Structural and functional abnormalities of the motor system in developmental stuttering

Area of Science:

• Neuroscience
• Speech and Language Sciences

Background:

• Stuttering (Developmental Stuttering) is a speech disorder with motor characteristics.
• Linguistic factors and altered auditory feedback influence stuttering frequency, suggesting non-motor system involvement.

Purpose of the Study:

• To investigate brain structure and function in motor and language areas in young people who stutter using functional and diffusion imaging.
• To identify neural correlates of stuttering during speech production.

Main Methods:

• Functional MRI (fMRI) and Diffusion Tensor Imaging (DTI) were used.
• Brain activity and white matter integrity were compared between individuals who stutter and controls during speech tasks.

Main Results:

• Individuals who stutter exhibited overactivity in the anterior insula, cerebellum, and midbrain (including substantia nigra and basal ganglia nuclei).
• Underactivity was observed in cortical motor and premotor areas (ventral premotor, Rolandic opercular, sensorimotor cortex) and left Heschl's gyrus.
• Reduced white matter integrity was found in the ventral premotor cortex of individuals who stutter, impacting speech articulation planning and execution.

Conclusions:

• Stuttering is linked to disruptions in neural systems supporting motor sequence selection, initiation, and execution for fluent speech.
• Findings suggest a combination of cortical and subcortical neural system dysfunction contributes to stuttering.