Brain gray matter phenotypes across the psychosis dimension

Abstract

This study sought to examine whole brain and regional gray matter (GM) phenotypes across the schizophrenia (SZ)-bipolar disorder psychosis dimension using voxel-based morphometry (VBM 8.0 with DARTEL segmentation/normalization) and semi-automated regional parcellation, FreeSurfer (FS 4.3.1/64 bit). 3T T1 MPRAGE images were acquired from 19 volunteers with schizophrenia (SZ), 16 with schizoaffective disorder (SAD), 17 with psychotic bipolar I disorder (BD-P) and 10 healthy controls (HC). Contrasted with HC, SZ showed extensive cortical GM reductions, most pronounced in fronto-temporal regions; SAD had GM reductions overlapping with SZ, albeit less extensive; and BD-P demonstrated no GM differences from HC. Within the psychosis dimension, BD-P showed larger volumes in fronto-temporal and other cortical/subcortical regions compared with SZ, whereas SAD showed intermediate GM volumes. The two volumetric methodologies, VBM and FS, revealed highly overlapping results for cortical GM, but partially divergent results for subcortical volumes (basal ganglia, amygdala). Overall, these findings suggest that individuals across the psychosis dimension show both overlapping and unique GM phenotypes: decreased GM, predominantly in fronto-temporal regions, is characteristic of SZ but not of psychotic BD-P, whereas SAD display GM deficits overlapping with SZ, albeit less extensive.

Fig. 1

Whole brain gray matter phenotypes (A) between the psychosis groups and healthy controls and (B) across the psychosis dimension derived from the voxel-based morphometry analyses. SZ—individuals with schizophrenia, SAD—individuals with schizoaffective disorder, BD-P—individuals with psychotic bipolar I disorder, HC—healthy controls, FDR—false discovery rate correction for multiple comparisons. (A) Gray matter volume differences between the psychosis groups and healthy controls (P<0.05, FDR corrected, k=100). (B) Gray matter volume differences across the psychosis dimension (P<0.001, uncorrected, k=100).

Fig. 2

Individual volumes of selected regional outcomes derived from FreeSurfer analyses. SZ—individuals with schizophrenia, SAD—individuals with schizoaffective disorder, BD-P—individuals with psychotic bipolar I disorder, HC—healthy controls, FDR—false discovery rate correction for multiple comparisons.