Impaired sensory processing as a basis for object-recognition deficits in schizophrenia

Objective: Individuals are able to recognize common objects even when porti ons of them are obscured from view, reflecting the operation of neural perc eptual closure processes. This study evaluates the integrity of object reco gnition and perceptual closure as a function of sensory and cognitive manip ulations. Method: Object recognition was examined in 26 subjects with schizophrenia a nd 23 nonpsychiatric comparison subjects of similar age with a presentation of fragmented pictures by means of the ascending method of limits. The eff ects of prior exposure to subsets of stimuli and of word prompting were exa mined in separate testing phases. Demographic and clinical characteristics were evaluated as covariates. Results: Although they had impairments in perceptual closure, schizophrenic patients showed improvement in performance equivalent to that of nonpatien t comparison subjects with prior exposure to the pictures (i.e., repetition priming) and with presentation of valid word prompts. A significant correl ation was found between impaired performance and the severity of negative s ymptoms. Conclusions: The results support models of widespread dysfunction in inform ation processing in patients with schizophrenia involving both sensory and cognitive regions. Perceptual closure is significantly impaired in schizoph renic patients; however, this deficit in sensory precision is dissociated f rom the effects of higher-order repetition priming and word prompting. Furt hermore, this work suggests that deficits in perceptual closure may contrib ute to the muted world experience of patients with the persistent negative symptoms of schizophrenia.