Aug 23, 2008
By: Dr. Adrian Preda
I apologize for the long delay in getting back to this column but I have a good excuse. We just recently had a baby, and boy, that takes care right there of the physical exercise need. Between carrying the baby upstairs and downstairs, running to get the baby, getting out of the bed and picking the baby up and putting the baby down a couple of times a night no you need not worry about getting your daily exercise dose in…Now, the majority of the answers to my post on the brain virtues of physical exercise suggests that most people think that the brain benefits of physical exercise are mostly to be understood as complementary effects of a healthy life style.
Is this correct? In my post today I will attempt to answer this question.
First, while generally healthier people seem to have healthier brains, the physical exercise effect on the brain seems to be independent of other things. One of the most important development in neuroscience was when the official dogma claiming that there was no neurogenesis (production of new brain cells) in the adult brain was toppled. Now we know that the brain is “plastic” meaning that, under the right circumstances, the brain can change in terms of both producing new cells and getting more cells connected to each other.
One of the places where neurogenesis has been shown to occur in the adult brain is the dentate gyrus, a strip of grey matter placed deep down in the brain. The dentate gyrus is a part of the hippocampus, the main memory structure, and has been shown to play a role in the forming of new memories. What can the dentate gyrus teach us with regards to physical exercise?
Following a series of extremely thought provoking experiments researchers from the Gage laboratory at UCSD concluded that exercise leads to the production of new brain cells in the dentate. First the researchers found that mice housed in an enriched environment (a larger cage with toys, tunnels, and more opportunity for physical activity, learning, and social interaction than in standard bare cage) have an increased number of new neurons in the dentate gyrus.
The enriched environment is a mice equivalent of not only healthy but good living: leisurely enjoying life, getting both physical and intellectual stimulation, socializing with friends. Now, the fact that new neurons were produced was a big enough news in itself but the Gage group did not stop there. Their next goal was to figure out if neurogenesis was the result of a sum of factors acting together (i.e. the enriched environment) versus a specific effect of individual factor. So, they first dissected the enriched environment in a number of “sub” environments. In their next experiment they placed the mice in a “learning environment” where they had access to a maze, a “physical exercise environment” where mice had unlimited access to a running wheel, in addition to enriched and standard (empty cage) environments. Then they compared the groups in terms of behavioral performance and eventually looked at their brains.
Their conclusion was anything but expected: while both enrichment and wheel running led to improved spatial memory function only physical exercise in a running wheel also promoted neurogenesis and enhanced the survival of newborn neurons in the dentate gyrus.
Bottom line: exercising seems to literally mean “exercising the brain”.
So, in lieu of conclusion, till next I wish you all happy trails (and I don’t mean it as just trails on the paper in a paper and pencil memory task)!
Adrian Preda, M.D. is an Associate Professor of Psychiatry and Human Behavior in the UC Irvine School of Medicine’s Department of Psychiatry and Human Behavior. His expertise in human behavior, psychology and spirituality is based on years of experience working as a psychiatrist, psychotherapist, teacher and researcher in a variety of academic clinical and non-clinical settings. He also teaches the UC Irvine Extension class The Mind that Changes the Brain: Wellness in the Second Millennium.
van Praag H, Christie BR, Sejnowski TJ, Gage FH (1999) Running enhances neurogenesis, learning, and long-term potentiation in mice. Proc Natl Acad Sci USA 96: 13427–13431
van Praag H, Kempermann G, Gage FH (1999) Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus. Nat Neurosci 2: 266–270.
Farmer J, Zhao X, van Praag H, Wodtke K, Gage FH, Christie BR (2004) Effects of voluntary exercise on synaptic plasticity and gene expression in the dentate gyrus of adult male Sprague-Dawley rats in vivo. Neuroscience 124: 71–79