Abstract
Background: The corpus callosum (CC) has been implicated in the pathogenesis of schizophrenia and bipolar disorder. Yet, it remains unclear whether CC alterations are related to the underlying familial diathesis for psychotic disorders. We examined CC, its subregion volumes, and their relationship to cognition, psychotic symptoms, and age in subjects with schizophrenia (SZ), psychotic bipolar disorder (PBD), schizoaffective disorder (SZA), their first-degree relatives, and in healthy controls. Methods: We present findings from morphometric and neurocognitive analyses of 1429 subjects (SZ [n = 224], PBD [n = 190], SZA [n = 142], nonpsychotic relatives with no psychotic symptoms (RNPS) (n = 483) (SZ relatives [195], PBD relatives [175], SZA relatives [113]), and controls (n = 342). MPRAGE T1 scans across 5 sites were obtained using 3.T magnets. Image processing was done using FreeSurfer 5.1. Five subregions of the CC were measured using the Witelson’s classification. Neurcognitive function was measured using the Brief Assessment of Cognition in Schizophrenia (BACS). Results: Anterior and posterior splenia were significantly reduced across the groups. SZ and PBD Probands showed robust and significant reductions while relatives showed significant reductions of intermediate severity. The splenial volumes were positively but differentially correlated with aspects of cognition in the probands and their relatives. Proband groups showed a significant age-related decrease in the volume of the anterior splenium in comparison with controls. Among the psychosis groups, the anterior splenium in PBD showed a stronger correlation with psychotic symptomatology as shown by the PANSS. All 5 subregions showed significantly high familiality. Conclusion: The splenial volumes were significantly reduced across the psychosis dimension. However, this volume reduction impacts cognition and clinical manifestation of the illnesses in the groups differentially.