title: Late, not early, stages of Kanizsa shape perception are compromised in schizophrenia.
abstract: BACKGROUND
  Schizophrenia is a devastating psychiatric disorder characterized by symptoms including delusions, hallucinations, and disorganized thought. Kanizsa shape perception is a basic visual process that builds illusory contour and shape representations from spatially segregated edges. Recent studies have shown that schizophrenia patients exhibit abnormal electrophysiological signatures during Kanizsa shape perception tasks, but it remains unclear how these abnormalities are manifested behaviorally and whether they arise from early or late levels in visual processing.
  
  
  METHODS
  To address this issue, we had healthy controls and schizophrenia patients discriminate quartets of sectored circles that either formed or did not form illusory shapes (illusory and fragmented conditions, respectively). Half of the trials in each condition incorporated distractor lines, which are known to disrupt illusory contour formation and thereby worsen illusory shape discrimination.
  
  
  RESULTS
  Relative to their respective fragmented conditions, patients performed worse than controls in the illusory discrimination. Conceptually disorganized patients-characterized by their incoherent manner of speaking-were primarily driving the effect. Regardless of patient status or disorganization levels, distractor lines worsened discrimination more in the illusory than the fragmented condition, indicating that all groups could form illusory contours.
  
  
  CONCLUSIONS
  People with schizophrenia form illusory contours but are less able to utilize those contours to discern global shape. The impairment is especially related to the ability to think and speak coherently. These results suggest that Kanizsa shape perception incorporates an early illusory contour formation stage and a later, conceptually-mediated shape integration stage, with the latter being compromised in schizophrenia.
authors: Rutgers - Robert Wood Johnson Medical School, 671 Hoes Lane, Piscataway, NJ 08854, USA; Rutgers University Behavioral Health Care, 151 Centennial Ave, Piscataway, NJ 08854, USA; Rutgers University Center for Cognitive Science, 152 Frelinghuysen Road, Piscataway, NJ 08854-8020, USA. Electronic address: Brian.Keane@gmail.com.
authors: Brian P
authors: BP
authors: Keane
authors: Rutgers University Behavioral Health Care, 151 Centennial Ave, Piscataway, NJ 08854, USA; Rutgers University Graduate School of Biomedical Sciences, Piscataway, NJ 08854, USA.
authors: Jamie
authors: J
authors: Joseph
authors: Rutgers - Robert Wood Johnson Medical School, 671 Hoes Lane, Piscataway, NJ 08854, USA; Rutgers University Behavioral Health Care, 151 Centennial Ave, Piscataway, NJ 08854, USA.
authors: Steven M
authors: SM
authors: Silverstein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009903:Optical Illusions / Q000502:physiology*; D010775:Photic Stimulation; D012559:Schizophrenia / Q000503:physiopathology*; D012684:Sensory Thresholds / Q000502:physiology*; D055815:Young Adult
keywords: Conceptual disorganization; Illusory contours; Kanizsa shape perception; Schizophrenia; Thought disorder; Visual completion