August 10, 2012 — The left pars opercularis (PO) in the brain appears to be the site of neurodevelopmental anomalies in patients with persistent developmental stuttering (PDS), a new study shows. The report also shows that only 1 week of behavioral therapy can reduce symptoms of stuttering.
Located in the inferior frontal cortex as part of the Broca region, the PO is where speech/language is processed.
"The findings suggest that stuttering is more likely to be a neurodevelopmental disorder associated with anomalies of the left inferior frontal cortex, and that the human brain is highly plastic as 1 week of therapy was enough to reorganize the brain, helping to reduce stuttering severity," said study author, Chunming Lu, PhD, assistant professor at the State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, in China.
The study was published online August 8 in Neurology.
Resting State Connectivity
People who stutter, many of whom have had the disability since childhood, not only have neurodevelopmental anomalies but have also developed forms of compensation, the authors note. The anomalies and the plastic compensations are indistinguishable, explained Dr. Lu.
The current study employed a pretherapy and post-therapy design to examine neural differences between people who stutter and fluent controls, and to identify which are stable and which change with treatment.
To do this, researchers documented resting state functional connectivity (RSFC) in 15 patients with PDS who received a short-term behavioral intervention, 13 patients with PDS who did not receive the intervention, and 13 control individuals with fluent language. All participants were male and right-handed. (Because the left hemisphere is the dominant hemisphere for speech and language for right-handed but not all left-handed people, most studies exclude left-handed participants.)
Study participants had a standard Stuttering Severity Instrument version III (SSI-3) score of at least mild. Groups were matched for educational level and handedness scores.
All study participants underwent magnetic resonance imaging (MRI) at the beginning and at the end of the study.
The therapist-supervised behavioral intervention consisted of 3 sessions per day over 7 consecutive days with 9 blocks of speech material per session. During sessions, participants were required to repeat random words read in standard Mandarin, and to read aloud visually presented words. They were also asked to practice the newly learned speaking patterns on their own.
Treatment aimed to facilitate phonologic and phonetic encoding, for example, being aware of which sounds are included in a word and how to arrange the sequences of a sound, explained Dr. Lu. It also focused on things like lip and tongue movements, he said.
"This therapy is useful in helping the brain reorganize its functional architecture in order to work efficiently during speech," said Dr. Lu. He added that the atypical planning and execution of people who stutter are associated with the basal ganglia–inferior frontal cortex and cerebellum–premotor area/insula circuits, respectively.
For participants who received treatment, improvement in average scores on stuttering tests and in percent of stuttered syllables was noted. No change in scores was reported for those who did not receive treatment.
MRI scans showed that before therapy, RSFC and cortical thickness were reduced in the left PO in all patients with PDS who also had increased strength of interactions in the cerebellum. The intervention did not alter functional connectivity of the Broca region (the left PO is part of this area), but it reduced functional connectivity in the cerebellum to the same level as that of control individuals.
These changes occurred while participants were resting — so, not speaking. This suggests that the Broca region plays an important role in therapy-induced reductions in stuttering symptoms.
"In previous studies about stuttering, both functional regional activity and functional connectivity [interactions between brain regions] anomalies of this region [the PO] have been reported in people who stutter," said Dr. Lu. "But in these findings, this region still mixed with other regions that are compensatory. By employing a short-term therapy design, the current study was able to identify the neural anomalies that are stable and those that are not. The findings showed that this region is stable across the therapy."
It is interesting to note that the study did not find any difference in the right frontal operculum–anterior insula. When the left brain is damaged, the right homologous regions typically compensate, and it is widely believed that overactivation of the right frontal regions plays a compensatory role in stuttering, said Dr. Lu.
Lack of overactivation could be explained by the scanning being carried out while at rest, or by the fact that right hemispheric compensations may be specific to speaking tasks, "that is, if the task demands differ, the compensations will differ, too," said Dr. Lu. On the other hand, researchers identified the cerebellum as an area that may play a compensatory role in stuttering.
These results suggest that different brain regions may have different forms of compensation, said Dr. Lu.
Stuttering affects about 1% of the adult population. The male-to-female incidence ratio is about 4:1, according to Dr. Lu. "Boys are more likely to start to show stuttering and [are] less likely to recover than girls."
Although many types of therapy for stuttering are used around the world (e.g., the Lidcome program in Australia, Kassel Stuttering therapy in Germany, Modifying Phonation Intervals in the United States), stuttering therapy in China "lags behind," said Dr. Lu.
"There is no widely accepted therapy, not enough therapists, and not much public attention given to people who stutter," he said. This presents a challenge; however, it also provides an opportunity to develop effective therapies for the population of Chinese people who stutter. "We also hope that our study and the therapy will be helpful for people in other countries," said Dr. Lu.
For Christian A. Kell, MD, from the Department of Neurology at Goethe University, in Frankfurt, Germany, who wrote an accompanying editorial, the study's main message is not just that behavioral therapy alone — without drug intervention — can modify how the brain works, but that these changes can be detected even in individuals at rest.
"One of the nice things about this study is that it shows that even if the subject or patient is not performing any task while in the scanner, the brain activity is modified by therapy," said Dr. Kell in an interview with Medscape Medical News.
He pointed out that people still think while at rest, even if they are not actually verbalizing.
"If you're in a scanner, you're thinking about what you're going to do next, whether you're going to go out shopping or go and do some sports, so you're thinking and planning, and all this you do verbally. So basically, it's speech production, only it's not overt speech production — it's covert."
What remains open to debate, said Dr. Kell, is whether the speech therapy mechanism itself or the simple fact of being in an organized speech program modifies brain activity.
Dr. Kell found the intervention incorporated in the study, which is not used in Germany, to be "a little unusual" in that it used words instead of sentences, although "it seems to be efficient."
Dr. Lu is funded by the National Natural Science Foundation of China. For full disclosure information, see the journal Web site. Dr. Kell has disclosed no relevant financial relationships.
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Cite this: Behavioral Intervention Reduces Stuttering in Only a Week - Medscape - Aug 10, 2012.