NEW YORK - Scientists have scanned the brains of young people when they are doing - well - nothing, and they found that a region active during this daydreaming state is the one hard-hit by the scourge of old age: Alzheimer's disease.
"We never expected to see this," said Randy L. Buckner, a Howard Hughes Medical Institute investigator at Washington University in St. Louis.
He said he suspects the daydream activity might, over decades of daily use, wear down the brain, sparking a chemical cascade that results in the disease's classic deposits and tangles that damage the brain.
The regions identified are active when people daydream or think to themselves, Buckner said. When these regions are damaged, an older person might not be able to access the thoughts to follow through on an action, or even make sense of a string of thoughts.
The study appears this week in the Journal of Neuroscience.
The scientists used a variety of brain-scanning devices in more than 760 adults of all ages. Usually, scanning is done when volunteers carry out a particular mental task, such as remembering a list of words. This time, they were scanned without anything to do.
What emerged on the images was what Buckner and his colleagues call the brain's "default" state. The brain remains in this state when it's not concentrating on a task, such as reading or talking. It's the place where the mind wanders. This default region lines up perfectly with the regions that are initially damaged in Alzheimer's.
"It may be the normal cognitive function of the brain that leads to Alzheimer's later in life," Buckner said. He suspects the brain's metabolic activity slows over time in this region, making it vulnerable to mind-robbing symptoms.
The scientists say this finding could prove useful as a way to identify the disease early, before symptoms appear.
"You have to get to this pathology before it has its biggest effect," said William Klunk, an associate professor of psychiatry at the University of Pittsburgh and a co-investigator in the current study. Klunk developed an imaging tool that tracks amyloid plaque deposited in the brains of living Alzheimer's patients.
The next step will be to see whether the sticky amyloid-filled plaques are dependent on the brain's metabolism. If so, there could be new ways to attack the disease.
The latest thinking among Alzheimer's scientists is that the underpinnings of the disease might be decades in the making.
A decade ago, David Snowdon of the University of Kentucky Medical Center published what has become a classic study of health and aging. He followed 678 nuns, ages 75 to 107, and analyzed journal entries and essays written when they joined the order as young women. He identified an association between the writing and the risk for Alzheimer's far into the future. The richer the detail in the essays, the less likely the writers were to develop Alzheimer's.
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