Structural And Functional Impairments In The Inferior Parietal Lobule Subregions In Schizophrenia

Objective:The structural and functional alterations in the inferior parietal lobule(IPL) in schizophrenia have been frequently reported. Based on the heterogeneity of the IPL in structure, connection and function, previous studies have subdivided the IPL as several subregions. Although, some researchers have found that the grey matter volume(GMV) and the resting-state functional connectivity(rsFC) of the IPL were abnormal in the schizophrenia patients. But it's still not clear if the GMV and the rsFC of each subregion in the IPL are changed in schizophrenia. Considering the complexity of the IPL in structure and function, we hypothesize that the GMV and the rsFC of the IPL subregions are differentially affected in schizophrenia. In this study, by comparing the differences of the GMV and the rsFC of each subregion of the IPL between schizophrenia patients and healthy controls, we explored the changes of the GMV and rsFC of the IPL in schizophrenia at the level of subregion.Subjects and Methods:This study included 95(53 males and 42 females) schizophrenia patients and 104(46 males and 56 females) age- and sex-matched healthy controls. MRI was performed using a 3.0-Tesla MR system(Discovery MR750, General), 3D high-resolution T1-weighted images and the resting-state fMRI images were acquired. The gradient-echo single-shot echo planar imaging sequence was used to obtain the resting-state fMRI data.The 3D high-resolution structural imaging were preprocessed using the SPM8. The IPL subregions were defined according to a connection-based parcellation study using diffusion MRI data, 11 subregions of the IPL were selected as region of interest(ROI). Then the GMV of each subregion for each subject was calculated and compared between the two groups using general linear model(GLM) after controlling for the effects of sex and age. Spearman's correlation coefficients were calculated between the GMVs of the IPL subregions with significant intergroup differences and the clinical parameters. Then for individual datasets, Pearson's correlation coefficients between the mean time series of each IPL subregion and time series of the voxel in other parts of the brain grey matter were computed. Then, a GLM was performed to compare the intergroup differences in rs FC of this IPL subregion after controlling the age and gender and the GMV of each subreion. At last, we extracted and calculated Spearman's correlation coefficients between the rsFCs of the IPL subregions with significant intergroup differences and clinical parameters(i.e., PANSS scores, illness duration, and antipsychotic dosage).Results:Compared with healthy subjects, schizophrenia patients showed significant GMV reduction in all the 5 anterior subregions and in only 1 middle and posterior subregion of the IPL. The GMV of the left PFt showed negative correlation with the duration of the illness(r =-0.212,p = 0.042) and the GMV of the right PF+PFt was positively correlated with the PANSS positive score(r = 0.231,p = 0.027). In terms of rsFC, among the 11 subregions in IPL, only the bilateral PFm(a transition zone of the IPL) subregions exhibited abnormal rsFC in schizophrenia, the left PFm showed increased rsFC with the bilateral lingual gyri in schizophrenia patients; the right PFm exhibited increased rsFC with the right lingual gyrus and inferior occipital gyrus, and bilateral mid-cingulate and sensorimotor cortices in schizophrenia patients.Conclusion: 1. The GMV of the IPL subregions, expecially the anterior subregions, was impaired in the schizophrenia patients; 2. There was a selective rsFC abnormality in the PFm in schizophrenia; 3. The abnormally increased rsFC between the PFm and the sensorimotor-related regions may indicate abnormalities in multi-sensory integration and sensorimotor integration in schizophrenia, which may further interfere the cognitive processing of the PFm of the IPL.