Towards a common neural substrate in the immediate and effective inhibition of stuttering.

Stuttering can be effectively inhibited via exogenous sensory signals (e.g., speaking in unison or using altered auditory feedback) or by using endogenous motoric strategies (e.g., singing or therapeutically implementing long vowel prolongations to reduce speech rates). We propose that these channels, which superficially appear to be diametrically opposite, centrally converge in the engagement of mirror neurons for fluent gestural productions. Sensory changes incurred via exogenous speech signals allow for direct engagement of mirror systems, while endogenous motor strategies appear to require significant departures from normal speech production (e.g., highly unnatural or droned speech) to engage mirror systems. Thus, paradoxically, stuttering is prone to resurface during attempts to impose naturalness upon therapeutic speech.