White matter abnormalities in schizophrenia patients and genetic high-risk subjects

Schizophrenia is a brain disorder that is associated with disorganization in the fluency of language and thought. A significant genetic component is contributed to the etiology of the disorder. Thus the young family members with heightened genetic risk for developing the disorder have received increasing attention in clinical and neuroimaging studies aimed at determining the underlying genetic vulnerability that leads to schizophrenia. The search for the presence of white matter (WM) abnormalities in patients with schizophrenia and the people at genetic high-risk has gained tremendous interest with recent advances in brain imaging techniques that allow the visualization of WM integrity. The significance of WM abnormalities is unknown. However, they could be associated with a developmental defect that weakens the neuronal connections necessary for cognitive processing, such as language processing. The early WM abnormalities in the young genetic high-risk people could play a role in the development of the disorder and the symptom of language dysfunction. In this study, we examined the voxel-based whole brain WM volume density and fiber track fractional anisotropy (FA) using the structural MRI and diffusion tensor imaging (DTI) data acquired from 19 patients with schizophrenia, 20 high-risk subjects, and 34 healthy controls. From the results of statistic analyses, schizophrenia patients showed significantly increased WM volume density in the right inferior longitudinal fasciculus (ILF) in the superior temporal lobe, compared with controls. The high-risk group showed significantly decreased WM density in right arcuate fasciculus (AF) close to the right supromarginal gyrus, compared with controls. Group comparisons of whole brain FA values showed that compared to controls, schizophrenia patients had significant FA reductions in a large number of regions from bilateral temporal and occipital lobe; and increased FA in bilateral frontal lobe. Genetic high-risk subjects showed significantly reduced FA in left superior temporal gyrus, right medial frontal gyrus, and right supramarginal gyrus, compared to controls. There was no significant group difference in WM density and FA between the schizophrenia patients and the high-risk people. The findings of this study suggested that structural brain abnormalities in the language-processing circuit exist before the onset of schizophrenia and may indicate the progressive pathology of the disorder.