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.

This study addresses the long-standing claim that stuttering reflects an impairment in the neuromotor coordination of multiple speech movements. Upper lip (UL), lower lip (LL), and jaw (J) kinematics for nonstuttered speech behaviours in stutterers and normal speakers were examined using quantitative indices of normal multiple movement coordination reported in recent studies of gait, reaching, grasping, and speech. While two measures of coordination--dynamic movement composition and intermovement motor equivalence--did not distinguish between stutterers and normals, stutterers manifested striking differences from normal on a third measure, the sequencing of UL, LL, and J movement onsets and velocity peaks. These findings suggest that, contrary to previous hypotheses, stutterers do not manifest general problems of coordination of speech movement. Instead, stuttering appears to be associated with a specific impairment in multiple movement coordination associated with sequencing of those movements.

No abstract

The purpose of this study was to investigate stop-gap duration, voice onset time (VOT), and vowel duration in intelligible speakers with amyotrophic lateral sclerosis (ALS). Broadband sound spectrograms were used to measure 8 normal and 8 ALS speakers' intelligible speech productions of monosyllabic words containing word-initial stop-plosive consonants (/p, t, k, b, d, g/). Significant differences were found between the two groups for both vowel duration and stop-gap duration; moreover, correlational analysis indicated that the ALS speakers, as a group, exhibited a direct relationship between stop-gap and vowel durations associated with productions of /t/ and /k/. No significant differences were found between the two talker groups for VOT. Results will be related to the neuroanatomical and physiological mechanisms involved in dysarthric (ALS) speech.

The creation of experimental varicocele generated an increase in germ cell apoptosis in the ipsilateral testis at 14 days compared with control animals.