IT HAS long been thought that exercise boosts the brain as well as the body. And now we are discovering why. Regular exercise in monkeys has been shown to increase the number of blood vessels in one part of the brain. But while exercise makes the monkey鈥檚 brains more active, it does not seem to make them any smarter.
Adult monkeys who ran on treadmills for an hour a day, five days a week for 20 weeks, had a greater volume of blood vessels in their motor cortex, the brain area that directs voluntary motion. 鈥淎 greater blood supply probably enhances the stamina of the motor cortex,鈥� says William Greenough, the neuroscientist at the University of Illinois at Urbana-Champaign who led the research.
The monkeys who exercised were also able to learn a cognitive task more quickly, in just four days compared with eight for their sedentary counterparts. But they did not actually perform any better once they mastered the test, and they made far more errors as they were learning, he told the Society for Neuroscience meeting in New Orleans this week.
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In people, numerous studies suggest that aerobic exercise can improve some kinds of cognitive function in older people, and also help prevent any decline with age. It has been suggested that this is because exercise boosts blood circulation as well as blood鈥檚 oxygen-carrying capacity, reversing any age-related decline in blood flow to parts of the brain. Greenough鈥檚 work suggests that exercise also has a more direct effect on the brain.
The researchers are now checking to see if exercise boosts the blood supply to brain areas responsible for cognitive function. They also want to know if exercise stimulates the growth of neurons as well as blood vessels in primates. In mice, exercise induces the birth of new neurons and increases the number of connections each neuron makes, all processes that slow down as we age.
The key to this may be the production of BDNF, or brain-derived neurotrophic factor, a protein that encourages the growth of different types of neurons. Exercise stimulates BDNF production in the mouse hippocampus, and helps mice learn faster.