title: Top-down influence on the visual cortex of the blind during sensory substitution.
abstract: Visual sensory substitution devices provide a non-surgical and flexible approach to vision rehabilitation in the blind. These devices convert images taken by a camera into cross-modal sensory signals that are presented as a surrogate for direct visual input. While previous work has demonstrated that the visual cortex of blind subjects is recruited during sensory substitution, the cognitive basis of this activation remains incompletely understood. To test the hypothesis that top-down input provides a significant contribution to this activation, we performed functional MRI scanning in 11 blind (7 acquired and 4 congenital) and 11 sighted subjects under two conditions: passive listening of image-encoded soundscapes before sensory substitution training and active interpretation of the same auditory sensory substitution signals after a 10-minute training session. We found that the modulation of visual cortex activity due to active interpretation was significantly stronger in the blind over sighted subjects. In addition, congenitally blind subjects showed stronger task-induced modulation in the visual cortex than acquired blind subjects. In a parallel experiment, we scanned 18 blind (11 acquired and 7 congenital) and 18 sighted subjects at rest to investigate alterations in functional connectivity due to visual deprivation. The results demonstrated that visual cortex connectivity of the blind shifted away from sensory networks and toward known areas of top-down input. Taken together, our data support the model of the brain, including the visual system, as a highly flexible task-based and not sensory-based machine.
authors.affiliation: NeuroImaging Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; Sensory Substitution Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; UPMC Eye Center, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Louis J. Fox Center for Vision Restoration, University of Pittsburgh and UPMC, Pittsburgh, PA, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Murphy
authors.affiliation: Sensory Substitution Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; UPMC Eye Center, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh and UPMC, Pittsburgh, PA, USA; Louis J. Fox Center for Vision Restoration, University of Pittsburgh and UPMC, Pittsburgh, PA, USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Nau
authors.affiliation: Sensory Substitution Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; UPMC Eye Center, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Fisher
authors.affiliation: NeuroImaging Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh and UPMC, Pittsburgh, PA, USA; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, Pittsburgh, PA, USA; Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea; Department of Biological Sciences, Sungkyunkwan University, Suwon, Republic of Korea.
authors.forename: Seong-Gi
authors.initials: SG
authors.lastname: Kim
authors.affiliation: Sensory Substitution Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; UPMC Eye Center, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh and UPMC, Pittsburgh, PA, USA; Louis J. Fox Center for Vision Restoration, University of Pittsburgh and UPMC, Pittsburgh, PA, USA; Clinical and Translational Science Institute, University of Pittsburgh, Pittsburgh, PA, USA; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, Pittsburgh, PA, USA.
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
authors.affiliation: NeuroImaging Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; UPMC Eye Center, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh and UPMC, Pittsburgh, PA, USA; Louis J. Fox Center for Vision Restoration, University of Pittsburgh and UPMC, Pittsburgh, PA, USA; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, Pittsburgh, PA, USA. Electronic address: chuenwing.chan@fulbrightmail.org.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Chan
mesh_terms: D000293:Adolescent; D000328:Adult; D001766:Blindness / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: Blindness; Cross-modal neuroplasticity; Functional MRI; Sensory substitution; Top-down; Vision