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Q&A: The key to a better brain is exercise

Q&A: The key to a better brain is exercise

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New research suggests that a sure way to slow the aging process of your brain is to exercise.

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Keeping your brain sharp may not, in fact, be about doing more challenging crossword puzzles or engaging in specialized digital games or relearning the quadratic equation. What can make all the difference is something more fun and far less intuitive: Toss a frisbee, dance, run, skip. Get active.

A fascinating new study done with mice that is about to published in the journal Neuroscience suggests that the number one thing we can do to preserve our brain function is to be physically active. It does not appear to matter how enriched our environment may be.

SmartPlanet tracked down the lead researcher of this study. An expert on new brain cell growth Justin Rhodes is assistant professor of psychology at the Beckman Institute at the University of Illinois.

SmartPlanet: Did the results from your work with exercise and its effect on the brain surprise you?

Justin Rhodes: The most remarkable thing for me is thinking about why physical exercise leads to enhanced cognitive performance. To me that’s not necessarily obvious. You’re not doing anything intelligent or thinking-wise when you’re running or swimming. Usually I just blank out.

As you age your brain tends to deteriorate in terms of its ability to function. Keeping physically active can help prevent that decline. That is a remarkable discovery, and it’s pretty clear that that’s true now. There are a lot of products out there that claim to be able to enhance, or maintain, prevent decline, and enhance performance by cognitively challenging you with different memory tests, different computer-based training. I think the point is that there appear to be some really important things about keeping active.

SP: Could you describe this amazing study that’s about to be published in the journal Neuroscience?

JR: Right, so what we wanted to do was figure out how important physical activity is for generating or growing new neurons in the hippocampus. First of all, so you understand how we measure cognitive performance in mice is with a water maze task. This task measures their ability to remember where a platform is relative to visual cues in this room. Mice don’t like to swim.

SP: I imagine they don’t.

JR: So they are placed in a tub of water with a little platform hidden underneath the water. When you put an animal in there, a mouse or a rat, they try to get out. They can’t see where the platform is but they may run into it, and then they’re like, oh I’m here, good. Then you take them out. The next day you put them in again, they swim around. Eventually they learn where that platform is even though they can’t see it. They navigate where it is relative to visual cues around the room.

SP: That’s a very interesting way to measure the cognitive ability of mice.

JR: We know that when you put animals on running wheels they typically display increased performance on that maze after they’ve been running for a while. But we wanted to know how much is it related to the actual physical activity versus maybe just the stimulation. How do you know that it’s the running that really did anything?

Many people have found that an enriched environment—an environment that includes lots of toys—enhances neurogenesis [the growth of new neurons in the brain] and performance on the water maze. And that’s led to this belief that the enriched environment, the stimulation from the toys and so on is what increases new neuron growth.

In our experiment we wanted to figure out what is the real contribution of physical exercise versus the stimulation or having fun with toys, and things like that, enriched environments, sensory stimulation.

So that’s how we designed this experiment where there are four groups: one with running wheels only, another with running wheels and the toys—including treats and drinks. Another with just the treats and toys. And then in another group that had nothing.

We discovered that the only thing that really mattered was the running. The groups that had just enrichment didn’t improve on the water maze and didn’t show any more new neurons than the animals that sat in their cages with nothing.

But any group with the runners actually showed increased neurogenesis that was directly related to how much they ran. Even if they spent eighty percent of their time with the toys, and only ran for a couple hours at night. It was running that mattered for the growth of the neurons, not the time they were playing with the toys.

SP: Do we have an idea of the amount of new neurons that tend to come with exercise?

JR: So in mice the amount of neurogenesis as measured by newly surviving cells can be quantified anywhere from double to six times as much in animals that are exercising versus animals that are not.

The part of your brain that’s critically involved in remembering things, the hippocampus, more than any other brain area, is the most highly implicated in learning, and memory, and cognitive processes. That part of your brain can vastly increase in size. The dentae gyrus part of the hippocampus specifically increases because we’ve seen that more cells are literally added to it.

SP: Do we know what is specific about exercise that increases the number of new cells in the hippocampus specifically?

JR: You might think oh your whole brain is really active when you’re running or something, no. One of the areas that happens to be really active is the hippocampus. But that’s nothing to do with learning and memory, it's running. So why is that happening? Some researchers theorize that, well the hippocampus is very famous for its role in special learning and memory, remembering where you are in space relative to cues around your environment. And that’s the obviously critical thing that animals need to do, especially when they are moving.

And if you need to remember where you are, you need to have some way or remembering, keeping track of the speed with which you’re moving through this map you must have in your brain. And one way that might be coded is by cells firing in that part of the brain. In other words, when you need to remember a lot of navigation usually you’re moving through the environment.

But those theories are pure speculation; no one knows. Those cells, however, are active when the animal’s actually moving and exercising heavily. So those cells actually are recruited, integrated, and they’re doing something. I don’t know what they’re actually doing, they’re doing something when the animals running. Also interestingly, and this is one of our papers, those same cells that are activated from running, and survive from running can also be involved in other tasks that the brain controls.

And that explains partly why the effects of exercise are broad. Some research suggests that neurons spawned from specific learning will only be activated in the future when the person is doing that very same task, and they would not be activated during any other task. That’s not true with exercise. Those cells born from exercise can also can be rooted in anything else they do. So that can help improve other things the hippocampus does in terms of learning and memory that doesn’t involve exercise. The question is why does that happen?

SP: So there’s kind of a limitation to neurons born to a certain type of learning environment, but the ones that are created through exercise are more nimble, they can multitask?

JR:That’s what it appears from the literature. However, I don’t know. I don’t think that any cell that survives from whatever you’re doing is going to be specific to that one task. I just disagree with that.

SP: So you think that all neurons can be nimble and multitask.

JR: Right. I can’t see why that wouldn’t be true for any neuron born from any activity.

SP: Well that’s an important question.

JR: Actually a related thing we’re interested in studying are the affects of amphetamines. Most people suggest that drugs of abuse decrease neurogenesis in the brain. However, many groups take amphetamines, stimulant drugs from the times they’re young to adulthood. Drugs like Adderall. We don’t  know the long-term effects of these stimulants. If they happen to decrease neurogenesis that’s not good. But certainly there’s been no suggestion that chronic use of these stimulants like amphetamines impair cognition; they appear to help it. It’ll be very interesting to see if there is increased growth from these amphetamines and then if the new neurons are also more nimble.

SP: We don’t know what sort of exercise—aerobic versus anaerobic—is particularly good for neurogenesis or new neuron growth correct?

JR:We know you don’t get benefits from stretching or toning your body. There’s some evidence that lifting weights or strength training can have some cognitive benefits. But most studies have looked at aerobic exercise. And personally for the mouse work, well, it’s really hard to get a model where mice are lifting weights. It would be really nice to train them to do bench presses but that’s really hard to do. We do know that new growth is very strongly correlated with the amount that the mice run. The more they run the more new neurons they have, so it seems to be quantitatively related to that running distance, the kind of endurance.

SP: Have the results of this experiment changed your physical fitness habits at all?

JR: No, my wife and I are pretty active already. I think as you age it’s a really critical thing. But it’s not like exercise will make you a huge amount smarter so that all of a sudden you can do calculus. But certainly it will protect the decline that naturally happens as you get older.  I do really believe that as you age if you don’t keep active you are not doing yourself a service.

[Photo via Old Shoe Woman]

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Christie Nicholson

Contributing Writer

Christie Nicholson produces and hosts Scientific American's podcasts 60-Second Mind and 60-Second Science and is an on-air contributor for Slate, Babelgum, Scientific American, Discovery Channel and Science Channel. She has spoken at MIT/Stanford VLAB, SXSW Interactive, the National Science Foundation, the National Research Council, the Space Studies Board and Brookhaven National Laboratory. She holds degrees from the Columbia University Graduate School of Journalism and Dalhousie University in Canada. She is based in New York. Follow her on Twitter. Disclosure