The findings, involving functional magnetic resonance imaging (fMRI), provide the first visible evidence for a relationship between behavioral performance and cortical processors involved in dual-task processing, said Arthur F. Kramer, a professor of psychology and researcher at the Beckman Institute for Advanced Science and Technology.
The study -- published online this month in advance of regular publication by the journal Neurobiology of Aging -- also adds to other emerging data that refute the idea that opposite brain areas become activated to help aging people compensate for a loss of cognition. Older studies, Kramer said, did not look at the impacts of training.
For the new study, researchers in Kramer's lab looked at areas of the brain known to be associated with executive control -- scheduling, planning, juggling multiple tasks and working memory. These areas, the ventral and dorsal prefrontal cortexes, are tied to cognitive declines in aging.
Participants were 32 men and women, ages 55 to 80, and 31 younger adults. They were divided into control and experimental groups, with the latter receiving training on a time-measured task of identifying green or yellow Xs and/or whether a letter on the computer monitor was a B or C. Researchers then analyzed comprehensive fMRI data compiled before and after training of various parts of the brain and of changes in performance and times involving the tasks.
Before and after results were dramatic in ventral regions of the brain, said lead author Kirk I. Erickson, a psychology postdoctoral research associate.
"You can see," Erickson said as he pointed to graphs showing results of activity in the left ventral region, "that even though the older adults start out with a lower amount of activation before training, those who were trained actually increased the amount of activity. You see a convergence with the young people. After training there are less age-related differences. Older adults begin to look more like the younger adults in brain activation."
Activation in this lower brain region jumped significantly among the older adults who received the training, while the older participants who did not get training experienced a dip in activation while doing the tasks. Younger trained participants started the tasks with higher activation but showed a slight reduction after training.
In the right hemisphere of this region, the young started out with higher activation levels than the old, and both groups showed sharp declines after training.
"Both old and young react pretty much the same way, even though they started differently," Erickson said. "Their brains do pretty much the same things with training."
Previous studies have repeatedly found that older adults show greater activation in both hemispheres, Kramer said. "The question is: Is that good or bad? Is there compensation occurring in one side of the brain? What we are seeing here is that the better you get at a task through training, one hemisphere goes up and one goes down. Older studies did not figure in the influence of training."
In the left dorsal prefrontal cortex, the results were similar to those in the left ventral region, with a convergence of brain activity after training. However, pre-training levels were much higher among older participants, but activation dropped -- at about the same level that activation rose for the younger trained participants.
Next door, in the right dorsal region, activation levels were nearly identical for both young and old before and after training.
"The results in the upper regions of the brain are a little more difficult to interpret, because the results are going in opposite directions for young and old adults," Kramer said. What may be happening, he said, relates to stress levels older people may experience while in competition with younger people.
"Older people are anxious and may be overcautious, but as they become more proficient they gain confidence," Kramer said. "Young people tend to be more lackadaisical, and they may be realizing that they need these brain areas for the task."
Thus, Kramer and Erickson said, differences in life experiences of the young and old could be at play, with the changes in brain activity reflecting adjustments to an optimal point for both age groups.
"Or we could be seeing that these two dorsal brain areas aren't necessarily beneficial for this particular task," Erickson said, adding that different tasks may affect different areas of the brain.
Overall, Kramer said, the findings say there is a strong relationship between brain activation and performance. The pattern shown in this study, he said, appears to have held in a subsequent unpublished study in which older individuals were able to transfer their training in one task for use with a new challenge.
Co-authors of the paper are Stanley J. Colcombe, Ruchika Wadhwa, Paige E. Scalf, Jennifery S. Kim and Maritza Alvarado, all affiliated with the U. of I. psychology department and the Beckman Institute; Louis Bherer of the University of Quebec at Montreal; and Matthew S. Peterson of George Mason University in Fairfax, Va.
The National Institute on Aging funded the research.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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