What have we learned from functional imaging studies in schizophrenia? The role of frontal, striatal and temporal areas

Objectives: Functional imaging technologies allow assessment of cerebral blood flow, cerebral metabolism, cellular metabolic processes, cerebral receptor density and occupancy. This review examines the contribution of such studies to our understanding of schizophrenia. The role of the frontal lobes, the basal ganglia, the temporal lobes and the neuronal circuits which connect them is examined with respect to this literature. Method: All studies in schizophrenia using positron emission tomography, single photon emission computerised tomography, xenon studies, functional and spectroscopic magnetic resonance imaging formed the basis of this review. Only those studies published in English were reviewed. Results: The most consistent finding in schizophrenia has been that of hypofrontality, while the results of studies examining subcortical structures provide preliminary support for the concept of fronto-striatal dysfunction. Functional imaging has not yet provided consistent results in the study of temporal lobe function. Although receptor studies have shed light on the actions of antipsychotic medications, the findings for dopamine receptor numbers remain controversial. Spectroscopic and functional MRI remain in their infancy as research tools in schizophrenia. Conclusions: Although there are significant methodological issues to be addressed, functional imaging technology is providing increasing insights into schizophrenia and its treatment. Future research will be truly multidisciplinary as it will require the collaboration of psychiatrists, imaging physicians, neuropsychologists and neuroscientists.