Researchers identify brain network linked to stuttering

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Research, by Te Whare Wānanga o Waitaha | Catherine Theys, associate professor at the University of Canterbury (UC), examines two different types of stuttering – developmental and acquired – to show a clear neural basis for speech disorders.

“Stuttering affects around 1% of adults and can cause significant communication problems and social anxiety, but the cause of stuttering is still unknown,” says Associate Professor Theys. “It is most commonly a developmental disorder, but can also be caused by focal brain damage following stroke or other neurological disorders. While most research treats 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 link.

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

While previous research has looked at specific locations of brain damage to try to discover how the brain works, Associate Professor Theys says this research uses a new technique that examines the brain networks affected by damage and whether there might be any have a common center.

“We used the first two datasets and lesion network mapping to test whether the lesions causing acquired stuttering corresponded to a common brain network. We then used the third dataset to test whether this lesion-based network was relevant to developmental stuttering.

“By examining each of the datasets, we were able to locate a common stuttering network, narrowing it down to a specific part of the left putamen, responsible for lip and facial movements, as well as speech timing and sequencing. We also identified two additional new areas of interest for research into speech imagery and stuttering, namely the claustrum and the amygdalostriatal transition zone. These are tiny areas of the brain – only a few millimeters wide – which is why they have not typically been identified in previous studies. This shows a plausible network for stuttering.

“People have always thought of acquired and developmental stuttering as two separate things, but we were able to show that in addition to similarities at the behavioral level, there are also similarities at the neural level.”

Dr. Theys says the findings are relevant to treatment.

“For people with acquired stuttering, this provides a good explanation of what might be happening. When we look at this part of the putamen, it's really the sequence of movements that seems to be a key underlying difficulty, and therefore an important aspect on which to focus our treatments. The identified network areas also provide insight into possible links to emotional responses related to stuttering. The findings of the claustrum and amygdalostriatal transition zone provide an important new direction in mapping the neural basis of stuttering and ensure the development of the best possible diagnostic and therapeutic approaches.

Reference: Theys C, Jaakkola E, Melzer TR et al. Localization of stuttering based on causal brain lesions. Brain. 2024:awae059. doi: 10.1093/brain/awae059

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