title: Tickling the retina: integration of subthreshold electrical pulses can activate retinal neurons.
abstract: The field of retinal prosthetics has made major progress over the last decade, restoring visual percepts to people suffering from retinitis pigmentosa. The stimulation pulses used by present implants are suprathreshold, meaning individual pulses are designed to activate the retina. In this paper we explore subthreshold pulse sequences as an alternate stimulation paradigm. Subthreshold pulses have the potential to address important open problems such as fading of visual percepts when patients are stimulated at moderate pulse repetition rates and the difficulty in preferentially stimulating different retinal pathways.
  
  
  
  As a first step in addressing these issues we used Gaussian white noise electrical stimulation combined with spike-triggered averaging to interrogate whether a subthreshold sequence of pulses can be used to activate the mouse retina.
  
  
  
  We demonstrate that the retinal network can integrate multiple subthreshold electrical stimuli under an experimental paradigm immediately relevant to retinal prostheses. Furthermore, these characteristic stimulus sequences varied in their shape and integration window length across the population of retinal ganglion cells.
  
  
  
  Because the subthreshold sequences activate the retina at stimulation rates that would typically induce strong fading (25 Hz), such retinal 'tickling' has the potential to minimize the fading problem. Furthermore, the diversity found across the cell population in characteristic pulse sequences suggests that these sequences could be used to selectively address the different retinal pathways (e.g. ON versus OFF). Both of these outcomes may significantly improve visual perception in retinal implant patients.
authors.affiliation: Institute for Ophthalmic Research, Eberhard Karls University, D-72076 Tübingen, Germany. Werner Reichardt Centre for Integrative Neuroscience (CIN), D-72076 Tübingen, Germany. Graduate Training Center of Neuroscience/International Max Planck Research School, D-72074 Tübingen, Germany. Bernstein Center for Computational Neuroscience Tübingen, D-72076 Tübingen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Sekhar
authors.forename: A
authors.initials: A
authors.lastname: Jalligampala
authors.forename: E
authors.initials: E
authors.lastname: Zrenner
authors.forename: D L
authors.initials: DL
authors.lastname: Rathbun
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D051379:Mice; D008810:Mice, Inbred C57BL; D008839:Microelectrodes; D009434:Neural Pathways / Q000502:physiology; D011474:Prosthesis Design; D012160:Retina; D012165:Retinal Ganglion Cells; D055351:Retinal Neurons / Q000502:physiology*; D057488:Visual Prosthesis