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Steven Silverstein, Brian Keane, Keith Feigenson, Yushi Wang, Deepthi Mikkilineni, Danielle Paterno; Reduced Sensitivity to the Ebbinghaus Illusion is State Related in Schizophrenia. Journal of Vision 2013;13(9):1261. doi: 10.1167/13.9.1261.
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© ARVO (1962-2015); The Authors (2016-present)
Background. The Ebbinghaus illusion causes a shape to appear as larger when surrounded by small shapes and as smaller when surrounded by large shapes. Persons with schizophrenia are less susceptible to the illusion, but it is unclear when this resistance first emerges or how it varies with symptoms. Method. Chronic schizophrenia patients (n=16), first episode psychosis patients (n=11) and healthy controls (n=26) completed a psychophysical task at two different time points, corresponding to hospital admission and discharge for patients (~2 weeks apart). The task required judging the relative size of two circular targets centered on either side of the screen. Targets were either presented without context, or were surrounded with shapes that made the size judgment harder or easier (misleading and facilitating contexts, respectively). Results. Performance without context was consistently the same across groups, indicating that all subjects were engaging in the task appropriately. At hospital admission, the accuracy difference between the facilitating and misleading conditions was larger in controls than in first episode patients, and larger in first episode than chronic patients. Notably, the chronic group was significantly more accurate than the other groups with misleading context, and less accurate with facilitating context, indicating reduced context sensitivity. At discharge, all groups performed similarly. Finally, a reduction in psychotic and disorganized symptoms across time points was correlated with a reduction in accuracy in the misleading condition, and an increase in accuracy in the facilitating condition for the chronic group. Conclusions. Resistance to the Ebbinghaus illusion arises by the first episode of psychosis, depends on current symptom level, and becomes more pronounced as more psychotic episodes are experienced. This suggests that visual context processing is a state-marker in schizophrenia, and that psychosis and disorganization can elucidate the mechanisms that subserve normal visual context processing.
Meeting abstract presented at VSS 2013
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