I found an interesting article in the NY Times: How Inactivity Changes the Brain by Gretchen Reynolds , dated Jan 22, 2014.
Below is a direct quote from that article:
“A number of studies have shown that exercise can remodel the brain by prompting the creation of new brain cells and inducing other changes. Now it appears that inactivity, too, can remodel the brain, according to a notable new report.
The study, which was conducted in rats but likely has implications for people too, the researchers say, found that being sedentary changes the shape of certain neurons in ways that significantly affect not just the brain but the heart as well. The findings may help to explain, in part, why a sedentary lifestyle is so bad for us.
Until about 20 years ago, most scientists believed that the brain’s structure was fixed by adulthood, that you couldn’t create new brain cells, alter the shape of those that existed or in any other way change your mind physically after adolescence.
But in the years since, neurological studies have established that the brain retains plasticity, or the capacity to be reshaped, throughout our lifetimes. Exercise appears to be particularly adept at remodeling the brain, studies showed.
But little has been known about whether inactivity likewise alters the structure of the brain and, if so, what the consequences might be.
So for a study recently published in The Journal of Comparative Neurology, scientists at Wayne State University School of Medicine and other institutions gathered a dozen rats. They settled half of them in cages with running wheels and let the animals run at will. Rats like running, and these animals were soon covering about three miles a day on their wheels.
The other rats were housed in cages without wheels and remained sedentary.”
After three months of resting or running, the rats’ brains were examined.
The rats who were resting had changes take place “in ways that made them likely to overstimulate the sympathetic nervous system, potentially increasing blood pressure and contributing to the development of heart disease.”
“This finding is important because it adds to our understanding of how, at a cellular level, inactivity increases the risk of heart disease.... "
"But even more intriguing, the results underscore that inactivity can change the structure and functioning of the brain, just as activity does.”