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Putting the ‘Plastic’ in ‘Synaptic Plasticity’


One of the interesting side effects of technology’s rapid advance over the past thirty years or so is the shrinking of the age gap between folks who are hip to new technologies hitting the market, and folks who just haven’t been able to keep up.

That gap is something I’ve been thinking about lately. Of course, it’s not just defined by age: Experience is a huge factor. For example, while I’m probably more proficient at video games than any adult should be, my wife—a year younger than I am, but with no recent or significant gaming experience to speak of (she had, like, a life and stuff)—sat down to play a game a week or two ago, and struggled.

Meanwhile, if you handed the same game to my 8-year-old nephew, he’d crush both of us.

We’ve all probably experienced something along those lines: Children displaying prowess far beyond anything we could match in areas we considered ourselves capable. They appear to make up for a lack of the aforementioned experience with the ability to learn at an extraordinary pace, surpassing their elders quickly. You may be relieved to know there’s a term, and full scientific explanation, for this phenomenon—beyond just your being out of touch.

It’s called synaptic plasticity, and it’s something Frances E. Jensen, MD, FACP, Chair of the department of Neurology and a professor of Neurology here at Penn Medicine—as well as the author of The Teenage Brain: A Neuroscientist’s Survival Guide to Raising Adolescents and Young Adults—can tell you all about.

There are 100 billion neurons in your brain, and they make somewhere around 100 trillion connections, Jensen explained. These connections are synapses. Cells talk to each other across synapses. One cell will send an outgoing message, which another cell will pick up. The second cell could, depending on what it’s being told, then send an outgoing message of its own to yet another cell. It’s a relay race, with cells handing the signal off to one another.

When you’re repeating an action, you’re activating the same path of cells over and over—and your brain responds by strengthening that pathway. That’s how we learn. That’s synaptic plasticity.

“If you use a certain set of synapses a lot, repeatedly, it sets off a chemical reaction to build a bigger, stronger synapse—a synapse with more receptors on it, which will therefore conduct a much more powerful signal,” Jensen said. “The more you use it, the more the synapse is molded by use. That’s the plastic part.”

So that explains why my wife might have trouble picking up a video game and rolling with it like she’s been playing ‘em her whole life, but how do children pick things up so quickly?

“In childhood, you have the most synapses you’ll ever have,” Jensen said. “Then you prune them. If you use the synapses, you keep them. If you don’t use them, you prune them. It’s ‘use it or lose it.’”

“You’re biologically built with more machinery when you’re younger, and then it slows down and gets to lower levels in adults,” Jensen added. “Adults can still learn, obviously. That’s what we do every day. You just have to be more persistent and use more repetition.”

That’s why, say, that nephew of mine can call me on my birthday and sing Happy Birthday in Hebrew and Chinese, while I’m on my fourth attempt of introductory Spanish. It’s also why ducklings imprint. It’s why any number of behaviors we pick up on early become ingrained much, much more easily.

“It’s called the critical period, early in development,” Jensen said. “They’re able to create connections at a much higher rate, and enhance and strengthen those connections. All of that molecular machinery is just set at higher levels in a young person.”

This means that learning—which we tend to think of as a more mental task than a physical one—is, in fact, physically impacting your brain’s makeup.

“Your brain map is changing,” Jensen explained. “If you were to do a functional MRI in somebody before they learned a skillset and after they learned it, they’d have a different activation pattern in their brain.”

It’s like a muscle: The more you exercise these pathways, the stronger the connections become, and the more adept you’ll be.

“When we learn something or create a memory, it’s because the synapse went from being a standard synapse to one that, because of overuse, now controls a much more powerful signal,” Jensen said.

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