Bite-block perturbation in people who stutter: immediate compensatory and delayed adaptive processes.

UNLABELLED: This exploratory study investigated sensory-motor mechanisms in five people who stutter (PWS) and five people who do not (PNS). Lip kinematic and coordination data were recorded as they produced bi-syllabic nonwords at two rates (normal and fast) in three conditions (jaw-free, immediately after insertion of a bite-block, and after a 10-min accommodation period). At normal speech rates, effects of bite-blocks on lip kinematics were similar for both PWS and PNS speakers showing larger amplitudes, peak velocities, shorter durations and more stable movement cycle patterns. However, at fast speech rates upper lip responses of PWS exhibited larger amplitudes and peak velocities. At both speech rates, the presence of a bite-block changed movement coordination patterns only for PNS. However, at fast speech rates bite-blocks decreased variability of coordination patterns for both groups. No adaptive changes in movement stability were found for either group, but a practice-related increase in lower lip peak velocity was found at normal speech rates. These findings indicate that bite-block perturbation did not exacerbate any hypothesized limitation or difficulty in controlling individual articulatory movements or their coordination in PWS. The results also support the position that specific motor control strategies are used by PWS as compared to PNS to compensate for bite-block perturbations under increased speech rate demands. LEARNING OUTCOMES: The reader will be able to: (1) distinguish between compensatory and adaptive responses to bite-block perturbation; (2) explain the measurement of articulatory stability; (3) summarize the potential role of motor control strategies in people who stutter; and (4) discuss the assumptions of the motor skills approach to stuttering.