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Title: Neurocognitive and MRI correlates of Attention-Deficit/Hyperactivity symptoms in Autism Spectrum Disorder (ASD)
Author: Lukito, Steve Daniel Adji Widjoyo
ISNI:       0000 0004 8499 8890
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2017
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Attention deficit and hyperactivity symptoms occur at high rates among individuals with ASD, resulting in a substantial proportion of people in the population meeting the dual diagnoses of ASD+ADHD. The current study aims to investigate the similarities and differences of the neurocognitive and neural underpinnings of ADHD symptoms in the ASD and ADHD populations and explore the mechanisms underlying the co-occurrence of both disorders. The thesis contains five studies. Study I explored the relationships among executive function (EF), theory of mind (ToM), and ASD and ADHD symptoms in a population-based sample of adolescents with ASD from the Special Needs and Autism Project (SNAP) using structural equation modelling. The study revealed that EF was specifically associated with ADHD symptoms while ToM was specifically associated with ASD symptoms in this population. Study II compared the cognitive performance of young adults with diagnoses of ASD, ADHD, or ASD+ADHD, and typically developing controls on a range of EF and social cognition (SC) tasks. The results of this study showed that individuals with ADHD and ASD+ADHD were predominantly impaired in EF relative to the pure ASD and control groups. The pure ASD group was more impaired than the pure ADHD and control groups in SC although this seemed to be IQ-dependent. Study III was a comparative meta-analysis of neural abnormalities in ASD and ADHD relative to typically developing controls. The study compared the disorder-specific and shared abnormalities in neural functions related to inhibition and structural grey matter volume in ASD and ADHD. The study showed that ASD and ADHD were largely distinct disorders with few overlapping abnormalities, suggesting that phenocopy might be one explanation for the difficulties in inhibitory function among individuals with ASD. Study IV and V compared the neural underpinning of response inhibition, error monitoring, and selective attention and duration discrimination among young adults with ASD, ADHD, and ASD+ADHD and typically developing controls. The findings from Study IV suggested that individuals with ASD+ADHD was the most impaired among the four groups during error monitoring, and they showed reduced activations in the bilateral inferior frontal, anterior insula, thalamus and parahippocampal gyrus typically associated with error monitoring. Both people with ASD+ADHD and with ASD shared impairments in the right precuneus during selective attention. Study V showed that individuals with ASD+ADHD also display impairments in the right inferior frontal gyrus during duration discrimination. The impairments in the ASD+ADHD group resembled those found in previous studies of children with ADHD, possibly suggesting persisting impairments. The overall findings of this study suggested that there were several pathways that lead to the increased ADHD symptoms among individuals with ASD.
Supervisor: Simonoff, Emily ; Rubia, Katya Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available