Journal
SCHIZOPHRENIA RESEARCH
Volume 95, Issue 1-3, Pages 205-214Publisher
ELSEVIER
DOI: 10.1016/j.schres.2007.07.001
Keywords
perceptual grouping; gestalt; color similarity proximity; critical stimulus duration
Categories
Funding
- NIMH NIH HHS [K02 MH01439, R37 MH049334-16, K02 MH001439-10, R37 MH049334, K02 MH001439, R37 MH49334, R01 MH066374-04, R01 MH66374, R01 MH066374] Funding Source: Medline
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Perceptual organization represents a basic and essential function that occurs at an intermediate level of visual processing. Much of the previous research on perceptual organization in schizophrenia employed indirect measurements, or included factors beyond sensory processing. The aims of the present study were to determine the integrity of perceptual organization in schizophrenia, as well as to determine the stimulus duration necessary to perform perceptual organization. Psychophysical measurements were compared between patients with schizophrenia and matched control subjects. Participants viewed dot patterns briefly presented on a computer monitor, and indicated whether stimuli appeared grouped as vertical or horizontal lines. Grouping was based upon either relative proximity or similarity in color. Across trials, relative proximity or color similarity was progressively reduced until stimuli became bi-stable (perceived as either of two patterns of grouping), establishing the grouping threshold. In separate conditions, stimuli were immediately followed by a mask to limit processing. Stimulus duration was progressively reduced until stimuli became bi-stable, establishing the critical stimulus duration (CSD). Schizophrenia patients demonstrated elevated grouping thresholds for grouping by proximity as well as color similarity. In addition, CSD was significantly extended for the schizophrenia group, with a nearly four-fold increase in duration of processing. These results provide direct evidence of impairment in schizophrenia for perceptual organization based upon spatial relationships and feature similarity, and suggest deficits in low-level perceptual organization processes. Although this study did not directly investigate the physiological correlates underlying perceptual impairments, these results are consistent with a theory of impaired lateral connections within visual cortical areas in schizophrenia. (c) 2007 Elsevier B.V All tights reserved.
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