Aging & Longevity
Elderly brains learn, but maybe too much
Not as good as younger people at filtering out
Subjects were shown a sequence of letters and numbers with the
distraction of dots moving in the background. Behind the
numerals the dot motion became more coherent (as indicated by
the arrows). Graphic by Brown University
Nov. 30, 2014 - A new study led by Brown University
reports that older learners retained the mental flexibility needed to
learn a visual perception task but were not as good as younger people at
filtering out irrelevant information.
The findings undermine the conventional wisdom that
the brains of older people lack flexibility, or "plasticity," but
highlight a different reason why learning may become more difficult as
people age: They learn more than they need to. Researchers call this the
"plasticity and stability dilemma." The new study suggests older people
may indeed be facing it.
"Plasticity may be kept OK, in contrast with the
view of many researchers on aging who have said that the degree of
plasticity of older people gets lower," said Takeo Watanabe, the Fred M.
Seed Professor at Brown University, corresponding author of the study in
"However, we have found that the stability is
problematic. Our learning and memory capability is limited. You don't
want older, existing important information that is already stored to be
replaced with trivial information."
Numerals, not dots
To conduct the study, Watanabe and his team
enrolled a group of 10 people between 67 and 79 years old and another
group of 10 people ages 19 to 30 for an experiment.
Over a nine-day period, they trained on a simple
visual exercise: Shown a quick sequence of six symbols - four letters
and two numerals - volunteers were asked to report the numerals they
saw. Their performance on a test at the end of training was compared to
their score on a pre-test.
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The volunteers were explicitly instructed to only
bother with spotting the two numerals, but each symbol they saw had a
background of moving dots. Unbeknownst to the subjects, those dots would
move with varying degrees of cohesiveness of direction. In the pre- and
post-tests the researchers also asked the volunteers to report the
direction of dot movement when they saw the numerals.
The results of the testing were telling. Older
people improved as much as younger people on the relevant task of
identifying the two numerals.
"These results indicate that older subjects as well
as younger subjects showed significant amounts of task-relevant
learning," the authors wrote. "No evidence was obtained that indicates
that older individuals have a problem with plasticity."
Last week, in fact, Watanabe and colleagues
study showing that
plasticity during visual learning occurs in older people as well as
younger ones, but it is manifest differently in the brains of the
But in this study when it came to the irrelevant
skill of discerning the prevailing direction of dot movement, older
people learned that, too, even when it was at its most obvious. Younger
people, meanwhile, only showed improvement on discerning movement when
it was insidiously subtle. If it was clear, they recognized it and
filtered it out.
The idea that the most obvious signals were the
most easily filtered, suggested that the difference between older and
younger learners was a matter of attention.
The researchers therefore subjected the volunteers
to another test for the ability to find a relevant stimulus amid a
number of distractors. Older people did notably worse than younger ones,
adding evidence that the attentional systems for filtering out
irrelevant stimuli were indeed weaker in older learners. Importantly,
the poorer an older subject was at the ability to filter out irrelevant
stimuli, the more irrelevant stimuli the subject learned.
Watanabe said the finding is not necessarily
discouraging news. Perhaps filtering can be improved with some kind of
"The hope is that maybe what older people need to
do is to learn a skill to avoid learning what is not necessary," he
In addition to Watanabe, other authors of the paper
are Li-Hung Chang, formerly of Brown but now of National Yang-Ming
University in Taiwan; Yuka Sasaki, associate professor (research) of
cognitive, linguistic, and psychological sciences, and Kazuhisa Shibata
of Brown; and George Andersen of the University of California-Riverside.
The National Institutes of Health supported the
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