You can grow new brain cells. Here's how | Sandrine Thuret | TED

Summary

In this enlightening talk, Sandrine Thuret explores the fascinating field of adult neurogenesis, debunking the myth that adults cannot grow new nerve cells. She explains the hippocampus's role in learning, memory, and mood, and how certain behaviors and diets can influence neurogenesis. Thuret's research reveals a link between neurogenesis and depression, showing that antidepressants boost neuron production and alleviate symptoms. She also discusses how physical activity, diet, and even the texture of food can impact the generation of new neurons, offering insights into improving memory and mood.

Takeaways

• 🧠 Adult neurogenesis is a real phenomenon where new nerve cells are generated in the adult brain, contrary to previous beliefs.
• 💊 Certain cancer treatments can halt neurogenesis, potentially leading to symptoms of depression in patients.
• 🌟 The hippocampus is a key region in the brain where new neurons are produced, playing a crucial role in learning, memory, mood, and emotion.
• 🔍 Research estimates that approximately 700 new neurons are produced daily in the human hippocampus.
• 🧪 Blocking neurogenesis in the hippocampus can impair memory functions, particularly spatial recognition.
• 🔗 There is a clear link between neurogenesis and depression, with antidepressants shown to increase neurogenesis and alleviate symptoms.
• 🏃‍♂️ Physical activity, such as running, has been shown to increase neurogenesis, suggesting the importance of exercise for brain health.
• 🍽️ Diet significantly impacts neurogenesis, with nutrient-rich foods like dark chocolate, blueberries, and fatty fish promoting new neuron production.
• 🚫 High saturated fat diets and alcohol consumption can negatively affect neurogenesis, while certain compounds like resveratrol can support neuron survival.
• 🧐 Neuroscientists are working to understand and control neurogenesis to improve memory, mood, and prevent cognitive decline associated with aging or stress.

Q & A

Can adults grow new nerve cells?

Yes, adults can grow new nerve cells, a phenomenon known as neurogenesis.

What is the role of the hippocampus in neurogenesis?

The hippocampus is one of the unique structures in the adult brain where new neurons can be generated and is important for learning, memory, mood, and emotion.

How many new neurons are produced in the human hippocampus per day?

It is estimated that approximately 700 new neurons are produced per day in the hippocampus.

How does neurogenesis relate to memory and learning?

Neurogenesis is important for learning and memory. Blocking the production of new neurons in the hippocampus can impair certain memory abilities, particularly spatial recognition.

What is the connection between neurogenesis and depression?

In animal models of depression, lower levels of neurogenesis are observed. Antidepressants can increase the production of new neurons and decrease symptoms of depression.

How can we influence neurogenesis through behavior?

Behaviors such as learning, stress, sleep deprivation, and physical activity like running can influence neurogenesis. Learning and running can increase it, while stress and sleep deprivation can decrease it.

What dietary factors can affect neurogenesis?

Calorie restriction, intermittent fasting, intake of flavonoids, and omega-3 fatty acids can increase neurogenesis, while a diet high in saturated fat and alcohol can decrease it.

How does the texture of food impact neurogenesis?

Consuming soft diets can impair neurogenesis, whereas food that requires chewing or is crunchy can promote it.

What is the role of exercise in neurogenesis?

Exercise, particularly aerobic activities that increase blood flow to the brain, can promote neurogenesis.

How can we use the knowledge of neurogenesis to improve mental health?

Understanding and controlling neurogenesis can help improve memory formation, mood, and potentially prevent cognitive decline associated with aging or stress.

What are the next steps for research in neurogenesis?

Neuroscientists need to further understand the function of new neurons and how to control their survival and production. Additionally, finding ways to protect neurogenesis in patients undergoing treatments that may inhibit it is crucial.

Outlines

00:00

🧠 Neurogenesis in Adults

This paragraph discusses the topic of neurogenesis, the process by which new nerve cells are generated in the adult brain. It begins with a dialogue between the speaker and a colleague, Robert, who is puzzled by cancer patients experiencing depression despite being cured. The speaker explains that the drugs used to treat cancer can also inhibit the growth of new neurons, which is a process known as neurogenesis. The speaker then takes Robert on a tour of the hippocampus, a part of the brain crucial for learning, memory, mood, and emotion, and where neurogenesis occurs. The paragraph also highlights the discovery that humans produce about 700 new neurons per day in the hippocampus, which can replace all the neurons in that area by the age of 50. The importance of these new neurons for learning and memory is emphasized, as well as the connection between neurogenesis and depression. The speaker concludes by suggesting that neurogenesis could be a target for improving memory, mood, and preventing cognitive decline associated with aging.

05:02

🏃‍♂️ Controlling Neurogenesis Through Behavior and Diet

In this section, the speaker explores ways to control neurogenesis through various behaviors and dietary choices. A quiz format is used to engage the audience in understanding which activities can increase or decrease neurogenesis. It is revealed that learning, stress, sleep deprivation, sex, aging, and running can all have an impact on the production of new neurons. The speaker then delves into the effects of diet on neurogenesis, mentioning that calorie restriction, intermittent fasting, flavonoid intake, and omega-3 fatty acids can promote neurogenesis, while a high-fat diet and alcohol consumption can have negative effects. The importance of food texture is also discussed, with crunchy foods being more beneficial than soft diets for neurogenesis. The speaker concludes by emphasizing that the effects of diet on mental health, memory, and mood are likely mediated by the production of new neurons in the hippocampus.

10:03

🏃‍♀️ The Impact of Exercise on Neurogenesis

The final paragraph is a dialogue between the speaker and Margaret Heffernan, where they discuss the impact of exercise on neurogenesis. The speaker clarifies that while the specific study mentioned was about running, any aerobic exercise that increases blood flow to the brain could be beneficial for neurogenesis. The conversation lightens up with a humorous exchange about whether a running wheel is necessary in the office, to which the speaker assures that it is not. The dialogue ends with a round of applause for the speaker, Sandrine Thuret, highlighting the engaging and informative nature of her talk on neurogenesis.

Keywords

💡Neurogenesis

Neurogenesis refers to the process by which new neurons are generated in the brain. In the video, it is highlighted as a significant and relatively new field of research that challenges the previous belief that adults do not grow new nerve cells. The script discusses how neurogenesis occurs in the hippocampus, a region vital for learning, memory, mood, and emotion, and how certain behaviors and substances can influence this process.

💡Hippocampus

The hippocampus is a seahorse-shaped structure located in the brain, known for its role in learning, memory, mood, and emotion. The video emphasizes that the hippocampus is one of the few regions in the adult brain where neurogenesis continues to occur. The script mentions that new neurons are generated here, which are crucial for cognitive functions and emotional well-being.

💡Depression

Depression is a mental health condition characterized by persistent feelings of sadness and a lack of interest or pleasure in activities. In the context of the video, it is linked to neurogenesis, as the script explains that lower levels of neurogenesis are observed in animal models of depression, and that antidepressants can increase neurogenesis, thereby alleviating symptoms of depression.

💡Antidepressants

Antidepressants are a class of medications used primarily to treat depression and other mood disorders. The video discusses how these drugs not only treat depression but also increase the production of new neurons in the hippocampus, suggesting a direct link between neurogenesis and the therapeutic effects of these medications.

💡Memory

Memory refers to the cognitive process of encoding, storing, and retrieving information. The video script explains that new neurons generated through neurogenesis are important for learning and memory, particularly for spatial recognition and the ability to differentiate between similar memories.

💡Stress

Stress is a physical or emotional response to demanding or threatening situations. The video points out that stress can negatively impact neurogenesis by decreasing the production of new neurons in the hippocampus, which can have broader implications for cognitive function and mental health.

💡Nutrition

Nutrition encompasses the intake of nutrients required for growth, maintenance, and repair of the body's cells and tissues. The script discusses how certain dietary habits, such as calorie restriction, intermittent fasting, and the intake of specific nutrients like flavonoids and omega-3 fatty acids, can positively influence neurogenesis.

💡Exercise

Exercise is any bodily activity that enhances or maintains physical fitness and overall health. The video suggests that physical activity, particularly aerobic exercise, can increase neurogenesis by promoting blood flow to the brain, which can contribute to better memory and mood.

💡Aging

Aging is the natural process of growing older and involves the gradual decline of various bodily functions. The script notes that while the rate of neurogenesis decreases as we age, it continues to occur, and that certain lifestyle factors can help maintain or enhance neurogenesis, potentially counteracting some age-related cognitive decline.

💡Neuroscience

Neuroscience is the scientific study of the nervous system, including the brain. The video is centered around the field of neuroscience, specifically focusing on the study of neurogenesis and its implications for learning, memory, mood, and mental health. The speaker, a neuroscientist, shares insights from research and experiments conducted in this field.

💡Cancer Treatment

Cancer treatment refers to medical interventions aimed at treating cancer. The video script mentions a side effect of certain cancer treatments that inhibit neurogenesis, which can lead to symptoms of depression in patients even after they have been cured of their cancer, highlighting the importance of understanding the broader impacts of medical treatments.

Highlights

Adults can grow new nerve cells, a phenomenon known as neurogenesis.

Neurogenesis is a new field of research that challenges traditional medical understanding.

Certain cancer drugs may stop the generation of new neurons in the brain.

The hippocampus is a key brain region for neurogenesis, important for learning, memory, mood, and emotion.

Humans produce approximately 700 new neurons per day in the hippocampus.

New neurons are crucial for learning and memory, especially spatial recognition.

Blocking neurogenesis in the hippocampus can impair memory abilities.

Neurogenesis is linked to depression; lower levels are seen in animal models of depression.

Antidepressants increase neurogenesis and can alleviate depression symptoms.

Blocking neurogenesis can negate the effects of antidepressants.

Neurogenesis is a potential target for improving memory, mood, and preventing cognitive decline.

Lifestyle factors such as learning, stress, sleep, and exercise can influence neurogenesis.

Diet significantly affects neurogenesis; certain nutrients like flavonoids and omega-3 fatty acids promote it.

High saturated fat and alcohol intake can decrease neurogenesis.

The texture of food, such as the need for chewing, can also impact neurogenesis.

Neuroscientists are working to understand and control the survival and production of new neurons.

Diet's impact on mental health is believed to be mediated by hippocampal neurogenesis.

Exercise, such as running, increases blood flow to the brain and may promote neurogenesis.

Transcripts

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.

[Neurogenesis]

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.

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.

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?

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.

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.

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.

So what about learning?

Increasing?

Yes.

Learning will increase the production of these new neurons.

How about stress?

Yes, stress will decrease the production of new neurons in the hippocampus.

How about sleep deprivation?

Indeed, it will decrease neurogenesis.

How about sex?

Oh, wow!

(Laughter)

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 --

(Laughter)

about too much sex leading to sleep deprivation.

(Laughter)

How about getting older?

So the neurogenesis rate will decrease as we get older,

but it is still occurring.

And then finally, how about running?

I will let you judge that one by yourself.

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.

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.

(Laughter)

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.

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.

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.

Thank you.

(Applause)

Margaret Heffernan: Fantastic research, Sandrine.

Now, I told you you changed my life --

I now eat a lot of blueberries.

Sandrine Thuret: Very good.

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?

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.

MH: So I don't have to get a running wheel in my office?

ST: No, you don't!

MH: Oh, what a relief! That's wonderful.

Sandrine Thuret, thank you so much.

ST: Thank you, Margaret.

(Applause)