30.3 DEPTH-DEPENDENT EXAMINATION OF INTRACORTICAL MYELIN IN SCHIZOPHRENIA USING ULTRA-HIGH FIELD IMAGING. (9th April 2019) - Frangou, Sophia
Abstract: Background: Abnormal myelination has been proposed as a pathogenetic mechanism for schizophrenia. Ultra-high-field magnetic resonance imaging (MRI) offers unprecedented spatial resolution and is ideally suited for the in vivo examination of schizophrenia-associated abnormalities in intracortical myelin. Methods: Twenty-two healthy individuals and 17 patients with schizophrenia were imaged at 7 Tesla MRI using a T1-weighted sequence optimized for intracortical myelin. T1 values were extracted at 20 cortical depth-levels covering the entire cortical ribbon from each of 148 cortical regions. In each cortical region, T1 values were used to infer myelin concentration and to compute a non-linearity index as a measure of the spatial organization of myelin across the cortical ribbon. These metrics were used to ascertain the effect of diagnosis, illness duration and medication using mixed-effects linear models. Results: We identified case-control differences in intracortical myelin concentration (P<0.007) that were region-dependent; patients showed a pattern of comparative decrease in auditory and visual cortices and increase in frontoparietal cortices in patients (P<0.01). The latter effect was most pronounced at 65% cortical depth-level (P=0.006). Intracortical myelin concentration was inversely related to illness duration while a positive association was found for antipsychotic dose. Further, patients had consistently reduced non-linearity indices (P=0.01), particularly in a large bilateral cluster of frontal regions, but also in sensory and somatosensory cortices, which was not associated with illness duration. Conclusions: This study identified schizophrenia-associated changes in the concentration and organization of intracortical myelin. Both medication and illness duration had an effect on intracortical myelin measures underscoring the need for larger, longitudinal studies to better characterize the role of intracortical myelin in the pathophysiology and treatment of schizophrenia.