0:00:02.134,0:00:06.615
Can we, as adults, grow new nerve cells?

0:00:07.358,0:00:10.473
There's still some confusion [br]about that question,

0:00:10.473,0:00:13.211
as this is a fairly new field of research.

0:00:13.743,0:00:16.994
For example, I was talking[br]to one of my colleagues, Robert --

0:00:16.994,0:00:18.487
who is an oncologist --

0:00:18.487,0:00:20.173
and he was telling me,

0:00:20.173,0:00:22.102
"Sandrine, this is puzzling,[br]

0:00:22.102,0:00:26.235
some of my patients that have been told[br]they are cured of their cancer,

0:00:26.235,0:00:28.863
still develop symptoms of depression."

0:00:29.695,0:00:30.999
And I responded to him,

0:00:30.999,0:00:33.203
"Well, from my point of view [br]that makes sense.

0:00:33.203,0:00:38.054
The drug you give to your patients[br]that stops the cancer cells multiplying,

0:00:38.054,0:00:43.010
also stops the newborn neurons[br]being generated in their brain."

0:00:43.997,0:00:46.688
And then Robert looked at me [br]like I was crazy and said,

0:00:46.688,0:00:49.252
"But Sandrine, these are adult patients --

0:00:49.252,0:00:51.606
adults do not grow new nerve cells."

0:00:52.494,0:00:56.720
And much to his surprise, I said,[br]"Well actually, we do."

0:00:57.161,0:01:01.665
And this is a phenomenon [br]that we call neurogenesis.

0:01:02.061,0:01:03.316
[Neurogenesis]

0:01:03.586,0:01:07.124
Now Robert is not a neuroscientist,

0:01:07.124,0:01:11.643
and when he went to medical school[br]he was not taught what we know now --

0:01:11.643,0:01:15.126
that the adult brain [br]can generate new nerve cells.

0:01:17.389,0:01:19.944
So Robert --[br]you know --

0:01:19.944,0:01:21.962
being a good doctor that he is,

0:01:21.962,0:01:23.620
wanted to come to my lab

0:01:23.620,0:01:26.480
to understand the topic[br]a little bit better.

0:01:27.070,0:01:29.429
And I took him for a tour

0:01:29.429,0:01:32.113
of one the of most exciting[br]parts of the brain

0:01:32.113,0:01:34.440
when it comes to neurogenesis --

0:01:34.440,0:01:36.661
and this is the hippocampus.

0:01:37.310,0:01:40.932
So this is this gray structure[br]in the center of the brain.

0:01:41.838,0:01:44.289
And what we've know since[br]already very long,

0:01:44.289,0:01:48.824
is that this is important [br]for learning, memory, mood and emotion.

0:01:49.477,0:01:52.471
However, what we[br]have learned more recently,

0:01:52.471,0:01:57.048
is that this is one of the unique[br]structures of the adult brain

0:01:57.048,0:01:59.933
where new neurons can be generated.

0:02:00.483,0:02:02.763
And if we slide[br]through the hippocampus,

0:02:02.763,0:02:04.131
and zoom in,

0:02:04.131,0:02:06.754
what you actually see here in blue

0:02:06.754,0:02:11.430
is a newborn neuron[br]in an adult mouse brain.

0:02:12.812,0:02:16.130
So when it comes to the human brain,

0:02:16.130,0:02:19.538
my colleague Jonas Frisén[br]from the Karolinska Institute,

0:02:19.538,0:02:25.168
has estimated that we produce[br]700 new neurons per day

0:02:25.168,0:02:26.763
in the hippocampus.

0:02:27.370,0:02:29.079
So you might think this is not much

0:02:29.079,0:02:31.818
according to the billions[br]of neurons we have,

0:02:31.818,0:02:35.079
but by the time we will turn 50,

0:02:35.079,0:02:39.633
we will have all exchanged the neurons[br]we were born with in that structure

0:02:39.633,0:02:41.654
with adult-born neurons.

0:02:43.438,0:02:46.628
So why are these new neurons important

0:02:46.628,0:02:48.728
and what are their functions?

0:02:49.568,0:02:53.155
So first, we know that they're important[br]for learning and memory.

0:02:53.155,0:02:54.715
And in the lab we have shown

0:02:54.715,0:02:58.052
that if we block the ability[br]of the adult brain

0:02:58.052,0:03:00.648
to produce new neurons[br]in the hippocampus,

0:03:00.648,0:03:03.148
then we block certain memory abilities.

0:03:04.341,0:03:10.817
And this is especially new and true[br]for spacial recognition --

0:03:10.829,0:03:13.638
so like, how you navigate[br]your way in the city.

0:03:14.412,0:03:16.011
So we are still learning a lot,

0:03:16.011,0:03:19.058
and they are not only important[br]for memory capacity,

0:03:19.058,0:03:21.427
but also for the quality of the memory.

0:03:21.912,0:03:25.833
And they will have been helpful[br]to add time to our memory

0:03:25.842,0:03:29.411
and they will help differentiate[br]very similar memories.

0:03:29.941,0:03:32.664
Like, how do you find your bike[br]

0:03:32.664,0:03:36.330
that you park at the station[br]everyday in the same area

0:03:36.330,0:03:38.723
but in a slightly different position?

0:03:40.181,0:03:42.794
And more interesting [br]to my colleague Robert,

0:03:42.794,0:03:47.438
is the research we have been doing[br]on neurogenesis and depression.

0:03:48.010,0:03:50.097
So in an animal model of depression,

0:03:50.097,0:03:54.640
we have seen that we have[br]a lower level of neurogenesis,

0:03:54.640,0:03:56.767
and if we give antidepressants,

0:03:56.767,0:04:00.245
then we increase the production[br]of these newborn neurons,

0:04:00.245,0:04:03.596
and we decrease[br]the symptoms of depression,

0:04:03.596,0:04:08.872
establishing a clear link [br]between neurogenesis and depression.

0:04:09.422,0:04:13.613
But moreover, if you [br]just block neurogenesis,

0:04:13.613,0:04:16.720
then you block the efficacy[br]of the antidepressant.

0:04:18.071,0:04:19.830
So by then, Robert had understood

0:04:19.830,0:04:23.515
that very likely his patients[br]were suffering from depression

0:04:23.515,0:04:25.972
even after being cured of their cancer

0:04:25.972,0:04:30.358
because the cancer drug had stopped[br]the newborn neurons to be generated --

0:04:30.358,0:04:31.934
and it will take time

0:04:31.934,0:04:36.269
to generate new neurons[br]that reach normal functions.

0:04:37.993,0:04:40.723
So, collectively, now,

0:04:40.723,0:04:43.096
we think we have enough evidence to say

0:04:43.096,0:04:46.096
that neurogenesis is a target of choice

0:04:46.096,0:04:49.729
if we want to improve[br]memory information or mood,

0:04:49.729,0:04:53.264
or even prevent their decline[br]associated with aging,

0:04:53.264,0:04:55.311
or associated with stress.

0:04:56.545,0:04:58.211
So the next question is,

0:04:58.211,0:05:00.436
can we control neurogenesis?

0:05:01.328,0:05:02.744
The answer is yes.

0:05:03.278,0:05:05.995
And we are now going to do a little quiz.

0:05:06.506,0:05:09.549
So I'm going to give you a set[br]of behaviors and activities,

0:05:09.549,0:05:14.114
and you tell me if you think[br]they will increase neurogenesis

0:05:14.114,0:05:16.612
or if it will decrease neurogenesis.

0:05:17.070,0:05:18.695
Are we ready?

0:05:18.695,0:05:19.973
Okay, let's go.

0:05:20.483,0:05:22.776
So what about learning?

0:05:22.776,0:05:23.827
Increasing?

0:05:23.827,0:05:24.709
Yes.

0:05:25.180,0:05:28.964
So learning will increase[br]the production of these new neurons.

0:05:29.330,0:05:31.732
How about stress?

0:05:31.732,0:05:36.067
Yes, stress will decrease the production[br]of new neurons in the hippocampus.

0:05:36.247,0:05:37.663
How about sleep deprivation?

0:05:39.733,0:05:42.232
Indeed, it will decrease neurogenesis.

0:05:42.472,0:05:43.540
How about sex?

0:05:44.678,0:05:45.626
Oh wow!

0:05:45.626,0:05:46.856
(Laughter)

0:05:47.325,0:05:50.529
Yes, you are right, it will increase[br]the production of new neurons.

0:05:50.854,0:05:53.060
However, it's all about balance here.

0:05:53.060,0:05:54.285
We don't want to fall in a situation --

0:05:54.285,0:05:57.285
(Laughter)

0:05:57.285,0:06:00.041
about too much sex [br]leading to sleep deprivation.

0:06:00.041,0:06:01.256
(Laughter)

0:06:02.997,0:06:05.157
So how about getting older?

0:06:07.757,0:06:11.518
So neurogenesis' rate[br]will decrease as we get older,

0:06:11.518,0:06:13.423
but it is still occurring.

0:06:14.328,0:06:16.789
And then finally, how about running?

0:06:18.206,0:06:21.015
So, I will let you judge[br]that one by yourself.

0:06:21.921,0:06:23.685
So this is one of the first studies[br]

0:06:23.685,0:06:26.251
that was carried out[br]by one of my mentors --

0:06:26.251,0:06:28.033
Rusty Gage from the Salk Institute --

0:06:28.033,0:06:30.341
showing that the environment[br]can have an impact

0:06:30.341,0:06:32.029
on the production of new neurons.

0:06:32.207,0:06:36.490
And here you see a section[br]of the hippocampus of a mouse

0:06:36.490,0:06:38.466
that had no running wheel in its cage.

0:06:38.940,0:06:42.603
And the little black dots you see[br]are actually newborn neurons-to-be.

0:06:43.445,0:06:48.694
And now, you see a section[br]of the hippocampus of a mouse

0:06:48.694,0:06:51.070
that had running wheel in its cage.

0:06:51.362,0:06:52.886
So you see the massive increase

0:06:52.895,0:06:55.708
of the black dots representing[br]the new neurons-to-be.

0:06:56.819,0:07:00.557
So activity impacts neurogenesis[br]but that's not all.

0:07:01.695,0:07:04.255
What you eat will have an effect

0:07:04.255,0:07:07.053
on the production of new neurons[br]in the hippocampus.

0:07:07.360,0:07:10.383
So here we have a sample of diet --

0:07:10.383,0:07:13.730
of nutrients that have been shown[br]to have efficacy.

0:07:14.140,0:07:16.787
And I'm just going[br]to point a few out to you.

0:07:17.089,0:07:21.663
So calorie restriction of 20% to 30%[br]will increase neurogenesis.

0:07:22.128,0:07:23.542
Intermittent fasting --

0:07:23.544,0:07:25.801
so spacings of time between your meals --

0:07:25.801,0:07:27.643
will increase neurogenesis.

0:07:27.932,0:07:29.420
Intake of flavonoids,

0:07:29.420,0:07:32.540
which are contained[br]in dark chocolate or blueberries,

0:07:32.540,0:07:34.108
will increase neurogenesis.

0:07:34.387,0:07:36.013
Omega-3 fatty acids,

0:07:36.013,0:07:38.180
present in fatty fish, like salmon,

0:07:38.184,0:07:40.622
will increase the production[br]of these new neurons.

0:07:41.701,0:07:45.611
Conversely, a diet rich[br]in high saturated fat

0:07:45.611,0:07:48.351
will have a negative impact[br]on neurogenesis.

0:07:49.085,0:07:51.836
Ethanol --[br]intake of alcohol --

0:07:51.836,0:07:53.782
will decrease neurogenesis.

0:07:54.100,0:07:56.735
However, not everything is lost --

0:07:56.735,0:07:59.857
resveratrol, which is[br]contained in red wine,

0:07:59.857,0:08:03.294
has been shown to promote[br]the survival of these new neurons.

0:08:03.852,0:08:05.743
So next time you are at a dinner party,

0:08:05.743,0:08:09.285
you might want to reach for this possibly[br]"neurogenesis-neutral" drink.

0:08:09.909,0:08:11.325
(Laughter)

0:08:12.327,0:08:14.904
And then finally, [br]let me point out the last one --

0:08:14.904,0:08:16.052
a quick one.

0:08:16.052,0:08:19.995
So Japanese groups[br]are fascinated with food textures,

0:08:19.995,0:08:25.143
and they have shown that actually[br]soft diet impairs neurogenesis,

0:08:25.143,0:08:28.186
as opposed to food[br]that requires mastication --

0:08:28.186,0:08:30.351
chewing, or crunchy food.

0:08:31.018,0:08:32.881
So all of this data,

0:08:32.881,0:08:35.304
where we need to look[br]at the cellular level,

0:08:35.304,0:08:38.168
has been generated using animal models.

0:08:38.588,0:08:42.999
But this diet has also been given[br]to human participants,

0:08:42.999,0:08:44.525
and what we could see

0:08:44.525,0:08:49.098
is that the diet modulates[br]memory and mood

0:08:49.098,0:08:52.516
in the same direction[br]as it modulates neurogenesis.

0:08:52.846,0:08:57.390
Such as, calorie restriction[br]will improve memory capacity,

0:08:57.390,0:09:02.614
whereas a high-fat diet will exacerbate[br]symptoms of depression --

0:09:02.614,0:09:06.451
as opposed to omega-3 fatty acids,[br]which increase neurogenesis,

0:09:06.451,0:09:11.024
and also help to decrease[br]the symptoms of depression.

0:09:12.356,0:09:16.362
So we think that the effect of diet

0:09:16.362,0:09:20.284
on mental health, on memory and mood,

0:09:20.284,0:09:24.575
is actually mediated by the production[br]of the new neurons in the hippocampus.

0:09:24.940,0:09:27.071
And it is not only what you eat,

0:09:27.071,0:09:30.097
but it's also the texture[br]of the food when you eat it,

0:09:30.097,0:09:32.256
and how much of it you eat.

0:09:34.135,0:09:35.190
On our side --

0:09:35.190,0:09:38.103
neuroscientists interested[br]in neurogenesis --

0:09:38.103,0:09:41.436
we need to understand better[br]the function of these new neurons,

0:09:41.436,0:09:45.453
and how we can control their survival[br]and their production.

0:09:46.046,0:09:50.435
We also need to find a way to protect[br]the neurogenesis of Robert's patients.

0:09:51.271,0:09:52.689
And on your side --

0:09:52.689,0:09:55.073
I leave you in charge[br]with your neurogenesis.

0:09:55.938,0:09:56.843
Thank you.

0:09:57.168,0:09:58.585
(Applause)

0:10:02.902,0:10:05.243
Margaret Heffernan: [br]Fantastic research, Sandrine!

0:10:05.243,0:10:07.317
Now, I told you you changed my life --

0:10:07.317,0:10:09.221
I now eat a lot of blueberries.

0:10:12.075,0:10:15.490
I'm really interested[br]in the running thing --

0:10:15.490,0:10:16.999
Do I have to run?

0:10:17.601,0:10:19.473
Or is it really just about[br]

0:10:19.473,0:10:22.007
aerobic exercise[br]getting oxygen to the brain?

0:10:22.007,0:10:24.158
Could it be any kind of vigorous exercise?

0:10:24.451,0:10:26.287
Sandrine Thuret: So for the moment,

0:10:26.287,0:10:29.504
we can't really say [br]if it's just the running itself,

0:10:29.504,0:10:34.124
but we think that anything that indeed[br]will increase the production --

0:10:34.124,0:10:37.891
of moving the blood flow to the brain --

0:10:37.891,0:10:39.019
should be beneficial.

0:10:39.019,0:10:41.970
MH: Right, so I don't have[br]to get a running wheel in my office?

0:10:41.970,0:10:43.386
ST: No, you don't!

0:10:43.386,0:10:44.742
MH: Oh, what a relief!

0:10:44.742,0:10:46.277
That's wonderful.

0:10:46.277,0:10:47.229
Thank you so much.

0:10:47.229,0:10:48.229
ST: Thank you, Margaret.

0:10:48.229,0:10:49.473
Thank you.

0:10:49.473,0:10:50.976
(Applause)