title: Deficits in local and global motion perception arising from abnormal eye movements.
abstract: Albino mammals exhibit a range of visual deficits including disrupted hemispheric pathways, an underdeveloped central retina, and nystagmus. Recently, it has been reported that albino animals also show deficits in the processing of visual motion, exhibiting higher motion coherence thresholds (MCTs; the proportion of coherently moving elements within a field of randomly moving distracters required to reliably report direction). Here we compare MCTs-collected from human observers with albinism-with an equivalent noise analysis of their fine-direction discrimination and report that their loss in motion sensitivity operates at both the level of local motion processing (of small objects) and at the later stage of global motion pooling. We also compare results from observers with aniridia (characterized by underdeveloped central retina and nystagmus but normal hemispheric visual pathways) and a rare group of observers with albinism who show no nystagmus. For the observers tested, nystagmus proved to be a common feature of individuals showing elevated MCTs. Since it is likely that motion perception is influenced by environmental factors early in development we postulate that the effect of congenital nystagmus on the temporal structure of the natural visual diet disrupts the ability of motion pathways to form normally.
authors.affiliation: Department of Visual Neuroscience, Institute of Ophthalmology, UCL, London, UK. Magella.Neveu@moorfields.nhs.uk
authors.forename: Magella M
authors.initials: MM
authors.lastname: Neveu
authors.forename: Glen
authors.initials: G
authors.lastname: Jeffery
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Moore
authors.forename: Steven C
authors.initials: SC
authors.lastname: Dakin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000417:Albinism / Q000503:physiopathology*; D015783:Aniridia / Q000503:physiopathology; D016477:Artifacts; D005074:Evoked Potentials, Visual / Q000502:physiology; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D020417:Nystagmus, Congenital / Q000503:physiopathology*; D009897:Optic Chiasm / Q000503:physiopathology*; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology; D014795:Visual Pathways / Q000503:physiopathology; D055815:Young Adult