November 9, 1999-Chalk up another benefit for regular exercise. Investigators from the Howard Hughes Medical Institute (HHMI) have found that voluntary running boosts the growth of new nerve cells and improves learning and memory in adult mice.
"Until recently it was thought that the growth of new neurons, or neurogenesis, did not occur in the adult mammalian brain," said Terrence Sejnowski, an HHMI investigator at The Salk Institute for Biological Studies. "But we now have evidence for it, and it appears that exercise helps this happen."
Sejnowski, Salk colleague Fred Gage, and postdoctoral fellows Henriette van Praag and Brian Christie, published their findings in the November 9, 1999 issue of Proceedings of the National Academy of Sciences.
The investigators began their study by comparing the memory skills of a group of sedentary mice to those of a group of mice who exercised freely on a running wheel for one month. Mice in the exercise group logged an average daily distance of 4.87 kilometers, or 2.92 miles.
Both groups were trained to locate a submerged camouflaged platform in a maze that was lying just below the surface in cloudy water. Mice dislike swimming and instinctively seek the platform as a refuge from the stressful activity.
"We can't ask a mouse if it remembered where the platform was located, so we measure long-term memory by having them swim to the platform," said Sejnowski.
After six days of training each group of mice for the swimming task, the researchers began the study. The group of mice that had been exercising made a beeline for the platform. In contrast, the sedentary mice took significantly longer paths and times to find the dock. The path chosen and time taken reflect long-term memory, or how well the mice recall the platform's location. Based on the swimming test, mice in the exercise group were better able to remember the platform's location compared to mice in the sedentary group.