Dissertation > Medicine, health > Neurology and psychiatry > Psychiatry > Schizophrenia

A Magnetic Resonance Imaging Study on the Gray Matter and Brain Networks in Patients with First-episode Schizophrenia

Author TaoHaoJuan
Tutor LiuZheNing
School Central South University
Course Clinical
Keywords first-episode psychosis schizophrenia structuralmagnetic resonance imaging voxel-based morphometry gray matter delusions of referencefirst-episode psychosis functionalmagnetic resonance imaging resting state functional connectivity brainnetwork
CLC R749.3
Type PhD thesis
Year 2012
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ObjectiveDelusions of reference (DOR) are one of the most common psychotic symptoms, which are closely linked with dopamine activities theoretically. This study using magnetic resonance imaging (MRI) aims to explore their neuroanatomical substrates, in particular in the basal ganglia.MethodsA total of44first-episode psychosis patients and25well-matched healthy controls were recruited. Patients were divided into three groups according to their clinical profile:(1) DOR group (n=15) with DOR as chief positive symptom,(2) non-DOR group (n=14) with positive symptoms other than DOR, and (3) negative group (n=15) with minimal positive symptoms. All participants underwent a structural magnetic resonance imaging scan of the brain. Voxel-based morphometry analysis was used to detect group differences in gray matter density. The relationship between DOR and structural anomalies was explored using Spearman’s correlation.ResultsSignificant group difference was observed in left and right caudate head, bilateral thalamus and left cerebellum. Post-hoc analysis showed that DOR patients had lower gray matter density in the caudate head bilaterally, which showed no difference among the other three groups. Gray matter density in the left and right caudate head was negatively correlated with DOR severity rho=-0.333and-0.383, both p<0.05). All patients exhibited reduced gray matter density bilaterally in the thalamus and left cerebellar posterior lobe compared with controls.ConclusionGray matter deficit in the caudate head is specifically observed in first-episode psychosis patients with DOR and is related to the severity of the symptom. Structural anomalies in the caudate may be related to the experience of DOR in psychosis. ObjectiveAbnormal Functional connectivity including corticol-subcortical brain regions in schizophrenia have been detected by Seed-based analysis and independent component analysis approach. However, in consideration of limitations, more holistic and objective approach is needed. A new holistic approach was used to construct the abnormal functional connectivity model within and between brain networks in patients of first episode schizophrenia and seek to provide new clues and evidences for the understanding of the pathology mechanism and biological makers of schizophrenia.MethodsForty-one patients with first-episode schizophrenia (FES) and33well-matched healthy controls (HC) were recruited. All participants underwent a resting state functional magnetic resonance imaging (fMRI) scan of the brain. Psychotic symptoms were assessed by SAPS and SANS. fMRI data preprocessing was conducted by SPM8(Statistical Parametric Mapping) and DPARSF (Data Processing Assistant for resting-state fMRI). Community discovery algorithm was used to explore and construct functional brain networks in healthy control subjects. A canonical template of connectivity in90different brain regions was constructed from healthy control subjects and this identified a six community structure with each network corresponding to a different functional system. An automated anatomical labeling atlas was used to parcellate the brain into90regions of interest (ROIs). The time series were extracted in each ROI by averaging the signals of all voxels within that region. Pearson correlation coefficients between all pairs of ROIs were first calculated (P-value<0.01). Significant correlations were detected with a90×90correlation matrix was obtained for each subject and then tested by partial correlation analysis (P-value<0.01).Odds ratio which represents the strength of association between functional connectivity and the disease was calculated and the differences of functional connectivities were compared between groups.Results(1) Six different brain functional networks were constructed using a community discovery algorithm. That is default mode network, attention network, auditory network, visual recognition network, the sensory-motor areas and subcortical network.(2) Compared with HC, patients with FES showed obviously decreased functional connectivity within default mode network, significantly decreased and increased functional connectivity between default mode network and attention network, significantly increased functional connectivity between default mode network and visual recognition network and auditory network, and decreased functional connectivity between default mode network and subcortical network.(3) Other abnormal functional connectivities within single brain network and between different brain networks were also detected in patients with FES. The abnormal functional connectivitiy model involved significantly decreased and increased functional connectivity within auditory network and visual recognition network, and significantly decreased functional connectivity within subcortical network. In addition, obviously decreased functional connectivity was also detected between attention network and visual recognition network.(4) Functional dysconnectivity of the left and right Brain’s Hemispheres existed in patients with FES.ConclusionAbnormal Functional connectivities involved all the different brain networks were observed in patients with FES. This may represent the pathophysiology underlying psychotic symptoms including hallucinations, delusions, positive formal thought disorder, bizarre behavior and congnitive dymentia.

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