The main objective of the study is to contribute to a better understanding of the physiopathology of schizophrenia, by studying causal relationships between cognitive deficits and the neurobiological basis for these deficits. Processing visual information involves both automatic grouping processes and control processes. Automatic grouping processes allow the building of a global configuration from local contour information. It is necessary in order to recognize objects. Control processes allow tending to and prioritizing information parts. The paradigm the investigators use allows to dissociate these processes, and is used in order to characterize the impairments observed in patients with schizophrenia. It is adapted to fMRI in order to explore the neurobiological basis of the deficits. The investigators will examine whether functional disconnectivity between activated areas subtend the impairments observed in patients.