Substantial evidence supports the neurodevelopmental hypothesis of schizophrenia.Meanwhile,progressive neurodegenerative processes have also been reported,leading to the hypothesis that neurodegeneration is a characteristic component in the neuropathology of schizophrenia.However,a major challenge for the neurodegenerative hypothesis is that antipsychotic drugs used by patients have profound impact on brain structures.To clarify this potential confounding factor,we measured the cortical thickness across the whole brain using highresolution T1-weighted magnetic resonance imaging in 145 first-episode and treatment-naive patients with schizophrenia and 147 healthy controls.The results showed that,in the patient group,the frontal,temporal,parietal,and cingulate gyri displayed a significant age-related reduction of cortical thickness.In the control group,age-related cortical thickness reduction was mostly located in the frontal,temporal,and cingulate gyri,albeit to a lesser extent.Importantly,relative to healthy controls,patients exhibited a significantly smaller age-related cortical thickness in the anterior cingulate,inferior temporal,and insular gyri in the right hemisphere.These results provide evidence supporting the existence of neurodegenerative processes in schizophrenia and suggest that these processes already occur in the early stage of the illness.
Identifying data-driven biotypes of major depressive disorder(MDD) has promise for the clarification of diagnostic heterogeneity. However, few studies have focused on white-matter abnormalities for MDD subtyping. This study included 116 patients with MDD and118 demographically-matched healthy controls assessed by diffusion tensor imaging and neurocognitive evaluation.Hierarchical clustering was applied to the major fiber tracts, in conjunction with tract-based spatial statistics, to reveal white-matter alterations associated with MDD.Clinical and neurocognitive differences were compared between identified subgroups and healthy controls. With fractional anisotropy extracted from 20 fiber tracts, cluster analysis revealed 3 subgroups based on the patterns of abnormalities. Patients in each subgroup versus healthy controls showed a stepwise pattern of white-matter alterations as follows: subgroup 1(25.9% of patient sample),widespread white-matter disruption;subgroup 2(43.1% of patient sample), intermediate and more localized abnormalities in aspects of the corpus callosum and left cingulate;and subgroup 3(31.0% of patient sample),possible mild alterations, but no statistically significant tract disruption after controlling for family-wise error. The neurocognitive impairment in each subgroup accompanied the white-matter alterations: subgroup 1, deficits in sustained attention and delayed memory;subgroup 2, dysfunction in delayed memory;and subgroup 3, no significant deficits. Three subtypes of white-matter abnormality exist in individuals with major depression, those having widespread abnormalities suffering more neurocognitive impairments, which may provide evidence for parsing the heterogeneity of the disorder and help optimize typespecific treatment approaches.
Sugai LiangQiang WangXiangzhen KongWei DengXiao YangXiaojing LiZhong ZhangJian ZhangChengcheng ZhangXin-min LiXiaohong MaJunming ShaoAndrew J. GreenshawTao Li
Over the last decade the combination of brain neuroimaging techniques and graph theoretical analysis of the complex anatomical and functional networks in the brain have provided an exciting new platform for exploring the etiology of mental disorders such as schizophrenia. This review introduces the current status of this work, focusing on the topological properties of human brain networks - called 'small-world brain networks'- and on the disruptions in these networks in schizophrenia. The evidence supporting the findings of reduced efficiency of information exchange in schizophrenia both within local brain regions and globally throughout the brain is reviewed and the potential relationship of these changes to cognitive and clinical symptoms is discussed. Finally we propose some suggestions for future research.
