Stuttering is a complex neurodevelopmental disorder that is likely caused by an interaction of multiple factors, including genetics, linguistic ability, motor development, temperament, and neural development (Smith & Weber, 2017). Previous research has reported that children who stutter exhibit lower phonological abilities than children who do not stutter. In addition, it is commonly reported that children who stutter, as a group, exhibit decreased white matter integrity along the left dorsal language pathway (Chang, Garnett, et al., 2018; Neef et al., 2015), which is critical in supporting phonological processing and production. In this study the phonological abilities were examined in children who stutter (N = 24) and children who do not stutter (N = 31) using whole-word measures that were produced during spontaneous connected speech. These phonological scores, phonological mean length of utterance (PMLU) and proportion of whole-word proximity (PWP), provide a quantitative measure of phonological complexity and accuracy. Examining whole-word segments instead of smaller segments of speech considers the fact that children's individual words become longer and more complex as vocabulary increases (Ingram, 2002). In addition to the analysis of phonological skills, the current study examined how phonological skills are associated with white matter integrity differences in children who stutter relative to children who do not stutter.Results from this study show that children who stutter have similar phonological skills as children that do not stutter, but the association between phonological ability and white matter integrity is significantly different between the two groups. The children who stutter exhibited a greater association between PWP and white matter integrity in the bilateral dorsal language pathways than children who do not stutter. Notably, these areas were along the arcuate fasciculus, and included the right IFG (BA 45/47), right insula, and left insula/Rolandic operculum. In addition, children who do not stutter showed robust white matter integrity scores in bilateral dorsal and ventral pathways associated with age, which was not observed children who stutter. Overall, major findings from this investigation indicate that: 1) children who stutter do not differ from children who do not stutter in terms of phonological complexity as measured from spontaneous speech samples, 2) there is greater association between PWP and increased white matter integrity in bilateral dorsal tracts in children who stutter relative to children who do not stutter, 3) children who stutter exhibit an overall attenuated age-related white matter integrity growth in areas overlapping with those that showed heightened PWP-white matter integrity associations. The greater association between PWP and the bilateral dorsal tracts in children who stutter in the face of attenuated age-related increases in the same areas, suggest that stronger links between PWP and dorsal pathway integrity may be needed in children who stutter to achieve comparable phonological development to children who do not stutter. These results provide novel insights into phonological development in children who stutter, and the behavior - neural development associations relevant to phonological development that seem to differ in children who stutter.
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