title: Upper threshold of extracellular neural stimulation.
abstract: It is well known that spiking neurons can produce action potentials in response to extracellular stimulation above certain threshold. It is widely assumed that there is no upper limit to somatic stimulation, except for cellular or electrode damage. Here we demonstrate that there is an upper stimulation threshold, above which no action potential can be elicited, and it is below the threshold of cellular damage. Existence of this upper stimulation threshold was confirmed in retinal ganglion cells (RGCs) at pulse durations ranging from 5 to 500 μs. The ratio of the upper to lower stimulation thresholds varied typically from 1.7 to 7.6, depending on pulse duration. Computational modeling of extracellular RGC stimulation explained the upper limit by sodium current reversal on the depolarized side of the cell membrane. This was further confirmed by experiments in the medium with a low concentration of sodium. The limited width of the stimulation window may have important implications in design of the electro-neural interfaces, including neural prosthetics.
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA. boinagrov@gmail.com
authors.forename: David
authors.initials: D
authors.lastname: Boinagrov
authors.forename: Susanne
authors.initials: S
authors.lastname: Pangratz-Fuehrer
authors.forename: Bongsoo
authors.initials: B
authors.lastname: Suh
authors.forename: Keith
authors.initials: K
authors.lastname: Mathieson
authors.forename: Natasha
authors.initials: N
authors.lastname: Naik
authors.forename: Daniel
authors.initials: D
authors.lastname: Palanker
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D045604:Extracellular Fluid / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D012165:Retinal Ganglion Cells / Q000502:physiology