BACKWARD VERSUS FORWARD VISUAL MASKING DEFICITS IN SCHIZOPHRENIC-PATIENTS - CENTRALLY, NOT PERIPHERALLY, MEDIATED

Objective: Schizophrenic patients have repeatedly demonstrated the ina bility to rapidly process information when tasks are timed or the proc essing load is relatively high. Schizophrenic patients show consistent deficits in the visual backward masking paradigm. In visual backward masking, an informational target stimulus is presented followed after an interstimulus interval by a masking stimulus that interferes with o r interrupts target identification. Method: In order to clarify whethe r the visual backward masking deficits of schizophrenic patients are i ndeed central rather than peripheral in origin, the authors compared v isual backward masking to psychometrically matched visual forward mask ing performance in 35 normal comparison subjects and then 35 schizophr enic patients. In visual forward masking, the mask precedes the target , and visual forward masking mechanisms are felt to be more peripheral (retinal) than are visual backward masking mechanisms. Results: For p sychometrically matched forward and backward masking tasks, the schizo phrenic patients had a selective and differential deficit in the backw ard masking condition. Conclusions: These results support the interpre tation that the observed visual backward masking deficits of schizophr enic patients are centrally mediated.