Assessments of prefrontal function using event-related fMRI

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Functional MRI, ERP, LORETA and can complement the time and spatial resolution of each other. The combination of functional MRI and LORETA is a strong method to evaluate information processing in schizophrenia. We focused on the two main systems; visual processing system and working memory system. Visual sensory inputs are processed in occipitemporal regions through feedforwad and feedback interactions between top-down and bottom-up process. And then mapping between stimulus and responses can be governed in the working memory system in prefrontal cortex. Working memory system has subsystems, called central executive system and slave systems. Experimental tasks and summaries results of are as follows:Working memory system in prefrontal cortex (PFC)Visual oddball paradigmUnderactive in PFC and ACC for infrequently and irregularly presented visual target stimuli/Overactive for task irrelevant novel stimuli in PFC1Deteriorated stimulus-response mapping during goal-directed response for tar … More gets and distractibility to task irrelevant novel stimuliAuditory oddball paradigmFront-temporal dysfunction in passive auditory novelty discriminationResponse competition Deteriorated central executive systemVisual Processing System in Occipitemporal RegionsFace, eyes, eye-movement recognitionUnderactive in face processing in occipitemporal cortex, extrastriatel Overactive for eyes and moving-eyes in the amygdale, insula, and extrastriate cortex 1hypersensitivity in processing of feature details before processing the gestalt of the face or facial expression as a whole, which might be implicated in their deficits in interpersonal skills or forming of a variety of their clinical manifestations such as fear of eye-to-eye confrontation or delusion of reference.Illusory contour perceptionUnderactive in IC processing in extrastriateOveractive for IC in ACC and insulaDeficient in perceptual integration during processing in the extrastriate cortex, which might consequently increase the loads needed in the higher processing in the prefrontal cortexGlobal-Local perceptionUnderactive in Global processing in right occipitemporal cortexOveractive in Local processing in left occipitemporal cortex and PFCLeft hemisphere overactive-right hemisphere underactive in schizophrenic patientsIn the first three experiments, we confirmed working memory deficits in schizophrenia. It is likely that both of subsystems are impaired. In the last three experiments, we confirmed that visual processing systems are impaired as well as working memory system. Deficient processing in the occipitemporal cortex might consequently increase the loads needed in the higher processing in the prefrontal cortex. Impairments of slave system and central executive system might be related with visual processing system. Failure in perceptual integration and bottom-up processing might be implicated in overactivation in insula and amygdala and distractibility in prefrontal cortex. Less