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Old and Young Brains Rely on Different Systems to Remember Emotional Content

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Duke Health News 919-660-1306

Neuroscientists from Duke University Medical Center have discovered
that older people use their brains differently than younger people when
it comes to storing memories, particularly those associated with
negative emotions.

The study, appearing online in the January
issue of Psychological Science, is a novel look at how brain
connections change with age.

Older adults, average age 70,
and younger adults, average age 24, were shown a series of 30
photographs while their brains were imaged in a functional MRI (fMRI)
machine. Some of the photos were neutral in nature and others had
strong negative content such as attacking snakes, mutilated bodies and
violent acts. While in the fMRI machine, the subjects looked at the
photos and ranked them on a pleasantness scale. Then they completed an
unexpected recall task following the fMRI scan to determine whether the
brain activity that occurred while looking at the pictures could
predict later memory. The results were sorted according to the numbers
of negative and neutral pictures that were remembered or missed by each
group.

The scientists found that older adults have less
connectivity between an area of the brain that generates emotions and a
region involved in memory and learning. But they also found that the
older adults have stronger connections with the frontal cortex, the
higher thinking area of the brain that controls these lower-order parts
of the brain.

Young adults used more of the brain regions typically involved in emotion and recalling memories.

"The
younger adults were able to recall more of the negative photos," said
Roberto Cabeza, PhD, senior author and Duke professor in the Center
for Cognitive Neuroscience. If the older adults are using more thinking
than feeling, "that may be one reason why older adults showed a
reduction in memory for pictures with a more negative emotional
content."

"It wasn't surprising that older people showed a
reduction in memory for negative pictures, but it was surprising that
the older subjects were using a different system to help them to better
encode those pictures they could remember," said lead author Peggy St.
Jacques, a graduate student in the Cabeza laboratory.

The
emotional centers of the older subjects were as active as those of
younger subjects -- it was the brain connections that differed.

"If
using the frontal regions to perform a memory task was always
beneficial, then the young people would use that strategy, too," Cabeza
said. "Each way of doing a task has some trade-offs. Older people have
learned to be less affected by negative information in order to
maintain their well being and emotional state - they may have
sacrificed more accurate memory for a negative stimulus, so that they
won't be so affected by it."

"Perhaps at different stages of
life, there are different brain strategies," Cabeza speculated.
"Younger adults might need to keep an accurate memory for both positive
and negative information in the world. Older people dwell in a world
with a lot of negatives, so perhaps they have learned to reduce the
impact of negative information and remember in a different way."
According to Cabeza, the results of the study are consistent with a
theory about emotional processes in older adults proposed by Dr. Laura
Carstensen at Stanford University, an expert in cognitive processing in
old age.

"One thing we might do in the future is to ask
subjects to try to actively regulate their emotions as they look at the
pictures," St. Jacques said. "Would there be a shift in the neural
networks for processing the negative pictures when we asked younger
people to regulate their emotional responses? How would that affect
their later recall of the negative pictures?"

The other
author on the study was Florin Dolcos, who is now at the Department of
Psychiatry, University of Alberta, in Edmonton, Canada. The study was
funded by the National Institutes of Health, a postdoctoral fellowship
from the Natural Sciences and Engineering Research Council of Canada,
an award from the Canadian Psychiatric Research Foundation, and a Young
Investigator Award from the U.S. National Alliance for Research on
Schizophrenia and Depression.

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