Run them legs - physical activity restores function following sensory visual deprivation in mice

I finally mustered up the strength to sign up for a half marathon in Huntington Beach for 2015. It's something that I've wanted to do for a while, but have always been too scared to see if I could run the 13.1 mile distance.

Although I'm not training until roughly October, I'm trying to run a couple times a week just to keep up endurance. What's the best thing about running?

For me, it's probably running in the early morning (before the sun rises), or late evening (dark runs). Sometimes I'll wake up around 6AM, have trouble sleeping, and just roll out of bed to get ready for a run (I even have running clothes near my closet so I can make a quick getaway without fumbling in the dark).

Photo courtesy of McKay Savage

Running, or any exercise, has several physical and mental benefits. While we've heard about how an active lifestyle wards you away from sickness more frequently, stimulates higher learning capacity, and even actually increases more brain growth, what about physical exercise following an injury?

Recently, running has been shown to help mice recover visual function following visual deprivation. A study published in eLife (Kaneko and Stryker, 2014) has shown that mice with monocular deprivation have recovery of visual function following sessions of running on a treadmill while viewing visual images.* The researchers created monocular deprivation only to one eye by suturing shut one of the mouse's eyes for 30 days. As a result, very little input comes into this sutured shut eye - in fact, this simulates a condition that often happens to some children called amblyopia, or "lazy eye." Amblyopia is where vision doesn't develop normally, sometimes as a result of eyes not aligned appropriately (an issue when eyes point in different directions). Think of your eyes as requiring training for them to function at their best - if during development one eye receives more information and training than the other (this eye being the dominant eye), the eye that receives less training is often the weaker eye and sometimes not even used. For kids that have amblyopia, one of the treatments is to force the weaker eye to train itself by closing shut the more powerful eye. By shutting the more dominant eye, the hope is that the weaker eye eventually becomes strong enough to work just as well as the dominant eye.

Form of treatment for amblyopia (Photo courtesy of National Institutes of Health (NIH))

 In this study, researchers tried to see if physical activity would help speed recovery of visual function after suturing shut the eyes. Mice that had deprivation to one eye were divided into the following groups: had no post-operative treatment, were allowed to run on a spherical treadmill (I'm trying to imagine cute little running mice), viewed different images to stimulate visual training, or had exercise while looking at different images. Surprisingly, the mice had recovery of vision in their sutured eye! What was strange, however, was the recovery observed was ONLY when the mice were running and looking at different visual images - the control groups showed no visual improvement.

These findings are incredibly exciting, but running won't necessarily solve everything. It's important to keep in mind that restoration of vision in this case, happened only in the situation of combining visual stimulation with physical activity.  As in running only promotes recovery following an injury in the specific brain pathways that are activated while you're running. So for example, running would only help you recover from damage in the area important for food processing only if you are smelling or even eating something (as in stimulating your food processing pathways).

It's a bit extreme, but these findings serve more to demonstrate the remarkable flexibility of the brain to recover. Also, just think - next time you decide to get all judgmental on that person on the treadmill reading their magazine, maybe they're stimulating and increasing their brain function!

Blur of legs at the gym sweating it hard (photo courtesy of Brandon Wiggins)

Until next time, happy eating all!

*Monocular deprivation was done by shutting one eye of mouse from postnatal day 21 (within the critical period) until mice were 5 months old. Mice that had visual deprivation were then either given a treadmill alone, treadmill with visual stimulation, or visual stimulation alone. Recovery of visual function was measured using optical imaging.


Reference:
Kaneko M and Stryker MP., 2014. Sensory experience during locomotion promotes recovery of function in adult visual cortex. eLife.