Electrophysiological correlates of planning and monitoring in first episode schizophrenia

The aim of this study was to investigate the functional basis of frequently described cognitive deficits in schizophrenia patients by exploring the electrophysiological correlates of planning processes during performance of the Trail-Making Test-B (TMT-B). Via concurrent recording of behavioral test performance, exploratory eye movements and electrical brain activity functional components critical for task performance were extracted and characterized. Participants comprised 12 first episode patients and 12 matched healthy controls who were examined with concurrent infrared oculography and electroencephalography (EEG) while they carried out a computerized TMT-B. The performance process was segmented into planning and monitoring phases based on the interaction of eye and hand movements. Brain electrical activity was analyzed using low-resolution electromagnetic brain tomography (LORETA). During planning fixations compared to monitoring fixations, both groups showed enhanced current density in dorsolateral prefrontal cortex, cingulate gyrus and inferior parietal lobe. Concurrent with poorer performance, schizophrenia patients exhibited hypoactivity within prefrontal brain areas during planning. Thus, poorer performance in schizophrenia seems to be attributable to impaired planning behavior based on hypoactivity of prefrontal areas, involved in the temporal scheduling of deliberate actions as well as visuomotor integration.