Visual Context Processing Deficits in Schizophrenia: Effects of Deafness and Disorganization

Abstract

Visual illusions allow for strong tests of perceptual functioning. Perceptual impairments can produce superior task performance on certain tasks (i.e., more veridical perception), thereby avoiding generalized deficit confounds while tapping mechanisms that are largely outside of conscious control. Using a task based on the Ebbinghaus illusion, a perceptual phenomenon where the perceived size of a central target object is affected by the size of surrounding inducers, we tested hypotheses related to visual integration in deaf (n = 31) and hearing (n = 34) patients with schizophrenia. In past studies, psychiatrically healthy samples displayed increased visual integration relative to schizophrenia samples and thus were less able to correctly judge target sizes. Deafness, and especially the use of sign language, leads to heightened sensitivity to peripheral visual cues and increased sensitivity to visual context. Therefore, relative to hearing subjects, deaf subjects were expected to display increased context sensitivity (ie, a more normal illusion effect as evidenced by a decreased ability to correctly judge central target sizes). Confirming the hypothesis, deaf signers were significantly more sensitive to the illusion than nonsigning hearing patients. Moreover, an earlier age of sign language acquisition, higher levels of linguistic ability, and shorter illness duration were significantly related to increased context sensitivity. As predicted, disorganization was associated with reduced context sensitivity for all subjects. The primary implications of these data are that perceptual organization impairment in schizophrenia is plastic and that it is related to a broader failure in coordinating cognitive activity.

Is disorganization a feature of schizophrenia or a modifying influence: Evidence of covariation of perceptual and cognitive organization in a non-patient sample

“…The methods for this task were identical to those used in several prior studies (Phillips et al, 2004; Doherty et al, 2008; Doherty et al, 2010; Horton and Silverstein, 2011). Stimuli were either 2 circles alone (control condition), or 2 circles each surrounded by 8 other circles around the edges of an imaginary square [(3 on top, 3 on the bottom, and 1 on either side of the target circle (context conditions)] (Fig.…”

“…To analyze context sensitivity, we calculated the difference in accuracy between the misleading and helpful context conditions, specifically in the 2 pixel condition (Doherty et al, 2008; Horton and Silverstein, 2011). Studies have shown that schizophrenia patients perceive stimuli more veridically (i.e., are less influenced by context and are more accurate than control subjects in the misleading condition) and that this is related to extent of disorganized symptoms (Uhlhaas et al, 2006; Horton and Silverstein, 2011; Silverstein et al, 2013).…”

“…Studies have shown that schizophrenia patients perceive stimuli more veridically (i.e., are less influenced by context and are more accurate than control subjects in the misleading condition) and that this is related to extent of disorganized symptoms (Uhlhaas et al, 2006; Horton and Silverstein, 2011; Silverstein et al, 2013). Higher accuracy on the misleading trials, therefore, indicates reduced PO and is represented by a smaller difference between helpful and misleading conditions.…”

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

“…This task has been used in four prior studies of the Ebbinghaus illusion, including one of schizophrenia (Phillips et al, 2004; Doherty et al, 2008, 2010; Horton and Silverstein, 2011). On each trial, the task was to press a key to indicate whether the target on the left or the right half of the screen was larger (see Figure 1).…”

“…On half of the trials, the targets were surrounded by larger or smaller circles that would make giving a correct response easier (helpful condition) or harder (misleading condition; see Figure 1). As discussed further below, we chose this illusion because it has been established over decades of research, because it is experienced to a lesser extent among schizophrenia patients relative to healthy and psychiatric controls (Uhlhaas et al, 2006a,b; Tibber et al, 2013), and because reduced illusions have been linked to a more acutely ill clinical state and to more disorganized symptoms in cross-sectional studies (Uhlhaas et al, 2006a,b; Horton and Silverstein, 2011). Another advantage to this task is that it can side-step generalized deficit confounds, in which low accuracy can be attributed to reduced motivation or attention (Knight and Silverstein, 2001; Silverstein, 2008).…”