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It’s one thing to learn that the brain sprouts new neurons. And yet it’s another to hear that our behavior actually affects how much our brain grows.

But it’s a whole different experience to be quizzed by one of the world’s leading neuroscientists who helped figure all this out in the first place.

A little nerve-racking. But not that bad, given that Fred Gage of the Salk Institute sports an utterly non-intimidating demeanor refreshing for a world-renowned scientist who flipped brain science on its head.

Gage spoke, alongside other leading stem cells scientists, at the American Association for the Advancement of Science meeting in San Diego over the weekend. If you’ve never heard such scientists present amongst themselves, there’s a distinguished array of acronyms and scientificese. (I may have adapted this word from its medical cousin, medicalese, but you get the point.)

I cornered Gage after the formal PowerPoint presentations. He tested my hippocampus. But more on that later.

About 10 years ago, Gage proved the brain is not a fixed object, but rather a biological organism capable of regeneration throughout our adult lives. This was revolutionary among neuroscientists who thought the human brain was static, kind of like

Copernicus announcing the earth revolves around the sun to astronomers.

Through Gage’s and others’ work, the fact that new cells are born — what scientists called neurogenesis — is now accepted fact.

So Gage’s lab tucked away on the Torrey Pines Mesa kept working and found the new brain cells are particular; they don’t grow just anywhere or do just anything.

“We now have an insight to what role these young cells are playing,” Gage said. “These new neurons that are driving stem cells in the hippocampus regulate the ability to distinguish between relatively related events. This is a process called hyper-separation.”

The new cells arise in the hippocampus, a seahorse-shaped memory center deep in the brain. They help us distinguish between two similar events, be they moments in time, places or even facial expressions.

So Thursday you go to work and park your car in the middle of the parking lot, say slightly northwest of center. But Friday you find a spot just northeast, a few spots over from that one. Do you recall where you’re parked at the end of the day?

It depends on the hippocampus, which catalogues and recalls those kinds of fine distinctions.

This is where Gage challenged my grey matter, for demonstration purposes.

“There’s the pen,” Gage explained as he placed my writing instrument on a nearby table. “Look at it. Now close your eyes.”

Shuffling sounds ensue.

“Okay, now look,” Gage points to my pen on the table right next to another one he’s added. “Which of those two pens is in the exact same location? It’s hard.”

I pause. I guess wrong. He admits it’s tough for most hippocampi.

But when Gage repeats the same experiment by placing the two pens several feet apart — instead of an inch or so — I get it. Whew.

But here’s where it gets exciting, even motivating, for the average person. Heck, even for Gage.

“I’m a neurobiologist. That means I think the brain is controlling our behavior,” he explained. “But now we find out that behavior — like physical exercise, enrichment, interaction — can change the number of cells that are being born in our brain.”

They’ve seen dramatic examples with mice in the lab. Those who enjoy a changing environment and some physical activity grow more brain cells. Not just that, more neurons survive.

So learning new things, moving your body (“It’s not a matter of marathon running. It’s just physically active, blood flow, these kinds of things,” Gage said), plenty of sleep and diet — unfortunately “dietary restrictions” — help too.

Stress is not friendly to the newborn neurons that tend towards hyperactivity anyway.

With that, I packed up my notebook (Gage made off with my pen), left the fluorescently lit lecture hall and exited the Convention Center for a stroll along the harbor.

— REBECCA TOLIN

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