Use it or lose it (contd)
by Fred Lane PhD.
“Use it or lose it,” has been a golden mantra for the elderly for years. Now, a couple of new studies at Columbia University in New York and the University of Illinois at Urbana-Champaign suggest that mild aerobic exercise not only preserves but also encourages the growth of new brain cells. This is in direct conflict with the age-old belief that, after a brief period in life, we were left with a certain number of brain cells and that all we could do was to lose them over time. Attempts to repair or replace damaged nerve cells and their dendrites through neurosurgery or medication have a history of a very low success rate.
New brain cells develop when multipotent neural stem cells divide into either neurons or glial cells. Many die in their process towards maturity, but those that make connections with other neurons (above) tend to survive over this month-long period. Growth factors assist in generating new cells and a brain-derived neurotropic factor keeps the successful cells alive. Any one of the billion or so mature cells in an adult brain brain cell might make 1000 or more connections through their delicate spider-web dendrites.
“Neurogenesis,” or the creation of new neurons, now seems possible according to an expanding body of research. This was spurred by 1998 mouse studies by Fred Gage at the Salk Institute, La Jolla, CA, where animals given running wheels were found to create two to three times the number of fresh neurons right up to the point of death, compared with others denied this form of exercise. The “exercise” mice were also better at solving traditional maze problems.
Mouse on a treadmill running wheel similar to that used by Fred Gage.
At Columbia University, men and women aged 21 to 45 were given moderate exercise for one hour, four times a week. The exercise group performed better on memory tests and those with the best oxygen intake improvement showed the best memory improvement. Magnetic Resonance Imaging (M.R.I.) analyses suggested increased blood flows in critical areas of the brain’s hippocampus, as well as increased oxygen intake. The hippocampus plays a large role in memory and learning. As we grow older, it typically shrinks. In Alzheimer’s disease the hippocampus is noticeably wasted.
At Urbana-Champaign, 59 sedentary elderly people aged 60 to 79 walked one hour three times a week in a series of experiments supervised by Art Kramer. After six months Kramer was particularly interested in the significant brain neuron growth shown by M.R.I. scans in the prefrontal and temporal cortices regions of the brain.
“Use it and grow”
No single theory explains these phenomena. Some scientists claim it is increased levels of serotonin, others say it is due to an insulin growth factor protein. It might well be both, or even a third variable. However, it is becoming increasingly clear that in addition to the old “use it or lose it” philosophy, there might well be a “use it and grow” corollary. Exercise, diet, and social and environmental stimulation seem even more important than ever for retirees.
Jacobs B.L., H. van Praag, and F. H. Gage. Depression and the Birth and Death of Brain Cells. American Scientist. 88/4, pp.340-44, 2006.
Colcombe, S.J., K.I. Erickson, P.E. Scalf, J.S. Kim, R. Prakash, E. McAuley, S. Elavsky, D.X. Marquez, L. Hu, and A. F. Kramer. Aerobic Exercise Training Increases Brain Volume in Aging Humans. Journal of Gerontology. Series A: Biological Sciences and Medical Sciences. 61: pp. 1166-1170, 2006.
Colcombe, S.J., and A.F. Kramer. Fitness effects on the cognitive function of older adults: A meta-analytic study. Psychological Science 14/2, pp.125-130, 2003.