title: Changes in ganglion cell physiology during retinal degeneration influence excitability by prosthetic electrodes.
abstract: OBJECTIVE
  Here we investigate ganglion cell physiology in healthy and degenerating retina to test its influence on threshold to electrical stimulation.
  
  
  METHODS
  Age-related Macular Degeneration and Retinitis Pigmentosa cause blindness via outer retinal degeneration. Inner retinal pathways that transmit visual information to the central brain remain intact, so direct electrical stimulation from prosthetic devices offers the possibility for visual restoration. Since inner retinal physiology changes during degeneration, we characterize physiological properties and responses to electrical stimulation in retinal ganglion cells (RGCs) of both wild type mice and the rd10 mouse model of retinal degeneration.
  
  
  RESULTS
  Our aggregate results support previous observations that elevated thresholds characterize diseased retinas. However, a physiology-driven classification scheme reveals distinct sub-populations of ganglion cells with thresholds either normal or strongly elevated compared to wild-type. When these populations are combined, only a weakly elevated threshold with large variance is observed. The cells with normal threshold are more depolarized at rest and exhibit periodic oscillations.
  
  
  CONCLUSIONS
  During degeneration, physiological changes in RGCs affect the threshold stimulation currents required to evoke action potentials.
authors.affiliation: Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: Alice
authors.initials: A
authors.lastname: Cho
authors.forename: Charles
authors.initials: C
authors.lastname: Ratliff
authors.forename: Alapakkam
authors.initials: A
authors.lastname: Sampath
authors.forename: James
authors.initials: J
authors.lastname: Weiland
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D004566:Electrodes; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D058117:Neural Prostheses; D012162:Retinal Degeneration / Q000235:genetics / Q000503:physiopathology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D057488:Visual Prosthesis