T137. THE RELATIONSHIP BETWEEN CORTICOSTRIATAL CONNECTIVITY AND STRIATAL DOPAMINE FUNCTION IN SCHIZOPHRENIA: AN 18F-DOPA PET AND DIFFUSION TENSOR IMAGING STUDY

BACKGROUND: Striatal dopamine dysfunction caused by cortical abnormalities is a leading hypothesis of schizophrenia pathophysiology, which underlies in majority of treatment-responsive patients. Although supported by findings that prefrontal cortical lesions lead to striatal dopamine dysregulation and that recently, prefrontal structural volume is negatively correlated with striatal dopamine synthesis, the relationship between corticostriatal connectivity and striatal dopamine synthesis has not been tested in patients with schizophrenia. We therefore investigated the relationship between corticostriatal connectivity and striatal dopamine synthesis capacity in treatment-responsive patients with schizophrenia, and compared them to treatment-resistant patients and healthy control subjects. METHODS: Twenty-four patients with schizophrenia and twelve matched healthy control subjects underwent 18F-DOPA PET scans to measure dopamine synthesis capacity (indexed as the influx rate constant Kicer), structural and diffusion 3T MRI. Connectivity(indexed as Fractional anisotropy, FA) were assessed in 3 major corticostriatal tracts (dorsolateral prefrontal cortex-associative striatum, ventromedial prefrontal cortex-limbic striatum, and pre/primary motor cortex-sensorimotor striatum). Furthermore, these measures were tested whether they were correlated with a measure of Wisconsin Card Sorting Test (WCST). RESULTS: Treatment responsive patients showed a negative correlation between connectivity of dorsolateral prefrontal cortex-associative striatum and striatal dopamine synthesis capacity of associative striatum, but this was not evident in treatment-resistant patients. Furthermore, WCST negatively correlated with Kicer in associative striatum and positively correlated with FA in dorsolateral prefrontal cortex-associative striatum in whole subjects and treatment responsive patients but not in treatment-resistant patients. DISCUSSION: These findings demonstrate that different mechanisms underlie the pathophysiology of treatment-responsive and treatment-resistant schizophrenia and especially, connectivity of dorsolateral prefrontal cortex-associative striatum is a core part for the different pathophysiology.