A study by researchers from the Perelman School of Medicine at the
University of Pennsylvania shows that declines in hearing ability may
accelerate gray mater atrophy in auditory areas of the brain and increase the
listening effort necessary for older adults to successfully comprehend speech.
When a sense
(taste, smell, sight, hearing, touch) is altered, the brain reorganizes and
adjusts. In the case of poor hearers, researchers found that the gray matter
density of the auditory areas was lower in people with decreased hearing
ability, suggesting a link between hearing ability and brain volume.
"As
hearing ability declines with age, interventions such as hearing aids should be
considered not only to improve hearing but to preserve the brain," said
lead author Jonathan Peelle, PhD, research associate in the Department of
Neurology. "People hear differently, and those with even moderate hearing
loss may have to work harder to understand complex sentences."
In a pair of
studies, researchers measured the relationship of hearing acuity to the brain,
first measuring the brain's response to increasingly complex sentences and then
measuring cortical brain volume in auditory cortex. Older adults (60-77 years
of age) with normal hearing for their age were evaluated to determine whether
normal variations in hearing ability impacted the structure or function of the
network of areas in the brain supporting speech comprehension.
The studies
found that people with hearing loss showed less brain activity on functional
MRI scans when listening to complex sentences. Poorer hearers also had less
gray matter in the auditory cortex, suggesting that areas of the brain related
to auditory processing may show accelerated atrophy when hearing ability
declines.
In general,
research suggests that hearing sensitivity has cascading consequences for the
neural processes supporting both perception and cognition. Although the
research was conducted in older adults, the findings also have implications for
younger adults, including those concerned about listening to music at loud
volumes. "Your hearing ability directly affects how the brain processes
sounds, including speech," says Dr. Peelle. "Preserving your hearing
doesn't only protect your ears, but also helps your brain perform at its
best."
The research
appears in the September 2011 The Journal of Neuroscience and
was funded by the National Institutes of Health.
Physicians
should monitor hearing in patients as they age, noting that individuals who
still fall within normal hearing ability may have increasing complaints of
speech comprehension issues. Patients should talk to their physician or an
audiologist if they are experiencing any difficulty hearing or understanding
speech.
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