title: Effect of planar microelectrode geometry on neuron stimulation: finite element modeling and experimental validation of the efficient electrode shape.
abstract: BACKGROUND
  Microelectrode arrays have been used successfully for neuronal stimulation both in vivo and in vitro. However, in most instances currents required to activate the neurons have been in un-physiological ranges resulting in neuronal damage and cell death. There is a need to develop electrodes which require less stimulation current for neuronal activation with physiologically relevant efficacy and frequencies.
  
  
  METHODS
  The objective of the present study was to examine and compare the stimulation efficiency of different electrode geometries at the resolution of a single neuron. We hypothesized that increasing the electrode perimeter will increase the maximum current density at the edges and enhance stimulation efficiency. To test this postulate, the neuronal stimulation efficacy of common circular electrodes (smallest perimeter) was compared with star (medium perimeter), and spiral (largest perimeter with internal boundaries) electrodes. We explored and compared using both a finite element model and in vitro stimulation of neurons isolated from Lymnaea central ganglia.
  
  
  RESULTS
  Interestingly, both the computational model and the live neuronal stimulation experiments demonstrated that the common circular microelectrode requires less stimulus to activate a cell compared to the other two electrode shapes with the same surface area. Our data further revealed that circular electrodes exhibit the largest sealing resistance, stimulus transfer, and average current density among the three types of electrodes tested.
  
  
  METHODS
  Average current density and not the maximum current density at the edges plays an important role in determining the electrode stimulation efficiency.
  
  
  CONCLUSIONS
  Circular shaped electrodes are more efficient in inducing a change in neuronal membrane potential.
authors.affiliation: Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Atefeh
authors.initials: A
authors.lastname: Ghazavi
authors.affiliation: Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Westwick
authors.affiliation: Department of Anatomy and Cell Biology, The Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Fenglian
authors.initials: F
authors.lastname: Xu
authors.affiliation: Department of Anatomy and Cell Biology, The Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Wijdenes
authors.affiliation: Department of Anatomy and Cell Biology, The Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Naweed
authors.initials: N
authors.lastname: Syed
authors.affiliation: Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada. Electronic address: cdalton@ucalgary.ca.
authors.forename: Colin
authors.initials: C
authors.lastname: Dalton
mesh_terms: D000818:Animals; D003198:Computer Simulation; D004558:Electric Stimulation / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D020342:Finite Element Analysis; D017952:Ganglia, Invertebrate / Q000502:physiology; D008195:Lymnaea; D008564:Membrane Potentials / Q000502:physiology; D008839:Microelectrodes; D008962:Models, Theoretical; D009474:Neurons / Q000502:physiology*
keywords: Electrode geometry; Finite element model; Lymnaea neurons; Neuro-electronics; Neuron stimulation; Neuron–electrode interface