Brain Link for Daydreams, Alzheimer's Disease

Scientists report that brain areas involved in daydreaming may become ground zero for Alzheimer's disease.

The researchers looked at brain imaging studies of 764 older adults. Some participants were healthy, some had dementia, and some were on the verge of dementia. Their findings:

—People facing dementia had protein deposits linked to Alzheimer's disease in certain brain areas.

—Those brain areas are active during the brain's down time, which is prime time for daydreaming.

Those patterns grabbed the researchers' attention. But patterns aren't proof, and the scientists aren't blaming daydreaming for Alzheimer's disease.

Their findings appear in The Journal of Neuroscience.

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Researcher's Comments

Researcher Randy L. Buckner, PhD, is a Howard Hughes Medical Institute researcher and an associate professor in the neurosciences program at Washington University in St. Louis. He commented on the findings in a news release.

"It may be the normal cognitive function of the brain that leads to Alzheimer's later in life. This was not a relationship we had even considered. The hypothesis is that the cascade of events that leads to Alzheimer's begins at young adulthood," says Buckner.

He and his colleagues emphasize the word "hypothesis." If that theory bears fruit, it could help researchers understand why some people may be more likely to develop Alzheimer's than others.

"We are very interested in exploring these new observations to understand who is at risk and who is protected from Alzheimer's," says Buckner.

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Active Brain, Idle Brain

The researchers looked at the brain's "default activity." That's what the brain does when it's not doing long division, writing memos, solving crossword puzzles, reading nutrition labels, or doing other thought-provoking tasks.

When the brain spools into default mode, it may start daydreaming, letting thoughts roam. Memory, which is often an early victim of Alzheimer's disease, is frequently involved, the researchers note. For instance, daydreams may delve into memories, replaying bygone events.

"We appear to use memory systems often in our default states. This may help us to plan and solve problems. Maybe it helps us to be creative. But it may also have metabolic consequences," says Buckner.

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How It Might Work

The researchers write that default brain activities may set the stage for certain proteins to be deposited in brain areas used in those brain activities.

The proteins — called tau and amyloid — are ingredients in brain plaque linked to Alzheimer's disease.

There could be other explanations, and it's going to take a lot more work to figure out the process, the researchers note.

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By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Buckner, R. The Journal of Neuroscience, Aug. 24, 2005; vol 25: pp 7709-7717. News release, Howard Hughes Medical Institute. Reuters.