Structural covariance in schizophrenia and first-episode psychosis: An approach based on graph analysis

• Graph measures are a novel way to assess brain abnormalities in mental disorders.
• Chronic schizophrenia showed reduced integrity-closeness in pars-orbitalis and insula.
• There were no differences between chronic schizophrenia and first episode patients.

Schizophrenia is a neurodevelopmental disorder that produces abnormalities across different brain regions. Measuring structural covariance with MRI is a well-established approach to investigate common changes in distinct systems. We investigated structural covariance in schizophrenia in a large Brazilian sample of individuals with chronic schizophrenia (n = 143), First Episode Psychosis (n = 32), and matched healthy controls (n = 82) using a combination of graph analysis and computational neuroanatomy.Firstly, we proposed the connectivity-closeness and integrity-closeness centrality measures and them compared healthy controls with chronic schizophrenia regarding these metrics. We then conducted a second analysis on the mapped regions comparing the pairwise difference between the three groups.Our results show that compared with controls, both patient groups (in pairwise comparisons) had a reduced integrity-closeness in pars orbitalis and insula, suggesting that the relationship between these areas and other brain regions is increased in schizophrenia. No differences were found between the First Episode Psychosis and Schizophrenia groups. Since in schizophrenia the brain is affected as a whole, this may mirror that these regions may be related to the generalized structural alteration seen in schizophrenia.

Graphical representation of the measures used in this study. First, the cortex was segmented in 64 regions. A correlation matrix was generated with the volume of all regions in the first step. To capture two distinct features that can represent how the brain is affected in schizophrenia, two measures were derived from the correlations: Connectivity-closeness, and integrity closeness.Figure optionsDownload as PowerPoint slide