- WASHINGTON (AP) -- Why is it you can't remember where you put your car keys
but you can't forget the theme song to the "Brady Bunch"? Scientists
have taken a big step toward solving the mystery, literally peering inside
the human brain at the split second it creates a memory.
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- In a unique pair of studies, scientists
at Harvard and Stanford universities used sophisticated imaging techniques
to watch people's neural activity and, for the first time, show which parts
of the brain determine whether a specific experience will be remembered
for forgotten.
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- The findings "mark a significant
step forward," said memory expert Michael D. Rugg of Britain's University
of St. Andrews, who critiqued the studies in Friday's edition of the journal
Science.
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- Yes, the discovery means advertisers
might one day figure out how to make commercials better stick inside the
consumer brain.
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- More important, because one of these
memory-making regions is ravaged in Alzheimer's disease, the scientists
now are studying whether their findings also could help detect the devastating
brain disease in its earliest stages.
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- "We're really excited about the
prospect of this being used for Alzheimer's disease," said Stanford
neuroscientist James Brewer, who led the memory study and was preparing
to scan the brain of an Alzheimer's patient Thursday. "If we were
able to detect Alzheimer's really early, the prospect for treatment is
much, much better."
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- Scientists have long suspected that how
well people remember depends on differences in how their experiences are
"encoded" into the brain at the time they occur. Studies of people
with brain damage have suggested various brain regions were involved, but
it wasn't clear if damage to those regions meant people couldn't make new
memories, retrieve old ones or store memories over time.
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- New, high-powered "magnetic resonance
imaging," or MRI, machines work fast enough that scientists can measure
split-second neural activity as a person's brain processes an experience.
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- At Harvard, neuroscientist Anthony Wagner
put healthy volunteers into these "functional MRI" machines and
rapidly flashed one word every two seconds onto a screen inside. At first,
the volunteers merely noted whether words were in upper- or lower-case
letters. With additional words, they were told to decide if each was concrete,
like "chair" or "book," or abstract, like "love"
or "democracy."
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- That's because psychologists already
knew that analyzing the meaning of a word helps people remember it.
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- In Stanford's study, Brewer showed volunteers
color photographs of indoor and outdoor scenes rather than words.
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- Neither set of volunteers had been told
this was a memory test. But after the MRI scans, they were asked which
words or pictures they remembered well, remembered vaguely or didn't remember.
The scientists compared those memories to the brain scans.
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- The longer that two brain regions --
the prefrontal lobes and the parahippocampal cortex -- both lit up on the
MRI scans, the better people remembered the items. Words or pictures that
caused weak activity in the two regions were forgotten.
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- What makes your brain more likely to
react to one item over another? "That's the million-dollar question,"
Wagner said.
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- The studies provided some hints. Wagner's
volunteers showed more neural activity and better memory during the "concrete-abstract"
word test than for other words, providing biological evidence that more
complex cognition increases the chances of memory.
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- And personal experiences probably play
a role. Perhaps Brewer flashes a photo of Zion National Park: Someone who
just visited there may react more than someone who says, 'Oh, a desert
scene.'
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- Most people think of memory problems
as "failing to retrieve an event," Brewer explained.
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- Instead, think of "what went on
when you put those car keys down that distracted your attention from where
you're putting them," he said. "But you're thinking of that stupid
piece of trivia, you're attending to it" -- so the trivia of, say,
a TV show becomes a memory.
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