title: Global shape processing deficits are amplified by temporal masking in migraine.
abstract: OBJECTIVE
  Individuals with migraine show subtle defects in a range of visual tasks compared to nonmigraineurs. Increased neuronal noise can account for some of these deficits. To examine the generality of increased noise in migraine, masking effects were compared in migraineurs and headache-free controls using a shape discrimination task, thought to involve processing in extrastriate cortical areas.
  
  
  METHODS
  Nine migraineurs with aura, nine migraineurs without aura, and nine headache-free controls participated. observers had to detect deviations in circular shapes with or without a larger contour mask. The nonoverlapping mask was presented at five temporal intervals (stimulus onset asynchronies, SOA): 0 (simultaneous), 66, 100, 133, and 250 ms.
  
  
  RESULTS
  Migraineurs with aura performed worse in all tests than migraineurs without aura and controls. Both migraine groups performed poorer than controls at discriminating shapes without masks. Typical masking functions were obtained from all groups, but they were steeper for migraineurs than controls with thresholds raised most dramatically (2.1 and 4.4 times for migraineurs without and with aura relative to controls, respectively) at SOAs where masks had their most detrimental effect (66-100 ms). Modeling the effect of masking showed that raised internal noise alone is insufficient to explain these deficits. Rather, an abnormal nonlinear transducer function (e.g., as part of gain-control) together with increased multiplicative noise is required to capture the data.
  
  
  CONCLUSIONS
  The findings are consistent with an extrastriate deficit in migraine that cannot be explained completely by defective inhibition.
authors: Department of Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom.
authors: Doreen
authors: D
authors: Wagner
authors: Velitchko
authors: V
authors: Manahilov
authors: Gael E
authors: GE
authors: Gordon
authors: Gunter
authors: G
authors: Loffler
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D020325:Migraine with Aura / Q000503:physiopathology*; D008959:Models, Neurological; D017711:Nonlinear Dynamics; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*; D055815:Young Adult