Speech rate association with cerebellar white-matter diffusivity in adults with persistent developmental stuttering

Area of Science:

• Neuroscience
• Speech and Language Pathology
• Neuroimaging

Background:

• Altered speech rate is a characteristic of speech disorders like persistent developmental stuttering.
• Adults who stutter (AWS) typically have a slower speech rate than fluent speakers.
• The cerebellum is implicated in speech production, with structural and functional abnormalities noted in people who stutter.

Purpose of the Study:

• To investigate the association between cerebellar peduncles and speech rate in AWS.
• To explore the role of cerebellar pathways in controlling speech rate in stuttering.

Main Methods:

• Diffusion MRI and speech rate data were collected from 42 participants (23 AWS, 19 controls).
• Deterministic tractography with Automatic Fiber Segmentation and Quantification (AFQ) was used to identify superior, middle, and inferior cerebellar peduncles (SCP, MCP, ICP).
• Fractional anisotropy (FA) and mean diffusivity (MD) were quantified along each tract.

Main Results:

• No significant differences in cerebellar peduncle diffusivity values were found between AWS and controls.
• AWS showed a significant negative association between speech rate and FA in the left inferior cerebellar peduncle (ICP).
• The ICP, a key pathway for sensory feedback to the cerebellum, was implicated.

Conclusions:

• Findings suggest the ICP's involvement in speech rate reduction observed in AWS.
• This aligns with theories of stuttering involving hyperactive speech monitoring.
• A plausible neural mechanism for altered speech rate in stuttering is proposed.