The development of executive functions and working memory in children and adolescents with Autism Spectrum Disorder: A longitudinal study of brain and behaviour

Children with Autism Spectrum Disorder (ASD) exhibit social and communicative problems, repetitive and restrictive patterns of behaviour, and a range of cognitive deficits, including executive functioning (EF) impairments. Literature in ASD has focused mostly on the behavioural phentotype of the disorder and less research has investigated the cognitive and EF profiles in this population. The objective of this thesis was to gain a greater understanding of EF deficits, their longitudinal development, their underlying neural correlates using neuroimaging techniques, and their impact on critical outcomes in children with ASD compared to typical developing (TD) individuals. Structural and functional brain disturbances were evident in children and adolescents with ASD, relative to controls. In a diffusion tensor imaging (DTI) study, significant white matter differences were found in tracts essential for higher order cognitive processing, such as EF, and general information processing in children with ASD (ages 7-15 years). White matter developmental trajectories did not appear to differ between groups. Functional neural systems associated with EF, specifically working memory, were also impaired in youth ASD (ages 7-13 years) relative to controls, particularly in parietal and temporal regions. In this functional magnetic resonance imaging (fMRI) study, children with ASD showed inadequate modulation of neural activity in response to increasing cognitive demands, which did not improve over two years. Last, children with ASD (ages 7-14 years) showed marked EF impairments in everyday settings as observed by parents, which persisted over time compared to TD children. Early EF deficits predicted later symptoms of co-morbid psychopathology and social difficulties in ASD. Findings suggest that children with ASD exhibit structural and functional neural deficits associated with EF across childhood that make them vulnerable to the increasing complexity of environmental demands as they mature. Results support EF as potential target in autism interventions for improving executive development, and also for preventing co-morbid psychopathology and promoting social competence in ASD.Ph.D.2019-02-09 00:00:0