Devoted to solving intricate physiological questions about the brain for almost her entire adult life, Wendy Suzuki, a neuroscientist at New York University, was proud of her work. But the long hours dedicated to research eventually left her feeling socially isolated and physically weak.
Taking up a habit of regularly visiting the gym changed all that — so profoundly that she decided to also change the focus of her studies and become a beginner researcher in the neuroscience of exercise at 51 years old. That meant giving up the reputation she had built over 25 years to enter a field where no one knew her.
“It was a hard decision and it was scary,” Suzuki said. “But once I made the decision I knew it was the right one.”
She also thought it was a particularly good decision because the results of her work, which focuses on understanding the effects of exercise on the brain, could quickly lead to tangible benefits.
“The thing that was really exciting and appealing is that this was the kind of research that could immediately be applied to helping people live their life better,” she said.
We’ve long known that exercise makes for a healthier, fitter body. But its similar effects on the brain have only come to light in recent years. In fact, just the idea that the brain can change at all in response to experiences is something that had not garnered much evidence until the late 20th century. One of the first experiments to show the flexibility of the brain was done in 1972, when researchers put mice in a fun cage equipped with running wheels and toys, and found the cortex area of the rodents’ brains grew thicker, whereas it didn’t in mice kept in a dull, small cage.
Later it was found that although we are endowed with a set amount of long-lasting neurons, new neurons could still be born in adulthood. More importantly, this occurs in the hippocampus, a critical structure for memory and learning. And what can boost the generation of new neurons there? Aerobic exercise.
The hippocampus is one of the primary targets of neurodegenerative diseases such as Alzheimer’s. So building up the hippocampus over a lifetime could potentially delay the effects of diseases.
“Exercise is not going to cure Alzheimer’s or dementia but it anatomically strengthens two of the key targets of both those diseases, the hippocampus and the prefrontal cortex,” Suzuki said. “Your hippocampus will be bigger if you exercise regularly, so that means that it’s going to take that much longer for the plaques and tangles of Alzheimer’s disease to cause behavioral effects. That means months, or hopefully years, of higher cognitive function.”
The creation of new neurons, or neurogenesis, doesn’t happen overnight, however. Neurons don’t just pop up fully formed and fully integrated. They are born as immature cells and take several months to grow.
But that’s not to say that all positive effects will be delayed by three or four months if you start exercising now. As many people have noticed firsthand, exercising also makes the mind sharper and attention more focused. That’s because another brain area heavily affected by aerobic exercise is the prefrontal cortex, an area in charge of high-level cognition, executive functions, decision-making and attention.
Exactly how it happens is not fully known, but it seems that the prefrontal cortex is actually relaxing during intense physical activity. It then gets a rebound increase in blood flow after the exercise, enabling it to work at full speed. It’s also possible that the same bodily changes that help new neurons grow in the hippocampus are also at work in the prefrontal cortex and help grow glial cells and blood vessels.
So which type of exercise is best from the brain’s point of view? Here’s what we can tell from research so far:
Mood: Walking, aerobic exercise and high-intensity interval training can improve your mood.
“We recently did a study comparing the three. All three of them improved mood but the one that did the most was walking. That’s good news for people who don’t have a high-level aerobic regime on hand,” Suzuki said.
Memory: The best evidence for hippocampal neurogenesis is continuous aerobic exercise.
“You have to get your heart rate up. So a good 45-minute workout,” Suzuki said.
Attention: Aerobic exercise is again the best option if you want to boost attention. But unlike with memory, the improvements are more acute and come faster. Jogging, biking and treadmill running are all good options for getting a boost in the prefrontal cortex.