FRIDAY, Aug. 31, 2001 (HealthDayNews) -- As we age, it seems two sides of our brains may be better than one.
A study from the University of Michigan shows that older adults reach into both hemispheres of their brain to perform the same memory tasks that younger adults accomplish using only one. This "recruiting" of extra neurons helps compensate for age-related memory declines, the researchers say, and for the most part it serves us well. The findings could lead to a better understanding of how our brains work as the years go by.
The study, which appears in a recent issue of the Journal of Cognitive Neurosciences, was presented by lead author Patricia Reuter-Lorenz at the annual meeting of the American Psychological Association in San Francisco last week.
"Older adults seem to be activating more of their brain for any given task," says Reuter-Lorenz. "It speaks to the generality of the phenomenon."
In the study, Reuter-Lorenz and her colleagues took older and younger adults, and asked each to perform short-term memory tasks. For example, in one experiment, the participants were shown four letters, then asked to decide whether a letter presented a few seconds later matched any of the previous four. Positron emission tomography (PET) scans taken of their brains during the tests showed that the older people tapped into both hemispheres of their brain, while the younger people tended to use only one hemisphere.
In general, also, the older adults did not perform as quickly as the younger adults. And when all were asked to simultaneously do a more complicated memory task and a simple memory task, the performance of the older adults worsened. The researchers say this suggests that the parts of the brain normally used for complex tasks were preoccupied with the simple task, and could not be recruited for the tougher memory challenge.
Other aging and cognition experts say the results fall in line with what laboratories around the country are finding.
"It's very interesting," says Andrew Monjan, chief of the Neurobiology of Aging Branch at the National Institute on Aging. "It's actually consistent with other findings. What it may indicate is in the older person, to reach the same level of function or performance, they need to utilize areas of their brains not used by younger adults. They're calling on more brain resources. The aging brain is able to reroute itself to get the message through."
Tim Salthouse, the Brown-Foreman Professor of Psychology at the University of Virginia, thinks there might be something to the two-hemisphere phenomenon because so many labs are discovering it. Yet, he adds, there are two schools of thought on exactly what is happening.
One theory suggests that as we age, our brain recruits more parts of itself to perform memory tasks to compensate for age-related declines in cognition. Another theory suggests the brain is malfunctioning and simply loses the ability to prevent other parts of the brain from getting involved in simple memory tasks.
"It may be a manifestation of something that's getting worse," he explains. "We still need to resolve this. I think you can believe these results. It's a question of how you interpret them. I'm still mixed. We really have to resolve it before we decide what's going on."
Salthouse says a larger study would help determine whether the brain is compensating or malfunctioning, but the cost of the PET scans run about $2,000 a person, so these types of studies tend to be small.
Reuter-Lorenz doesn't disagree with the observation, but she notes her findings point her toward the recruitment theory. Future studies will try to look at what these recruited brain cells actually do, she adds.
"The jury is still out on that," she adds. But because her older adults performed well on a memory test given before the experiments, she thinks the activation of more brain cells is a good thing. And, she adds, her younger adults activated more brain cells when they are asked to perform tougher tasks.
"These areas come into play when the going gets rough," she says. "I think that what we're seeing in this study is there is a lifelong potential for plasticity. We may be able to harness this potential. We're seeing new ways of accomplishing a task, as opposed to just decline. I think this is a sign that there's reason to be hopeful."
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