WEDNESDAY, Nov. 5, 2007 (HealthDay News) -- In a finding that uncovers the biological underpinnings of "senior moments," new research shows that communication between different parts of the brain begins to break down as a person grows older.
"We wanted to see how the brain changes in cognition in normal aging," said lead researcher Randy Buckner, a professor of psychology at Harvard University. "We were interested in normal aging, aging that isn't accompanied by even the earliest signs of Alzheimer's disease."
Buckner noted that it's sometimes tough even for neurologists to understand the difference between normal aging and Alzheimer's. "There are subtle changes in how brain areas communicate and coordinate with each other," he said. "As we age, we see that communication between these areas changes."
The report appears in the Dec. 6 issue of Neuron.
In the study, Buckner's team used a brain-imaging technique called functional magnetic resonance imaging (fMRI) to study the brains of 55 adults aged 60 and over, and 38 adults aged 35 and younger. To guarantee that none of the older subjects were in the early stages of Alzheimer's, the researchers checked for the presence of amyloid in the brains of those volunteers. If that telltale sign was detected, the person was not included in the study.
Among the adults they observed, they found that in the younger people, regions of their brains communicated easily with one another. However, this was not so with the older people.
In older people, the white matter of the brain that connects various brain areas had started to deteriorate, a chemical fact that would account for the lack of communication that affects cognitive function, Buckner said.
When these changes start isn't clear, Buckner said. "They appear to start slowly in the seventh and eighth decade of life," he said. "We also don't know what factors cause these changes to accelerate."
The cognitive changes caused by deterioration of white matter are subtle, Buckner said. "The changes in the crosstalk of brain regions are correlated with mild cognitive changes," he said. "People who have these changes are aging gracefully."
These shifts affect people differently, and not all the older people showed the alterations, Buckner said. Interestingly, some networks, such as the visual system, remained intact.
It may be possible to slow even this normal process of aging, Buckner said. "Maybe we can find ways to age even more gracefully," he added.
Buckner believes living right may help. "There are indications that staying cardiovascularly fit and healthy helps our brains age gracefully," he said. "We now have a way to study aging and to understand the factors that might help all of us age optimally."
The study points out the differences between healthy brain aging and Alzheimer's, one expert said.
"It's interesting that the normal process of brain aging is different from what we see in pre-clinical Alzheimer's," said Paul Sanberg, director of the University of South Florida Center of Excellence for Aging and Brain Repair. "One can tease away what is related to aging, and what is related to a disease."
It's important in developing therapies for Alzheimer's to be able to tell the difference between normal aging and disease, Sanberg said, because "it helps us make sure that we are affecting the right problems."
In addition, knowing how the brain ages normally might make it possible to create cognitive enhancers, Sanberg said.
Another expert noted that Buckner's group looked for signs of Alzheimer's in fewer than 20 percent of the older adults in the study.
"Since one can expect 20 to 30 percent of people in their 80s to develop Alzheimer's and Alzheimer's takes decades to develop, 20 to 30 percent of the aged 'normal' subjects were probably actually on their way to Alzheimer's disease," said Greg M. Cole, associate director of research at the Geriatric Research Education and Clinical Center of the Greater Los Angeles Veterans Administration Medical Center.
However, the study is a significant advance and the authors are correct in that they are seeing age-related changes that are not caused by Alzheimer's per se, said Cole, who is also the associate director of the UCLA Alzheimer's Disease Research Center.
"Many of the old subjects retain measures of connectivity on a par with the younger group, so these changes are not necessarily an inevitable outcome of aging," Cole added. "Whatever the cause of the declines, we'd all like to know the secrets of the group that stays in the younger performance range."
More information
For more information on Alzheimer's disease, visit the Alzheimer's Association.
