title: Successful tactile based visual sensory substitution use functions independently of visual pathway integrity.
abstract: OBJECTIVE
  Neuronal reorganization after blindness is of critical interest because it has implications for the rational prescription of artificial vision devices. The purpose of this study was to distinguish the microstructural differences between perinatally blind (PB), acquired blind (AB), and normally sighted controls (SCs) and relate these differences to performance on functional tasks using a sensory substitution device (BrainPort).
  
  
  METHODS
  We enrolled 52 subjects (PB n = 11; AB n = 35; SC n = 6). All subjects spent 15 h undergoing BrainPort device training. Outcomes of light perception, motion, direction, temporal resolution, grating, and acuity were tested at baseline and after training. Twenty-six of the subjects were scanned with a three Tesla MRI scanner for diffusion tensor imaging (DTI), and with a positron emission tomography (PET) scanner for mapping regional brain glucose consumption during sensory substitution function. Non-parametric models were used to analyze fractional anisotropy (FA; a DTI measure of microstructural integrity) of the brain via region-of-interest (ROI) analysis and tract-based spatial statistics (TBSS).
  
  
  RESULTS
  At baseline, all subjects performed all tasks at chance level. After training, light perception, time resolution, location and grating acuity tasks improved significantly for all subject groups. ROI and TBSS analyses of FA maps show areas of statistically significant differences (p ≤ 0.025) in the bilateral optic radiations and some visual association connections between all three groups. No relationship was found between FA and functional performance with the BrainPort.
  
  
  CONCLUSIONS
  All subjects showed performance improvements using the BrainPort irrespective of nature and duration of blindness. Definite brain areas with significant microstructural integrity changes exist among PB, AB, and NC, and these variations are most pronounced in the visual pathways. However, the use of sensory substitution devices is feasible irrespective of microstructural integrity of the primary visual pathways between the eye and the brain. Therefore, tongue based devices devices may be usable for a broad array of non-sighted patients.
authors.affiliation: Department of Radiology, University of Pittsburgh Pittsburgh, PA, USA.
authors.forename: Vincent K
authors.initials: VK
authors.lastname: Lee
authors.affiliation: Sensory Substitution Laboratory, Department of Ophthalmology, Eye and Ear Institute, University of Pittsburgh Pittsburgh, PA, USA ; Department of Ophthalmology, University of Pittsburgh Medical Center Pittsburgh, PA, USA ; McGowan Institute for Regenerative Medicine, University of Pittsburgh Pittsburgh, PA, USA ; Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh Pittsburgh, PA, USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Nau
authors.affiliation: Department of Radiology, University of Pittsburgh Pittsburgh, PA, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Laymon
authors.affiliation: Department of Ophthalmology, University of Pittsburgh Medical Center Pittsburgh, PA, USA ; McGowan Institute for Regenerative Medicine, University of Pittsburgh Pittsburgh, PA, USA ; Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh Pittsburgh, PA, USA ; Department of Bioengineering, University of Pittsburgh Pittsburgh, PA, USA ; Center for the Neural Basis of Cognition, University of Pittsburgh-Carnegie Mellon University Pittsburgh, PA, USA.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Chan
authors.affiliation: Department of Radiology, University of Pittsburgh Pittsburgh, PA, USA.
authors.forename: Bedda L
authors.initials: BL
authors.lastname: Rosario
authors.affiliation: Sensory Substitution Laboratory, Department of Ophthalmology, Eye and Ear Institute, University of Pittsburgh Pittsburgh, PA, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Fisher
keywords: BrainPort; blindness; diffusion tensor imaging; fractional anisotropy; sensory substitution; visual pathways