Carbamazepine reduces short-interval interhemispheric inhibition in healthy humans.

Objective: We sought to elucidate the influence of centrally active drugs on interhemispheric inhibition (IHI) between primary motor cortices in healthy humans.

Methods: We therefore studied IHI before and 2h after intake of a single oral dose of carbamazepine, dextrometorphane, lorazepam, or placebo and compared it with the well known results for short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Drugs were tested in separate sessions and in random order.

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.