Verified by 
“To move is all mankind can do . . .whether in whispering a syllable or in felling a forest.”
- Sir Charles S. Sherrington (1857-1952)
Charles Sherrington is widely considered to be a pioneer in neuroscience. He had an amazingly distinguished career and won the Nobel Prize for Physiology or Medicine in 1932. He’s one of my own personal superheroes of science. But it’s the more philosophical quote above that he wrote in 1924 that serves as a great lead in for this post. This idea of movement being the de facto reason for function in the nervous system has great resonance today.
If our brains evolved to control movement as Daniel Wolpert has eloquently argued, then it stands to reason that movement and sensations associated with moving can serve as powerful signals for our brains. That’s because controlling movement involves more than just sending commands to our muscles. It also includes getting sensory feedback from the movement that occurs. This can have specific and general effects on how we perceive what we are doing, and how we feel.
There are lots of examples of this. Even before Wagemaker and Goldstein wrote about “the runner’s high” back in 1980, this was probably one of the best known examples illustrating how getting out and moving around can literally make you feel better.
Lots of empirical data in human and animal models show clearly that physical exertion can reduce feelings of stress, elevate mood, and alter pain perception. More recently, David Raichlen and colleagues at the University of Arizona and University of Texas Health Science Center, suggested that we—and our dogs—really are “wired to run”. And that high levels of exertion produce feedback that reinforces repeated activity and that “runner’s high”.
These earlier studies really focused on the hormonal and neurotransmitter effects of physical exertion. The more “rapid” and possibly transitory effects of activity we might say. More recently the outcomes of being physically active—and again gauged using running—have now begun to be characterized in terms of affecting brain structure.
Schoenfeld and colleagues at Princeton recently published a study in the Journal of Neuroscience that illuminates this. As I wrote above, it’s been known for quite some time that physical activity can reduce anxiety. To look at the issue of stress and anxiety in an animal model, the researchers at Princeton took inactive (sedentary) mice and those that had done lots of training on a running wheel (“runners”) and measured how these two groups of animals responded to a very stressful stimulus.
They immersed the two groups of mice in cold water and then examined what happened in the ventral hippocampus, a part of the brain known to help regulate anxiety. They found some pretty interesting things. The neurons of the sedentary mice showed dramatic increases in activity that would lead to structural changes. In contrast, the runners had no changes. Also, inhibitory connections in the hippocampus thought to contribute to anxiety regulation were enhanced in the “runners” compared with the sedentary mice.
This study suggests an interesting mechanism. The authors propose that running may reduce activity in circuitry that would instead produce anxiety. That is, running has a “calming” effect. As a result of the running training the hippocampus in runners may be optimally tuned to produce the best response to stress in different environments.
The bottom line is that this work shows that physical activity helps offset the effects of stress. This has huge implications for most of us who find ourselves in an ever increasing world of anxiety and stress.
Your brain needs to move your body to keep itself in shape. And, while much of this recent work was in a rodent model with the all the implied and actual caveats, keep this in mind—people are animals too. So maybe you should go out and do some activity with your pets. All the brains will benefit.
© E. Paul Zehr (2013)
