[A deficit in preattentive processing of visual information in schizophrenic patients].

Schizophrenia is associated with deficits in information processing. Several studies have shown impairments in attentional functions of visual perception in schizophrenic patients. Attentional function is thought to consist of two stages; preattentive processing and attentive processing. Preattentive processing enables an individual to detect a target without scanning stimuli one by one. The search time is almost constant as distoractors increase. On the other hand, attentive processing needs sequential scanning of stimuli to detect a target. Here, the search time increases as distractors increase. In this paper, preattentive information processing was investigated in 30 schizophrenic patients and 30 control subjects using visual search tasks. Subjects were instructed to find a target and press a button in two kinds of visual search tasks. The figures of tasks were constructed with one 'L' and 5, 17, 35 'X's in the high-pop-out task, and one 'L' and 5, 17, 35 'T's in the low-pop-out task. The performance of the high-pop-out task requires preattentive processing. The time to push the button, the time for the viewpoint to reach the target and the direction of the first saccade were recorded using the eye-mark recorder. The reaction time to push the button in schizophrenics was generally longer than that in controls, irrespective of the levels of pop-out. In addition, the time for the viewpoint to reach the target was also greater in schizophrenics. Also, in the direction of the first saccade, schizophrenics showed a lower rate of making the first saccade toward the target than controls in the high-pop-out task. In conclusion, the present results suggests that there is some kind of deficit in preattentive processing of visual information in schizophrenic patients.