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 mis-coordination 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.”

Find more research at Stuttering Foundation of America (click here)