For the first time, researchers have used fMRI to understand how some older adults can learn and remember new information as well as a 25-year-old.
From:
MASSACHUSETTS GENERAL HOSPITAL
July
6, 2021 -- BOSTON -- As we age, our brains typically undergo a slow process of
atrophy, causing less robust communication between various brain regions, which
leads to declining memory and other cognitive functions. But a rare group of
older individuals called "superagers" have been shown to learn and
recall novel information as well as a 25-year-old. Investigators from
Massachusetts General Hospital (MGH) have now identified the brain activity
that underlies superagers' superior memory. "This is the first time we have
images of the function of superagers' brains as they actively learn and
remember new information," says Alexandra Touroutoglou, PhD, director of
Imaging Operations at MGH's Frontotemporal Disorders Unit and senior author of
the paper published in Cerebral Cortex.
In 2016, Touroutoglou and her fellow
researchers identified a group of adults older than 65 with remarkable
performance on memory tests. The superagers are participants in an ongoing
longitudinal study of aging at MGH led by Bradford Dickerson, MD, director of
the Frontotemporal Disorders Unit at MGH, and Lisa Feldman Barrett, PhD, a research
scientist in Psychiatry at MGH. "Using MRI, we found that the structure of
superagers' brains and the connectivity of their neural networks more closely
resemble the brains of young adults; superagers had avoided the brain atrophy
typically seen in older adults," says Touroutoglou.
In the new study, the investigators gave
40 adults with a mean age of 67 a very challenging memory test while their
brains were imaged using functional magnetic resonance imaging (fMRI), which,
unlike typical MRI, shows the activity of different brain areas during tasks.
Forty-one young adults (mean age of 25) also took the same memory test while
their brains were imaged. The participants first viewed 80 pictures of faces or
scenes that were each paired with an adjective, such as a cityscape paired with
the word "industrial" or a male face paired with the word
"average." Their first task was to determine whether the word matched
the image, a process called encoding. After 10 minutes, participants were presented
with the 80 image-word pairs they had just learned, an additional 40 pairs of
new words and images, and 40 rearranged pairs consisting of words and images
they had previously seen. Their second task was to recall whether they had
previously seen each specific word-picture pair, or whether they were looking
at a new or rearranged pair.
While the participants were in the
scanner, the researchers paid close attention to the visual cortex, which is
the area of the brain that processes what you see and is particularly sensitive
to aging. "In the visual cortex, there are populations of neurons that are
selectively involved in processing different categories of images, such as
faces, houses or scenes," says lead author Yuta Katsumi, PhD, a
postdoctoral fellow in Psychiatry at MGH. "This selective function of each
group of neurons makes them more efficient at processing what you see and
creating a distinct memory of those images, which can then easily be
retrieved."
During aging, this selectivity, called
neural differentiation, diminishes and the group of neurons that once responded
primarily to faces now activates for other images. The brain now has difficulty
creating unique neural activation patterns for different types of images, which
means it is making less distinctive mental representations of what the person
is seeing. That's one reason older individuals have trouble remembering when
they may have seen a television show, read an article, or eaten a specific
meal.
But in the fMRI study, the superagers'
memory performance was indistinguishable from the 25-year-olds', and their
brains' visual cortex maintained youthful activity patterns. "The
superagers had maintained the same high level of neural differentiation, or
selectivity, as a young adult," says Katsumi. "Their brains enabled
them to create distinct representations of the different categories of visual
information so that they could accurately remember the image-word pairs."
An important question that researchers
still must answer is whether "superagers' brains were always more
efficient than their peers, or whether, over time, they developed mechanisms to
compensate for the decline of the aging brain," says Touroutoglou.
Previous studies have shown that
training can increase the selectivity of brain regions, which may be a
potential intervention to delay or prevent the decline in neural
differentiation in normal aging adults and make their brains more like those of
superagers. Currently the researchers are conducting a clinical trial to
evaluate whether noninvasive electromagnetic stimulation, which delivers an
electrical current to targeted areas of the brain, can improve memory in older
adults. The researchers also plan to study different brain regions to further
understand how superagers learn and remember, and they will examine lifestyle
and other factors that might contribute to superagers' amazing memory.
https://www.eurekalert.org/pub_releases/2021-07/mgh-srs070621.php
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