Abstract
Widespread regional gray matter volume (GMV) alterations have been reported in bipolar disorder (BD). Structural networks, which are thought to better reflect the complex multivariate organization of the brain, and their clinical and psychological function have not been investigated yet in BD. 24 patients with BD type-I (BD-I), and 30 with BD type-II (BD-II), and 45 controls underwent MRI scan. Voxel-based morphometry and source-based morphometry (SBM) were performed to extract structural covariation patterns of GMV. SBM components associated with morphometric differences were compared among diagnoses. Executive function and emotional processing correlated with morphometric characteristics. Compared to controls, BD-I showed reduced GMV in the temporo-insular-parieto-occipital cortex and in the culmen. An SBM component spanning the prefrontal-temporal-occipital network exhibited significantly lower GMV in BD-I compared to controls, but not between the other groups. The structural network covariance in BD-I was associated with the number of previous manic episodes and with worse executive performance. Compared to BD-II, BD-I showed a loss of GMV in the temporal-occipital regions, and this was correlated with impaired emotional processing. Altered prefrontal-temporal-occipital network structure could reflect a neural signature associated with visuospatial processing and problem-solving impairments as well as emotional processing and illness severity in BD-I.
Highlights
Bipolar disorders (BD) affect up to 4% of the general population (Merikangas et al, 2007)
Between‐group analyses IC19 loadings showed a significant effect of diagnosis (F(2,96) = 4.21, p = 0.018), and planned comparisons revealed significant differences only between healthy controls (HC) and Bipolar type-I (BD-I) (p = 0.028)
IC13 loadings showed a significant effect of diagnosis (F(2,96) = 3.33, p = 0.040)), and planned comparisons revealed only a trend for significance for the comparison between HC and BD-I (p = 0.067)
Summary
Bipolar disorders (BD) affect up to 4% of the general population (Merikangas et al, 2007). These disorders are often unrecognized due to the heterogeneity of the clinical features (Hirschfeld et al, 2003), which results in delayed diagnosis, inadequate treatment, high medical costs, and disability, partly due to cognitive alterations (Keck et al, 2008). Neuroimaging literature has reported anatomical alterations in several regions. Previous meta-analyses of voxelbased morphometry (VBM) studies in BD indicated reduced gray matter volume (GMV) in the frontal-insular cortex and temporal regions (Bora et al, 2012). A further meta-analysis of 50 studies, revealed reduced GMV in the prefrontal cortex, temporal cortex, insula, and anterior cingulate cortex in BD (Wang et al, 2019).
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