The application of voxel-based methods to magnetic resonance imaging in the study of psychiatric disorder.
While there are a number of psychiatric disorders as classified by the major international coding systems, however, the application of modem neuroimaging methods has only been utilised on a limited basis with some disorders receiving more research attention than others. Consequently, psychiatric phenotypes that have been relatively understudied are investigated further in this thesis. These disorders correspond to psychiatric disorder in: 22ql 1 deletion syndrome, temporal lobe epilepsy, antisocial personality disorder and Asperger syndrome. Subjects with each of these diagnoses were recruited and then compared to healthy matched controls using the application of novel whole-brain voxel-based analyses to their magnetic resonance imaging data whereby white matter integrity and/or brain tissue volume was assessed in each experimental study of this thesis.
In Study 1, young people with 22ql 1 deletion syndrome were found to have significant differences in both white matter microstructure and volume. Additionally, there was preliminary evidence that within 22ql 1 deletion syndrome, some regional differences in fractional anisotropy were associated with allelic variation in COMT and with schizotypy. In Study 2, while significant grey and white matter volume deficits were found in temporal lobe epilepsy with comorbid psychosis, these abnormalities encompassed not only the medial temporal lobe structures but also extended to lateral temporal and extratemporal regions whereby some of the deficits also overlapped with those found in schizophrenia.
In Study 3, reduced fractional anisotropy was found in antisocial personality disorder and psychopathy in tracts of interhemispheric, posterior brain and frontal lobe networks. Additionally, fractional anisotropy deficits in the frontal lobe demonstrated a significant negative correlation with psychopathy measures. Finally, in Study 4, adults with Asperger syndrome were specifically recruited and found to not only demonstrate impairments in white matter microstructural integrity in regions relevant to social skills and behaviour but also in more widespread white matter networks.