogenesis,

0:08:25.019,0:08:29.740
as opposed to food that requires[br]mastication -- chewing -- or crunchy food.

0:08:30.827,0:08:32.620
So all of this data,

0:08:32.644,0:08:35.225
where we need to look[br]at the cellular level,

0:08:35.249,0:08:37.756
has been generated using animal models.

0:08:38.470,0:08:42.851
But this diet has also been given[br]to human participants,

0:08:42.875,0:08:49.033
and what we could see is that[br]the diet modulates memory and mood

0:08:49.057,0:08:52.541
in the same direction[br]as it modulates neurogenesis,

0:08:52.565,0:08:57.322
such as: calorie restriction[br]will improve memory capacity,

0:08:57.346,0:09:02.445
whereas a high-fat diet will exacerbate[br]symptoms of depression --

0:09:02.469,0:09:06.333
as opposed to omega-3 fatty acids,[br]which increase neurogenesis,

0:09:06.357,0:09:10.540
and also help to decrease[br]the symptoms of depression.

0:09:11.643,0:09:16.460
So we think that the effect of diet

0:09:16.484,0:09:20.079
on mental health, on memory and mood,

0:09:20.103,0:09:24.575
is actually mediated by the production[br]of the new neurons in the hippocampus.

0:09:24.994,0:09:26.914
And it's not only what you eat,

0:09:26.938,0:09:30.003
but it's also the texture[br]of the food, when you eat it

0:09:30.027,0:09:31.851
and how much of it you eat.

0:09:33.841,0:09:37.874
On our side -- neuroscientists[br]interested in neurogenesis --

0:09:37.898,0:09:41.563
we need to understand better[br]the function of these new neurons,

0:09:41.587,0:09:45.571
and how we can control their survival[br]and their production.

0:09:45.896,0:09:50.435
We also need to find a way to protect[br]the neurogenesis of Robert's patients.

0:09:51.271,0:09:52.648
And on your side --

0:09:52.672,0:09:55.102
I leave you in charge[br]of your neurogenesis.

0:09:55.691,0:09:56.849
Thank you.

0:09:56.873,0:10:02.832
(Applause)

0:10:02.856,0:10:05.188
Margaret Heffernan:[br]Fantastic research, Sandrine.

0:10:05.212,0:10:07.457
Now, I told you you changed my life --

0:10:07.481,0:10:09.259
I now eat a lot of blueberries.

0:10:09.283,0:10:10.830
Sandrine Thuret: Very good.

0:10:11.528,0:10:13.972
MH: I'm really interested[br]in the running thing.

0:10:14.869,0:10:16.520
Do I have to run?

0:10:17.368,0:10:20.010
Or is it really just[br]about aerobic exercise,

0:10:20.034,0:10:21.639
getting oxygen to the brain?

0:10:21.663,0:10:23.798
Could it be any kind of vigorous exercise?

0:10:24.101,0:10:25.838
ST: So for the moment,

0:10:25.862,0:10:29.102
we can't really say[br]if it's just the running itself,

0:10:29.126,0:10:34.163
but we think that anything that indeed[br]will increase the production --

0:10:34.187,0:10:37.267
or moving the blood flow to the brain,

0:10:37.291,0:10:38.893
should be beneficial.

0:10:39.353,0:10:41.980
MH: So I don't have to get[br]a running wheel in my office?

0:10:42.004,0:10:43.167
ST: No, you don't!

0:10:43.191,0:10:45.284
MH: Oh, what a relief! That's wonderful.

0:10:45.308,0:10:47.061
Sandrine Thuret, thank you so much.

0:10:47.085,0:10:48.284
ST: Thank you, Margaret.

0:10:48.308,0:10:50.976
(Applause)