title: Visual recovery in cortical blindness is limited by high internal noise.
abstract: Damage to the primary visual cortex typically causes cortical blindness (CB) in the hemifield contralateral to the damaged hemisphere. Recent evidence indicates that visual training can partially reverse CB at trained locations. Whereas training induces near-complete recovery of coarse direction and orientation discriminations, deficits in fine motion processing remain. Here, we systematically disentangle components of the perceptual inefficiencies present in CB fields before and after coarse direction discrimination training. In seven human CB subjects, we measured threshold versus noise functions before and after coarse direction discrimination training in the blind field and at corresponding intact field locations. Threshold versus noise functions were analyzed within the framework of the linear amplifier model and the perceptual template model. Linear amplifier model analysis identified internal noise as a key factor differentiating motion processing across the tested areas, with visual training reducing internal noise in the blind field. Differences in internal noise also explained residual perceptual deficits at retrained locations. These findings were confirmed with perceptual template model analysis, which further revealed that the major residual deficits between retrained and intact field locations could be explained by differences in internal additive noise. There were no significant differences in multiplicative noise or the ability to process external noise. Together, these results highlight the critical role of altered internal noise processing in mediating training-induced visual recovery in CB fields, and may explain residual perceptual deficits relative to intact regions of the visual field.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Cavanaugh
authors.forename: Ruyuan
authors.initials: R
authors.lastname: Zhang
authors.forename: Michael D
authors.initials: MD
authors.lastname: Melnick
authors.forename: Anasuya
authors.initials: A
authors.lastname: Das
authors.forename: Mariel
authors.initials: M
authors.lastname: Roberts
authors.forename: Duje
authors.initials: D
authors.lastname: Tadin
authors.forename: Marisa
authors.initials: M
authors.lastname: Carrasco
authors.forename: Krystel R
authors.initials: KR
authors.lastname: Huxlin
mesh_terms: D000328:Adult; D016477:Artifacts; D019575:Blindness, Cortical / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D020127:Recovery of Function / Q000502:physiology*; D014793:Visual Cortex / Q000503:physiopathology*; D014794:Visual Fields / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*