Limited compensation but preserved motor variability in vocal pitch control of adults who stutter

Our motor system uses sensory feedback to maintain the desired performance. From this view, motor fluctuation is not simply ‘noise’ inevitably caused in the nervous system but would play a role in generating variabilities to explore better outcomes via sensory feedback. This behavior is typically observed as a compensatory response in vocalized pitches. Previous studies on adults who do not stutter (ANS) have shown that larger spontaneous fluctuations correlate with greater compensation in vocal pitch, suggesting the functional role of motor variability in the exploration of better vocal outcomes. Here, we assessed whether the same thing can be observed in adults who stutter (AWS). As a result, the AWS group exhibited vocal variability at a comparable level with ANS, while they showed reduced compensation responses. These findings suggest that pathological speech production in stuttering does not originate from the ability to generate motor variability in vocalization, but is associated with integrating feedback signals into the compensatory motor response.