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Hannah R. Moser, Li Shen Chong, Marisa J. Sanchez, Scott R. Sponheim, Michael-Paul Schallmo; Visual contrast processing in people with psychosis. Journal of Vision 2020;20(11):406. https://doi.org/10.1167/jov.20.11.406.
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People with psychosis commonly experience abnormal visual perception characterized by clinical symptoms (e.g. hallucinations) as well as differences in performance on various psychophysical tasks. These differences in perceptual experience are present across different diagnoses involving psychosis and are related with disease severity and outcomes, yet the underlying neural processes are not well understood. As part of the ongoing Psychosis Human Connectome Project, this study was designed to examine differences in visual contrast processing in people with psychotic disorders including schizophrenia, schizoaffective disorder, or bipolar disorder. Behavioral and 7 tesla fMRI data were acquired during visual contrast detection tasks in 35 people with psychosis, 25 unaffected first-degree biological relatives, and 20 healthy controls. In experiments performed outside the scanner, a psychophysical adaptive staircase method was used to determine contrast discrimination thresholds at seven contrast pedestals. Thresholds were defined by the minimum difference in contrast between two stimuli that participants could discriminate with 80% accuracy. During a similar contrast discrimination task, fMRI responses were measured in primary visual cortex. People with psychosis exhibited increased visual contrast discrimination thresholds as compared to relatives or controls. There were no differences in visual contrast discrimination thresholds between diagnostic groups, suggesting that this difference in visual perception is not associated with a specific diagnostic phenotype. Behavioral data were fit with a contrast response function in order to model a predicted neural response for each participant group. Estimated slope parameters differed between relatives and controls, predicting a steeper contrast response for people with a genetic liability for psychosis. Accordingly, contrast-dependent fMRI responses in primary visual cortex exhibited differences in slope across groups. These data suggest that contrast perception is impaired across the psychosis spectrum, which may be related to abnormal neural processing within early visual cortex.
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