- Aerobic exercise like running promotes the birth of adult-born neurons via neurogenesis in early adulthood.
- Humans and mice who run regularly during young adulthood tend to have more adult-born neurons.
- Running throughout middle age keeps adult-born neurons alive and well "wired," a new mouse study found.
Neuroscientists have known for decades that aerobic exercise—such as running, brisk walking, or doing cardio on stationary equipment—stimulates the birth of new neurons (neurogenesis) in the hippocampus brain region of both humans and mice. The hippocampus is the mammalian brain's memory hub.
A new study on mice sheds light on how running throughout middle age keeps adult-born neurons in the hippocampus alive and well-wired to other brain areas in a way that may offset age-related cognitive decline and lower dementia risk. These findings (Vivar et al., 2023) were published on May 15 in eNeuro.
The researchers found that long-term running helps adult-born neurons survive during mid-life. It also helps them stay "wired" to cortical and subcortical brain regions within a hippocampus-rooted neural network that supports memory function.
This study's findings suggest that sticking with a regular running routine throughout middle age (and beyond) may help adult-born neurons created via neurogenesis during early adulthood stay alive and continue to thrive as the brain ages.
"Our research shows that the afferent network of adult-born neurons is drastically changed by long-term running," the authors explain in their paper's introduction. "We show that long-term running increases hippocampal neurogenesis and modifies the network of new neurons born in young adult mice in a manner that optimally supports memory function at middle age."
Running Gives Rise to Adult-Born Neurons in Humans and Mice
If left to their own devices, mice are more likely to pursue voluntary running than most humans. Unlike many people—who often let home cardio equipment collect dust in the corner or avoid outdoor aerobic exercise altogether—if mice are given access to running wheels in their laboratory habitats, most of them voluntarily run multiple times a day.
For their latest adult-born neuron research, first author Carmen Vivar and colleagues randomly separated a sample of mice who'd grown up with the same level of physical activity as youngsters into two groups just as they entered the equivalent of mid-life in human years.
One group of mice wasn't given access to running wheels in their habitat and couldn't run regularly throughout middle age. These "sedentary" mice served as a control group. The other cohort of mice was given continuous access to running wheels across their lifespan and kept running voluntarily throughout middle age. These long-term runners were classified as the "voluntary running group."
During the next phase of this study, Vivar et al. compared how running vs. not running throughout middle age affected the survival rate and synaptic connectivity of adult-born neurons in the sedentary control group and the voluntary running group.
Mid-Life Running Fortifies Existing Adult-Born Neurons
The researchers found that consistently running throughout middle age preserved the benefits of neurogenesis in the mouse brain by helping adult-born neurons survive and stay wired to memory-related neural areas. Conversely, middle-aged mice who didn't continue running throughout middle age didn't experience these brain benefits.
"Long-term exercise profoundly benefits the aging brain and may prevent aging-related memory function decline by increasing the survival and modifying the network of the adult-born neurons born during early adulthood, and thereby facilitating their participation in cognitive processes," corresponding author Henriette van Praag wrote in a May 2023 news release.
"Our study provides insight as to how chronic exercise, beginning in young adulthood and continuing throughout middle age, helps maintain memory function during aging, emphasizing the relevance of including exercise in our daily lives," Vivar added.
Use It or Lose It: Staying Active as We Age May Preserve Neurogenesis' Benefits
If you're looking for a neuroscience-based source of motivation to keep exercising throughout middle age, this research suggests that doing cardio as we get older may help preserve the brain benefits of neurogenesis gained from being physically active during young adulthood. Running throughout middle age appears to help adult-born neurons survive and preserves memory-related neural wiring as the brain ages.
"While [our] findings are limited to the circuitry of adult-born neurons, we expect that they are representative and indicative of the effects of running on the brain as a whole and provide novel insight as to how exercise helps maintain memory function during aging," the authors conclude.
Although the mammalian brain (in humans and mice) tends to have similar neurogenesis-related responses to aerobic activity, human studies are needed to confirm that middle-aged people reap the same brain benefits from long-term running observed in this study's mice.
Carmen Vivar, Ben Peterson, Alejandro Pinto, Emma Janke, Henriette van Praag. "Running Throughout Middle-Age Keeps Old Adult-Born Neurons Wired." eNeuro (First published: May 15, 2023) DOI: 10.1523/ENEURO.0084-23.2023