Study shows noticeable differences in
brain function across the day
Toronto, Canada – Older adults who
are tested at their optimal time of day (the morning), not only
perform better on demanding cognitive tasks but also activate the
same brain networks responsible for paying attention and suppressing
distraction as younger adults, according to Canadian researchers.
The study, published online July 7th in
the journal Psychology and Aging (ahead of print publication), has
yielded some of the strongest evidence yet that there are noticeable
differences in brain function across the day for older adults.
"Time of day really does matter
when testing older adults. This age group is more focused and better
able to ignore distraction in the morning than in the afternoon,"
said lead author John Anderson, a PhD candidate with the Rotman
Research Institute at Baycrest Health Sciences and University of
Toronto, Department of Psychology.
"Their improved cognitive
performance in the morning correlated with greater activation of the
brain's attentional control regions – the rostral prefrontal and
superior parietal cortex – similar to that of younger adults."
Asked how his team's findings may be
useful to older adults in their daily activities, Anderson
recommended that older adults try to schedule their most
mentally-challenging tasks for the morning time. Those tasks could
include doing taxes, taking a test (such as a driver's license
renewal), seeing a doctor about a new condition, or cooking an
unfamiliar recipe.
In the study, 16 younger adults (aged
19 – 30) and 16 older adults (aged 60-82) participated in a series
of memory tests during the afternoon from 1 – 5 p.m. The tests
involved studying and recalling a series of picture and word
combinations flashed on a computer screen. Irrelevant words linked to
certain pictures and irrelevant pictures linked to certain words also
flashed on the screen as a distraction. During the testing,
participants' brains were scanned with fMRI which allows researchers
to detect with great precision which areas of the brain are
activated.
Older adults were 10 percent more
likely to pay attention to the distracting information than younger
adults who were able to successfully focus and block this
information. The fMRI data confirmed that older adults showed
substantially less engagement of the attentional control areas of the
brain compared to younger adults. Indeed, older adults tested in the
afternoon were "idling" – showing activations in the
default mode (a set of regions that come online primarily when a
person is resting or thinking about nothing in particular) indicating
that perhaps they were having great difficulty focusing. When a
person is fully engaged with focusing, resting state activations are
suppressed.
When 18 older adults were morning
tested (8:30 a.m. – 10:30 a.m.) they performed noticeably better,
according to two separate behavioural measures of inhibitory control.
They attended to fewer distracting items than their peers tested at
off-peak times of day, closing the age difference gap in performance
with younger adults. Importantly, older adults tested in the morning
activated the same brain areas young adults did to successfully
ignore the distracting information. This suggests that 'when' older
adults are tested is important for both how they perform and what
brain activity one should expert to see.
"Our research is consistent with
previous science reports showing that at a time of day that matches
circadian arousal patterns, older adults are able to resist
distraction," said Dr. Lynn Hasher, senior author on the paper
and a leading authority in attention and inhibitory functioning in
younger and older adults.
The Baycrest findings offer a
cautionary flag to those who study cognitive function in older
adults. "Since older adults tend to be morning-type people,
ignoring time of day when testing them on some tasks may create an
inaccurate picture of age differences in brain function," said
Dr. Hasher, senior scientist at Baycrest's Rotman Research Institute
and Professor of Psychology at University of Toronto.
The Baycrest study was funded by the
Canadian Institutes for Health Research, and the Natural Sciences and
Engineering Research Council.
Contact: Kelly Connelly
416-785-2432
Baycrest Centre for Geriatric Care
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