Analyzing quantitatively and topologically the white matter organization in 22Q11.2 deletion syndrome

Abstract

At the convergence of neuroimaging, genetic polymorphism and psychiatry, this thesis highlights through two published articles the importance of genes in brain white matter (WM) development and organisation leading to schizophrenic symptoms. We investigate brain structure in a population with a high risk of developing schizophrenia due to a microdeletion in chromosome 22q11.2. We implement analytical tools for enhancing differences in their WM connections compared to typically developing individuals (TD). After exploring the limits of voxel-wise analysis via TBSS (Tract-Based Spatial Statistic), we used the Connectome Mapper (merging Diffusion and T1 images) to reconstruct the WM bundles linking pairs of cortical regions, creating the connectome, therefore the Network of the brain. Compared to TD connectomes, the 22q11.2DS connectivity reveals altered fronto-temporal connections. Network analysis shows specific dysconnected hubs compared to TD and lower efficiency of Broca and Wernike areas in 22q11.2DS with hallucinations compared to those without.