A temporal window for the central inhibition of stuttering via exogenous speech signals in adults.

We explored a possible temporal window for central stuttering inhibition via exogenously presented speech signals. Thirteen adults who stutter were asked to read while listening to a continuous vowel /a/, or a repeating 1 s vowel /a/ followed by 1, 3 and 5 s silences. In all conditions, stuttering was significantly reduced. However, the continuous and 1 s repeating conditions showed the greatest reduction in stuttering relative to all other conditions. Furthermore, these conditions did not differ significantly from each other, suggesting a temporal window of at least 1 s for stuttering inhibition induced by a 1 s stimulus. We propose that exogenous speech signals provide an additional speech source that engages mirror neurons for 'on-line' stuttering inhibition during continous speech. Employing dual speech sources results in 'on-line' stuttering inhibition and continuous speech flow. In contrast, endogenous (single source) inhibitory techniques require speech flow to be interrupted and go 'off-line' to derive the mirror neuronal.