Summary: New research from Texas A&M confirms that exercise increases hippocampal neurogenesis without causing loss of previously formed memories.
Contradicting earlier findings, researchers confirm exercise benefits the brain
Researchers at Texas A&M College of Medicine report that voluntary running increases the production of new neurons in the hippocampus, a brain region vital for learning, memory and mood regulation, and that this enhanced neurogenesis does not erase older memories. Their peer-reviewed study was published in the Journal of Neuroscience.
Exercise is widely recognized for improving cognition and mood, effects commonly attributed to increased neurogenesis in the hippocampus. In 2014, a prominent study using mice raised concern by suggesting that exercise-induced neurogenesis might eliminate memories that were formed before the exercise began. That result surprised the field and suggested a potential downside to the otherwise well-known cognitive benefits of physical activity.
Ashok K. Shetty, PhD, professor in the Department of Molecular and Cellular Medicine at Texas A&M College of Medicine, associate director of the Institute for Regenerative Medicine, and research career scientist at the Central Texas Veterans Health Care System, explained that the 2014 study was carefully done and therefore led many researchers to question whether the memory benefits of exercise might come at a cost.
To re-examine the issue, Shetty and colleagues replicated a similar experiment using rats rather than mice, since rats are physiologically and neurologically closer to humans in many respects. Their design measured learning and recall before and after a period of voluntary running, then assessed hippocampal neurogenesis and spatial memory retention.
The research team trained rats on a spatial task across multiple sessions to ensure stable learning and memory consolidation. After this training period, half of the animals were housed in environments that included running wheels for several weeks while the control group remained sedentary. During the exercise period, the running rats logged substantial activity—on average about 78 kilometers (roughly 48 miles) over four weeks—and showed a twofold increase in new neuron formation in the hippocampus compared with sedentary rats.
Despite these increases in neurogenesis, the rats that exercised displayed the same ability to recall the spatial task learned prior to running as the sedentary group. Both moderate and brisk runners retained comparable memory performance, indicating that even substantial amounts of voluntary exercise did not disrupt recall of previously formed memories.
Maheedhar Kodali, PhD, a postdoctoral fellow at the Institute for Regenerative Medicine and first author of the study, emphasized the contrast with the earlier mouse study. “We obtained findings that contradict the 2014 report,” Kodali said. “In our rat model, enhanced neurogenesis from voluntary running did not impair retrograde memory recall.” He noted that further work across additional species will help clarify whether the earlier mouse result represents a species-specific phenomenon or depends on other experimental variables.
The Texas A&M team highlights two important conclusions: first, voluntary running robustly increases hippocampal neurogenesis, which is associated with improved mood regulation and the formation of new memories; second, this increase does not appear to erase memories acquired before the exercise period, at least in the rat model used. These conclusions support the broader literature showing exercise as an effective strategy for cognitive health and emotional well-being.
About the study
Funding for this research came from the State of Texas and the U.S. Department of Veterans Affairs. The study, titled “Voluntary Running Exercise-Mediated Enhanced Neurogenesis Does Not Obliterate Retrograde Spatial Memory,” was authored by Maheedhar Kodali, Tarick Megahed, Vikas Mishra, Bing Shuai, Bharathi Hattiangady, and Ashok K. Shetty and published in the Journal of Neuroscience (published online August 3, 2016). The findings indicate that in rats, voluntary running increased hippocampal neurogenesis by about 1.5- to 2.1-fold without impairing recall of previously learned spatial information.
These results reinforce exercise as a safe and beneficial intervention for maintaining cognitive function and mood. For individuals concerned that regular physical activity could cause loss of older memories, this study provides reassurance that exercise promotes neurogenesis without erasing past learning in this animal model.