PREATTENTIVE VISUAL-SEARCH AND PERCEPTUAL GROUPING IN SCHIZOPHRENIA

To help determine whether patients with schizophrenia show deficits in the stimulus-based aspects of preattentive processing, we undertook a series of experiments within the framework of feature integration the ory. Thirty subjects with a DSM-III-R diagnosis of schizophrenia and 3 0 age-, gender-, and education-matched normal control subjects complet ed two computerized experimental tasks, a visual search task assessing parallel and serial information processing (Experiment 1) and a task which examined the effects of perceptual grouping on visual search str ategies (Experiment 2). We also assessed current symptomatology and it s relationship to task performance. While the schizophrenia subjects h ad longer reaction times in Experiment 1, their overall pattern of per formance across both experimental tasks was similar to that of the con trol subjects, and generally unrelated to current symptomatology. Pred ictions from feature integration theory about the impact of varying di splay size (Experiment 1) and number of perceptual groups (Experiment 2) on the detection of feature and conjunction targets were strongly s upported. This study revealed no firm evidence that schizophrenia is a ssociated with a preattentive abnormality in visual search using stimu li that differ on the basis of physical characteristics. While subject and task characteristics may partially account for differences betwee n this and previous studies, it is more likely that preattentive proce ssing abnormalities in schizophrenia may occur only under conditions i nvolving selected 'top-down' factors such as context and meaning. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.