title: Behavioral measures of cortical hyperexcitability assessed in people who experience visual snow.
abstract: OBJECTIVE
  To determine whether visual perceptual measures in people who experience visual snow are consistent with an imbalance between inhibition and excitation in visual cortex.
  
  
  METHODS
  Sixteen patients with visual snow and 18 controls participated. Four visual tasks were included: center-surround contrast matching, luminance increment detection in noise, and global form and global motion coherence thresholds. Neuronal architecture capable of encoding the luminance and contrast stimuli is present within primary visual cortex, whereas the extraction of global motion and form signals requires extrastriate processing. All these tasks have been used previously to investigate the balance between inhibition and excitation within the visual system in both healthy and diseased states.
  
  
  RESULTS
  The visual snow group demonstrated reduced center-surround contrast suppression (p= 0.03) and elevated luminance increment thresholds in noise (p= 0.02). Groups did not differ on the global form or global motion task.
  
  
  CONCLUSIONS
  Our study demonstrates that visual perceptual measures involving the suprathreshold processing of contrast and luminance are abnormal in a group of individuals with visual snow. Our data are consistent with elevated excitability in primary visual cortex; however, further research is required to provide more direct evidence for this proposed mechanism. The ability to measure perceptual differences in visual snow reveals promise for the future development of clinical tests to assist in visual snow diagnosis and possibly a method for quantitatively assaying any benefits of treatments.
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia. allisonm@unimelb.edu.au.
authors.forename: Allison M
authors.initials: AM
authors.lastname: McKendrick
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia.
authors.forename: Yu Man
authors.initials: YM
authors.lastname: Chan
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia.
authors.forename: Melissa
authors.initials: M
authors.lastname: Tien
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia.
authors.forename: Lynette
authors.initials: L
authors.lastname: Millist
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia.
authors.forename: Meaghan
authors.initials: M
authors.lastname: Clough
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia.
authors.forename: Heather
authors.initials: H
authors.lastname: Mack
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia.
authors.forename: Joanne
authors.initials: J
authors.lastname: Fielding
authors.affiliation: From the Department of Optometry and Vision Sciences (A.M.M., Y.M.C.), the Department of Neurology, Royal Melbourne Hospital (M.T., L.M., M.C., J.F., O.B.W.), and the Faculty of Medicine, Dentistry and Health Sciences, and Department of Surgery (H.M.), The University of Melbourne; School of Psychological Sciences (M.C., J.F.), Monash Institute of Cognitive and Clinical Neurosciences, Monash University; and Department of Ophthalmology (H.M.), Royal Melbourne Hospital, Australia.
authors.forename: Owen B
authors.initials: OB
authors.lastname: White
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology; D010468:Perceptual Disorders / Q000473:pathology* / Q000503:physiopathology*; D010775:Photic Stimulation; D014793:Visual Cortex / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult