title: A simulation of current focusing and steering with penetrating optic nerve electrodes.
abstract: OBJECTIVE
  Current focusing and steering are both widely used to shape the electric field and increase the number of distinct perceptual channels in neural stimulation, yet neither technique has been used for an optic nerve (ON)-based visual prosthesis. In order to evaluate the effects of current focusing and steering in penetrative stimulation, we built an integrated computational model to simulate and investigate the influence of stimulating parameters on ON fibre recruitment.
  
  
  METHODS
  Finite element models with extremely fine meshes were first established to compute the 3D electric potential distribution under different stimulating parameters. Then the external electric potential was fed to randomized multi-compartment cable models to predict the distribution of fibres generating an action potential. Finally a statistical process was conducted to quantify the recruitment region.
  
  
  RESULTS
  The simulation results show that a two-electrode mode is superior to a three-electrode mode in current steering. The three-electrode mode performs poorly in current focusing, albeit the localized recruitment from both configurations implies that current focusing might be unnecessary in penetrative ON stimulation.
  
  
  CONCLUSIONS
  This study provides useful information for the optimized design of penetrating ON electrodes and stimulating strategies. The Monte Carlo style computation paradigm is designed to simulate neural responses of an ensemble of ON fibres, which can be immediately transferred to other similar problems.
authors.affiliation: Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, People's Republic of China. School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
authors.forename: Menghui
authors.initials: M
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.forename: Qixin
authors.initials: Q
authors.lastname: Wang
authors.forename: Honghong
authors.initials: H
authors.lastname: Zhao
authors.forename: Xinyu
authors.initials: X
authors.lastname: Chai
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Sui
authors.forename: Qiushi
authors.initials: Q
authors.lastname: Ren
authors.forename: Liming
authors.initials: L
authors.lastname: Li
mesh_terms: D000818:Animals; D004567:Electrodes, Implanted / Q000639:trends*; D008954:Models, Biological; D009010:Monte Carlo Method; D009900:Optic Nerve / Q000502:physiology*; D011817:Rabbits; D011897:Random Allocation; D057488:Visual Prosthesis / Q000639:trends*