title: Flicker-defined form stimuli are minimally affected by centre-surround lateral contrast interactions.
abstract: OBJECTIVE
  Flicker-defined form (FDF) stimuli have recently been adopted for visual field testing. A key difference between FDF and traditional perimetric stimuli is that the entire display background contains flickering dots. The purpose of this study was to determine whether the perception of FDF stimuli is influenced by lateral interactions involving regions beyond the stimulus border in young healthy observers.
  
  
  METHODS
  Experiment 1 measured the effect of surround size and retinal eccentricity on the detection of the FDF contour. Psychometric functions were collected for surround diameters of 20°, 30° and 40°, and with stimuli centred at eccentricities of 0°, 10° and 20°. Experiment 2 measured the effect of target-surround temporal phase difference on apparent temporal contrast (flicker strength) of the target for both the FDF stimulus and a solid-field stimulus. Psychometric functions were collected for target-surround phase differences of 0°, 45°, 90°, 135° and 180°.
  
  
  RESULTS
  Our results show a mild surround-suppression effect for FDF stimuli that is independent of surround size. Magnitudes of FDF surround suppression were consistent with the reduced temporal contrast energy of the stimulus compared to solid-field stimuli.
  
  
  CONCLUSIONS
  FDF stimuli necessarily have both flickering target and background. Our results suggest that visual field defects outside the target are unlikely to markedly influence the detection and perception of the FDF stimulus. Nevertheless, mild surround suppression of contrast arises for FDF stimuli, hence interactions between the background and the target area may influence FDF results in conditions that alter centre-surround perceptual effects.
authors.affiliation: Department of Optometry & Vision Sciences, University of Melbourne, Melbourne, Australia.|School of Computing & Information Systems, University of Melbourne, Melbourne, Australia.|Visual Neuroscience Group, School of Psychology, University of Nottingham, Nottingham, UK.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Denniss
authors.affiliation: Department of Optometry & Vision Sciences, University of Melbourne, Melbourne, Australia.
authors.forename: Allison M
authors.initials: AM
authors.lastname: McKendrick
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D005425:Flicker Fusion / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011594:Psychometrics; D012684:Sensory Thresholds / Q000502:physiology; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult
keywords: centre-surround; flicker; flicker-defined form; lateral interactions; perimetry; phantom contour