Normal interhemispheric inhibition in persistent developmental stuttering.

Imaging studies suggest a right hemispheric (pre)motor overactivity in patients with persistent developmental stuttering (PDS). The interhemispheric inhibition (IHI) studied with transcranial magnetic stimulation is an established measure of the interplay between right and left motor areas. We assessed IHI in 15 young male adults with PDS and 15 age-matched fluent-speaking subjects. We additionally studied the ipsilateral silent period (iSP) duration. We found no significant between-group difference for IHI or for iSP duration. We conclude that the interplay between the primary motor cortices is normal in patients with PDS. The abnormal right motor and premotor activity observed in functional imaging studies on PDS are not likely to reflect altered primary motor cortex excitability, but are likely to have a different origin.