May 2005
Volume 46, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2005
How the Retinal Network Reacts to Epiretinal Stimulation to Form the Prosthetic Visual Input to the Cortex: Computational Modeling of a Normal Retina
Author Affiliations & Notes
  • S.D. Elfar
    Ophthalmology/Kresge Eye Inst, Wayne State Univ Sch of Med, Detroit, MI
  • N.P. Cottaris
    Ophthalmology/Kresge Eye Inst, Wayne State Univ Sch of Med, Detroit, MI
  • R. Iezzi
    Ophthalmology/Kresge Eye Inst, Wayne State Univ Sch of Med, Detroit, MI
  • G.W. Abrams
    Ophthalmology/Kresge Eye Inst, Wayne State Univ Sch of Med, Detroit, MI
  • Footnotes
    Commercial Relationships  S.D. Elfar, None; N.P. Cottaris, None; R. Iezzi, None; G.W. Abrams, None.
  • Footnotes
    Support  Ligon Research Center of Vision
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 5275. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      S.D. Elfar, N.P. Cottaris, R. Iezzi, G.W. Abrams; How the Retinal Network Reacts to Epiretinal Stimulation to Form the Prosthetic Visual Input to the Cortex: Computational Modeling of a Normal Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5275.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract
 
Abstract:
 

We examined how the normal, intact retinal network may interact with electrical epiretinal stimulation in shaping the spike trains of ON and OFF ganglion cells, and thus the synaptic input to first–stage cortical neurons. This information is crucial for interpreting results from experiments in which the efficacy of epiretinal stimulation is assessed in normally–sighted animals.

 

We developed a biophysical model of the retinal network that includes the basic retinal cell types and their interconnections, and first–stage visual cortex neurons (simple cells). Neurons were modeled as leaky integrators with added membrane and synaptic conductances. Epiretinal stimulation via a planar disk electrode was modeled. It was assumed that only cell bodies are stimulated by the extracellular potential gradient. Retinal output was assessed at the level of simple cells which receive convergent but opponent input from ON and OFF ganglion cells.

 

Our simulations of electrical stimulation of a fully–functional retina show that epiretinal stimulation alone causes an indiscriminate excitation of ON and OFF ganglion cells, resulting in a patchy input to the cortex with isolated regions of excitation amid regions of no net excitation. The retinal network progressively biases the excitation of ON relative to OFF ganglion cells, shaping the synaptic input to the cortex. These interactions gradually interpolate and focus the initially patchy synaptic input. Compared to results from simulations of a retina in an early phase of a degenerative disease, the normal retina exhibits spatiotemporally tighter, but otherwise similar, dynamics in response to electrical stimulation.

 

Neurophysiological experiments using sighted animals may be a valid approach to assess the effects of epiretinal stimulation in initial stages of retinal degeneration as long as the differences described above are taken into consideration. Currently, we are testing the model's predictions in vivo by recording the cortical activation patterns in response to electrical epiretinal stimulation.

 

 

 
Keywords: computational modeling • retinal connections, networks, circuitry • visual cortex 
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×