- HAMBURG, Germany (UPI) -- Stuttering could be
caused by a structural defect in the left hemisphere of the brain that
triggers nerve disconnection in the regions controlling speech, a new study
released Thursday suggests.
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- Researchers from the Universities of Hamburg and Göttingen
report chronic stuttering seems to be the result of a lapse in the brain's
cortex in the left hemisphere, the area responsible for speech. To demonstrate
this, the researchers compared 15 individuals with persistent stutters
to 15 people with normal speech.
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- Using magnetic resonance imaging or MRI, they reviewed
the brain tissue structure in each participant. They found the tissue structure
of a region in the left hemisphere of the brain was significantly different
among stuttering patients compared to the normal group. Fiber tracts in
this region act as links for brain structures involved in the articulation
and planning of speech. The defect could explain how disrupted signal transmissions
between brain structures in this area prevent an individual from speaking
fluidly.
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- "Stutterers have none or a less developed pathway
connecting language areas with the mouth motor output areas," in the
brain, Cornelius Weiller, director of the University of Hamburg's neurology
institute, told United Press International.
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- "We know now where to look for treatment,"
Weiller said. "So far, some believed an overactive right hemisphere
would be the problem, which would have resulted in a suppression of right
hemisphere activity. Our results suggest a left hemisphere problem."
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- It is possible this structural change occurs during childhood
when early language and speech-acquisition skills are being developed,
Weiller said. However, it is unclear why some children who stutter go on
to become fluent speakers and others must endure persistent stuttering
through adulthood.
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- Dr. Anne Foundas, a neurology professor at Tulane University
in New Orleans, has studied stuttering and also found structural differences.
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- "We found that there were differences in the anatomy
of some of these gray matter regions in (the brains of) adults with persistent
developmental stuttering," Foundas said. "We did not study the
white matter connections."
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- This German study, she added, "did not study gray
matter anatomy, so it may be that both are affected in people who stutter.
A lot more research needs to be done to learn more about the neural mechanisms
that induce stuttering."
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- Martin McKeown, a neurologist at Duke University Medical
Center in Durham, N.C., agreed the mystery behind stuttering has not been
completely solved, though these findings provide important clues.
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- "Because speech is a really complicated sequence
of motor movements that requires coordination between different brain areas,"
McKeown told UPI, "it is therefore reasonable that abnormalities of
the connections between these areas of the brain may play role in this
disorder."
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- The findings appear in the August 3 issue of The Lancet.
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