Stuttering Linked to Specific Brain Network

Summary: A new study has identified a common brain network responsible for stuttering, regardless of its cause. Researchers found that strokes causing stuttering and developmental stuttering both affect the same brain areas.

These findings could lead to targeted treatments, such as brain stimulation, to help individuals who stutter. The study highlights key brain regions involved in motor function and emotion regulation.

Key Facts:

  • Common Network: Stuttering from different causes affects the same brain network.
  • Key Brain Regions: Putamen, amygdala, and claustrum are crucial in stuttering.
  • Treatment Potential: Findings open possibilities for targeted brain stimulation treatments.

Source: University of Turku

Stuttering is a speech rhythm disorder characterised by involuntary repetitions, prolongations or pauses in speech that prevent typical speech production.

Approximately 5–10% of young children stutter, and an estimated 1% continue to stutter into adulthood. A severe stutter can have a profound negative impact on the life of the individual affected.

This shows the outline of a head.
The findings from brain imaging studies are partly contradictory, and it is challenging to determine which changes are the root cause of stuttering and which are merely associated phenomena. Credit: Neuroscience News

“Stuttering was once considered a psychological disorder. However, with further research, it is now understood to be a brain disorder related to the regulation of speech production,” says Professor of Neurology Juho Joutsa from the University of Turku.

Stuttering may also be acquired as a result of certain neurological diseases, such as Parkinson’s disease or a stroke. However, the neurobiological mechanisms of stuttering are not yet fully understood, and where it originates in the brain remains uncertain.

The findings from brain imaging studies are partly contradictory, and it is challenging to determine which changes are the root cause of stuttering and which are merely associated phenomena.

Stuttering localised in the same brain network regardless of its cause

Researchers from Finland, New Zealand, the United States and Canada developed a new research design that could provide a solution to this problem. The study included individuals who had suffered a stroke, some of whom developed a stutter immediately after it.

The researchers discovered that although the strokes were located in different parts of the brain, they all localised to the same brain network, unlike the strokes that did not cause stuttering.

In addition to people who had suffered a stroke, the researchers used magnetic resonance imaging (MRI) to scan the brains of 20 individuals with developmental stuttering. In these individuals, the stuttering was associated with structural changes in the nodes of the brain network originally identified in relation to causal stroke lesions – the greater the changes, the more severe the stuttering.

This finding suggests that stuttering is caused by a common brain network, regardless of the aetiology (developmental or neurological).

The key nodes of the network identified by the researchers were putamen, amygdala and claustrum located deep within the brain, and the connections between them.

“These findings explain well-known features of stuttering, such as the motor difficulties in speech production and the significant variability in stuttering severity across emotional states.

“As major nuclei in the brain, the putamen regulates motor function and the amygdala regulates emotions. The claustrum, in turn, acts as a node for several brain networks and relays information between them,” explains Joutsa.

The results of the study provide a unique insight into the neurobiological basis of stuttering. Locating stuttering in the brain opens up new possibilities for medical treatment.

Researchers hope that in the future, stuttering could be effectively treated, for example, with brain stimulation that can be targeted specifically to the now identified brain network. 

About this stuttering and neuroscience research news

Author: Tuomas Koivula
Source: University of Turku
Contact: Tuomas Koivula – University of Turku
Image: The image is credited to Neuroscience News

Original Research: Open access.
Localization of stuttering based on causal brain lesions” by Juho Joutsa et al. Brain


Localization of stuttering based on causal brain lesions

Stuttering affects approximately 1 in 100 adults and can result in significant communication problems and social anxiety. It most often occurs as a developmental disorder but can also be caused by focal brain damage.

These latter cases may lend unique insight into the brain regions causing stuttering.

Here, we investigated the neuroanatomical substrate of stuttering using three independent datasets: (i) case reports from the published literature of acquired neurogenic stuttering following stroke (n = 20, 14 males/six females, 16–77 years); (ii) a clinical single study cohort with acquired neurogenic stuttering following stroke (n = 20, 13 males/seven females, 45–87 years); and (iii) adults with persistent developmental stuttering (n = 20, 14 males/six females, 18–43 years).

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

In our literature dataset, we found that lesions causing stuttering occurred in multiple heterogeneous brain regions, but these lesion locations were all functionally connected to a common network centred around the left putamen, including the claustrum, amygdalostriatal transition area and other adjacent areas.

This finding was shown to be specific for stuttering (PFWE < 0.05) and reproducible in our independent clinical cohort of patients with stroke-induced stuttering (PFWE < 0.05), resulting in a common acquired stuttering network across both stroke datasets.

Within the common acquired stuttering network, we found a significant association between grey matter volume and stuttering impact for adults with persistent developmental stuttering in the left posteroventral putamen, extending into the adjacent claustrum and amygdalostriatal transition area (PFWE < 0.05).

We conclude that lesions causing acquired neurogenic stuttering map to a common brain network, centred to the left putamen, claustrum and amygdalostriatal transition area. The association of this lesion-based network with symptom severity in developmental stuttering suggests a shared neuroanatomy across aetiologies.

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