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Scott Sponheim, Seung Suk Kang, Victor Pokorny, Michael-Paul Schallmo, Cheryl Olman; Localization and Timing of Cortical Processes Related to the Use of Perceptual Context During Contour Detection: Evidence for Early and Mid-Latency Abnormalities in Schizophrenia. Journal of Vision 2020;20(11):210. doi: https://doi.org/10.1167/jov.20.11.210.
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© ARVO (1962-2015); The Authors (2016-present)
Spatial context has a large influence on contour detection, but it is unclear when such context exerts influence on brain processes supporting perception. In the current work we investigated neural contributions to contextual influences on contour detection. Because schizophrenia is associated with poor contour detection and weak effects of perceptual context we also examined neurophysiological responses to identify abnormal mechanisms in the disorder related to contour perception. In a study of the diagnostic specificity and genetic relevance of perceptual context, we gathered electroencephalography (EEG) data from people with schizophrenia (PSZ) and bipolar disorder (PBP), as well as first-degree biological relatives of PSZ (RelPSZ) while they completed a contour detection task that included a manipulation of spatial context through shifting the orientation of elements neighboring the contour (i.e., flankers). A second study determined the likely cortical sources related to contour perception during the task. Event-related potentials (ERPs) derived from EEG revealed that occipital N1 and P2 responses were sensitive to perceptual context as was the central parietal P300 response. PSZ and RelPSZ showed reduced dependence on the orientation of flankers for contour detection and in their P300 responses, while PBP showed intact perceptual context effects but generally reduced ERPs. Cortical source estimations derived from MEG (guided by MRI) revealed that theta frequency responses at 125ms and 400ms within visual areas (V1, V3 and LO) were sensitive to contours and perceptual context. PSZ showed diminished responses in V1, V3, and LO that failed to be modulated by perceptual context. Results indicate that perceptual context influences early processing in primary visual cortex, and later responses in V1, V3, and LO. Schizophrenia and genetic liability for the disorder are associated with alterations in the dependence of contour detection on perceptual context that may contribute to perceptual distortions central to the mental disorder.
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