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Justine Spencer, Jelena P. King, Patrick J. Bennett, Allison B. Sekuler, Bruce Christensen; Effects of face inversion and noise in persons with schizophrenia. Journal of Vision 2009;9(8):486. doi: 10.1167/9.8.486.
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There is substantial evidence that people with schizophrenia show alterations in several domains of visual processing, including deficits in face processing and a reduced face inversion effect compared to healthy controls. However, the mechanisms underlying this observation are not yet known. Eye movement studies have found that people with SCZ do not concentrate on the most informative regions for face identification (e.g., the eyes). Consequently, people with SCZ may be less able to extract relevant information, suggesting a decrease in calculation efficiency. Previous research with non-face stimuli also suggests that SCZ is associated with increased levels of cortical internal noise. Moreover, both calculation efficiency and internal noise have been shown to be important mechanisms underlying face perception among healthy observers. The current study applies noise masking to upright and inverted faces to determine if face processing differences in SCZ are a result of changes in efficiency, internal noise, or both. Groups of community-based controls (n=24) and patients with SCZ (n=23) were presented with a target upright or inverted face, embedded in low or high levels of Gaussian white noise, for 200 ms. The target was followed immediately by the presentation of two faces and the task was to select the face corresponding to the target. A threshold was estimated by varying the contrast of the target face. Groups were matched for age, sex, and education. Similar to previous results, compared to controls, people with SCZ exhibited higher thresholds with upright and inverted faces, but also showed a reduced face inversion effect. Manipulation of noise had a smaller effect on performance in people with SCZ. Overall, the results suggest that people with schizophrenia have decreased calculation efficiency and increased internal noise compared to controls: Both factors act to impair face discrimination and reduce the face inversion effect in people with schizophrenia.
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