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Rohit S Kamath, Kimberly B Weldon, Marisa J Sanchez, Cheryl A Olman, Scott R Sponheim, Michael-Paul Schallmo; Contour-object perception in psychosis. Journal of Vision 2020;20(11):544. doi: https://doi.org/10.1167/jov.20.11.544.
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Visual contour integration, the process that represents spatially separated elements as a single unified contour, has been consistently found to be impaired in schizophrenia. Recent work suggests that this deficit could be associated with psychotic symptoms and not specific to a diagnosis of schizophrenia. We examined a transdiagnostic sample of 37 participants with psychosis, 25 unaffected first degree relatives, and 20 healthy controls as a part of the Psychosis Human Connectome Project. We obtained a behavioral index of contour perception by measuring orientation jitter thresholds in a psychophysical task. People with psychosis showed impaired contour perception (i.e., tolerating less contour jitter) in agreement with previous findings. People with schizophrenia also showed significantly lower accuracy in discriminating contour objects without jitter than people with bipolar disorder. However, we found no relationship between tolerance of jitter and severity of psychosis symptoms or level of disorganization, measured using the Scale for Assessment of Positive Symptoms, the Brief Psychiatric Rating Scale, and the Sensory Gating Inventory. We also used 7 tesla functional MRI (fMRI) to measure responses in primary visual cortex (V1) during an analogous task inside the scanner. Across participant groups, V1 fMRI responses were lower for aligned versus scrambled contours. This effect of contour alignment appears consistent with previous studies of predictive coding in visual cortex. Additionally, we quantified task-based functional connectivity using a psychophysiological interaction analysis. Preliminary results showed stronger functional connectivity between the lateral geniculate nucleus and V1 for aligned verses scrambled contour stimuli among healthy controls. Our results may suggest a relationship between abnormal neural response modulation in early visual cortex, and well-known impairments in visual contour perception among people with psychosis.
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