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 Additional
Information: Current Research
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Are
We Getting Any Closer to Finding the Cause of Stuttering?
The latest in
research news….(American Institute for Stuttering,
Spring, 2003)
Some significant
research has been done in the last several years that indicates
stuttering is likely to be an inherited neurophysiological
disorder. In simpler terms, this means that:
- People are
born with an inherited predisposition to stutter
- The brain
is not signaling the vocal and speech mechanism properly
- this breakdown
likely underlies the miscoordination in the muscle movements
required for speech
So, it appears
that stuttering really is a physical problem and is NOT
caused by psychological factors, although we are well aware
that there are usually psychological and emotional layers
because of the stuttering. For most people, stress seems
to worsen stuttering because stress causes muscles to tense,
which then directly affects the way the speech muscles work.
Also, people learn to expect stuttering because of previous
experiences. This expectation then helps to create more
tension and thus, more disfluency. Here are some highlights
of recent research findings.
- Differences
in Brain Activity:
From: Perspectives on Fluency and Fluency Disorders (August
2002), Christy Ludlow, Ph.D. “In recent brain imaging
studies during stuttering, an abnormal network of brain
activation has been shown to relate to the severity of
stuttering rather than an abnormality in one particular
brain region. The findings suggest increased brain activity
in regions {that are} normally less active during speech
associated with speech disfluency (Braun et al., 1997;
Fox et al., 2000)….In addition, deficits in sensory
processing {in the brain} have been found in adults who
stutter (DeNil & Abbs, 1991)….The occurrence
of stuttering following brain injury in adults could indicate
which brain regions may be involved in the maintenance
of fluent speech….In fact, lesions affecting any
part of the neural network involved in speech motor control
can induce disfluency, suggesting again that stuttering
is the result of abnormalities in the physiology of the
speech motor control network rather than {that} of one
particular brain region (Helm, Butler & Canter, 1980;
Ludlow et al., 1987).”
- Differences
in Brain Matter and Structure: From:
Stuttering Foundation (Fall 2002), “….{a}
study, published in the lancet medical journal (August
3, 2002) indicates that a disconnection of speech-related
areas in the brain is the cause of stuttering. Specifically,
Dr. Martin Sommer and colleagues from the universities
of Hamburg and Gottingen in Germany found that the tissue
structure of a region in the left hemisphere of the brain
in people who stutter was significantly different from
that of the control group….that fibers in the area
are related to the parts of the brain used for articulation
and speech, and the abnormality disrupts speech by disturbing
the transmission of signals, causing stuttering to occur
as the right side of the brain overcompensates….Sommer
and his colleagues suggested that this white matter abnormality
disconnects portions of speech-relevant brain areas in
adults with persistent developmental stuttering….The
results reported by Sommer and colleagues are very important
and offer further support for a structural abnormality
within speech-language areas in individuals who stutter.”
- The
Search For the Stuttering Gene: Perspectives
on Fluency and Fluency Disorders (August 2002), Ehud Yairi,
Ph.D. and Nicoline Ambrose, Ph.D. “….we have
advanced from simplistic, casual observations that stuttering
runs in families, arriving just recently at a point where
we are within arm’s reach of identifying the actual
genes underlying stuttering….Finally, one must keep
in mind that when a gene (or genes) is identified as a
factor in a disorder, it may not be known, at least for
awhile, what the specific gene actually does: what is
it that is inherited via genes or how much of a disorder
is governed by them….In shore, much work awaits
us before the cause of stuttering is understood.”
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