Revista de Fonoaudiologia e Terapia

Abstrato

Opening and Closing Jaw Movements of Young Children who Stutter

Anthony P Buhr, Patricia Zebrowksi, Jerald Moon, Victoria Tumanova, Richard Arenas and Torrey Loucks

Objective: In this longitudinal study, we investigated the hypothesis that kinematic measures of jaw movement produced by children who stuttered (CWS) and children who did not stutter (CWNS) would differ between opening and closing speech gestures, across phonetic contexts, and across development.

Methods: Mean amplitude, velocity, and duration of jaw opening and closing gestures during repeated productions of bilabial syllables were analyzed longitudinally at 1-year intervals for 13 CWS and 7 children CWNS. The utterances ranged across four phonetic contexts: single-syllable, two-syllable, three-syllable, and six-syllable. For jaw movement transduction, a strain gauge was attached to a football helmet in a novel design to minimize head movement. All kinematic measures were made from jaw movement tracings in Windaq (Dataq Instruments, Inc.) software, based on a standard millimeter to voltage conversion.

Results: The main finding of the study was that opening gestures were produced by both CWS and CWNS with greater amplitude and duration compared to closing gestures. However, the kinematics associated with opening and closing jaw movements did not differ between CWS and CWNS, suggesting that the intrinsic articulatory dynamics of the two groups were similar. In addition, adapting the kinematics of opening and closing jaw movements across the four phonetic contexts did not differ between the groups for either movement amplitude or velocity. However, CWS produced the closing gesture with significantly greater duration compared to multi-syllable conditions, relative to CWNS. Finally, CWS and CWNS exhibited different longitudinal patterns for jaw amplitude and peak velocity.

Conclusion: The speech motor systems of CWS and CWNS exhibited broadly similar organization of intrinsic articulatory dynamics, but groups may differ in how underlying dynamics are adapted to changing phonetic contexts across development. It is possible that the speech fluency of CWS might benefit from greater articulatory constraints, as the main between-group difference was identified when degrees of freedom of movement were greatest. Implications of findings are discussed within the development of a hierarchically organized speech motor system.