Abstract
Abnormal visual percepts (e.g., hallucinations) are a common and often debilitating symptom of schizophrenia and other psychotic disorders. Data from several studies suggest that contextual modulation of visual stimuli, such as contrast surround suppression, is reduced among people with schizophrenia. We have previously shown that occipital neural responses in healthy controls mirror perceptual surround suppression under various stimulus conditions (e.g., orthogonal versus parallel surrounding stimuli, as well as monoptic versus dichoptic presentation), suggesting at least 2 separable neural mechanisms contribute to this suppression. Here we utilized a similar experimental paradigm to examine the neural basis of abnormal contrast surround suppression in schizophrenia. NVIDIA 3D Vision glasses were used to present contrast gratings with parallel or orthogonal surrounding gratings either monoptically or dichoptically, in order to quantify surround suppression of perceived contrast in healthy controls (n=21) and people with schizophrenia (n=9). Electroencephalography (EEG) data were also obtained during a comparable surround suppression task. Behavioral data from both healthy controls and people with schizophrenia showed stronger suppression with parallel versus orthogonal surrounds, as well as with monoptic versus dichoptic surrounds, as expected. Preliminary results from people with schizophrenia tended to show less center surround suppression compared to healthy controls. In EEG, event-related potentials (ERPs) over occipital brain areas showed greater suppression for parallel versus orthogonal surrounding stimuli, consistent with the previous work. As data collection continues, examination of perceptual suppression and the time-course of ERPs elicited across surround conditions may help elucidate the underlying neural mechanisms of abnormal visual perception in schizophrenia.