Motor impairment is argued to be central to ASD, however, its interaction with speech motor control has not been studied in-depth. This study examined this interaction by investigating why higher rates of speech sound errors are identified in children with ASD and whether this could be related to a single underlying motor impairment. A small number of studies found residual and non-developmental speech errors are significantly higher in children with ASD (33-40%) than the normal adult population (1-2%; Cleland, Gibbon, et al., 2010; Shriberg et al., 2001). Others argue that speech follows a typical developmental trajectory (Kjelgaard & Tager-Flusberg, 2001). In this study ten children with ASD and ten age and gender matched typically developing peers aged 6-12 years were compared. Behavioural assessments were carried out to examine nonverbal IQ, language ability, gross, and fine motor control. These were correlated with clinical assessments of speech in both single syllabic and multisyllabic contexts. Speech motor control was measured using a Diadochokinesis (DDK) task recorded with simultaneous ultrasound tongue imaging and acoustic recordings. The analysis carried out looked at tongue shape variation and mean syllable duration at slowest and fastest syllable repetition rates.
There were no correlations between DDK measures in the ASD group with movement and language, speech, non-verbal IQ, and autistic symptomatology. However, correlations were found within the subtests. There were no significant differences between the TD and ASD group in maximum rate, consistency, or accuracy of the DDK tasks. When using ultrasound to measure tongue shape variance, surprisingly, the TD group had more significant differences of tongue shape in the more motorically complex sequences (tk and ptk) than the ASD group. While children in the ASD group had significantly poorer motor performance in the movement assessment, this did not correlate with the in-depth analysis of speech motor control. Children in the ASD group often performed with less variability in the DDK tasks than the TD group, suggesting rigidity in motor plans. The results indicate that while no speech motor impairment was present, there were indicators that children with ASD had difficulty with speech attunement, being unable to sufficiently attune to the ambient speech environment. The presence of a significant fine and gross motor impairment as well as impairment in language may further impede speech sound development.
|Date of Award||18 May 2022|
- University Of Strathclyde
|Sponsors||University of Strathclyde|
|Supervisor||Joanne Cleland (Supervisor) & Jonathan Delafield-Butt (Supervisor)|