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Brian Keane, Danielle Paterno, Sabine Kastner, Steven Silverstein; Visual shape completion deficits arise in first-episode and chronic schizophrenia, but are less severe in bipolar disorder: Evidence for a novel behavioral biomarker . Journal of Vision 2016;16(12):955. doi: 10.1167/16.12.955.
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© ARVO (1962-2015); The Authors (2016-present)
Background. Behavioral and electrophysiological studies indicate that people with chronic schizophrenia poorly integrate elements to form visually completed shapes. Is this deficit specific to schizophrenia? If so, may it be found as early as the first psychotic episode? Affirmative answers would potentially validate the impairment as an illness biomarker. Methods. To address the issue, we report data from two separate studies—the first comparing chronic schizophrenia (SZ), healthy control, and bipolar disorder (BD) patients (Study 1); the other comparing SZ, healthy control, and first episode (FE) psychosis patients (Study 2). In each case, subjects judged whether four pac-men formed a fat or thin illusory square (illusory condition) or whether four downward-pointing pac-men were individually rotated left or right (fragmented condition). Task difficulty depended on pac-man rotational magnitude, with larger rotations making the response alternatives easier to distinguish. An adaptive staircase determined threshold—the amount of rotation needed for 80% discrimination accuracy. Visual shape completion ability was measured as the extent to which performance in the illusory condition exceeded that of the fragmented. Results. In Study 1, shape completion was worse in SZ patients than in BD patients (p< .05) or controls (p< .001); and it was marginally worse in BD patients than in controls (p=.07). In Study 2, completion was better in controls than in FEs and SZs (ps< .01), but the latter groups were indistinguishable (p>.5). Interestingly, in each study, the schizophrenia patients who most clearly demonstrated completion deficits were those who suffered from higher levels of conceptual disorganization, a clinical symptom that impedes clear thinking and verbal communication. Conclusions. These results suggest that poor visual shape completion furnishes a biomarker for schizophrenia: the deficit arises by the first psychotic episode, is more pronounced than in bipolar disorder, and may be most apparent in a conceptually disorganized patient subtype.
Meeting abstract presented at VSS 2016
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