BACKGROUND - Aberrations in body perception are common in psychotic disorders. The insula and temporoparietal junction (TPJ) are involved in body ownership and spatial perception suggesting that abnormal structure of these regions might be related to the expression of perceptual aberrations in psychosis.
METHODS - 58 individuals with a primary psychotic disorder and 40 healthy subjects completed the Chapman Perceptual Aberration Scale (PAS) and underwent structural magnetic resonance imaging (MRI). Grey matter volume was extracted from a-priori defined TPJ, whole insula, and insula sub-division regions-of-interest (ROIs) and correlated with PAS scores. Additionally, a voxel-based morphometry (VBM) analysis examining the correlation between voxel-wise grey matter volume and PAS scores was conducted.
RESULTS - PAS scores in psychosis patients correlated with bilateral whole insula (right: r=-0.30, p=0.026; left: r=-0.35, p=0.011) and right TPJ (r=-0.27, p=0.024) volumes. The correlation between grey matter volume and PAS was strongest for the posterior sub-division of the insula (right: r=-0.32, p=0.017; left: r=-0.37, p=0.006). VBM analyses confirmed the ROI results: negative correlations with PAS were identified in clusters within the posterior and dorsal anterior insula, and the right TPJ. An exploratory, whole-brain analysis also revealed two additional regions located in the left middle orbitofrontal gyrus and left inferior temporal gyrus that inversely correlated with PAS scores.
CONCLUSIONS - Perceptual aberrations in individuals with psychosis are related to lower grey matter volume in the insula and TPJ. This relationship was strongest in the posterior region of the insula and right TPJ; brain areas that have been implicated in interoception and somesthesis.
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