Links between physical exercise and improved neurological health are hardly surprising news at this point, but in case you need a little post-Mardi Gras workout inspiration, a team from Brigham Young University have discovered that running counteracts the mental declines caused by chronic stress – well, at least in mice.
It is not yet clear whether exercise has the same protective effect in humans.
Chronic stress, quantified by persistently increased levels of the hormone cortisol, is known to do a great many bad things to your body. One such unpleasant effect is impaired learning and memory formation, arising because neurons in the hippocampus area of the brain are less able to form new synaptic connections, a process called long-term potentiation (LTP), under the changed physiological conditions.
The study, now published in Neurobiology of Learning and Memory, revealed that the neurons of mice who were exposed to environmental stresses but then allowed to run had the same LTP capability as unstressed mice.
“The ideal situation for improving learning and memory would be to experience no stress and to exercise. Of course, we can’t always control stress in our lives, but we can control how much we exercise,” said senior author Jeff Edwards in a statement. “It’s empowering to know that we can combat the negative impacts of stress on our brains just by getting out and running.”
His team’s series of experiments involved several groups of mice: an exercise group that had access to wheels and ran an average of 5 kilometers (3 miles) per day, and a sedentary group that had no outlet to run. During a 4-week period, half of the mice in each group were also regularly exposed to stress in the form of swimming in cold water or having to walk along elevated platforms. Subsequent LTP status was assessed by examining the electrical connectivity of hippocampus neurons in brain tissue samples.
To determine the impact on real-life cognitive function, separate groups of mice (with brains fully intact) were put through a memory-based maze following six weeks of stress conditions. Stressed mice who had been allowed to run made fewer mistakes navigating the maze than those who were stressed and sedentary.
Exactly how, on a chemical level, the act of cardiovascular exercise results in boosted LTP will need to be investigated further, but the authors’ preliminary gene expression analysis gives us a good direction to start looking. Running mice produced higher levels of a molecule and its receptor, called brain-derived neurotrophic factor and TrKB, respectively, that promote neuron growth and synaptic development.