Dissociable morphometric differences of the inferior parietal lobule in schizophrenia

Inferior parietal lobule (IPL) forms an integral part of a critical frontoparietal network, which has been implicated in various clinical symptoms and cognitive deficits seen in schizophrenia. Despite its functional relevance, the relatively few studies that have investigated the structural changes in the IPL report inconsistent findings concerning the nature and localization of these changes. We employed a blinded, automated labelling procedure to measure cortical thickness, surface area and the degree of cortical folding of the two distinct subregions of the IPL (Angular Gyrus and Supramarginal Gyrus) in 57 patients with schizophrenia and 41 controls using high-resolution magnetic resonance imaging. Within the IPL, we observed more pronounced morphological changes in supramarginal gyrus compared to angular gyrus in schizophrenia. While supramarginal gyrus in patients showed reduced gyrification, contracted surface area and thinning, the morphometric changes in angular gyrus were largely confined to a reduction in surface area. Significant hemispheric asymmetry was observed in the gyrification of the supramarginal gyrus. Our findings suggest that in addition to abnormalities in the neurodevelopmental processes that contribute to regional surface area and cortical thickness, a specific defect in cortical folding, especially affecting the left hemisphere, is likely to occur in schizophrenia.