Cortical thinning in the posterior cingulate gyrus: an endophenotype for schizophrenia?

Background: Studies investigating cortical thickness in schizophrenia using genetically sensitive samples are still scarce. The evidence to date suggests that decreased cortical thickness of the posterior cingulate and temporal gyrus may be influenced by genetic factors, which is based on regions of interest analyses. The present family study examined whether decreased cortical thickness can be found as an indicator of genetic liability for the disorder, using a whole brain analyses approach. Methods: T1-weightedMRI scans were acquired on a 3 Tesla scanner from 92 patients with schizophrenia, 98 non-psychotic siblings and 91 controls. BrainVoyagerQX was used to measure cortical thickness using the Laplace method. Group differences were assessed with whole brain, vertex-based, analyses (ANCOVA), performed in surface space after cortex based alignment of segmented cortices, and adjusted for potential confounders. Results: Analysis showed significant clusters of cortical thinning in patients compared to controls in the left and right superior parietal lobe, the right postcentral gyrus, the left collateral sulcus, the left middle occipital gyrus, the left extrastriate cortex, the left lateral occipitotemporal gyrus and the right posterior cingulate gyrus; increases were found in the left precentral gyrus. Siblings showed thinner cortex compared to the controls in the right collateral sulcus and the right posterior cingulate gyrus; increases were found in the right inferior frontal gyrus, the left lateral sulcus, the right postcentral sulcus, the left middle temporal gyrus and the left cingulate sulcus. Patients had thinner cortices than their siblings in the left and right superior frontal gyrus, the left postcentral gyrus and sulcus, the right precuneus, the right intraparietal sulcus, the left inferior temporal sulcus, the right collateral sulcus, the left lateral occipitotemporal gyrus, the left middle occipital gyrus, the left medial occipitotemporal gyrus and the left cuneus. Conclusions: Psychotic patients and their non-psychotic siblings were found to have widespread cortical thickness alterations compared to controls, as evinced by decreases and increases in several brain regions. Decreased cortical thickness in the right posterior cingulate gyrus was present in both patients with psychosis and their siblings. Thus, decreased cortical thickness in the right posterior cingulate gyrus may be influenced by genes that are associated with schizophrenia