title: Prolonged temporal interaction for peripheral visual processing in schizophrenia: evidence from a three-flash illusion.
abstract: BACKGROUND
  Coherent perception of the visual world requires orderly processing of spatially and temporally distributed visual information across the visual field. The organization of this visual information is impaired in schizophrenia. We previously found that visual temporal integration in patients is prolonged, using flashes presented to the central fovea. In this study, we investigated this temporal interaction in both the fovea and fairly far out in the peripheral visual field.
  
  
  METHODS
  We used a 'three-flash' illusion paradigm in which two spatially-coincident light pulses (of 1 ms each) are perceived by healthy individuals as one, two or three flashes depending on the time interval between the pulses. In each trial, two light pulses were presented in the fovea or 34° out in the right visual field. The inter-stimulus pulse interval (ISI) ranged from 30 to 310 ms. The task for patients (n=28) and controls (n=26) was to indicate the number of flashes (one, two or three) perceived after each two-pulse presentation.
  
  
  RESULTS
  For the controls, the peak of the three-flash illusion was shifted to longer ISIs (150 ms) in the periphery compared to the fovea (110 ms). For the patients, the three-flash illusion was greater and occurred at longer ISIs (270 ms in the periphery and 190 ms at the fovea).
  
  
  CONCLUSIONS
  Compared to the central visual field, the range of temporal interactions in the periphery is prolonged to a greater extent in schizophrenia. This exacerbated temporal expansion in peripheral vision suggests a coarse temporal resolution for visual and cognitive organization in this mental disorder.
authors.affiliation: McLean Hospital, Department of Psychiatry, Harvard Medical School, United States. Electronic address: ychen@mclean.harvard.edu.
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Psychology, Boston University, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Norton
authors.affiliation: Division of Applied Sciences and Engineering, Harvard University, United States (emeritus).
authors.forename: Charles
authors.initials: C
authors.lastname: Stromeyer
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D005584:Fovea Centralis; D006801:Humans; D007088:Illusions; D008297:Male; D010775:Photic Stimulation; D011601:Psychophysics; D012559:Schizophrenia; D012565:Schizophrenic Psychology; D013997:Time Factors; D013998:Time Perception; D014794:Visual Fields; D014796:Visual Perception
keywords: Fovea; Perceptual organization; Periphery; Schizophrenic; Temporal processing; Vision