Aging Brains Use Extra Regions to Shore Up Eroding Abilities

November 13, 2011

Old age is tough on brains, sapping them of a variety of abilities. But brains have their own resources to cope. Both sides of brain aging—the decline and the ability to compensate—were discussed here during the Society for Neuroscience meeting, a gathering of 30,000 researchers that concludes on Wednesday.

"There are definitely losses that come with age, but they seem to prompt people to try extra hard," says Julie A. Dumas, an assistant professor of psychiatry at the University of Vermont, who presented a study of women with cognitive complaints. And trying, which includes bringing extra regions of the brain to bear on a task, can work: Ms. Dumas found no decrease in performance when those women were compared to a normal group.

But the difficulties faced by an aging brain are many. There are structural changes, like shrinkage of the frontal lobes, areas linked to decision-making abilities. And there are functional losses that show up on neuropsychological tests, like diminished working memory and slower information processing.

Some consequences, like planning poorly for the future, were demonstrated in an experiment by researchers from the University of Iowa. Natalie L. Denburg, an assistant professor in the department of neurology, and a graduate student, Kameko M. Halfmann, gave a kind of gambling task to groups of young and middle-aged people, as well as older people (from their 60s to their 90s) who showed signs of impaired decision-making. Essentially, they could draw cards from a deck that was likely to give them a small payout in one week, or another deck with cards likely to give them a larger payout in two weeks.

Middle-aged people were the most patient, Ms. Halfmann says, and preferred the deck likely to give them a bigger but distant payout. Older impaired adults, in contrast, went for the immediate low-dollar reward. "We may be picking up some early signs of frontal-lobe changes," Ms. Halfmann says. "It's incredibly important to understand this. Because we've never had as many people as old as this in society. They are healthy and living in the community, but they can easily outlive their savings. So discounting the future, as they do in this task, is a real problem."

Compensation Mechanisms

One way that people try to cope with the cognitive slowing that seems to accompany aging is to bring more resources to bear on the problem. That's what Ms. Dumas and her colleagues found. They examined 22 women with an average age of 55, half of whom complained of memory problems. All the women were shown a series of letters, and every time a letter matched one just shown to them, they were supposed to signal that they recognized the match. The task was made progressively harder, as the women were asked to signal if the letter matched to one shown two places back in the series, or three places back.

While this was going on, the women were having their brains imaged to detect areas of activity. The complaining women showed greater activation in parts of the frontal lobes associated with memory and attention than did the other women. "As the task got harder, these women recruited even more brain areas," Ms. Dumas says. "And the more complaints about memory they had, the more we saw this extra activation." When all was said and done, those women did just as well on the test as the noncomplainers. "My guess is there could be something happening in the brain, and people are trying to compensate for it with these extra areas," Ms. Dumas says. "And they are doing it successfully."

Another imaging study showed a similar compensation effort might help older people react to social situations. Angela H. Gutchess, an assistant professor of psychology at Brandeis University, showed older and younger people some photos—pictures of a woman, say—and then cued them to evaluate the woman socially by telling them she wore a large hat in a crowded movie theater. "We're trying to get them to think about what would happen if this person was in their life," Ms. Gutchess says.

People in their 20s, when asked about the woman and the hat, show activity in several brain areas. "They do a lot of detective work to infer more," Ms. Gutchess says, and they draw on a variety of cognitive abilities. But older people, age 65 and up, do a little extra. They add another brain area, one known to process knowledge about the personalities and behaviors of others. "They seem to emphasize other processes, and rely on what they already know about people," says the psychologist, who did the research with a graduate student, Brittany S. Cassidy. Ms. Gutchess speculates that the areas used by younger people—such as ones that recall minute details—don't provide aging adults with sufficient information.

Those efforts to shore up aging weak spots support a theory called "scaffolding," developed by Denise C. Park, co-director of the Center for Vital Longevity at the University of Texas at Dallas, and her colleague Patricia Reuter-Lorenz, a professor of psychology at the University of Michigan at Ann Arbor. Scaffolding holds that as parts of the brain decline, alternate neural circuits are called upon to perform the same task, preserving overall performance. "We know from this kind of work that the brain tries to maintain itself," Ms. Park says. "Now we have to figure out what kinds of interventions we can do, if any, that might help it."