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Rest and reaction time to speech: Comparison of stuttering and fluent speakers
Abstract
Purpose: to verify the rest and reaction time to fluent speech in fluent and stuttering adults. Method: 22 adults, divided in two groups: G1-11 fluent individuals; G2-11 stuttering individuals. The electromyography records were collected in two different situations: rest and reaction time to speech. Results: the groups were significantly different on rest, with higher scores on G2. Groups are not significantly different about latency and the muscle activity. There was a strong positive correlation between latency time and speech muscle activity only on G2. Conclusion: therapy procedures aiming adequate rest and favoring speech timing may promote fluency.
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Neural processes underlying speech initiation may involve reduction in the excitability of sensory input from mechanoreceptors that mediate speech movements. It is suggested that this reduced excitability is not as great in individuals who stutter. The present experiment was intended to test this hypothesis by analyzing lip-muscle reflexes prior to speech initiation in stutterers and comparing these data to those obtained in an earlier study with nonstutterers (McClean & Clay, 1994). Mechanically evoked reflexes were studied in 14 adult stutterers prior to production of monosyllabic words beginning with the consonant p. The first component of the lip-muscle reflexes (R1) was quantified in terms of percent modulation of mean response levels of upper- and lower-lip EMG relative to reflexes elicited during no-response trials. In the previous study, 11 of 14 nonstutterers showed significant attenuation of R1 across the upper and lower lip recording sites. In contrast, significant R1 attenuation was observed in only 4 of 14 stutterers tested here. As a group, stutterers showed less R1 attenuation prior to fluent speech at the lower-lip recording site compared to the nonstutterers. Reflex modulation associated with disfluent speech was quantified in three stutterers. Two showed marked increases in relative magnitude of R1 prior to disfluent compared to fluent speech trials. Based on these various results, it is suggested that reduced attenuation of mechanoreceptor input at the time of speech-movement initiation contributes to speech disfluency.
Laryngeal muscle activity during fluent and stuttered utterances was investigated via electromyography. Analysis revealed that stuttering was accompanied by high levels of laryngeal muscle activity and disruption of normal reciprocity between abductor and adductor muscle groups. Results are interpreted as demonstrating the existence of a laryngeal component in stuttering and showing a strong correlation between abnormal laryngeal muscle activity and moments of stuttering.
Six adult stutterers and six normal speakers were instructed to make the smallest possible movements of the jaw, lower lip, tongue and right index finger, both with and without continuous visual feedback. In the non-visual (kinaesthetic) condition, the stutterers showed significantly larger minimal displacements (MDs) than did the non-stutterers for oral but not for finger movements. However, movements made in the presence of visual feedback were consistently smaller for all subjects than those made without, and no differences in MD were found between the stutterers and the non-stutterers when visual feedback was provided. The results suggested the presence of a sensorimotor deficit among at least some adult stutterers that is confined to oral movements. Given the importance of somatic sensory feedback during speech production, these observed orosensory deficiencies among stutterers may provide important insights into causal factors which contribute to the breakdowns in stutterers' speech.
The capability to record muscle-specific reflexes in the perioral muscles with surface electrodes could have practical significance for the study of speech production disorders. In the present study, surface electrodes were used to describe the perioral reflexes in 7 stutterers and 5 nonstutterers. Electromyographic (EMG) recordings were obtained at electrode sites associated with the orbicularis oris inferior muscle (OOI) and depressor labii inferior muscle (DLI) during lower-lip press and depression gestures. During postural maintenance of these gestures, innocuous mechanical stimuli were applied at the corner of the mouth. Signal averages on the two EMG signals for the two gestures and electrode sites revealed four distinct reflex response components: two excitatory (E1 and E2) and two suppression components (S1 and S2). During lip pressing, the OOI electrode site showed a prominent E1 response in all subjects, and, during lip depression, the DLI site showed an initial S1-E2 response pattern in the nonstutterers. These observations are consistent with previous descriptions of the perioral reflexes involving intramuscular electrodes. Quantitative differences in the perioral reflexes were not seen in the stutterers and nonstutterers. However, a difference was noted in the pattern of reflex response between the two groups during lip depression at the DLI electrode site.
acoustic analyses of speech naturalness.
to use voice onset time (VOT) measure as a parameter of speech naturalness, comparing the outcome of two stuttering treatment procedures.
12 adult stutterers were divided in two groups and submitted to the same Fluency Promotion Program (FPF). For GI: surface electromyography (EMG) was used as biofeedback.
the results indicate that for GI 50% of the participants presented a more natural sounding speech after the FPF, whereas for GII only 17% of the participants demonstrated adequate speech naturalness in the same period.
although the number of participants of this research was small, the association of EMG to a FPP seems to produce a more natural sounding speech.