Altered contextual modulation of primary visual cortex responses in schizophrenia P Sterzer1, K Seymour2 |
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1Visual Perception Laboratory, Charité - Universitätsmedizin Berlin, Germany |
| While schizophrenia is commonly linked to high-level cognitive dysfunction, recent models of schizophrenia suggest that these cognitive symptoms reflect a more pervasive deficit, starting with alterations at the earliest stages of sensory processing. Based on previous behavioural work, we tested whether contextual modulation of neural responses in primary visual cortex (V1) is reduced in patients with paranoid schizophrenia. Eighteen patients and 18 control participants underwent fMRI while viewing a central grating stimulus in the presence of a contextual surround grating oriented either orthogonal or parallel to the central grating’s orientation. Phase-encoded retinotopic mapping was performed to define V1 regions of interest in each participant individually. In controls, suppression of the fMRI signal in V1 was stronger for parallel compared to orthogonal surround gratings, consistent with previous findings of orientation-specific contextual suppression. In contrast, in schizophrenic patients the surround grating’s orientation exerted no detectable influence on fMRI signal suppression in V1. The between-group difference in orientation-specific contextual suppression was reflected in a significant group-by-orientation interaction. By providing direct neurophysiological evidence for a perturbation of early sensory neural mechanisms, our results support current psychobiological models that link alterations of sensory processing to positive symptoms of schizophrenia, such as hallucinations and delusions. |
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