For instance, running and other kinds of endurance exercise can boost the number of memory and learning neurons in the brain. Also, lab animals and people improve their performance on cognition tests after weeks of exercising.
But how exactly does exercise enhance the brain's functioning?
A new study published in Learning & Memory shows that the key lies in the muscles.
When you exercise, your muscles create substances that produce even bigger, stronger muscles. The study's lead scientist, Henriette van Praag of the National Institute on Aging, hypothesized that some of those compounds might travel to the brain.
But since it would nearly impossible to isolate the compounds to see the effect of each, Dr. van Praag decided to use drugs that produce effects in the body (er, mice bodies) that mimic exercise.
When given to sedentary animals, the two drugs, Aicar and GW1516, instigated changes in their muscles as though the animals had exercised. For instance, Aicar boosts muscle production of an enzyme called AMPK that is produced through regular endurance exercise such as running. Previous experiments had shown the sedentary mice who took Aicar could run 44% faster in treadmill tests than sedentary mice who didn't receive the drug. The other compound, GW1516, didn't have much effect in sedentary mice, but it increased endurance in animals who ran so that they were able to run farther than mice who ran but did not receive the drug.
So, Dr. van Praag and her colleagues gave unexercised animals these drugs to see what happened to their muscles and then their brains. After a week of receiving one of the two drugs and not exercise, the mice performed much better on memory and learning tests than animals who had not exercised nor received drugs.
A peek through a microscope showed that the mice who had received the drugs had many more neurons in the learning and memory areas of their brains than the control mice.
Muscles, not drugs, are the key
Dr. van Praag says she is fairly certain the drugs themselves did not cause the brain changes because of the blood-brain barrier. For that reason, she told The New York Times, "we could be fairly confident that the changes we were seeing were related to an exercise-type reaction in the muscles” and not to the brain's response to the drugs. She wasn't sure of the process but speculated that some of the AMPK enzyme produced during exercise enters the bloodstream and travels to the brain.
But don't get all excited that you could just take drugs to get the mental boost. The scientists found that when they injected the mice with Aicar for another week, the mice lost their improved mental performance, showing that the drugs are an insufficient substitute for real exercise.
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via: The New York Times