Regional thinning of cerebral cortical thickness in first-episode and chronic schizophrenia

Abstract

First-episode schizophrenia and chronic schizophrenia have different patterns of cortical gray matter loss, due to differences in the period of illness. Differences in the reduction of cortical thickness between first-episode and chronic schizophrenia has not yet been addressed using a technique of measuring cortical thickness. The goal of this study is to identify differences in cerebral cortical thickness between first-episode schizophrenic patients and matched normal controls as well as between chronic schizophrenic patients and matched normal controls. Thirty-five chronic and 24 first-episode schizophrenic patients were compared with each age- and sex-matched control group, respectively. To measure cortical thickness, we utilized an inner and outer cortical surface reconstruction algorithm. Cortical thickness was directly measured as the distance between the two surfaces. Statistical analysis was performed with diffusion smoothing along cortical manifolds, and surface normalization on a sphere model. There were no significant changes in global mean thickness and cerebral gray matter volume in both first-episode and chronic schizophrenia patients. However, we observed regional thinning of cortical thickness, most significantly in the superior temporal gyrus of first-episode schizophrenic patients. In chronic schizophrenia, larger regions including the prefrontal cortex (PF) were significantly thinned compared to the first-episode group. This suggests that the duration of illness affects cortical thinning in the PF, as well as the extent of cortical thinning.