16.1 Visual Shape Completion Deficits Arise in First-episode and Chronic Schizophrenia, but Are Less Severe in Bipolar Disorder: Evidence for a Novel Behavioral Biomarker
Year: 2019
Type: conference-abstract
Abstract: Visual shape completion is a fundamental process that constructs contours and shapes on the basis of the geometric relations of spatially separated edge elements. Behavioral and electrophysiological studies indicate that people with chronic schizophrenia are poor at visual shape completion but at what point does the impairment emerge, how does it evolve over time, and how specific is it to schizophrenia spectrum disorders? Addressing these questions could validate the impairment as an illness biomarker and identify visual neurodegenerative changes that accompany illness onset and progression. We report data from two separate studies—the first comparing chronic schizophrenia patients (SZ), healthy controls, and bipolar disorder patients (Study 1); the other comparing SZ, healthy controls, and first episode psychosis patients (FE; Study 2). In each case, subjects judged whether four sectored circles (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. A Bayesian adaptive staircase determined threshold, which corresponded to the amount of rotation needed for 80% discrimination accuracy. Visual shape completion was quantified as the extent to which performance in the illusory condition exceeded that of the fragmented condition. Illusory contour salience was also manipulated: in Study 1, half the trials contained distractor lines, which disrupt illusory contour formation and thereby worsen illusory shape discrimination; in Study 2, half of the trials incorporated wire edge elements, which augment illusory contour salience and thereby improve illusory shape discrimination. For Study 1, visual shape completion was worse in SZ patients than in bipolar patients (p< .05) and controls (p< .001), and marginally worse in bipolar patients than in controls (p=.07). For Study 2, completion was worse in FEs and SZs than in controls (ps< .01), but the patient groups were indistinguishable (p>.5). Patients’ visual shape completion deficits could not be explained in terms of age, motivation, or poor orientation tuning. The deficits did correlate with increased cognitive disorganization and worse premorbid functioning during early adolescence. A somewhat surprising result was that each patient group in each study responded normally to alterations in illusory contour salience, indicating that the groups could form but not appropriately use illusory contours to discriminate shape. Poor visual shape completion furnishes a potential biomarker for schizophrenia: the deficit arises maximally by the first psychotic episode, is more pronounced than in bipolar disorder, and may be most clearly observed among those with cognitive disorganization and poor premorbid functioning during early adolescence.
Source: Schizophrenia Bulletin
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2935900714