EXERCISE MAKES YOUR BRAIN GROW

What goes on inside your brain when you exercise? That question has preoccupied a growing number of scientists in recent years, as well as many of us who exercise. In the late 1990s, Dr Fred Gage and his colleagues at the Laboratory of Genetics at the Salk Institute in San Diego elegantly proved that human and animal brains produce new brain cells (a process called neurogenesis) and that exercise increases neurogenesis. The brains of mice and rats that were allowed to run on wheels pulsed with vigorous, newly born neurons, and those animals then breezed through mazes and other tests of rodent I.Q., showing that neurogenesis improves thinking.

The answers to how this may actually happen are becoming more clear cut with further research: Bone-morphogenetic protein or BMP is one of the key ingredients. The more active BMP and its various signals are in your brain, the more inactive your stem cells become and the less neurogenesis you undergo. Your brain grows slower, less nimble, older. But exercise countermands some of the numbing effects of BMP.

Another ingredient is an interestingly named brain protein called Noggin: Noggin acts as a BMP antagonist. The more Noggin in your brain, the less BMP activity exists and the more stem cell divisions and neurogenesis you experience. Mice at Northwestern whose brains were infused directly with large doses of Noggin became little mouse geniuses, if there is such a thing. They aced the mazes and other tests.

Whether exercise directly reduces BMP activity or increases production of Noggin isn’t yet known and may not matter – The results speak for themselves.

But in a twist of nature where there are always negative and positive feedback loops BMP was found to be playing a surprising, protective role for the brain’s stem cells. When stem cells from mouse brains were infused with large doses of Noggin, hindering BMP activity, the stem cells began dividing rapidly, producing hordes of new neurons. But over time, they seemed unable to stop, dividing and dividing again until they effectively wore themselves out. The same reaction occurred within the brains of living (unexercised) mice given large doses of Noggin. Neurogenesis ramped way up, then, after several weeks, sputtered and slowed.  An overabundance of Noggin seemed to cause stem cells to wear themselves out, threatening their ability to make additional neurons in the future.

Thankfully you cannot overdose on Noggin by exercising because it seems that the effects of exercise are constrained and soon plateau, causing enough change in the activity of Noggin and BMP to shake slumbering adult stem cells awake, but not enough to goose them into exhausting themselves.

Still, if there’s not yet any discernible ceiling on brain-healthy exercise, there is a floor. You have to do something. Walk, jog, swim, pedal — the exact amount or intensity of the exercise required has not been determined, although it appears that the minimum is blessedly low…

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