How Activity and Free Choice Stimulate Neurogenesis

Résultat de recherche d'images pour "Neurogenesis"It’s been well reported that regular exercise and continued learning throughout one’s lifetime contribute immensely to improved health and well-being. But can physical activity and stimulating experiences help build and maintain more than muscle and memory by actually growing new brain cells?

John Ratey, MD, an associate professor of psychiatry at Harvard Medical School and author of the book A User’s Guide to the Brain from Vintage and an increasing number of neuroscientists say yes. And surprisingly, free choice may be the most important contributor to the effectiveness of exercise and experience in building healthier brains.

Exercise Spurs Cell Growth

Neuroscientific research in the late 1990’s overthrew a long-held scientific belief that the brain is hardwired and fixed by adulthood, and proved that brain cells keep regenerating (neurogenesis) throughout one’s lifetime. Studies have shown that exercise not only improves physical fitness and mood by stimulating pleasure chemicals such as serotonin and dopamine, it actually changes the brain by spurring it to grow new cells.

Ratey calls exercise “…Miracle-Gro for the brain,” and experiments bear out the fact that mice given a wheel to run on have bigger, quicker brains than sedentary mice. Research results published confirm that exercise produces a chemical that stimulates stem cell production and maturation.

Enriched Environment Builds More Networks

The continuing inquiry into what contributes to neurogenesis in the human brain shows that exercise and an enriched environment that includes complex and diverse social and cognitive elements can work together to replace damaged or aging brain cells and successfully integrate them into the brain’s circuitry. Scientists suspect that after exercise generates new cells, stimulating experiences help support the survival of those cells by creating more intricate connections between nerve cells.

The discovery of how exercise and experience work together to renew the brain has come through a series of test results. A team of Berkley scientists showed in the 1960’s that rats raised in enriched environments that included toys, mazes and frequent handling by scientists not only grew bigger brains, but were better at solving mazes than rats raised in barren isolation in a dark and silent room. Subsequent studies at the University of Illinois revealed that rats raised in enriched environments had denser and more extensive connectors between neurons, with meant richer, more complicated brain circuits.

Rich Experiences Boost Older Brains

Then in 1997 Salk Institute Professor Rusty Gage and his colleagues wanted to know if an enriched environment would increase neurogensis in the already developed brains of young adult mice. Their study determined that new neurons increased by 15 percent in the part of the brain that involves learning and memory. A later study showed that older mice—the equivalent of a sixty-five year year old person—got an even greater boost from an enriched environment than younger mice, with new brain cells developing three times the number of the isolated group in the same study.

Free Will Required to Stimulate Neurogenesis?

But Gage also uncovered an interesting twist. Freedom of choice also affect the brain enhancement. Given the fact that exercise alone grew bigger brains, he wanted to know if there was a difference between forced exercise and voluntary exercise. He set up an experiment where one set of mice were free to jump on and off the wheel at will, while another group were placed on a treadmill and prevented from getting off.

What he learned was startling. Forced exercise did not promote the development of new brain cells. And while the stress hormones generated by forced exercise might account for the loss of cells and damaged connections, the voluntary exercise subjects were different in another way. Theta waves, the same brain rhythms that are present when you pay close attention to something, were present in their brains. Gage believes the voluntary component of exercise might be the key to it stimulating neurogenesis.

Gage summarizes his conclusions in a conversation recounted in Sharon Begley’s Train Your Mind Change Your Brain from Ballantine Books : “It seems like the effects of running on neurogenesis and learning are dependent on volition. It has to be a voluntary act. It’s not just the physical activity itself.” Scientists still aren’t clear on exactly what is most important in a complex environment. Does one aspect – exercise, learning or social behavior – contribute more to neurogenesis than the other? The jury may be out on how the pieces connect, but evidence is mounting that by choosing regular exercise and engaging in activities that are interesting and challenging, the human brain can be vigorous and healthy for life.