Doctors study how brains stay sharp

Doctors study how brains stay sharp

By Lauran Neergaard, Associated Press
Oct. 17, 2007

WASHINGTON
— When aging hampers memory, some people’s brains compensate to stay
sharp. Now scientists want to know how those brains make do — in hopes
of developing treatments to help everyone else keep up.

This is not Alzheimer’s disease, but the
wear-and-tear of so-called normal aging. New research is making clear
that memory and other brain functions decline to varying degrees even
in otherwise healthy people as they age, as anyone who habitually loses
car keys probably suspected.

The question is how to gird our brains against
time’s ravages, a question becoming critical as the population grays.
If you’re 65 today, odds are you’ll live to 83. But improving health
care means people in their 50s today may live another 40 years.

"I don’t think we’ve recognized, as scientists
or a society, (that) this is the front-and-center public health issue
we face as a nation," Dr. Denise Park, director of the University of
Illinois’ Center for Healthy Minds, told fellow brain specialists
assembled by the government last week.

"We need to understand how to defer normal cognitive aging … the way we’ve invested in fighting heart disease and cancer."

There are intriguing clues, gleaned from
discoveries that some seniors’ brains literally work around aging’s
damage, forging new pathways when old ones disintegrate.

"It’s not just fanciful or pie-in-the-sky" to
try harnessing that ability, said Dr. Richard Hodes, director of the
National Institute on Aging, which organized last week’s meeting to
seek advice on the most promising research.

High on the list: Simple physical exercise. It seems to do the brain as much good as the body.

Other options aren’t as well-studied, but range
from brain-training games to medications that may keep brain networks
better connected. In fact, an old blood-pressure pill named guanfacine
improves memory in old rats and monkeys by doing just that — but it
hasn’t yet been tested in older people with memory problems.

What’s normal aging and what signals impending
Alzheimer’s? That is a big question for elders worried about periodic
memory lapses. Science can’t yet tell for sure, but there seem to be
distinct differences.

Consider: A healthy brain is a bushy one.
Branch-like tentacles extend from the ends of the brain’s cells,
enabling them to communicate with each other. The more you learn, the
more those connections form.

Alzheimer’s kills neurons, so the cells disappear along with connections their neighbors need.

With normal aging, the cells don’t die but their
bushes can shrivel to skinny twigs, explained Dr. Carol Barnes of the
University of Arizona. Cells that are less connected have a harder time
sending messages. You may know someone’s name, but not be able to
recall it.

Moreover, Alzheimer’s seems to first target a different spot in the hippocampus, the brain’s memory center, than aging does.

There are two capacities for fighting back:

•Some brains withstand a lot of assault before
showing symptoms, something called "cognitive reserve." Indeed,
striking autopsy studies have found between 20% and 40% of elders who
displayed no confusion actually had brains riddled with Alzheimer’s
trademark plaques. Presumably, they had such bushy brains that even
when some neurons died, enough were left to function.

•Compensation is how the brain adapts when old
pathways quit functioning, to reroute itself and use alternates. Brain
scans show younger people tend to use different neural networks than
older people when performing the same task.

What’s the advice for now?

Physical exercise is the best-proven
prescription so far, the scientists agreed. Memory improved when
72-year-olds started a walking program three days a week, and
sophisticated scans showed their brains’ activity patterns started
resembling those of younger people.

Then there’s the "use-it-or-lose-it" theory,
that people with higher education, more challenging occupations and
enriched social lives build more cognitive reserve than couch potatoes.

It’s never too late to start building up that
reserve, said Columbia University neuroscientist Yaakov Stern. But,
"the question is how. What is the recipe?"

Everything from doing crossword puzzles to
various computer-based brain-training programs has been touted, but
nothing is yet proven to work. Johns Hopkins University has a major
government-funded study underway called the "Experience Corps," where
older adults volunteer to tutor school students 15 hours a week, to see
if such long-term stimulation maintains the elders’ brains.

What about medication? Companies have been
reluctant to test side effect-prone drugs in an otherwise healthy aging
brain, but scientists cited animal studies suggesting low-dose estrogen
and drugs that might mimic or ramp up brain signaling are promising
possibilities.

And recall that old blood pressure drug
guanfacine? It is now being studied as a potential treatment for
children with attention-deficit disorder — and it works in the same
brain region, the prefrontal cortex, where elderly brains forge new
networks.

"If it works in a 6-year-old, we hope it will work in the elderly," said Yale University neurobiologist Amy Arnsten.

Lauran Neergaard covers health and medical issues for The Associated Press in Washington.

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