Melbourne School of Psychological Sciences - Theses
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ItemDiffusion weighted imaging analysis of children with attention deficit hyperactivity disorder and language problems( 2017)BACKGROUND: Research indicates that children with Attention Deficit Hyperactivity Disorder (ADHD) have three times the risk of co-occurring language problems (LP) compared to typically developing children (Sciberras et al, 2014). The specific types and magnitude of these LP, and neurobiology underlying the co-occurrence remains unclear. OBJECTIVES: a) to establish empirically derived data on the types and effect size of LP seen in children with ADHD compared to controls; and b) to characterise white matter microstructural differences in the dorsal and ventral language networks of children with ADHD (with and without LP), children with LP alone, and non-ADHD controls. METHOD: For Part a) of this study, a systematic review and meta-analyses were conducted according to PRISMA guidelines and rigorously defined inclusion criteria. For Part b) of this study, 163 children (9–11 years) received structural T1 and diffusion magnetic resonance imaging (63: ADHD, 76: Controls met diagnostic criteria). LP were identified using a standardised measure of language ability. High angular resolution diffusion imaging and whole brain tractography were generated using constrained spherical deconvolution. Dorsal and ventral language tracts were defined using include/exclude regions-of-interest on a cohort-specific template. Tract diffusion parameters were compared across groups via linear regression covarying for age, sex, and respective whole brain diffusion parameters. The model was then re-analysed with the addition of an inattention covariate. RESULTS: The review of previous literature for Part a) found evidence of overall, expressive, receptive and pragmatic LP in children with ADHD across the 21 included studies (Hedges g: .98–1.23; ADHD: 1,209; Control: 1,101). While children with ADHD+LP and those with LP alone performed equally poor on a measure of language function, Part b) neuroimaging analysis revealed significant differences in the white matter microstructure of dorsal and ventral language tracts between the groups, and specific aberrations unique to children with LP alone and ADHD+LP respectively. Children with LP alone were right lateralised in their dorsal language stream compared to all other groups. White matter abnormalities in the ventral tracts (the left uncinate fasciculus in particular) were unique to children with ADHD+LP compared to other groups. Finally, dorsal white matter tracts no longer showed a significant association with language ability when inattention was accounted for in the model. DISCUSSION: Part a) of this study provides the first empirical data to demonstrate large and consistent deficits in specific domains of language for children with ADHD. Part b) neuroimaging findings of white matter abnormalities in the language network may account for such language deficits. The results indicate that different neural origins may underlie the development of LP in isolation, compared to co-occurring ADHD and LP. The results further suggest that in some cases, the abnormal white matter tracts are influenced by factors other than language performance, such as inattentive factors. The findings support a need to examine children presenting with ADHD for potentially co-occurring LP so that they do not go undetected and untreated. It is possible that certain LP seen in ADHD are the result of inattention, which has a secondary negative effect on performance on a language measure. To this end, interventions utilising a combination of attention-based and traditional language-based speech-pathology services for these children may be a fruitful area for further investigation.