Updated 4 months, 3 weeks ago

Jogging the brain

Physical activity boosts the flow of blood to the part of the brain that is responsible for memory and learning, promoting the production of new brain cells. Several schools in the US and the Netherlands have taken note. Pupils at Naperville Central High School near Chicago, for example, start the day with a fitness class they call "Zero Hour PE". Equipped with heart monitors, they run laps of the playground, and teachers say exam results have soared since the keep-fit initiative kicked off.

Now, neuroscientists at Cambridge University have confirmed that running stimulates the brain to grow fresh grey matter and it has a big impact on mental ability. John Ratey, an associate professor of psychiatry at Harvard Medical School in Boston and the book's author, says that exercise stimulates our grey matter to produce what he calls "Miracle-Gro" for the brain. "I can't understate how important regular exercise is in improving the function and performance of the brain," he says. "It's such a wonderful medicine."

Researchers studied two groups of mice, one of which had unlimited access to a running wheel throughout. The other mice formed a control group. In a brief training session, the mice were put in front of a computer screen that displayed two identical squares side by side. If they nudged the one on the left with their nose they received a sugar pellet reward. If they nudged the one on the right, they got nothing.

After training the mice went on to do the memory test. The more they nudged the correct square, the better they scored. At the start of the test, the squares were 30cm apart, but got closer and closer together until they were almost touching. This part of the experiment was designed to test how good the mice were at separating two very similar memories. The human equivalent could be remembering what a person had for dinner yesterday and the day before, or where they parked on different trips to the supermarket.

The running mice clocked up an average of 15 miles (24km) a day. Their scores in the memory test were nearly twice as high as those of the control group. The greatest improvement was seen in the later stages of the experiment, when the two squares were so close they nearly touched.

A second study focused on binge drinking. Researchers from the University of Houston inserted tubes into the stomachs of female rats to provide consistent doses of either alcohol or nonalcoholic liquid every Monday night for 11 weeks. Half the rats in each of these two groups were then kept idle in their cages for the rest of the week, while the other half ran on wheels for up to two hours, three days a week.

In each study, the brains of the rodents that exercised after receiving alcohol were substantially different from those of their sedentary counterparts. The inactive mice had weakened mitochondria in many neurons; the runners had hardy mitochondria. The sedentary rats given alcohol had almost 20 percent fewer neurons in their hippocampi than the control animals. The rats who were made to work out, though, had as many neurons as the controls, even if they were given alcohol.

“It’s well known that running increases neurogenesis” — that is, the creation of new brain cells — according to J.L. Leasure, the associate professor of psychology at the University of Houston who oversaw the rat study. So it seems likely that running stabilized the total number of brain cells in the bingeing rats, she says, even if some neurons died as a side effect of alcohol consumption. Exercise is also known to improve mitochondrial health in the brain.

Finally, you don't have to become a marathon runner to benefit your brain. The mainstay of exercise is simple, brisk walking. You'll feel the benefit even from a 30-minute walk.

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