Cover Story
Have you noticed any of your colleagues bingeing on blueberries since returning from APA's 2001 Annual Convention in San Francisco in August?
They probably attended the "Healthy Minds" symposium at which Jim Joseph, PhD, of the U.S. Department of Agriculture talked about the huge boost in mental capacity seen in rats that ate a diet high in darkly colored fruits and vegetables--in particular, blueberries.
He joined psychologists Denise C. Park, PhD, Patricia Reuter-Lorenz, PhD, and Arthur Kramer, PhD, to discuss research on how our brains age and what we can do to delay the process. The symposium was part of the "APA presidential initiative on emerging opportunities in science."
Studying the aging mind and ways to keep it healthy is a "no-brainer," as it were, said Park, the symposium chair. Soon, there will be more people in the United States over age 65 than there are children, and understanding how their mental abilities are changing has enormous implications for the nation's work force. Not to mention that such research is important for promoting quality of life for the nation's senior adults.
"We're at the place now with our understanding of the aging brain where we were 30 years ago with our understanding of cardiovascular disease and smoking," said Park, professor of psychology at the University of Michigan and senior research scientist at the university's Center for Applied Cognitive Research on Aging. "The aging mind is a new frontier."
Shrinking memory
So, what exactly happens to the mind as we age? That's the question Park and Reuter-Lorenz set out to tackle. The answer is fascinating.
Their research shows that as we grow older, there's a steady decline in how fast we can process information and in how much we can store in working memory. In addition, said Reuter-Lorenz, we begin to need more of our brain to accomplish tasks that used to be handled by more automatic functions.
Reuter-Lorenz and her colleagues demonstrated the changes in brain use in a series of imaging studies, focusing on tasks that require recognition of items maintained in working memory. For example, they showed study participants four letters, asked them to remember them and then showed them a single letter and asked them if it was one of the letters they'd seen earlier.
The elderly participants--ages 62 to 75--were slower to perform the task but only slightly less accurate than young participants--ages 18 to 30. What was more interesting was that while young participants used areas of the brain's left hemisphere associated with verbal working memory, elderly participants used these areas as well as areas in the right hemisphere and in the front of the brain associated with more executive, higher-level processing. They found that older people also regions of both hemispheres when performing a spatial working memory task.
"Older adults are more bilateral and they use executive processing that young adults don't need for the same task," said Reuter-Lorenz, associate professor of psychology at the University of Michigan.
So, although age differences on these tasks were not readily apparent in people's behavior, brain-imaging studies reveal significant differences in the brain areas that older people use to perform the tasks. Indeed, the aging brain appears to recruit help from other parts to compensate for age-related declines, said Reuter-Lorenz. That's certainly a sign of the brain's ability to compensate, but it also might be a liability because monopolizing certain brain areas for simple tasks may make them unavailable for more complex tasks, she said.
On the positive side, older adults don't tend to lose their memories for information they already have in storage, said Park. In fact, verbal ability and other knowledge-based abilities seem to improve with age. Overall, "age-related changes are most important for novel situations," said Park, "and have little implication for everyday life until we're very old."
Eat your blueberries
That said, most of us would like to maintain our mental flexibility and vitality as long as possible. And we've begun to look for magic bullets that will help. Psychologists are no different. They've turned to studies of how diet and exercise might keep our brains young.
Many people have already heard about research claiming that a very low calorie diet can prolong life--at least in rats and monkeys. The USDA's Joseph and his colleagues at the USDAHuman Nutrition Research Center on Aging at Tufts University wondered whether quality rather than quantity could be equally powerful--particularly in terms of preventing age-related cognitive declines.
They turned to deeply colored fruits and vegetables, such as blueberries and carrots, which are high in antioxidants and thought to combat free radicals and inflammation in brain tissue. The brain becomes far more vulnerable to these insults as it ages, which in turn may lead to age-related declines in its ability to send and receive chemical signals.
To test their theory, Joseph and his colleagues created rat food pellets made with the top 10 antioxidant fruits and vegetables, including strawberries, blueberries, spinach and kale. For two months they fed the pellets to 19-month-old rats who were already showing signs of aging, from declines in motor function to poorer memory. They tested each food separately, each day feeding the rats the human equivalent of a normal serving of the food--for example, a large spinach salad, a half-cup of blueberries or a pint of strawberries.
The effect of the foods was dramatic, said Joseph. The rats' motor function and memory improved significantly at both the statistical and functional level. And change was most dramatic in those who ate blueberries.
At the molecular level, Joseph and his colleagues found that animals who ate blueberries, and to a lesser extent the other foods, had healthier-looking brains. In addition, the researchers found that the membranes of the rats' brain cells were more fluid and better able to move chemicals in and out, which, presumably improves how well the brain sends and receives signals. And, they have preliminary data showing that the chemicals that carry signals in the brain are better able to do their job. "We saw a direct correlation between diet, behavior and molecules," he said.
Exercising mind and body
A growing body of research also shows that exercise is key to maintaining a healthy mind.
Indeed, animal research finds cellular and biochemical differences between animals who exercise and those who don't--differences that seem to help alleviate the ravages of age on the mind, said Kramer, professor of psychology at the University of Illinois, Urbana-Champaign.
Cross-sectional data in humans suggest large and robust cognitive benefits of physical fitness. But longitudinal studies have shown more mixed results. He and his colleagues set out to reexamine the issue with a quantitative meta-analysis of 18 studies of people ages 55 to 76.
They found "a pretty hefty effect" with exercise groups doing much better on tests of cognitive function, spatial ability and processing speed. The effect was largest when the exercise program coupled aerobic training with strength or flexibility training and lasted longer than 30 minutes. And most helped were women and people older than 65.
They're now using brain-imaging data to home in on what it is about physical fitness that might improve people's cognitive skills. A pilot study indicates that during a processing speed task, the brains of fit older adults anticipate better than less fit older adults--the area of the brain used in the task "lights up" in preparation for the task. Interestingly, neither the low-fit older study participants nor the young participants showed any sign of anticipating the task.
Though these data are intriguing, before researchers will understand the link between physical fitness and cognition, they will need better-articulated models based on both animal and human data. "Neuroimaging can provide insights, but the work needs to be closely coupled with animal research projects with multidisciplinary teams of researchers," Kramer said.
Park agreed that's the prescription for all research on the aging brain: "We desperately need large collaborative studies to address these issues across the lifespan."
Beth Azar is a writer in Portland, Ore.
