Grandma Moses first picked up a paintbrush at 78, reportedly after arthritis forced her to give up the embroidery for which she was already well-known. She went on to paint for more than 20 years, finishing her last big canvas at 101.
Giuseppe Verdi, the Italian composer, was also no slouch in old age. He produced his greatest masterpiece, “Otello,” at age 74, and his final opera, “Falstaff,” at 80.
Albert Einstein didn’t rest on his youthful laurels, either. After winning the Nobel Prize in physics at age 42, he became a political activist, crusading against atomic weapons until his death at 76.
And Nelson Mandela? The anti-apartheid leader didn’t even become president of South Africa until he was 76.
Despite such dazzling late-in-life success stories, neuroscientists for decades were pessimistic about the aging brain. Sure, a few standout individuals blossomed in their 70s and beyond, but they could point out that for every Einstein, there was an Isaac Newton, an equally great scientist who spent his later years preoccupied with alchemy and other pseudoscience.
The neuroscientists’ gloom was based on their belief that aging causes a steady loss of neurons (brain cells) all over the brain. They “knew” the adult brain could not generate new neurons. Worst of all, scientists assumed that nothing could be done to boost the odds of having a healthy, aging brain.
“It was thought that these changes began among individuals in young adulthood and progressed inexorably across the adult lifespan,” said Marilyn Albert, director of the Gerontology Research Unit at Massachusetts General Hospital.
Much of that, scientists have learned over the past decade, was too pessimistic. The aging brain, it turns out, is surprisingly “plastic” – capable of remodeling itself, growing new cells, and compensating in remarkable ways for the very real losses in processing speed that come with aging. And the brain is quite good at using the knowledge accumulated over decades to function well in everyday life.
Today, thanks to better techniques for studying post-mortem brain tissue, more sophisticated brain scans of living people and perhaps most important, a shift in emphasis from studying sick older people to studying healthy ones, neuroscientists have a much rosier view.
“The changes that occur with aging are much less widespread in the brain than we used to think,” Albert said. “And we now know there is a lot that people can do to maximize brain function in later life.” Many studies have contributed to this increasingly optimistic view of brain aging, but a few have proved pivotal.
In 1998, a team led by Fred H. Gage, a neuroscientist at the Salk Institute in La Jolla, Calif., showed that, contrary to popular belief, the adult human brain contains cells that can divide and become healthy, new neurons.
Though this had been previously shown in rats, cats and some monkeys, the Gage study electrified researchers in part because dividing brain cells were found even in the hippocampus, a region crucial for learning and memory. Equally impressive, dividing cells were found in people as old as72.
“The good news is that the adult brain retains the capacity for cell genesis and neurogenesis,” Gage said. “And this capacity persists throughout life. It is amazing.”
Just as important, Gage noted, researchers are discovering that physical exercise and intellectual enrichment can help stimulate this capacity.
Marian Diamond, a neuroanatomist at the University of California at Berkeley, has pioneered the study of brain improvement with more than 30 years of testing the mental capacities of rats in different types of cages normal cages with little inside and enriched cages containing lots of toys.
After leaving the animals in the cages for specified periods of time, Diamond sacrifices them and examines their brains to count the number of dendrites – filaments that extend outward from brain cells to pick up information. Whether the rats were young or old (the equivalent of 90 in human years), an enriched environment seems to stimulate proliferation of dendrites, she found.
“This is why we’ve gone to the optimistic view of aging,” Diamond said.
Gage’s team, too, has shown the power of an enriched environment to keep aging brains healthy. In fact, his team has shown that an enriched environment leads not just to new dendrites but to a 15 percent increase in new brain cells in the hippocampus of rats, even those that, until the experiment, had spent their whole lives in normal, that is, boring, cages.
Even more important, Gage said, what really matters in an enriched environment is exercise. Rats given the chance to run to their hearts’ content on running wheels doubled the rate at which new brain cells evolved into mature neurons, he said.
Other animal studies published in 1998 and 1999 suggest one reason for this. Exercise seems to trigger an increase in secretion of a natural chemical called brain-derived neurotrophic factor, or BDNF, which stimulates brain cell growth. But only vigorous, aerobic exercise – not stretching or toning – produces this effect.
In humans, physical exercise is also now known to be one of four key ways to protect cognitive function, according to a coalition of researchers sponsored by the MacArthur Foundation Research Network on Successful Aging. The other three protective factors are education (the more, the better), good lung function to maintain good oxygenation of the brain, and having a sense of control over one’s life.
Granted, it’s a bit of a leap from having a sense of control over one’s life to proving that stress is bad for aging brains, but psychologist Elizabeth Gould at Princeton University has shown that, at least in rats, this is true. Stress hormones block production of new brain cells in the hippocampus, she said, and other studies show that levels of stress hormones increase in aging humans. That suggests that stress may adversely affect the aging human brain and, possibly, that stress reduction techniques might offset it.
Amid the encouraging news, it is still true, as earlier studies suggested, that there is some shrinkage of brain tissue with aging, primarily in the frontal cortex, which is responsible for executive functions such as planning and organizing.
There is also some brain cell loss in clumps of nerve cells deep in the brain, such as the nucleus basalis and the substantia nigra. The loss of these cells is believed to decrease the brain’s ability to produce certain chemical messengers, such as acetylcholine, dopamine and serotonin.
And it’s well-documented that older people process information more slowly and have more trouble switching between tasks, said Jordan Grafman, chief of the neuroscience section of the National Institute of Neurological Disorders and Stroke. But it’s also well-documented that older people have bigger vocabularies and larger stores of acquired knowledge.
Moreover, even when older people do suffer losses in specific skills such as certain types of memory, their brains can compensate, said Denise C. Park, a psychologist at the University of Michigan. Brains scans such as PET and functional MRIs show that for intellectual tasks that a younger person would perform using only one hemisphere of the brain, an older person often recruits the other hemisphere or other areas in the same hemisphere to help out.
“You don’t need tremendous processing speed and working memory in everyday life, so long as you are in familiar surroundings,” Park said. “In real life, what counts is stored knowledge, wisdom and well-learned skills.”
So, Park suggested, the next time you wonder whether an older person is still competent, Park suggests, ponder this: A 1999 study that she did showed that it’s not older folks who forget to take their pills – it’s harried, middle-aged professionals.
SIDEBAR: Some Mental Skills Decline With Age… But Wisdom And Common Sense May Increase.
KEEPING THE BRAIN IN MIND
A growing body of research suggests there are a number of things you can do to improve brain function in later life.
- Physical exercise: It helps build new brain cells, as well as strong muscles.
- Mental exercise: Duke University neurobiologist Larry Katz, author of”Keep Your Brain Alive,” suggests doing “neurobics” to keep your brain humming with novelty, including simple tricks like brushing your teeth with your non-dominant hand, taking a different route to work and finding your car keys by touch instead of sight
- Stress reduction: Nobody has proved in humans that lower levels of stress hormones help maintain healthy brain function, but they have shown that stress harms the brains of rats.
- Stay connected: Harvard psychiatrist George Vaillant, author of the forthcoming book called “Aging Well,” said that maintaining rich emotional ties is crucial to healthy aging of mind and body.
- Be creative: Your older years may be your best ones, said Dr. Gene Cohen, author of “The Creative Age.” Many people, he said, enter a liberation phase in their 60s and 70s and use a newly found sense of inner freedom to paint, write or create new social programs.
- Finally, ask your doctor if you should take ibuprofen or similar drugs. A growing body of evidence suggests these medications help prevent cognitive decline and Alzheimer’s disease, probably by blocking inflammation that can destroy brain cells.