By: Josh Fischman, The Chronicle of Higher Education
Monday, November 21, 2011
Here's a photo of a woman, Angela H. Gutchess tells people as she goes about her work, and this woman wears a large hat in a movie theater. Then Ms. Gutchess, assistant professor of psychology at Brandeis University, poses a question: Do you want this woman to play a role in your life?
The people hearing this are part of a brain study, and Ms. Gutchess and her team map the activity inside their heads while they are thinking of a response. What she's learned, she told a session at the Society for Neuroscience meeting here last week, is that the older brain may be an exceptionally social one. 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," Ms. Gutchess says, and they draw on a variety of cognitive abilities. But older people, age 65 and higher, do even more. They add another brain area linked to knowledge about the personalities and behaviors of others. "They seem to emphasize other processes," the psychologist says, speculating that the initial areas—such as ones that recall minute details—no longer provide the older people with sufficient information.
The finding is part of an emerging picture of the aging brain, one shorn of many abilities by the ravages of time but trying to compensate by bringing other brain areas, with different capabilities, to bear on problems. So with age, more of the brain, not less, comes into play. "Scaffolding" is what Denise C. Park, co-director of the Center for Vital Longevity at the University of Texas at Dallas, calls this effort to shore up aging weak spots. Short-term memory and processing speed fade away. But using a stored history of social cues to navigate social situations, which is what older people viewing the woman with bad manners appear to be doing, is one of several ways the brain tries to keep from slipping further into the dark.
A number of talks at the neuroscience meeting provided evidence for scaffolding, a theory Ms. Park developed with a colleague, Patricia Reuter-Lorenz of the University of Michigan at Ann Arbor. Ms. Park has been testing many of these ideas in the Dallas Lifespan Brain Study, a grand project following 350 people whose ages range from 20 to 90. "I think she does amazing work," says Julie A. Dumas, an assistant professor of psychiatry at the University of Vermont who presented work showing the activation of larger brain areas in people with memory complaints. "She's got such a large study, with so many dimensions, that she can ask lots of key questions and try and answer them with brain imaging and biological markers of change."
The theory "has been very influential," says Darlene V. Howard, a professor of psychology at Georgetown University who directs the cognition and aging laboratory there. "It fits in with growing attempts in the field to understand how the aging brain adapts."
When Ms. Park talks about scaffolding, she usually begins by showing a very depressing graph. It has 14 lines on it, each charting the performance on a particular cognitive test of people in every decade of life, from their 20s through their 80s. And 11 of the lines plunge inexorably, distressingly, down. "We have people come in and we give them a battery of tests, done either on the computer or with paper and pencil," she says. "To measure the speed at which they process information, for instance, we'll show them a series of strings of different digits. And we'll ask them whether the pattern in successive strings is the same or different." As age advances, so does the error rate in the answers, and that holds true on three different kinds of speed tests.
The same grim tale is told in four tests of working memory. "We'll ask 'What's four plus eight?' and also ask them 'What was the first word in that sentence?'" Ms. Park says. "It measures how much information you can take in, a kind of test of multitasking." People also do worse on that sort of test as they get older. Long-term memory is measured on four types of tests that rely on a time lapse. People are shown a picture, for instance, and then are asked to draw it themselves. Accuracy again shows that steady plunge from the heights of youth.
"We know there are brain changes that happen during this time, and we think they are linked to performance," Ms. Park says. She points to three types of degradation. One is that the frontal lobes, which are associated with decision-making abilities, shrink. The second is a change in white matter, which is material the brain uses to insulate neural pathways and keep signals from losing power as they travel around. With age, white matter becomes more porous, letting water move in and out. It's as if the insulation around electrical wiring were wearing thin. And third, a protein called beta-amyloid—a substance than seems to run amok in the brains of people with Alzheimer's disease—is deposited in larger amounts.
"So if we look at behavior and at brain structure, it's a very despairing scenario," Ms. Park says. An experiment reported at the neuroscience meeting by University of Iowa researchers underscored this. They found that older adults, with decreased activity in their frontal lobes and poor performance on cognitive tests, tended to plan poorly for the future: They were more willing to take an immediate, low-dollar reward than to wait one more week for a higher payout. (In this their decision-making was similar to that of young adults, who also wanted less money more quickly.)
But step back and look at overall cognitive functioning, Ms. Park says, and "the picture is more encouraging." World knowledge, illustrated by things like vocabulary tests, does not decrease with age. That is represented by the remaining three lines on her graph. In some cases it actually seems to improve, with people in their 70s doing a bit better than people in their 20s.
How does this happen? That's where scaffolding, and brain-imaging experiments, come in. Functional magnetic resonance can measure brain activity when people are challenged to perform a particular task. The images show that the brains of older people are just not as specialized as younger brains. For example, there are minute areas in the brain called voxels. Some light up in younger people when they are shown faces, and different ones light up when they see places. "Older adults don't show this," Ms. Park says. "Face voxels are used for places, and vice versa."
Simply put, older people may be calling on more brain resources to get the job done. In a paper published on October 29 in the journal Neuropsychologia, Ms. Park and several colleagues showed that when confronted with particular memory tasks, younger people tended to use neurons from one brain hemisphere. But older people, doing the same task, recruited neurons from a parallel spot in the opposite hemisphere. And the greater that degree of recruitment, the better they performed on the task.
That same principle may be at work in the experiment that Ms. Dumas, from Vermont, described at the neuroscience meeting. She and her colleagues gave a memory test to 22 women who averaged 55 years of age. They were shown a series of letters, and every time a letter matched one just shown to them, they were supposed to signal it. The task was made progressively harder, as the women were asked to signal if the letter matched one shown two places back in the series, or three places back.
The key here is that half of these women came into the study complaining that they had memory problems. The tests didn't show that they had more deficits than the other women, but they definitely had more complaints. And those women, when their brains were imaged during the memory test, 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."
"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. "They are doing it successfully, but they are doing it by working extra hard."
She, along with Ms. Gutchess of Brandeis and Ms. Park, are quick to point out these are small experiments tackling a vastly complex issue. But they are adding more bricks to the scaffolding idea.
If compensation is indeed a natural process within the brain, Ms. Park wants to know if there are things we can do to help it along. "What interventions work? What doesn't?" she asks. "Generally science hasn't provided good answers on this." She is now analyzing the results of a three-month experiment with older people in which she put them in an enriched, challenging environment filled with socializing and photography classes and the like. Tests showed some improvement in processing speed, but Ms. Park wants to see if this is sustained over the coming years.
Sustainability is important, because Ms. Park suspects that knowledge of the world, represented by the undiminished lines on her graph, may actually be the basis of what we commonly think of as a quality that comes with age: wisdom. "These strategies can be effective," she says. "Maybe one reason you don't have young, quick-thinking people running the world is because they don't have this wisdom."