Aivojen konnektiivisuus autismikirjon häiriössä
Year: 2026
Type: dissertation
Study design: Observational Study
Abstract: Autism spectrum disorder (ASD), characterized by impairments in social interaction and communication, and restricted, repetitive patterns of behavior, interests, or activities, is a neurodevelopmental disorder affecting almost one percent of the population. Asperger syndrome belongs to ASDs, and although it previously had its own diagnostic codes, in the most recent diagnostic manuals, it is included under the ASD umbrella term. Although the heritability of autism is high, no single locus has been implicated indicating that autism may be a behavioral manifestation of multiple underlying genetic, epigenetic, and environmental factors. This genetic heterogeneity combined with a diversity of symptoms varying in their severity suggests that also the neurobiological background of autism is complex involving multiple brain areas. It has been suggested, indeed, that there are widely distributed abnormalities in brain connectivity in individuals with ASD. Earlier, the brain connectivity in ASD was investigated with functional magnetic resonance imaging (MRI), which showed reduced long-distance and increased short-distance functional connectivity in ASD. More recently, diffusion MRI enabled the investigation of structural brain connectivity. However, the findings in diffusion MRI studies in ASD are inconsistent. This could be partly due to the use of different acquisition and analysis approaches, but also due to the variation in the age and cognitive profile of the subjects. The aim of this dissertation was to investigate anatomical brain connectivity in high-functioning adults with ASD. To narrow down the clinical and cognitive profile of the subjects, we only included patients with Asperger syndrome in the study. We used several methods that complement each other to explore different aspects of brain connectivity, but also to confirm that the results support each other. We also performed a naturalistic functional MRI study, where the subjects watched a movie during the MRI acquisition. We found global and widespread local differences in the white matter microstructure in ASD compared to age- and IQ-matched controls. We localized these differences into specific white matter tracts using both voxel-based and tract-level analyses. In addition, we found decreased integration of the brain networks on the global scale and local alterations most prominent in the right caudate and the right superior temporal pole. Thus, our results support the theory of abnormal brain connectivity in ASD and were partly in concordance with earlier studies. The results of the functional MRI study showed that brain activity correlated better within the subjects in the control group than in the patient group in multiple areas related to social cognition. In the future, we should acquire larger patient and control groups, and if possible, perform longitudinal studies starting already in childhood. The genetic and phenotypic heterogeneity of individuals with ASD should be considered. A more advanced multi-shell diffusion MRI acquisition not available at the time of this study would allow more accurate investigation of microstructure and connectivity. In addition, the role of specific tracts, such as the left inferior longitudinal fasciculus, the right caudate, and the right superior temporal pole in the neurobiology of ASD should be further investigated.
Source: Työväentutkimus Vuosikirja
Author: Roine, Ulrika
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7213729946