Introduction

Schizophrenia is a chronic mental illness whose symptoms are thought to have a strong neurobiological basis. This work is to study the resting state networks (RSNs) changes in first-episode schizophrenia patients by resting-state functional magnetic resonance imaging (fMRI).

Methods

Forty-eight patients with first-episode schizophrenia and forty healthy age-matched controls were recruited at the First Affiliated Hospital of Zhengzhou University. Eight of all the subjects were excluded due to the exceeded head movement, therefore, 45 first-episode schizophrenia patients and 35 healthy controls were scanned by a 3.0 Tesla MR scanner (Discovery MR750, General Electric, Milwaukee, WI, USA). Functional MRI data were obtained using a single-shot GRE-EPI sequence (TR/TE = 2000/41 ms; field of view = 220×220mm²; matrix = 64×64; flip angle = 90°; slice thickness = 3 mm; 1mm gap; 34 slices; 190 time points). Anatomical images were acquired using a T1-weighted 3D SPGR sequence (TR/TE = 8.2/3.2 ms; FOV = 256×256 mm²; matrix = 256×256; slice thickness = 1.0 mm, no gap; 188 slices). Resting-state fMRI data pre-processing was conducted with the DPARSFA software package. Pre-processing steps include: format conversing, excluding time point, time correction, head movement correction, spatial normalization and spatial smoothing. After then, independent component analysis(ICA) were performed on fMRI data to identify RSNs associated with schizophrenia and healthy controls using GIFT software. Differentiations of functional connectivity in each RSN between schizophrenia and control groups were computed and analyzed using SPM8 software. The voxel-wise two sample t-test (FDR-corrected) were performed to compare the group differences in function connectivity of each RSN.

Results

Eleven RSNs, including anterior default network front (aDMN), posterior default network (pDMN), sensorimotor network (SMN), medial visual network (mVN), lateral visual network (lVN), occipital pole visual networks (pVN), auditory network (AN), dorsal attention network (DAN), left frontoparietal network (lFPN), right frontoparietal network (rFPN) and central-executive network (CEN), derived from first-episode schizophrenia and healthy controls were obtained. Compared with healthy controls, first-episode schizophrenia showed significantly increased or decreased function connectivity (p<0.05, FDR-corrected, voxel level) in some brain regions of each RSN as indicated in Table 1. In detail, positive T value means first-episode schizophrenia had significantly increased function connectivity in some brain region than that of healthy control groups, while negative T value is the opposite. Take aDMN for example, compared with healthy control groups, three abnormal brain regions including left frontal gyrus (t=3.840, p<0.05), right frontal gyrus (t=2.514, p<0.05) and left medial frontal gyrus (t=-3.270, p<0.05) were found in this study which showed significantly change in function connectivity. At the same time, corresponding T value maps of eleven RSNs were showed in Figure 1-3.

Discussion

Previous studies have shown that the default network is perturbed in people suffering from schizophrenia ^{[1, 2]}. The post cingulate cortex (PCC), precuneus, medial prefrontal cortex (MPFC) and anterior cingulate cortex (ACC) of DMN are the main brain region for higher cognition function, which is involved in the processes of higher cognition and many psychiatric disorders ^[3]. In this study, the finding of abnormal functional connectivity in the frontal lobe, precuneus and cingulate is consistent with previous study above which is related to episodic memory and high cognition dysfunction. Central-executive network in human brain is related to signal processing which guide human response to any stimulation. The finding of increased function connectivity in left insular lobe and right cingulate of first-episode schizophrenia reveals that there is feedback loop damage in patients’ brain. Previous studies have demonstrated that there are not only some abnormity of function connectivity and lateralization index in FPN, but also high correlation with score of schizophrenia ^[4]. In this study, abnormity of function connectivity in some brain regions of bilateral frontal parietal network also has been found, and there may be related to some impairment of language, memory and attention in first-episode schizophrenia patients. Salience network including the insula lobe and the anterior cingulate is an important network in schizophrenia research. Numerous resting-state fMRI studies ^[5-9] have revealed high correlation between the abnormity of this network and symptoms of schizophrenia, such as delusion and photism. In this study, the main overlapping brain regions of salience network showed significantly change between two groups.

Conclusion

In conclusion, function connectivity from different networks may help explain the complex relationships between distributed cerebral sites in the brain and possibly provide new understanding of neurological and psychiatric disorders such as schizophrenia. The current study explored that there were RSNs damages or multiple brain regions functional connectivity abnormalities in first-episode schizophrenia patients compared with healthy controls, which behave functional connectivity increase and decrease.

Acknowledgements

No acknowledgement found.