Effects of short-term inpatient treatment on sensitivity to a size contrast illusion in first-episode psychosis and multiple-episode schizophrenia

Abstract

Introduction: In the Ebbinghaus illusion, a shape appears larger than its actual size when surrounded by small shapes and smaller than its actual size when surrounded by large shapes. Resistance to this visual illusion has been previously reported in schizophrenia, and linked to disorganized symptoms and poorer prognosis in cross-sectional studies. It is unclear, however, when in the course of illness this resistance first emerges or how it varies longitudinally with illness phase.Method: We addressed these issues by having first-episode psychosis patients, multiple-episode schizophrenia patients and healthy controls complete a psychophysical task at two different time points, corresponding to hospital admission and discharge for patients. The task required judging the relative size of two circular targets centered on either side of the screen. Targets were presented without context (baseline), or were surrounded by shapes that made the size judgment harder or easier (misleading and helpful contexts, respectively). Context sensitivity was operationalized as the amount of improvement relative to baseline in the helpful condition minus the amount of decrement relative to baseline in the misleading condition.Results: At hospital admission, context sensitivity was lower in the multiple-episode group than in the other groups, and was marginally less in the first episode than in the control group. In addition, schizophrenia patients were significantly more and less accurate than the other groups in the misleading and helpful conditions, respectively. At discharge, all groups exhibited similar context sensitivity. In general, poorer context sensitivity was related to higher levels of disorganized symptoms, and lower level of depression, excitement, and positive symptoms.Discussion: Resistance to the Ebbinghaus illusion, as a characteristic of the acute phase of illness in schizophrenia, increases in magnitude after the first episode of psychosis. This suggests that visual context processing is a state-marker in schizophrenia and a biomarker of relapse and recovery.

On the functions, mechanisms, and malfunctions of intracortical contextual modulation

“…This has now been demonstrated in over 50 studies (reviewed in Silverstein & Keane, 2011). These findings are not due to medication effects, or to generalized performance deficits: in cases where grouping of targets and distracters interferes with task accuracy, schizophrenia patients demonstrate greater accuracy than controls (e.g., Place & Gilmore, 1980;Silverstein et al, 2013;Uhlhaas et al, 2006). These perceptual organization impairments are considered examples of failures of dynamic grouping because they are demonstrated most clearly when non-contiguous elements need to be combined and where prepotent stimulus structure is weak.…”

“…For example, patients have demonstrated weaker suppression for contrast (Dakin, Carlin and Hemsley, 2005;Tibber et al, 2013), and size (Uhlhaas et al, , 2006Silverstein et al, 2013), with mixed evidence on orientation (Schallmo, Sponheim, and Olman, 2013;Tibber et al, 2013;Yoon et al, 2009Yoon et al, , 2010. There is negative evidence in the case of luminance, the earliest processed of the dimensions studied, and that suggests a cortical locus for reduced surround suppression .…”

Space and Objects: On the Phenomenology and Cognitive Neuroscience of Anomalous Perception in Schizophrenia (Ancillary Article to EAWE Domain 1)

“…Changes in size and color could be partly due to momentary weakening or intensification of size and color constancy mechanisms, but there are currently no data to support this view. While some data exist demonstrating size constancy abnormalities in schizophrenia [34] , and their expected brain function correlates [35] , it is not clear whether similar mechanisms are operative in disturbances of spatial perception outside of a laboratory context. It is also not clear whether and to what extent changes in perception are driven by emotional factors, and, if so, how this operates.…”

Comparison of visual perceptual organization in schizophrenia and body dysmorphic disorder

“…The effect has been known for over 100 years (Titchener, 1902), and has been the subject of numerous experiments, especially since the 1970s (e.g., Massaro and Anderson, 1971; Girgus et al, 1972; Weintraub and Schneck, 1986; Coren and Enns, 1993; Rose and Bressan, 2002; Doherty, 2010; Schwarzkopf and Rees, 2013). Patients with schizophrenia have demonstrated reduced illusion effects, expressed as more accurate size perception compared to controls when judging target circle size in misleading context conditions (Uhlhaas et al, 2006; Silverstein et al, 2013; Tibber et al, 2013). This effect is most pronounced when patients have active psychotic symptoms (Silverstein et al, 2013).…”