Cortical-Striatal Dysfunction and Schizophrenia

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DESCRIPTION (provided by applicant): This project will test the hypothesis that specific cortical-striatal circuits are dysfunctional in schizophrenia. While there is evidence of striatal dysfunction in the few relevant studies of schizophrenia patients, the effect of schizophrenia on striatal functioning was inextricably confounded with the effects of the anti-psychotic medications used to treat schizophrenia. This project will avoid this pitfall by studying two groups of adolescents with liability to schizophrenia (patients with prodromal symptoms of schizophrenia and siblings of patients with childhood onset of schizophrenia), but who are not psychotic and therefore not treated with anti-psychotic medications. Prior research, including ours, suggests that the cognitive DLPFC/Caudate and the "reward" anterior cingulate/ventral striatum and LOF/ventral caudate circuits are impaired in schizophrenia, while the motor cortex/putamen circuit is intact. A combination of skill learning tasks and fMRI will be used to test this hypothesis. In the first year of the grant we will develop a reward-processing task that separately evaluates the effect of reward magnitude and reward predictability on fMRI activation and develop cognitive habit and motor skill learning tasks with comparable psychometric properties. In the second and third years of the grant we will conduct a large-scale pilot study of 20 siblings of childhood onset schizophrenia patients, 40 patients with prodromal symptoms of schizophrenia, and 20 adolescent controls. We will test the hypothesis that skill learning performance and fMRI indices of dysfunction of different cortical-striatal dysfunction will correlate with distinctive clinical features, neuropsychological deficits, and functional outcomes in individuals with liability to schizophrenia, depending on the putative circuit affected. This is the first schizophrenia study to: 1) use the convergence of evidence from psychometrically matched tasks and fMRI activation to test hypotheses about impairments of specific striatal circuits, 2) separately evaluate the effects of reward magnitude and predictability on brain activity, 3) demonstrate that specific cortical-striatal impairments are not due to the effects of anti-psychotic medication by studying adolescents with vulnerability to schizophrenia who have never been psychotic and therefore are not treated with antipsychotic medications.