Speech Production in People Who Stutter: Testing the Motor Plan Assembly Hypothesis

Abstract

The main purpose of the present study was to test the hypothesis that persons who stutter, when compared to persons who do not stutter, are less able to assemble abstract motor plans for short verbal responses. Subjects were adult males who stutter and age-and sex-matched control speakers, who were tested on naming pictures and words, using a choice-reaction time paradigm for both tasks. Words varied in the number of syllables (1, 2, and 3 syllables) and, for the bisyliabic words, also in the number of consonants (one or more) at the onset of the second syllable, Measurements consisted of speech reaction times, word durations, and measures of relative timing of specific motor events in the respiratory, phonatory, and articulatory sub systems.Results indicated that, in spite of longer speech reaction times for persons who stutter in ' i comparison to control speakers, there was no interaction with word size, a finding that does not lend support to the abovementioned hypothesis. Word durations were found to be longer for persons who stutter, and, in addition, there was an interaction of group with word size. Both i findings were associated with longer delays for persons who stutter in the onset of upper lip i integrated electromyographic (IEMG) activity and thoracic compression, and a group effect, on the order of upper tip and lower lip IEMG onset. Findings are taken to suggest the possibility that persons who stutter may use different motor control strategies to compensate for a reduced verbal motor skill, and although the nature of this reduced skill is unknown, it is speculated that it relates to the processes involved in the integration of sensory-motor information. i i

Effects of perceptual and conceptual similarity in lexical priming of young children who stutter: Preliminary findings

“…Rather, it is also possible that speech motor control/productive processes could contribute to these betweengroup differences, although not as the only factor accounting for the differences. Van Lieshout, Hulstijn, and Peters (1996), for example, suggested that atypical motor control in individuals who stutter is neither the sole cause nor sole factor to consider when studying the development of stuttering. Indeed, it is recognized that SRT is the end-product of several processes (e.g., cognitive + linguistic +motoric); however, in the present study we attempted to minimize between-condition differences in motoric demands while allowing linguistic differences to vary in known or prescribed ways.…”

From Planning to Articulation in Speech Production: What Differentiates a Person Who Stutters From a Person Who Does Not Stutter?

“…One reason that might account for not finding the inter action between word size and group effects in the study of Van Lieshout et al (1996) was the manipulation of word size, in particular for the picture-naming task. For that task, all three-syllable words were formed by adding grammatical suffixes to bisyilabic words to indicate a plural form of these 20f course, when the motor plan consists of more than a single word (stress-group), the muscle command preparation stage will also take more time because more units in the motor plan will Increase the time to search the short-term motor buffer (Levait, 1989; Sternberg et al, 1978).…”

“…In addition, in the study of Peters et al (1989), word size was varied along a somewhat wider range con trasting monosyllabic words with three-to four-syllable words. So, it is possible that a wider range in number of syllables within a word than used in Van Lieshout et al (1996) would be more successful in eliciting the potential problems people who stutter may have in processing infor mation at the motor plan assembly stage.…”

“…To replicate and extend the significance of this finding, a study by Van Lieshout et al (1996) contrasted monosyllabic words with polysyllabic words (2/3 syllables) in two different choice reaction time tasks. One task was a word-naming task of the same type used in Peters et al (1989) in order to replicate their finding most directly.…”

“…If people who stutter are different from control speakers in the way they prepare muscle commands, this could also give rise to group differences in the time course of EMG signals (Aimé & McAllister, 1987;Guitar et ai., 1988;Hulstijn, Van Lieshout, & Peters, 1991;Van Lieshout, Peters, Stark weather, & Hulstijn, 1993;Van Lieshout et al, 1996) and/or their amplitudes (Freeman & Ushijima, 1978;Kalotkin, Manschreck, & O'Brien, 1979;Murray, Empson, & Weaver, 1987;Shapiro, 1980;Van Lieshout et al, 1993; but see Caruso, Gracco, & Abbs, 1987;McClean, Goldsmith, & Cerf, 1984;Smith, 1989;Smith, Denny, & Wood, 1991). This, in turn, may lead to group differences in kinematic characteristics of the resulting movement patterns (e.g., Alfonso, 1991; Ca ruso, Abbs, & Gracco, 1988;Van Lieshout, Alfonso, Hulstijn, & Peters, 1994;Van Lieshout et al, 1996;Zimmermann, 1980aZimmermann, , 1980b, and, indirectly, to group differences in the duration of acoustic events (e.g., Borden, 1983;Healey & Ramig, 1986;McMillian & Pindzola, 1986;…”