Melbourne School of Psychological Sciences - Theses
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ItemNeuropsychology and functional brain organisation of working memory in children and adolescents with agenesis of the corpus callosum( 2017)Background: The corpus callosum is the largest brain white matter pathway. Its main function is to coordinate and transfer information between the two hemispheres, thus contributing to higher cognitive functions including working memory (WM). Developmental absence of the corpus callosum, or Agenesis of the Corpus Callosum (AgCC), is one of the most common brain malformations but its consequences on neurobehavioural functioning and functional brain organisation in school-age children are not well understood. Aims: The goal of the current work was: 1) To describe the impact of AgCC on neurobehavioural functioning, including WM functions, in school-age children; and investigate the role of age, social, and neurological factors that might underlie neurobehavioural outcomes in children with AgCC; 2) To investigate the functional brain organisation of WM in school-age children with AgCC using functional magnetic resonance imaging (fMRI). Methods: 28 children diagnosed with AgCC based on MRI and a control sample of 16 typically developing children, aged 8 to 17 years, completed a neurobehavioural assessment and brain imaging with anatomical T1 sequences and an fMRI task (AgCC, n=9; controls, n=16) tapping WM processes, i.e., encoding, maintenance and retrieval. Parents and teachers completed questionnaires to evaluate executive, behavioural and social functions. Results: In our cohort, ~50% experienced general intellectual, academic, executive, social and/or behavioural difficulties and ~20% reached a level comparable to typically developing children. Social risk was found to have an important impact on variability in functional outcomes. Additional brain anomalies or complete AgCC were associated with lower mathematics performance and poorer executive functioning. fMRI findings showed that globally similar brain regions were recruited in the AgCC and the control groups during the WM task, despite significant disparity in brain development, i.e., bilateral occipito-frontal activations during verbal encoding, and bilateral fronto-parietal executive control network during retrieval. However, there were notable differences in activations between groups that might reflect different susceptibility to concurrent tasks during WM, subsequent to different degrees of hemispheric lateralisation during the task. Conclusion: This work constitutes the first comprehensive report of cognitive, executive, behavioural and social consequences of AgCC in school-age children, and provides a first step towards a better understanding of functional brain networks underlying higher cognitive functions in children with AgCC.