Exercise increases birth of new nerve cells
Fred Gage, a neuroscientist at the Salk Institute for Biological Studies who led both studies, explained that the researchers were “very surprised” to find that the physical activity of a mouse “affects the number of new brain cells and impacts its ability to remember things.” At the time, scientists largely agreed the brain affects behavior. Gage’s studies suggested the opposite was also true.
Exercising monkeys learn faster
To test whether moderate exercise changes the brain, Judy Cameron, a neuroscientist at the University of Pittsburgh, trained a group of middle-aged and older monkeys to run on a treadmill for one hour each day, five days per week for five months — a running regimen similar to that recommended for average, middle-aged adults. As the one group of monkeys ran, a second group of monkeys sat on the treadmills. Over the course of the study the researchers evaluated the monkeys’ ability to learn new things.
Regardless of the age of the monkeys, Cameron’s group discovered that the monkeys on the running regimen learned new things twice as fast as the sedentary animals.
According to Cameron, it’s possible that the cognitive improvements associated with exercise are the result of increased blood flow to the brain. The greater the blood flow, the faster oxygen and other important nutrients can reach nerve cells.
Brain benefits across lifespan
As people get older, it is natural for some regions of the brain to begin to shrink. For instance, studies show the hippocampus shrinks one to two percent annually in people without dementia — a loss that is associated with an increased risk for developing cognitive difficulties. Curious about whether exercise could help slow or reverse these changes, Kramer and his colleagues recruited a group of healthy, sedentary adults from ages 55 to 80 to participate in a yearlong exercise program.
These adults were divided into two teams — one spent their time walking for 40 minutes three days per week while the other performed a variety of strength and balance exercises during this time. At the start, middle, and completion of the study, the researchers used magnetic resonance imaging (MRI) to measure the volume of the hippocampus.
The size of the hippocampus increased by 2 percent on average in the adults that completed the walking regimen and memory improved. In contrast, the participants who completed a yearlong balance and strength training program experienced a 1 percent decrease in the volume of the hippocampus.
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