Repetitive behaviour in autism: Imaging pathways and trajectories

Repetitive behaviour in autism: Imaging pathways and trajectories Repetitive and rigid behaviour is one of the core symptoms of autism, a severe and lifelong child psychiatric disorder. Although repetitive behaviour symptoms often form a significant impairment for affected individuals, systematic study of the phenomenology and in particular the neurobiology of repetitive behaviour has been lacking. In this thesis we address this gap by using neuroimaging techniques (structural magnetic resonance imaging (MRI), diffusion tensor imaging and magnetisation transfer imaging) to investigate brain differences associated with repetitive behaviour in autism. We compared groups of individuals (children and adolescents, as well as adults) with and without autism and examined anatomical differences in specific structures and networks of the brain and related these to behavioural measurements. Furthermore, we explored the involvement of differences in developmental trajectories of these structures and networks in autism. Our studies showed differences in grey and white matter of the corticostriatal system, a complex of brain regions known to be involved in motor, cognitive and emotional-motivational behaviour. These differences were found in all age-groups studied, suggesting that the corticostriatal system continues to be involved in autism over development. Closer examination of the developmental trajectories of grey matter structures in striatum and white matter pathways between striatum and the frontal cortex showed differences in development of this brain network for individuals with autism. Furthermore, the studies in this thesis showed associations between corticostriatal grey and white matter and repetitive behaviour. In conclusion this thesis: - Implicates changed development of corticostriatal grey and white matter in autism, especially in the repetitive behaviour which characterises the disorder. - Emphasises the dynamics of the brain in autism: it is the time course of brain development rather than the outcome that seems to be most disturbed. - Emphasises that the brain needs to be considereda complexof inter- and intra-communicating networks in constant interaction with the environment, rather than a collection of isolated structures or regions. - Highlights the need for research strategies that take the heterogeneity of autism into account: Narrow the field of view by reclassifying autism as more homogeneous and well-phenotyped symptom-groups. - Highlights the need for research strategies that take the etiologic overlap with other disorders into account:Broaden the field of view by including other diagnostic groups with similar symptomatology