Full Program »
132. Event-Related Potential Correlates of Weakened Surround Suppression Evident in Schizophrenia
People with schizophrenia (PSZ) show visual abnormalities in their daily lives and on laboratory-based visual tasks. Specifically, PSZ show weak reliance on perceptual context in making judgments about the contrast of stimuli (i.e., limited surround suppression). To a lesser extent, people with bipolar disorder (PBP) show weakened surround suppression, but first-degree biological relatives of PSZ and PBP do not, suggesting the abnormality is related to the appearance of psychopathology and not genetic liability. To investigate neurophysiological processes underlying surround suppression, we recorded EEG from PSZ (n=22), PBD (n=25), PSZ relatives (n=19), PBP relatives (n=14), and controls (n=25) while they were shown two circular stimuli and asked to select which had higher contrast. One stimulus had a surrounding annulus which was either parallel to the inner circle or rotated by 20, 45, 70 or 90 degrees. Analysis of ERP data revealed differences in P1, N1, and P2 mean amplitude between the parallel and orthogonal conditions for controls, with no differences between conditions for PSZ. Reduced modulation in early neural responses over occipital brain regions in schizophrenia appears to reflect limited use of perceptual context. Analysis of PBP and relatives of patient groups will be presented.