title: Lateral geniculate body evoked potentials elicited by visual and electrical stimulation.
abstract: OBJECTIVE
  Blind individuals who have photoreceptor loss are known to perceive phosphenes with electrical stimulation of their remaining retinal ganglion cells. We proposed that implantable lateral geniculate body (LGB) stimulus electrode arrays could be used to generate phosphene vision. We attempted to refine the basic reference of the electrical evoked potentials (EEPs) elicited by microelectrical stimulations of the optic nerve, optic tract and LGB of a domestic pig, and then compared it to visual evoked potentials (VEPs) elicited by short-flash stimuli.
  
  
  METHODS
  For visual function measurement, VEPs in response to short-flash stimuli on the left eye of the domestic pig were assessed over the visual cortex at position Oz with the reference electrode at Fz. After anesthesia, linearly configured platinum wire electrodes were inserted into the optic nerve, optic track and LGB. To determine the optimal stimulus current, EEPs were recorded repeatedly with controlling the pulse and power. The threshold of current and charge density to elicit EEPs at 0.3 ms pulse duration was about ±10 µA.
  
  
  RESULTS
  Our experimental results showed that visual cortex activity can be effectively evoked by stimulation of the optic nerve, optic tract and LGB using penetrating electrodes. The latency of P1 was more shortened as the electrical stimulation was closer to LGB. The EEPs of two-channel in the visual cortex demonstrated a similar pattern with stimulation of different spots of the stimulating electrodes. We found that the LGB-stimulated EEP pattern was very similar to the simultaneously generated VEP on the control side, although implicit time deferred.
  
  
  CONCLUSIONS
  EEPs and VEPs derived from visual-system stimulation were compared. The LGB-stimulated EEP wave demonstrated a similar pattern to the VEP waveform except implicit time, indicating prosthetic-based electrical stimulation of the LGB could be utilized for the blind to perceive vision of phosphenes.
authors.affiliation: Department of Ophthalmology, Wonkwang University Hospital, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Chang Wook
authors.initials: CW
authors.lastname: Choi
authors.affiliation: Department of Ophthalmology, Wonkwang University Hospital, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Pan Sang
authors.initials: PS
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Wonkwang University Hospital, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Sun Ae
authors.initials: SA
authors.lastname: Shin
authors.affiliation: Hanson Institute, University of Adelaide, Adelaide, Australia.
authors.forename: Ji Yeon
authors.initials: JY
authors.lastname: Yang
authors.affiliation: Department of Ophthalmology, Wonkwang University Hospital, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Yun Sik
authors.initials: YS
authors.lastname: Yang
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005829:Geniculate Bodies / Q000502:physiology*; D008297:Male; D009900:Optic Nerve / Q000502:physiology; D065866:Optic Tract / Q000502:physiology; D010775:Photic Stimulation; D034421:Sus scrofa; D014793:Visual Cortex / Q000502:physiology*
keywords: Electrical evoked potentials; Geniculate bodies; Visual evoked potentials