Psychiatry - Research Publications
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ItemModulation of Brain Resting-State Networks by Sad Mood Induction(PUBLIC LIBRARY SCIENCE, 2008-03-19)BACKGROUND: There is growing interest in the nature of slow variations of the blood oxygen level-dependent (BOLD) signal observed in functional MRI resting-state studies. In humans, these slow BOLD variations are thought to reflect an underlying or intrinsic form of brain functional connectivity in discrete neuroanatomical systems. While these 'resting-state networks' may be relatively enduring phenomena, other evidence suggest that dynamic changes in their functional connectivity may also emerge depending on the brain state of subjects during scanning. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we examined healthy subjects (n = 24) with a mood induction paradigm during two continuous fMRI recordings to assess the effects of a change in self-generated mood state (neutral to sad) on the functional connectivity of these resting-state networks (n = 24). Using independent component analysis, we identified five networks that were common to both experimental states, each showing dominant signal fluctuations in the very low frequency domain (approximately 0.04 Hz). Between the two states, we observed apparent increases and decreases in the overall functional connectivity of these networks. Primary findings included increased connectivity strength of a paralimbic network involving the dorsal anterior cingulate and anterior insula cortices with subjects' increasing sadness and decreased functional connectivity of the 'default mode network'. CONCLUSIONS/SIGNIFICANCE: These findings support recent studies that suggest the functional connectivity of certain resting-state networks may, in part, reflect a dynamic image of the current brain state. In our study, this was linked to changes in subjective mood.
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ItemMedial temporal lobe glutathione concentration in first episode psychosis: A H-1-MRS investigation(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2009-03-01)Glutathione (GSH) is implicated in the pathophysiology of schizophrenia. Previous brain spectroscopy studies, however, have been inconsistent, and there is little data available from first episode psychosis patients. This study compared brain GSH in a first episode cohort (n=30) to controls (n=18), using magnetic resonance spectroscopy (MRS), examining a temporal lobe voxel. Short-echo (TE 30 ms) acquisition proton MRS was performed on a 3T clinical magnetic resonance scanner. Comparison of the first-episode and control groups' GSH concentrations revealed a significant main effect of group (F(1,46)=4.7, p=0.035), but no main effect of hemisphere (F(1,46)=2.3, p=0.137) or group-by-side interactions (F(1,46)=0.4, p=0.513). Medial temporal lobe GSH concentrations in the first episode group were 22% higher than those in the control group. This study provides further evidence of significant perturbations in brain GSH in first episode psychosis, and supports a broader involvement of GSH in the pathophysiology of schizophrenia.
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ItemFollow-up MRI study of the insular cortex in first-episode psychosis and chronic schizophrenia(ELSEVIER SCIENCE BV, 2009-03-01)Morphologic abnormalities of the insular cortex have been described in psychotic disorders such as schizophrenia, but it remains unknown whether these abnormalities develop progressively over the course of the illness. In the current study, longitudinal magnetic resonance imaging data were obtained from 23 patients with first-episode psychosis (FEP), 11 patients with chronic schizophrenia, and 26 healthy controls. The volumes of the short (anterior) and long (posterior) insular cortices were measured on baseline and follow-up (between 1 and 4 years later) scans and were compared across groups. In cross-sectional comparison at baseline, the FEP and chronic schizophrenia patients had significantly smaller short insular cortex than did controls. In longitudinal comparison, the FEP patients showed significant gray matter reduction of the insular cortex over time (-4.3%/2.0 years) compared with controls (0.3%/2.2 years) without significant subregional effects, but there was no difference between chronic schizophrenia patients (-1.7%/2.4 years) and controls. The gray matter loss of the left insular cortex over time in FEP patients was correlated with the severity of positive and negative symptoms at follow-up. These findings indicate that patients with psychotic disorders have smaller gray matter volume of the insular cortex especially for its anterior portion (short insula) at first expression of overt psychosis, but also exhibit a regional progressive pathological process of the insular cortex during the early phase after the onset, which seems to reflect the subsequent symptomatology.