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Wednesday
Apr052017

How should we be using exercise as a tool to protect our brains?

It is well-accepted that physical exercise is beneficial for your health, but researchers are still investigating how exactly these benefits translate in the brain.  Many studies have shown that aerobic exercise increases neurogenesis and improves cognitive performance, but the exact mechanism connecting these two observations is still unclear. Two recent publications have reported interesting results describing how exercise type, genetic variance, and external stress affect the brain. The experiments are both done in rodents, so take the results with a grain of salt.

What the best type of exercise I can do for my brain?

While most clinicians are likely to encourage any physical activity, Nokia et al investigated the effects of three different types of exercise on neurogenesis in the hippocampus, the region of the brain critical for memory, learning, and stress response. Rodent exercise research generally employs a running wheel to simulate aerobic exercise, but here the authors compared three different exercise regimens: 1) sustained aerobic endurance exercise (ie. Voluntary running wheel or motorized treadmill), 2) high-intensity interval training (speed intervals on treadmill) and, 3) anaerobic resistance training (ie. weighted climbing). Interestingly, the authors found markers of cell proliferation, maturation, and survival- all indicative of neurogenesis- were only significant in rats that had completed the endurance training, which included voluntary running on a running wheel 3 times per week for 6 weeks. Moreover, they found the effects were most significant in rats genetically predisposed to respond to physical exercise (ie. maximal running distance increased following 8 weeks of treadmill training as opposed to no change). Take home: Sustained aerobic exercise is the most effective training paradigm to promote hippocampal neurogenesis, especially if you are running voluntarily and genetically predisposed to show gains in aerobic fitness with training.

Can exercise protect my brain?

Stress is known to negatively impact mood and impair memory, while simultaneously eliminating dendritic spines in the brain. Because exercise is known to improve memory function, Chen et al investigated whether exercise could rescue the negative effects of stress on behavior and spine stability. This study was carried out in mice who expressed fluorescent protein in their cortical neurons enabling in vivo transcranial monitoring of dendritic spine dynamics before and after exercise/stress intervention. Mice were physically stressed for 14days with or without one hour of continuous treadmill exercise, followed by behavioral testing, imaging, and brain protein/transcript quantification. The results showed that exercise not only prevented stress-induced anxiety and working memory loss, but also physically prevented spine elimination and enhancing survival of newly formed spines. The authors confirmed that the observed neuroprotective effects of exercise were conferred through the BDNF/TrkB pathway. Take home: Regular sustained aerobic activity can prevent the deleterious effects of stress on your brain.

Better get moving!

MMR

Chen et al. Treadmill exercise suppressed stress0induced dendritic spine elimination in mouse barrel cortex and improved working memory via BDNF/TrkB pathway. Transl Psychiatry (2017) 7, e1069.

Nokia et al. Physical exercise increases adult hippocampal neurogenesis in male rats provided it is aerobic and sustained. J. Physiol 594. (2016) pp 1855-1873.

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