Visual perceptual and working memory impairments in schizophrenia.

BACKGROUND: Impairments in working memory have been proposed to underlie a broad range of cognitive deficits seen in schizophrenia. Visual working memory impairments are frequently reported in schizophrenia. Investigations of visual working memory generally assume intact visual information processing, despite evidence of visual perceptual impairments in schizophrenia. In this study, we evaluated the integrity of the perceptual system for object and spatial visual information and the relevant working memory system, after adjusting for individual perceptual performance differences.
METHODS: Thirty patients with schizophrenia and 20 healthy control subjects underwent testing using a task of perceptual discrimination of spatial and object visual stimuli. For testing visual working memory, a delay was introduced to the perceptual discrimination task. A thresholding procedure was used so that each subject adequately perceived the information during the working memory test.
RESULTS: Subjects with schizophrenia exhibited impaired performance relative to controls for object and spatial visual perceptual discrimination. The extent of impairment was greater for the object than for the spatial test. After controlling for perceptual impairments, the subjects with schizophrenia exhibited impaired performance relative to controls for the spatial working memory test but not the object working memory test.
CONCLUSIONS: Findings implicate dysfunction of posterior brain areas that mediate visual perceptual processing and the prefrontal areas involved in the active maintenance of information during delay intervals. However, the systems that govern object and spatial visual perception and working memory appear to be affected differentially by schizophrenia.