According to a new study, stuttering could be caused by a structural fault in the left hemisphere of the brain that triggers nerve disconnection in the regions controlling speech. Researchers from the Universities of Hamburg and Gottingen 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 10 individuals with persistent stutters to 10 people with normal speech.
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.
Cornelius Weiller, director of the University of Hamburg's neurology institute told that stutterers have none or a less developed pathway connecting language areas with the mouth motor output areas, in the brain. Weiller felt that, they know now where to look for treatment. 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.
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.
Dr. Anne Foundas, a neurology professor at Tulane University in New Orleans, has studied stuttering and also found structural differences. Foundas felt that they found that there were differences in the anatomy of some of these gray matter regions in (the brains of) adults with persistent developmental stuttering. We did not study the white matter connections.
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. 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. According to him, speech is a really complicated sequence of motor movements that requires coordination between different brain areas.