Abstract
Introduction: Individuals with schizophrenia have consistent gray matter reduction throughout the cortex when compared to healthy individuals. However, the reduction patterns vary based on the quantity (concentration or volume) utilized by study. The objective of this study was to identify commonalities between gray matter concentration and gray matter volume effects in schizophrenia.Methods: We performed both univariate and multivariate analyses of case/control effects on 145 gray matter images from 66 participants with schizophrenia and 79 healthy controls, and processed to compare the concentration and volume estimates.Results: Diagnosis effects in the univariate analysis showed similar areas of volume and concentration reductions in the insula, occipitotemporal gyrus, temporopolar area, and fusiform gyrus. In the multivariate analysis, healthy controls had greater gray matter volume and concentration additionally in the superior temporal gyrus, prefrontal cortex, cerebellum, calcarine, and thalamus. In the univariate analyses there was moderate overlap between gray matter concentration and volume across the entire cortex (r = 0.56, p = 0.02). The multivariate analyses revealed only low overlap across most brain patterns, with the largest correlation (r = 0.37) found in the cerebellum and vermis.Conclusions: Individuals with schizophrenia showed reduced gray matter volume and concentration in previously identified areas of the prefrontal cortex, cerebellum, and thalamus. However, there were only moderate correlations across the cortex when examining the different gray matter quantities. Although these two quantities are related, concentration and volume do not show identical results, and therefore, should not be used interchangeably in the literature.
Highlights
Individuals with schizophrenia have consistent gray matter reduction throughout the cortex when compared to healthy individuals
Numerous structural MRI studies report cortical reductions in individuals with schizophrenia compared to healthy controls in the frontal and temporal lobes, thalamus, and cerebellum (McCarley et al, 1999; Wright et al, 2000; Shenton et al, 2001; Honea et al, 2005; Glahn et al, 2008; Segall et al, 2009; Turner et al, 2012; Gupta et al, 2015)
Imaging and behavioral data were from the Center for Biomedical Research Excellence (COBRE) dataset, accessed via COINS and Schizconnect [RRID:SCR_010482,1,2; (Scott et al, 2011)]
Summary
Individuals with schizophrenia have consistent gray matter reduction throughout the cortex when compared to healthy individuals. In individual studies the results can largely depend on pre-processing protocols, statistical analyses, and sample sizes (Senjem et al, 2005; Silver et al, 2011; Chen et al, 2014; Radua et al, 2014). Study-specific decisions in preprocessing protocols can result in different smoothing kernel sizes, segmentation parameters, and the addition of Jacobianscaled modulation. All of these decisions can change the resulting estimates of diagnostic group differences (Eckert et al, 2006; Radua et al, 2014)
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