0:12
Can we, as adults, grow new nerve cells? There's still some confusion about that question, as this is a fairly new field of research. For example, I was talking to one of my colleagues, Robert, who is an oncologist, and he was telling me, "Sandrine, this is puzzling. Some of my patients that have been told they are cured of their cancer still develop symptoms of depression." And I responded to him, "Well, from my point of view that makes sense. The drug you give to your patients that stops the cancer cells multiplying also stops the newborn neurons being generated in their brain." And then Robert looked at me like I was crazy and said, "But Sandrine, these are adult patients -- adults do not grow new nerve cells." And much to his surprise, I said, "Well actually, we do." And this is a phenomenon that we call neurogenesis.
1:14
Now Robert is not a neuroscientist, and when he went to medical school he was not taught what we know now -- that the adult brain can generate new nerve cells. So Robert, you know, being the good doctor that he is, wanted to come to my lab to understand the topic a little bit better. And I took him for a tour of one of the most exciting parts of the brain when it comes to neurogenesis -- and this is the hippocampus. So this is this gray structure in the center of the brain. And what we've known already for very long, is that this is important for learning, memory, mood and emotion. However, what we have learned more recently is that this is one of the unique structures of the adult brain where new neurons can be generated. And if we slice through the hippocampus and zoom in, what you actually see here in blue is a newborn neuron in an adult mouse brain. So when it comes to the human brain -- my colleague Jonas Frisén from the Karolinska Institutet, has estimated that we produce 700 new neurons per day in the hippocampus. You might think this is not much, compared to the billions of neurons we have. But by the time we turn 50, we will have all exchanged the neurons we were born with in that structure with adult-born neurons.
2:54
So why are these new neurons important and what are their functions? First, we know that they're important for learning and memory. And in the lab we have shown that if we block the ability of the adult brain to produce new neurons in the hippocampus, then we block certain memory abilities. And this is especially new and true for spatial recognition -- so like, how you navigate your way in the city.
3:25
We are still learning a lot, and neurons are not only important for memory capacity, but also for the quality of the memory. And they will have been helpful to add time to our memory and they will help differentiate very similar memories, like: how do you find your bike that you park at the station every day in the same area, but in a slightly different position?
3:51
And more interesting to my colleague Robert is the research we have been doing on neurogenesis and depression. So in an animal model of depression, we have seen that we have a lower level of neurogenesis. And if we give antidepressants, then we increase the production of these newborn neurons, and we decrease the symptoms of depression, establishing a clear link between neurogenesis and depression. But moreover, if you just block neurogenesis, then you block the efficacy of the antidepressant. So by then, Robert had understood that very likely his patients were suffering from depression even after being cured of their cancer, because the cancer drug had stopped newborn neurons from being generated. And it will take time to generate new neurons that reach normal functions.
4:48
So, collectively, now we think we have enough evidence to say that neurogenesis is a target of choice if we want to improve memory formation or mood, or even prevent the decline associated with aging, or associated with stress.
5:07
So the next question is: can we control neurogenesis? The answer is yes. And we are now going to do a little quiz. I'm going to give you a set of behaviors and activities, and you tell me if you think they will increase neurogenesis or if they will decrease neurogenesis. Are we ready? OK, let's go.
5:31
So what about learning? Increasing? Yes. Learning will increase the production of these new neurons.
5:39
How about stress? Yes, stress will decrease the production of new neurons in the hippocampus.
5:47
How about sleep deprivation? Indeed, it will decrease neurogenesis.
5:53
How about sex? Oh, wow!
5:56
(Laughter)
5:57
Yes, you are right, it will increase the production of new neurons. However, it's all about balance here. We don't want to fall in a situation --
6:06
(Laughter)
6:08
about too much sex leading to sleep deprivation.
6:10
(Laughter)
6:13
How about getting older? So the neurogenesis rate will decrease as we get older, but it is still occurring.
6:25
And then finally, how about running? I will let you judge that one by yourself.
6:32
So this is one of the first studies that was carried out by one of my mentors, Rusty Gage from the Salk Institute, showing that the environment can have an impact on the production of new neurons. And here you see a section of the hippocampus of a mouse that had no running wheel in its cage. And the little black dots you see are actually newborn neurons-to-be. And now, you see a section of the hippocampus of a mouse that had a running wheel in its cage. So you see the massive increase of the black dots representing the new neurons-to-be.
7:07
So activity impacts neurogenesis, but that's not all. What you eat will have an effect on the production of new neurons in the hippocampus. So here we have a sample of diet -- of nutrients that have been shown to have efficacy. And I'm just going to point a few out to you: Calorie restriction of 20 to 30 percent will increase neurogenesis. Intermittent fasting -- spacing the time between your meals -- will increase neurogenesis. Intake of flavonoids, which are contained in dark chocolate or blueberries, will increase neurogenesis. Omega-3 fatty acids, present in fatty fish, like salmon, will increase the production of these new neurons. Conversely, a diet rich in high saturated fat will have a negative impact on neurogenesis. Ethanol -- intake of alcohol -- will decrease neurogenesis. However, not everything is lost; resveratrol, which is contained in red wine, has been shown to promote the survival of these new neurons. So next time you are at a dinner party, you might want to reach for this possibly "neurogenesis-neutral" drink.
8:20
(Laughter)
8:23
And then finally, let me point out the last one -- a quirky one. So Japanese groups are fascinated with food textures, and they have shown that actually soft diet impairs neurogenesis, as opposed to food that requires mastication -- chewing -- or crunchy food.
8:41
So all of this data, where we need to look at the cellular level, has been generated using animal models. But this diet has also been given to human participants, and what we could see is that the diet modulates memory and mood in the same direction as it modulates neurogenesis, such as: calorie restriction will improve memory capacity, whereas a high-fat diet will exacerbate symptoms of depression -- as opposed to omega-3 fatty acids, which increase neurogenesis, and also help to decrease the symptoms of depression. So we think that the effect of diet on mental health, on memory and mood, is actually mediated by the production of the new neurons in the hippocampus. And it's not only what you eat, but it's also the texture of the food, when you eat it and how much of it you eat.
9:44
On our side -- neuroscientists interested in neurogenesis -- we need to understand better the function of these new neurons, and how we can control their survival and their production. We also need to find a way to protect the neurogenesis of Robert's patients. And on your side -- I leave you in charge of your neurogenesis.
10:06
Thank you.
10:07
(Applause)
10:13
Margaret Heffernan: Fantastic research, Sandrine. Now, I told you you changed my life -- I now eat a lot of blueberries.
10:20
Sandrine Thuret: Very good.
10:22
MH: I'm really interested in the running thing. Do I have to run? Or is it really just about aerobic exercise, getting oxygen to the brain? Could it be any kind of vigorous exercise?
10:35
ST: So for the moment, we can't really say if it's just the running itself, but we think that anything that indeed will increase the production -- or moving the blood flow to the brain, should be beneficial.
10:50
MH: So I don't have to get a running wheel in my office?
10:53
ST: No, you don't!
10:54
MH: Oh, what a relief! That's wonderful. Sandrine Thuret, thank you so much.
10:58
ST: Thank you, Margaret.
10:59
(Applause)
0:12
我們，作為成人，還能生長 新的神經細胞嗎？ 這個問題還未完全清晰， 因為這還是新的研究領域。 比方說，我跟我的同事羅伯特說， 羅伯特是一名腫瘤學家， 他告訴我， 「桑德琳，這很令人疑惑。 我的一些病人，即使被告知 他們的癌症已治癒， 仍有抑鬱的症狀。」 我回答道， 「嗯，在我看來這是可以解釋的。 你給病人開的， 用以阻止癌細胞增生的藥 同時也阻止了他們大腦中 生長出新的神經元。」 羅伯特看著我，仿佛我瘋了似的， 「但是桑德琳，他們是成年的病人-- 成人不會生長新的神經細胞。」 非常驚訝，我說， 「事實上，我們可以。」 這個現象我們稱之為 神經生成。
1:12
[神經生成]
1:14
羅伯特不是一名腦神經科學家， 當他在醫學院上學的時候 並沒有學到我們現在所知道的 成人大腦能夠生成新的神經細胞。 因此羅伯特， 作為一名好醫生， 想要到我的實驗室來 更深層的了解一下這個研究。 我向他展示了 大腦最令人興奮的部分 有關神經生成的活動-- 這是海馬體。 就是大腦中心這個灰色的結構。 我們早已得知， 這對學習，記憶，情緒和情感 很重要。 然而，我們進來新研究出的是 這是一個對成人大腦來說 很特別的結構， 這裡能夠生成新的神經元。 當我們切開海馬體 並放大， 你所看到的這些藍色物質 就是成年老鼠大腦中 新生張出來的神經元。 在人類大腦中-- 我來自卡羅林斯卡學院的同事 Jonas Frisén說， 人類每天生長約700個新的神經元 在海馬體內。 你可能認為這並不是很多， 因為人體有數十億神經元。 但是當我們快到50歲的時候， 我們出生時所有的神經元 都會變成那個結構中 成人時期生長出的神經元。
2:54
為什麼新的神經元是重要的 它們有怎樣的作用呢？ 首先，我們指導它們對於 學習和記憶功能來說很重要。 在實驗室中，我們發現 如果我們阻止了成人大腦中 海馬體生長新的神經元的功能， 那意味著我們也阻止了 某些記憶能力。 這對空間識別感 非常重要-- 就像，你如何在城市中活動。
3:25
我們仍在學習， 神經元對於記憶能力， 以及記憶的質量來說 非常重要。 他們能夠幫助我們的記憶 加入時間概念 他們也會幫助我們區分 非常相近的記憶，比如： 如何尋找你的自行車 你每天都將它停在 車站附近的同一塊地方， 但是在這片地不同的位置？
3:51
對我的同事羅伯特來說 更有意思的是 我們正在做有關神經生成 和抑鬱的研究。 在這個關於抑鬱的動物模型， 我們可以看到 它的神經生成在較低的水平， 如果給牠們服用抗抑鬱劑， 我們增加了新生的神經元， 於是抑鬱的症狀就減輕了， 在細胞生成和抑鬱症狀間 建立了清晰地聯繫。 此外，如果你阻止了細胞生成， 那你也就阻止了抗抑鬱劑的功效。 那時，羅伯特理解到 他的病人們很有可能會 遭受抑鬱的症狀 即使在癌症治癒以後， 因為抗癌藥物阻止了 身體新的神經元的生成。 那需要一些時間 生成新的神經元 讓它達到正常的運作。
4:48
總的來說， 我想我們有足夠的證據 來表明細胞生成是一個目標方法， 如果我們想要提高記憶力 或是提高情緒， 或是防止衰老， 或是抗擊壓力。
5:07
下一個問題就是： 我們能夠控制神經生成嗎？ 答案是，是。 我們現在進行一個小問答。 我會給你們一組行為或是活動， 你們來判斷 這些能否促進細胞新生 或是這些會降低細胞生成。 準備好了嗎？ 現在開始。
5:31
學習？ 增長？ 是的。 學習能夠提高神經細胞的生成。
5:39
壓力？ 是的，壓力會降低海馬體內 神經細胞的生成。
5:47
那麼睡眠匱乏呢？ 確實，它會降低神經生成。
5:53
性愛呢？ 哇！
5:56
（笑聲）
5:57
是，你們是對的，它能促進 神經新生。 然而，這一切都有關平衡。 我們不希望出現這樣的情況--
6:06
（笑聲）
6:08
太多的性愛導致睡眠匱乏。
6:10
（笑聲）
6:13
年齡增長？ 細胞生成率會隨著我們變老而降低， 但它仍會生成。
6:25
最後，跑步？ 這要看你們各自的情況自己決定。
6:32
這是第一個研究 是我在索爾克研究所的導師 Rusty Gage做的， 顯示出環境對於 生長新的神經有影響。 這幅圖片是老鼠的海馬體， 它的籠子裡沒有滾動跑輪。 黑色的小點點 是將要新生的神經元。 現在，這幅是老鼠的海馬體 它的籠子裡有滾動跑輪。 你可以看到數量巨大的 黑色小點點顯示出 它的神經元生成狀況。
7:07
所以，活動會影響神經生成， 但並不只是如此。 你吃的東西會影響到 海馬體生長新的神經元。 這裡我們有一個健康飲食的樣本-- 這些有功效的營養物質。 我要指出一些來： 卡路裡保持在20%-30% 會增強細胞生長。 間歇地斷食-- 在餐與餐之間空下時間-- 會提高神經細胞新生。 攝入黃酮類物質， 在黑巧克力或藍莓中， 會提高神經細胞新生。 歐米伽-3 脂肪酸， 在脂質魚中，比如三文魚， 會提高神經細胞新生率。 相對的，那些高飽和脂肪 會對神經生成有不好的影響。 乙醇--酒精中攝取-- 會降低神經新生。 然而，並不是所有都不好， 白藜蘆醇，紅酒中的物質， 就能夠促進新生神經的存活率。 下次你再去晚宴派對的時候， 你也許想要喝這種 可能「神經新生——中立」飲品。
8:20
（笑聲）
8:23
最後， 讓我在說最後一點—— 古怪的一點 日本人著迷於食物的質感， 軟質飲食減少神經生成， 相對於那些需要咀嚼，或是脆的食物。
8:41
這些數據， 我們用於觀察細胞水平的， 都是通過動物模型完成。 但這樣的飲食同樣也給與了人類參與者， 我們能看到的是 飲食調節記憶和情緒 和它調節神經生成同樣的方向， 比如：卡路裡限制會 提高記憶能力， 反之，一個高脂肪的飲食會 加劇抑鬱的症狀。 相反的，歐米伽-3脂肪酸， 會提高神經生成， 同時也會幫助減緩 抑鬱的症狀。 因此我們認為飲食的效用 在神經健康、記憶和情緒， 是通過在海馬體內 製造新的神經元間接完成的。 不只是你吃什麼， 還有食物的質地， 什麼時候吃 吃了多少來決定。
9:44
在我們神經科學家這邊-- 有興趣的神經生成-- 我們需要更好的了解 這些新生神經的功能， 以及我們如何控制 它們的存活率和製造情況。 我們同樣也要尋找一個方法 來保護羅伯特病人的神經生成。 在你們這邊-- 請你們自己決定自己的細胞生成。
10:06
謝謝
10:07
（鼓掌）
10:13
瑪格麗特•赫夫南： 太精彩的研究，桑德琳。 現在，我告訴你你改變了我的生活-- 我現在開始吃大量的藍莓。
10:20
桑德琳•蘇瑞：這太好了。
10:22
瑪格麗特：我很好奇 關於跑步的那個討論。 我需要跑步嗎？ 還是指我們要做有氧運動， 讓大腦吸氧？ 可以是任何激烈運動嗎？
10:35
桑德琳：此時此刻， 我們無法準確說明 是否只能跑步， 但我想任何事 能夠提高生成-- 或是血液移動到大腦的， 應該都是有益的。
10:50
瑪格麗特： 那我不需要在我的辦公室放一個轉輪了？
10:53
桑德琳：不，你不需要！
10:54
瑪格麗特：真是鬆了口氣！太精彩了。 桑德琳•蘇瑞，非常感謝你。
10:58
桑德琳：謝謝你，瑪格麗特。