V7. Impaired postural knowledge in schizophrenia is associated with structural gray and white matter alterations in the praxis network.

Abstract

Background Higher order processes such as recognition of gestures rely on a network of distinct and distant brain areas. Particularly the role of key regions such as the left inferior frontal gyrus (IFG) and the inferior parietal lobe is subject to ongoing debate. Schizophrenia patients suffer from impaired gesture performance and recognition. However, neural correlates of impaired gesture recognition have not yet been investigated. We therefore aim to test associations between structural brain imaging and postural knowledge in schizophrenia using voxel based morphometry (VBM) and tract based spatial statistics (TBSS). Methods In total, 44 patients with schizophrenia (DSM-5 criteria; 59% men, mean age 38) underwent structural MR imaging and performed the comprehensive postural knowledge task (PKT) for hand gestures. All patients except four were treated with antipsychotics. T1-weighted images were processed using SPM8 and DTI-data using FSL TBSS routines. We explored correlations of PKT scores and gray matter (GM) volume in VBM data and correlations of PKT scores and white matter (WM) integrity in TBSS data. Results were corrected for multiple comparisons using family wise error correction. Results Impaired postural knowledge was related to reduced GM volume and WM integrity. Whole brain analyses revealed effects of postural knowledge on gray matter volume within the bilateral insula extending to the IFG, the left primary motor cortex, the left superior parietal lobe and the bilateral hippocampi. Furthermore, significant correlations within fiber tracts connecting these regions – particularly alterations within the bilateral cingulum bundle and cingulum, the right superior longitudinal fasciculus, the right anterior limb of internal capsule, and the left uncinated fasciculus – were associated with PKT performance. Conclusions Poor postural knowledge in schizophrenia was associated with GM volume reductions in the praxis network. Our results are in line with the literature as particularly lesions in the left IFG were found to predict poor gesture recognition in brain damaged patients. In addition an effect of postural knowledge on WM integrity was shown within fiber tracts connecting key regions of gesture processing. Furthermore, the hippocampus is engaged in spatial memory and navigation. The results suggest that structural brain alterations in the common gesture network contribute to impaired postural knowledge in schizophrenia ( Fig. 1 ).