Patients with a confirmed diagnosis of schizophrenia, schizophreniform disorder, schizoaffective disorder or psychotic disorder not otherwise specified (NOS), who are medication naive or medication free for a period of at least 2 weeks will be included. Patients will be tested before and after 8 weeks of treatment with an atypical antipsychotic. In the scanner patients will perform a working memory task, a language task and a visual-motor task. At study entry and after 8 weeks the PANSS, Clinical Global Impressions (CGI) and CDSS (Calgary Depression Scale of Schizophrenia) will be performed. Besides these patients, we will also include a group of matched healthy controls. We hypothesize that in medication naive or patients of-medication lateralization is reduced, and that efficiency of the working memory system is reduced. Lateralization is expected to correlate negatively with positive functions. We expect that antipsychotic treatment will normalize brain function and that the degree of normalization is correlated with the clinical measures of treatment efficacy.