Abstract
Patients with schizophrenia show specific abnormalities in visual perception, and patients with bipolar disorder may have related perceptual deficits. During tasks that highlight perceptual dysfunction (e.g., backward masking, contour integration), patients with schizophrenia show abnormal activity in visual brain areas including the Lateral Occipital Complex (LOC) and early retinotopic cortex. It is unclear whether the anatomical structure of such visual areas is atypical in schizophrenia and bipolar disorder. Using structural and functional MRI, we compared the cortical thickness of LOC and early retinotopic cortex in patients with schizophrenia (N=33), patients with bipolar disorder (N=31), and healthy controls (N=30). We identified LOC and early retinotopic cortex individually for each participant using functional localizers (objects vs. scrambled objects and phase-encoded retinotopic mapping, respectively). We measured the cortical thickness of each of those functionally-defined regions of interest (ROIs) using high-resolution anatomical scans processed with FreeSurfer 5.3.0 (Martinos Center for Biomedical Imaging, Charlestown, Mass.). In both LOC and early retinotopic cortex, patients with schizophrenia had the thinnest cortex, healthy controls had the thickest cortex, and bipolar disorder patients had intermediate cortical thickness. Within several sub-regions of early retinotopic cortex -- V1, V2, and V3 -- there was a trend for the same pattern of group differences. However, a control region, motor cortex, did not show this pattern of group differences. Although patients were on clinically determined doses of medication, there were no significant relationships between medication dosage and the cortical thickness of any ROI in either patient group. The thickness differences that exist in LOC and early retinotopic cortex could be an anatomical substrate for abnormalities in visual processing that have been identified with both neural and behavioral measures in schizophrenia and other severe mental illnesses.
Meeting abstract presented at VSS 2016