Boston, Feb. 16, 2002 -- The gradual loss of cognitive functions, especially memory skills, is often a consequence of human aging. Now, research from the Howard Hughes Medical Institute at Washington University in St. Louis has used sophisticated brain imaging techniques to pinpoint cognitive mechanisms behind age-related memory difficulties and to confirm that some factors associated with these difficulties can be reversed with the proper support.
"Our study shows that older adults have plenty of underutilized cognitive resources in the left frontal cortex that can be harnessed and used for more efficient memory processing," said Randy L. Buckner, senior author of the study, which is scheduled for online publication Feb. 16 in the journal Neuron. Jessica Logan, a graduate student in psychology at Washington University, is lead author on the study.
Buckner, an associate professor of psychology in Arts and Sciences at Washington University and an investigator with the Howard Hughes Medical Institute, will discuss his research at the American Association for the Advancement of Science meeting in Boston on Feb. 16.
Buckner's study is the first to provide clear evidence that the aging process does not physically destroy the cognitive mechanisms responsible for effective memory creation in the frontal lobes; aging merely makes it increasingly difficult for older adults to spontaneously access and utilize those frontal regions of the brain routinely used by young adults for successful memory processing.
While healthy young adults use regions in the left frontal cortex almost exclusively for certain memory-related cognitive processes, older adults seem gradually to lose control of robust memory functions in these regions.
"We suspect that these phenomena reflect a breakdown in the ability of older adults to connect with and use various regions of the left frontal cortex," Buckner said. "It appears that older adults gradually lose the ability to select and control left cortex regions that are most suited for memory processing in healthy young adults. Many older adults are processing memories without ever getting to parts of the brain that young people use for memory encoding."
On the bright side, Buckner’s study offers strong evidence that older adults can be provided with specialized guidance, support and strategies to help them recover cognitive abilities long lost to the aging process.
"Some older adults have the cognitive resources to successfully process memory tasks, but they are not using them effectively," Buckner said. "Our study shows that they can begin utilizing these areas as long as we provide them with a lot of support. The resources are there, which is the good news."
This study builds on previous research in which Buckner developed innovative functional magnetic resonance imaging (fMRI) techniques to pinpoint several areas of the brain that healthy young adults use almost exclusively during successful memory creation. In particular, Buckner showed that increased activity levels in a region called the prefrontal cortex could be used to predict accurately whether an individual had successfully created the memory of a specific word.
His current study again relies on fMRI imaging to track activity in these brain areas as young and old adults complete tasks involving the memorization of verbal cues (words) and visual cues (pictures of human faces). Findings suggest that certain components of memory problems in older adults stem from two distinct and separate breakdowns in cognitive function: 1) an inability to locate and select those areas of the brain best suited to the memorization task at hand; and 2) an inability to self-initiate successful strategies for fully utilizing appropriate cognitive resources in those brain areas eventually selected.
Buckner's fMRI brain images show that as young adults focus on a word-based memory task, the right frontal cortex is usually activated for only a fleeting moment. Then, almost instantaneously, young minds transfer the task to the left frontal cortex, where it is processed with a flurry of activity in only that region. Older adults, however, when left to their on self-initiated memorization strategies, seem unable to effectively transfer and tightly focus these memory tasks in the preferred region of the left frontal cortex, often activating other areas of the brain that are poorly equipped for the job at hand.
However, when older adults are provided with an array of support and guidance designed to help them process memory tasks in a deeper, more semantic, meaning-based fashion, they responded very positively, more fully using left frontal areas to effectively process memories at levels approaching those of young healthy adults.
Although older adults could be helped to more fully utilize memory resources in the left frontal cortex, no amount of coaching helped them to effectively transfer and focus only on the optimal memory-processing centers. Buckner suggests that this may be one reason why the older adults memory performance improves, but never fully reaches young adult levels.
"It's a glass half-empty, half-full situation," Buckner said. "With the proper cognitive therapy and support, it may be possible to train older adults to better utilize resources of the left frontal cortex for memory processing at a level almost as efficient as that of young adults. But under no circumstances were we able to help them revert to using only the left frontal cortex and not other regions for the processing of these memory-intensive cognitive tasks. "
Washington University neurologist John Morris, a senior author of the Neuron study, said "these results show that the reduction in processing capacity of the brain with aging is not completely an irreversible process. They give us a basis for believing that cognitive rehabilitation therapies might be helpful in aging-related cognitive illnesses. And, the findings emphasize that the aging brain still can function at a very high level and keep healthy older people living active, independent lives."
According to Morris, an important question to address in future studies is the relation between the cognitive deficits found in healthy elderly people and in those with Alzheimer's disease. "Are the kinds of deficits reported in these studies truly age-related and separate from Alzheimer's disease, or is one just an elaboration of the other? We really don't know the answer," he said.
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