Effects of bipolar disorder on intrinsic brain networks
Master Thesis
2016
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University of Cape Town
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Introduction: Bipolar disorder (BD) is a brain network disorder that affects cognitive and emotional functioning, and is associated with prefrontal and/or limbic dysfunction. Functional Magnetic Resonance Imaging (fMRI) allows identification of intrinsic brain networks (IBN), like the default mode network (DMN) and executive control network (ECN), which are consistent with previously established functional and anatomical relationships within the brain. Analysing the functional connectivity (integrity, extent and inter-relationships) of these networks, allows a deeper understanding of brain function in health and disease. In BD, there are functional connectivity changes in the DMN, ECN and cerebellar network (CERN). We evaluate IBN in BD, to explore changes in the functional connectivity between the cerebellum, fronto-cortical and paralimbic regions. Methods: Data from 14 BD subjects and 10 control subjects was analysed after fMRI. Changes were evaluated in 3 IBN (DMN, ECN and CERN) using an FMRIB Software Library (FSL) pipeline: MELODIC/ICA-AROMA, dual-regression, randomise and Local False Discovery Rate (FDR) to identify changes in functional connectivity bipolar subjects compared to controls. Results: Subjects with BD showed decreased connectivity between the CERN and a cluster in the right precuneus; and between the ECN and a cluster in the left OFC. There was also increased connectivity between the ECN and a cluster in the left temporal pole. No connectivity changes involving the DMN were identified. Voxels within the clusters were significant at p < 0.05 with local FDR. Peaks within the clusters remained significant after further Bonferroni correction for multiple comparisons (p < 0.017). Conclusion: The finding of altered functional connectivity in BD, in networks and regions involved in cognitive/emotional processes, highlights its complex neurobiology, and suggests that abnormal connectivity may help to explain the clinical picture. These findings should be replicated with larger samples, but may represent a further advance in understanding the role of functional connectivity in the pathology of BD, and contribute to laying the foundation for functional neuroimaging as a diagnostic tool in psychiatry.
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Starke, J. 2016. Effects of bipolar disorder on intrinsic brain networks. University of Cape Town.