Stuttering is a fluency disorder with an incidence rate of 3% and a prevalence of 1%. Several theories accounting for stuttering within a motor framework have been proposed. Studies of speech motor performance in adults who stutter have resulted in the identification of poor speech motor coordination and, arguably, immature speech motor learning systems as factors contributing to the observed differences between persons who stutter and typically fluent speakers. Presently, there are also several theories and some empirical support for the role of phonological skills in stuttering. Recent findings, although limited to adults, suggest altered dynamics between the linguistic-phonemic and the speech motor systems in persons who stutter. The three experiments outlined in this proposal are designed to test emerging interactions between the linguistic-phonemic and speech motor systems in children and adults who stutter using nonwords. Participants are 3 age groups of children who stutter and a group of young adults who stutter matched in age and sex to typically fluent speakers. In Experiment 1 the time course of monitoring word- and segment-sized units will be investigated using rhyme and phoneme monitoring during silent naming. In addition, changes in general processing speed with age will be tested by comparing performance in the verbal tasks with a nonverbal tone monitoring task. In Experiment 2 changes in movement execution and coordination with the production of nonwords varying in syllable and phonemic complexity will be investigated in the stuttering and nonstuttering groups. In Experiment 3 speech motor practice and learning effects associated with repeated production of lengthy nonwords will be investigated. The central tenets tested are: a) The time course of emergence of stable dynamics between the linguistic-phonemic and speech motor systems in PWS is protracted compared to typically fluent speakers;b) The altered course of evolving dynamics will result in a speech motor system that is destabilized by increasing nonword complexity and that exhibits limited improvements in practice and learning- induced movement stability and coordination. The proposed experiments will elucidate emerging dynamics between the linguistic-phonemic and speech motor systems using nonwords in children and adults who stutter, thus offering an opportunity to study the speech planning and production processes implicated in stuttering causation.
The proposed experiments will test the time course of acquisition of linguistic-phonemic skills and the changes in movement execution and coordination in children and adults who stutter compared to fluent speakers. The use of nonwords to test such skills allows the study of the effects of phonemic complexity on movement coordination while limiting influences of the semantic/lexical variables. The findings will elucidate the nature of interactions between the linguistic-phonemic and speech motor systems in persons who stutter.
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