Dissection of early bottom-up and top-down deficits during visual attention in schizophrenia

Objective: To characterize the interplay of bottom-up and top-down processing deficits of the early visual ERP component N1 in schizophrenia. Methods: Thirty-three schizophrenic patients and 61 healthy controls underwent a visual selective attention paradigm while 32-channel electroencephalogram was recorded. Visual N1 responses were calculated and source localization was applied. Results: Significant reductions of the cue N1 as well as the target N1 components were found in schizophrenia patients. Linear regression slopes for the cue N1 and for the cue-locked target N1 indicated significantly reduced early bottom-up and top-down modulation in patients relative to controls. Source analyses indicated that bottom-up as well as top-down N1 deficits in schizophrenia are associated with partially overlapping current density deficits in posterior cortex areas. Differential functional deficits were observed in right parietal lobe during bottom-up processing and in anterior cingulate cortex during top-down attention. Conclusions: The results provide evidence for both early visual bottom-up and top-down deficits in schizophrenia and illustrate how disturbances in these processing streams converge on the visual N1 amplitude. Significance: Visual top-down disturbances in schizophrenia appear to be confounded by visual bottom-up deficits. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.