This
article appeared in Aging Today, May/June 1998, copyright American Society
on Aging, 1998. It appeared in the newspaper's Research Today section, aupported
by a grant from the AARP Andrus Foundation.
MARIAN DIAMOND'S
OPTIMISM ABOUT
THE AGING BRAIN
"People in the cars think I'm crazy, but it doesn't bother me," said Marian C. Diamond with a smile. Most any morning, drivers heading toward the Lawrence Berkeley Laboratory at the University of California (U.C.) might spot her, smartly dressed and sporting a wave of white hair, as she walks along the six-inch-wide curb, gyrating her arms over her head in a test of balance. "I know it's good for the cerebellum," she said citing research showing that exercises such as tai chi or curb walking--"it's just like a balance beam"--are likely to sharpen the brain's control center for physical coordination.
Few people in the world know more about the science of the brain than Diamond, distinguished professor of anatomy at U.C. Berkeley, former director of the Lawrence Hall of Science and recipient of the first Senior Scholar Award from the American Association of University Women. Her use-it-or-lose-it lecture, titled "An Optimistic View of the Aging Brain," fascinated registrants at the 44th Annual Meeting of the American Society on Aging in San Francisco with a survey of the latest brain research. Diamond, one of the few scientists allowed to study tissue from Albert Einstein's brain, burst myths about the brain's inevitable decline with passing years.
THREE MYTHS
Population trends show that by 2050 there will be 30 million Americans age 85 or older, about as many as there are 65 or more today, Diamond noted. "Our challenge then is to learn ways to keep the brain functioning at an optimum level for a lifetime," she said, adding that we need to "change our negative attitudes toward aging for ourselves and for others."
She debunked three common myths about normal aging brains: that they "go downhill" after age 30, that they lose 100,000 nerve cells per day and that "you can't teach old dogs new tricks."
Following the brain's most "explosive growth" period until the age of 10, Diamond explained, the human cortex, which handles our highest mental functions, can increase or decrease at any age, "depending on the level of stimulation." She said that the three-pound neural package is so complex that each of its 100 billion cells can received input from 100,000 other cells.
Diamond conducted research with rodents two decades ago that questioned early data showing the loss of 100,000 neurons in the cortex each day in mature brains. Other investigators have since proved the same is true of human brains. She explained that previous researchers apparently did not distinguish whether older brains they studied were from people who had been bed-ridden or otherwise unhealthy. "When they recounted, they took healthy, active brains. They didn't show significant differences between the 60 year old and the 20 year old. It's amazing."
Cell generation can happen in unexpected places. Diamond showed more than a decade ago that cell growth happened in the hippocampus region of rat brains, a section long regarded as having no potential for cell development. Until recently such growth was believed to be limited to rats and birds. Widely reported new findings, though, from researchers at Princeton University in New Jersey and Rockefeller University in New York City, were published in March by the National Academy of Science. The findings reveal such cell production in marmoset monkeys, suggesting that similar cell fabrication is probable in humans. Because the hippocampus deals with memory processing, scientists say, the discovery holds promise that stimulation of cell growth could one day help counteract some of the effects of diseases like Alzheimer's and Parkinson's.
Generally, Diamond added, the susceptibility of the hippocampus to reduced functionality when oxygen is diminished suggests that swimming and other oxygen-circulating activities may be especially beneficial to elders, because "as we get old our blood vessels become less efficient."
MAGIC TREES
Diamond, whose new book is Magic Trees of the Mind (New York City: Dutton, 1998), written with science journalist Janet Hopson, said that a brain "impoverished" of any stimulation can certainly atrophy, but one in an "enriched" environment will send out fresh branches of dendrites that take in new information and axons that transmit signals. The cortex will grow or shrink relative to its use, she affirmed, "just like a muscle." (Not only does the brain's anatomy increase, so does its chemical productivity. She explained that in her rodent studies, total protein in the brain rose by a "highly significant" 8%.)
By enriching the living conditions of rodents, Diamond and her colleagues have been able to measure thickening of the cortex exceeding 10% in some cases. She and her research staff found that they could extend the lives of laboratory rats to as much as 904 days, the equivalent of 90 years in humans, by treating them with TLC--that's right, tender loving care. Rather than moving the rodents by their tails, a standard, efficient lab practice, investigators began hugging them for a few moments against their white lab coats.
At 766 days Diamond's research team moved half of the rats into an impoverished environment--a no-frills cage with a single rat family--and half into an enriched environment. The more stimulating cages contained several families for social interaction and plenty of engaging toys to activate multiple senses (bells, running ladders, things with odors, and so on). New items were introduced at least twice a week. These animals were the ones that lived to be the rat equivalents of nonagenarians. "We've been able to show the positive aspect at every age we've worked with this," she said. Not only did the stimulated rat brains not lose neurons, they showed they could learn to grow.
Even in rat brains where scienists inflicates surgical lesions to simulate damage from injury or illness, she said, "those little dendrites were more prolific in the enriched than in the nonenriched animals."
Diamond expects one day to see experiments that may yield the rat equivalent of human centenarians. Her son, an architect who conducted doctoral research on what elders desire in retirement housing, found that although areas for socializing are vital to the residents' happiness, so are private living areas.
Someone, Diamond said, someday will design a rat environment featuring both the enriched common cage and small private compartments radiating out from a central communal hub, to see whether this arrangement affects rat longevity. Such research may help establish that the human instinct for "quiet time" and similar stress reduction, especially as people age, can be show to have a basis in the science of the brain.