Personality may influence brain shrinkage in
aging
Psychologists at Washington University in
St. Louis have found an intriguing
possibility that personality and brain aging
during the golden years may be linked.
Studying MRI images of 79 volunteers between
the ages of 44 and 88 — who also had
provided personality and demographic data —
the researchers found lower volumes of gray
matter in the frontal and medial temporal
brain regions of volunteers who ranked high
in neuroticism traits, compared with higher
volumes of gray matter in those who ranked
high in conscientious traits.
The orbitofrontal cortex, which is part of
the prefrontal region and involved in
social/emotional processing, showed similar
associations with personality.
"This is a first step in seeing how
personality might affect brain aging," says
Denise Head, PhD, assistant professor of
psychology in Arts & Sciences at Washington
University. "Our data clearly show an
association between personality and brain
volume, particularly in brain regions
associated with emotional and social
processing. This could be interpreted that
personality may influence the rate of brain
aging."
She notes also that the results could be
seen as "the tail wagging the dog." That is,
it is actually brain changes during aging
that influence personality.
"Right now, we can't disentangle those two,
but we plan to in the future by conducting
ongoing studies of the volunteers over time
to note future structural changes," Head
says.
Head's graduate student Jonathan Jackson,
first author of a recently published paper
on the research inNeurobiology in Aging,
says that he, and co-authors Head and David
A. Balota, PhD, professor of psychology,
tested the hypotheses that aging individuals
high in neuroticism would show lower brain
volume, while those high in either
conscientiousness or extroversion would have
larger brain volume. The extroversion
results were not clear, but the data
validated the other two hypotheses.
"There are lots of nonhuman animal studies
that suggest that chronic stress is
associated with deleterious effects on the
brain, and this helped us form the
hypothesis that we'd see similar effects in
older adults." Jackson says.
"We assumed that neuroticism would be
negatively related to structural volume,"
Jackson says.
"We really focused on the prefrontal and
medial temporal regions because they are the
regions where you see the greatest age
changes, and they are also seats of
attention, emotion and memory.
"We
found that more neurotic individuals had
smaller volumes in certain prefrontal and
medial temporal parts of the brain than
those who were less neurotic, and the
opposite pattern was found with
conscientiousness."
"A unique thing that we've done is to
reliably measure personality differences and
associate them with age-related effects on
brain structures in healthy middle-aged and
older adults" Head says.
"Specifically, we found that neuroticism was
associated with greater age-related decline
in brain volume, whereas conscientiousness
was associated with less age-related
decline."
The researchers were interested in healthy
aging brains because, down the road, the
findings might serve as a useful marker for
later diagnosis of dementia.
The volunteers they studied are normal
control participants at Washington
University's Alzheimer's Disease Research
Center (ADRC), led by John C. Morris, MD,
the Friedman Distinguished Professor of
Neurology and director of the ADRC.
One of the first changes in Alzheimer's
disease may be in personality. There is
accumulating research from the ADRC and
other institutions that suggest that people
tend to become more neurotic and less
conscientious in early-stage Alzheimer's.
"It might be that changes in personality
track onto those people more likely to
develop Alzheimer's," Jackson says. "It's
why we looked at older healthy adults
because it's important to track these
relationships in healthy populations before
you look at pathological ones.
"We know that there are degenerative
processes going on before the diagnosis of
Alzheimer's.
"We
want to be able to see if the subtle
personality changes might be particular to
an early clinical picture and possibly see
if one can predict who will become demented
based on personality changes," Jackson says.
Another way of looking at the findings, Head
says, is that neuroticism might add an
increasing vulnerability to the pathological
processes that go on in aging, particularly
in Alzheimer's.
"We will continue to pursue the relationship
between personality and brain structure as
one of the earlier processes in Alzheimer's
and hence a possible risk factor," Head
says.
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