BACKWARD-MASKING IN SCHIZOPHRENIA - TIME-COURSE OF VISUAL PROCESSING DEFICITS DURING TASK-PERFORMANCE

Backward masking deficits have been put forward as potential psycholog ical markers for vulnerability to schizophrenia. This study was conduc ted to investigate whether schizophrenic patients improve their perfor mance on a backward masking task during a single test session. The abi lity of a degraded stimulus version of the masking task to act as a sp ecific diagnostic marker for paranoid schizophrenia (versus affective disorder) was also investigated. The backward masking task was perform ed on 18 paranoid schizophrenic patients, 18 unipolar depressed patien ts, and 18 non-psychiatric controls. Paranoid schizophrenic patients w ere included because they tend to show normal performance with traditi onal masking protocols. Schizophrenic patients made significantly more detection errors compared to depressives and non-psychiatric controls where interstimulus intervals (ISIs) longer than 14 ms were used. Unl ike depressed patients and non-psychiatric controls, schizophrenic pat ients showed no reduction in error rate during the entire period over which the backward masking task was performed. The constant error rate which was observed at an ISI of 114 ms suggests that schizophrenic pa tients cannot attenuate the disruption effect due to deflection of att ention from the target to the mask. The backward masking deficit in sc hizophrenia appears to arise from a temporarily stable visual processi ng impairment in performance within a single test session. (C) 1998 El sevier Science B.V. All rights reserved.