Kinematic analyses of speech, orofacial nonspeech, and finger movements in stuttering and nonstuttering adults

This work investigated the hypothesis that neuromotor differences between individuals who stutter and individuals who do not stutter are not limited to the movements involved in speech production. Kinematic data were obtained from gender- and age-matched stuttering (n = 10) and nonstuttering (n = 10) adults during speech movements, orofacial nonspeech movements, and finger movements. All movements were performed in 4 conditions differing in sequence length and location of the target movement within the sequence. Results revealed statistically significant differences between the stuttering and nonstuttering individuals on several measures of lip and jaw closing (but not opening) movements during perceptually fluent speech. The magnitude of these differences varied across different levels of utterance length (larger differences during shorter utterances) and across different locations of the target movement within an utterance (larger differences close to the beginning). Results further revealed statistically significant differences between the stuttering and nonstuttering groups in finger flexion (but not extension) movement duration and peak velocity latency. Overall, findings suggest that differences between stuttering and nonstuttering individuals are not confined to the sensorimotor processes underlying speech production or even movements of the orofacial system in general. Rather, it appears that the groups show generalized differences in the duration of certain goal-directed movements across unrelated motor systems.