To help compensate for the mental declines that come with age, older adults recruit parts of the brain not used by younger adults to perform the same tasks, researchers say. The findings will be presented next week at the annual meeting of the American Psychological Association.

Patricia Reuter-Lorenz of the University of Michigan and her colleagues conducted several studies aimed at better understanding the aging brain. Using functional positron emission tomography (PET) imaging, the researchers recorded brain activity while older and younger subjects performed various tasks. As expected, younger subjects outperformed older ones on tasks relating to short-term memorymemorizing a series of letters, for example. But whereas younger adults exhibited activity primarily in the left brain hemisphere, older adults employed both brain hemispheres. Similarly, when given a task testing spatial memory, younger adults showed mostly right brain activity, while older adults activated both hemispheres.

Older and younger subjects performed equally well when asked to determine the accuracy of a math equation. When they were asked to memorize a word in addition to doing a math problem, however, adult performance plummeted. "Recruiting additional regions of the brain seems to assist older adults in basic memory storage tasks," Reuter-Lorenz reports. "But when it comes to more complex processing tasks, this strategy isn't as successful." She suggests that the seniors used the so-called dorsolateral prefrontal cortex to assist with the short-term memory task but in so doing made it less available for the more complex tasks. Still, overall she believes that older adults benefit from tapping into both hemispheres.