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MANOUSH ZOMORODI, HOST:
OK, so quick recap - every minute, babies develop up to 500,000 neurons. And the brain continues to grow and transform all the way through adolescence until about the age of 26. Beyond that, people used to believe that the adult brain stopped growing new neurons. But that's not the case.
SANDRINE THURET: Yeah, yeah, of course. Yeah, yeah, yeah. I mean, on average, people would produce 700 new neurons per day.
ZOMORODI: This is neuroscientist Sandrine Thuret.
THURET: We all agree that this is a very small number. You know, you don't need a lot of these new neurons because it's part of a network. You don't need a lot to disturb the whole network.
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THURET: So I think that although this is a small number, but it doesn't prevent them from having very specific functions, let's say, or important functions.
ZOMORODI: Sandrine studies neurogenesis, the process of creating new neurons.
THURET: And when you are very young - so let's say, you know, until four years old - you have a lot of neurogenesis going on. You would have a burst of neurogenesis. But it goes down as you age. And that continues well into the 90s. So there is something that is happening, but it's not everywhere in the brain.
ZOMORODI: For adults, that growth is happening in one area of the brain - the hippocampus.
THURET: So the hippocampus is really a hub that's going to have multiple role. I mean, most people will think that, yeah, this is for memory. And it's right, it is for memory formation, but it's also important for mood and emotion. So indeed, in the hippocampus, you still keep adding neurons that are important for your mental health in general, like cognition and, you know, mood. And this is something that you can try to control to some extent without stressing yourself too much.
ZOMORODI: Can we just pause here and say, like, what a relief it is to know that there is neural activity, neural growth in the adult brain? But it does sound like you're saying, you know, it's not just the way the brain works, it's that we actually can do something about it, too.
THURET: So yeah. Well, exactly. I mean, like, what if you are aware of it, right? What do you do about it now? Because it's a very sensitive phenomenon, that, you know, you can increase it or decrease it, like, super quickly, you know, with lots of intervention that you do every day.
ZOMORODI: In just a minute, neuroscientist Sandrine Thuret on what we adults can do to promote our neurogenesis and help our brains be healthier. On the show today, healthy brain development at every stage of life. I'm Manoush Zomorodi, and you're listening to the TED Radio Hour from NPR. Stay with us.
It's the TED Radio Hour from NPR. I'm Manoush Zomorodi. Today on the show, how our brains change through every stage of life. And we were just hearing neuroscientist Sandrine Thuret explain the process of neurogenesis, our brain's ability to create new neurons. And even though adults won't grow as many neurons as kids or teenagers, our daily choices can help.
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THURET: Can we control neurogenesis? The answer is yes. And we are going to do now a little quiz. So I'm going to give you a set of behavior and activity, and you tell me if you think they will increase neurogenesis or if they will decrease neurogenesis.
ZOMORODI: This is Sandrine Thuret on the TED stage. During this quiz, she went through six ways that we adults can promote our brain health.
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THURET: So what about learning - increasing? Yes. So learning will increase the production of these new neurons.
So we know that learning itself will increase neurogenesis. So learning, you know, a new language, of course - why not? But, you know, the hippocampus is one of the center for spatial recognition. So maybe not exercising always the same route - you know, if you go outside for a walk or for a run, maybe taking a new one or maybe even taking a way you don't know yet.
ZOMORODI: OK, so let's move to the second one, which was stress.
THURET: So, yeah, stress. Well, this - you know, chronic stress, that's really bad for neurogenesis. And I know at the moment it's very difficult to do anything against, you know, stress, but this is really detrimental for neurogenesis. So having positive action, like learning - you know, this is how you maybe could counteract some of the detrimental effect of the stress.
ZOMORODI: OK, so sleep deprivation was the next one. This makes sense to me.
THURET: Yeah. Yeah. So it's quite intuitive, indeed. You know, when you are sleep deprived, you know, you cannot think straight, but it's over time. If you are going to look at this chronic sleep deprivation, that would be negative.
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THURET: How about sex? Oh, wow.
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THURET: 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...
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THURET: ...About too much sex leading to sleep deprivation.
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ZOMORODI: This one got a laugh from the audience.
THURET: Yeah, intercourse. Yes. Yes. So, yeah. So that's a good one to keep in mind, indeed.
ZOMORODI: And finally, diet and exercise.
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THURET: How about running? So I will let you judge that one by yourself. So activity impacts on neurogenesis, but that's not all. What you eat will have an effect on the production of new neuron in the hippocampus. So calorie restriction of 20 to 30% will increase neurogenesis. Intermittent fasting - so spacing the time between your meal - will increase neurogenesis. Intake of flavonoid, which is contained in dark chocolate or blueberry, will increase neurogenesis. Omega-3 fatty acid, 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.
ZOMORODI: So, you know, I do understand that research has not definitively shown that these things promote neurogenesis. But listening to you, part of me wants to fast and only eat salmon, blueberries and dark chocolate and run six miles a day and make sure I get nine hours of sleep every night because it makes me think, like, wow, I might have some control over my body. But also, like, Sandrine, we are only human, and it's just not possible to do all these things. So I guess I'm wondering, like, what is the biggest single piece of advice you have for us on how to make sure our brains stay healthy?
THURET: Yeah. So I think people will have to find their own balance because if you are pushing yourself too hard, then this is another form of stress, right?
ZOMORODI: (Laughter).
THURET: So...
ZOMORODI: Right.
THURET: You want to do something that feels good to you, right? But, yeah, people have to find what works for them, I think, because otherwise if you have to force yourself, then it's counterproductive because it's going to be a stress.
ZOMORODI: You know, I'm at that age where I'm starting to - I'm in my late 40s. I'm starting to think about the next phase. I'm not there yet. But is there some way to sort of prepare myself for the senior years, as it were?
THURET: I don't know (laughter).
ZOMORODI: Yeah, right?
THURET: I mean, I think...
ZOMORODI: That's the big question, isn't it?
THURET: Yeah, that's a really good question. I'm sure you can. I'm sure we can all do our best. You know, from the data we have, it does show that what you do in your younger year will have an impact, you know, on the long term. So I think you can prepare now, indeed. And hoping for the best, like I do.
ZOMORODI: That's neuroscientist Sandrine Thuret. She leads the Adult Neurogenesis and Mental Health Laboratory at King's College London. You can check out her full talk at ted.com.
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