Glutamatergic excess altering brain connectivity might provide an explanation for why those with longer duration of untreated psychosis have worse clinical outcomes. The investigators propose to use neuroimaging to study 67 first episode psychosis subjects before and after sixteen weeks of treatment with risperidone, a common antipsychotic. We will measure (1) glutamate and (2) structural and functional brain connectivity and test the hypotheses that glutamatergic abnormalities are present in first episode patients and that longer duration of untreated psychosis is associated with greater connectivity abnormalities that set the stage for poor response to treatment. 67 demographic-matched controls will also be recruited as a comparison group - healthy controls will not receive antipsychotic medication.