Working memory dysfunction in schizophrenia compared to healthy controls and patients with depression: Evidence from event-related fMRI

Studies on working memory (WM) dysfunction in schizophrenia have reported several functionally aberrant brain areas including the lateral prefrontal cortex, superior temporal areas and the striatum. However, less is known about the relationship of WM-dysfunction, cerebral activation, task-accuracy and diagnostic specificity. Using a novel WM-task and event-related functional magnetic resonance imaging (fMRI), we studied healthy control subjects (n = 17) and partially remitted, medicated inpatients meeting DSM-IV criteria for schizophrenia (n = 19) and major depressive disorder (n = 12). Due to the event-related technique, we excluded incorrectly performed trials, thus controlling for accuracy-related activation confounds. Compared with controls, patients with schizophrenia showed less activation in frontoparietal and subcortical regions at high cognitive load levels. Compared with patients with depression, schizophrenic patients showed less prefrontal activation in left inferior frontal cortex and right cerebellum. In patients with schizophrenia, a lack of deactivation of the superior temporal cortex was found compared to both healthy controls and patients with depression. Thus, we could not confirm previous findings of impaired lateral prefrontal activation during WM performance in schizophrenic patients after the exclusion of incorrectly performed or omitted trials in our functional analysis. However, superior temporal cortex dysfunction in patients with schizophrenia may be regarded as schizophrenia-specific finding in terms of psychiatric diagnosis specificity.