How Our Behaviors and Activities Control the Growth of New Cells

Hippocampus neurogenesis
Sandrine Thuret studies the way adult brains create new nerve cells in the hippocampus — a brain area involved in memory and mood. Her work is focused on answering two big questions:

  1. How can we help our healthy brains create new nerve cells throughout our lives, through diet and behavior changes?
  2. How can we study the effects of diseases such as depression and Alzheimer's on our brains' ability to grow?

We can grow new nerve cells as adults. This is a fairly recent field of research, but early answers are encouraging and they can have broad impact. Thuret says a conversation with a colleague gave her the opportunity to illustrate this new finding:

Robert, who is an oncologist, 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."

I responded, “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.”

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.

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, being the good doctor he is, wanted to come to my lab to understand the topic a little bit better.

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. This is this gray structure in the center of the brain.

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.

This is good news, because it means our brain continues to produce new neurons as adults.

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.

“Neurons are not only important for memory capacity, but also for the quality of the memory,” she says. It gives our memory legs and sophistication, like remembering where we left our bike at the station, or our car in a big lot without resorting to using the remote opener.

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.

Activities and reelatioship to neurogenesis

Activities like learning, sex, and running will increase the production of new neurons, while stress, sleep deprivation will decrease neurogenesis. Getting older slows it down, but it is still occurring.

This is good news for runners. But is the benefit limited only to running? How about other forms of aerobic physical activity? Dr. Charles Hillman at the University of Illinois focuses on the relationship between both acute and chronic physical activity participation and cognitive function — attention, memory, and processing speed.

Results from his research have suggested that cardiovascular activity benefits cognitive processing for tasks that require greater effort. A twenty-minute walk does generate an increase in brain activity.

Thuret says, “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.”


What we eat also makes a difference. Calorie restriction of 20 to 30 percent, intermittent fasting, intake of flavonoids found in dark chocolate or blueberries, Omega-3 fatty acids will all increase the production of these new neurons.

Under the things that have a negative impact on neurogenesis Thuret lists a diet rich in high saturated fat. She says:

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.

An interesting note about food texture.

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.

Watch the full talk below.


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