Identifying the neural network responsible for stuttering: New research

New research published in Brain has identified a specific brain circuit center that plays a key role in stuttering.

The study, led by Associate Professor Catherine Tice from the University of Canterbury (Te Whare Wānanga o Waitaha), looks at two different types of stuttering - developmental and acquired - to show a clear neural basis for it speech disorder.

“Stuttering affects approximately 1% of adults and can lead to significant communication problems and social anxiety, but the cause of stuttering is still unknown,” says Associate Professor Theis.

"It most often occurs as a developing disorder, but can also be caused by localized damage to the brain following a stroke or other neurological conditions. While most studies treat these different types of stuttering as separate conditions, this study takes a unique approach by combining data sets to see if we can identify a common connection."

The multidisciplinary study, conducted in collaboration with researchers from the University of Turku (Finland), the University of Toronto, Boston University and the Brigham and Women's Hospital of Harvard Medical School, used three independent data sets: case reports from the published literature on acquired neurogenic stuttering after stroke; a clinical trial involving patients with acquired neurogenic stuttering after stroke; and adults with persistent developmental stuttering.

While previous studies have looked at specific locations of brain damage to try to figure out how the brain works, Associate Professor Theis says this study uses a new technique that looks at the brain networks affected by the damage and finds out if there is a common center.

"We used the first two datasets and lesion network mapping to test whether the lesions causing acquired stuttering were consistent with a general brain network. We then used the third dataset to test whether this network pattern was relevant to developmental stuttering.

"By looking at each of the data sets, we were able to find a common stuttering network, narrowing it down to a specific part of the left putamen, which is responsible for lip and facial movements, as well as speech timing and sequencing.

"We also identified two new areas of interest for research on speech imaging and stuttering: the claustrum and the amygdalostriatal transition area. These are tiny regions of the brain—just a few millimeters wide—which likely explains why they were not identified in previous studies. This shows a plausible stuttering network.

"Previously people viewed acquired and developmental stuttering as two separate phenomena, but we were able to show that, in addition to similarities at the behavioral level, there are also similarities at the neural level."

Dr. Theis says the findings have implications for treatment.

"For people with acquired stuttering, this provides a good explanation of what is happening. When you look at this part of the putamen, it is clear that the key problem is the sequence of movements, and this is an important aspect to pay attention to in treatment. Network areas identified also provide insight into possible connections to emotional reactions in stuttering.

"The discovery of the claustrum and amygdalostriatal transition region represents an important new direction in mapping the neural basis of stuttering, providing the opportunity to develop the best diagnostic and therapeutic approaches."