Speech-motor control and interhemispheric relations in recovered and persistent stuttering.

Area of Science:

• Neuroscience
• Speech and Hearing Sciences
• Developmental Psychology

Background:

• Stuttering is linked to neurological anomalies in interhemispheric relations and speech-motor control, particularly involving the supplementary motor area (SMA).
• Many children recover from stuttering without intervention, suggesting underlying developmental changes.
• The study explores if SMA maturation underlies this spontaneous recovery.

Purpose of the Study:

• To investigate the neurological mechanisms associated with persistent stuttering and spontaneous recovery.
• To examine the role of the supplementary motor area (SMA) and interhemispheric relations in stuttering.
• To differentiate the neurological profiles of persistent stutterers, ex-stutterers, and non-stutterers.

Main Methods:

• Four experimental tasks were administered: Sequence Reproduction Finger Tapping, Bimanual Crank Turning, and two Divided Visual Field tasks.
• Participants included adults with persistent stuttering, adults who recovered from childhood stuttering (ex-stutterers), and adults who never stuttered (controls).
• Tasks assessed SMA functioning, bimanual coordination, and hemispheric activation asymmetries.

Main Results:

• Persistent stutterers showed motor-perceptual anomalies compared to non-stutterers.
• Bimanual coordination deficits in stutterers were kinesthetically based and linked to anterior callosal systems, including the SMA.
• Ex-stutterers performed similarly to non-stutterers on motor tasks but showed perceptual asymmetries like persistent stutterers.

Conclusions:

• Anomalies in interhemispheric relations and speech-motor control are necessary but not sufficient for stuttering.
• Recovery from childhood stuttering appears to reflect a maturation of speech-motor control mechanisms, particularly within the SMA.
• These findings support a neurodevelopmental model of stuttering and its resolution.