title: Ion diffusion may introduce spurious current sources in current-source density (CSD) analysis.
abstract: Current-source density (CSD) analysis is a well-established method for analyzing recorded local field potentials (LFPs), that is, the low-frequency part of extracellular potentials. Standard CSD theory is based on the assumption that all extracellular currents are purely ohmic, and thus neglects the possible impact from ionic diffusion on recorded potentials. However, it has previously been shown that in physiological conditions with large ion-concentration gradients, diffusive currents can evoke slow shifts in extracellular potentials. Using computer simulations, we here show that diffusion-evoked potential shifts can introduce errors in standard CSD analysis, and can lead to prediction of spurious current sources. Further, we here show that the diffusion-evoked prediction errors can be removed by using an improved CSD estimator which accounts for concentration-dependent effects.NEW & NOTEWORTHYStandard CSD analysis does not account for ionic diffusion. Using biophysically realistic computer simulations, we show that unaccounted-for diffusive currents can lead to the prediction of spurious current sources. This finding may be of strong interest for in vivo electrophysiologists doing extracellular recordings in general, and CSD analysis in particular.
authors.affiliation: Faculty for Science and Technology, Norwegian University of Life Sciences, Ås, Norway; geir.halnes@nmbu.no.
authors.forename: Geir
authors.initials: G
authors.lastname: Halnes
authors.affiliation: NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Tuomo
authors.initials: T
authors.lastname: Mäki-Marttunen
authors.affiliation: Letten Centre and GliaLab, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway; and.
authors.forename: Klas H
authors.initials: KH
authors.lastname: Pettersen
authors.affiliation: NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Ole A
authors.initials: OA
authors.lastname: Andreassen
authors.affiliation: Faculty for Science and Technology, Norwegian University of Life Sciences, Ås, Norway.|Department of Physics, University of Oslo, Oslo, Norway.
authors.forename: Gaute T
authors.identifier: 0000-0002-5425-5012
authors.initials: GT
authors.lastname: Einevoll
mesh_terms: D000200:Action Potentials; D000818:Animals; D000838:Anions / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D003198:Computer Simulation; D004058:Diffusion; D005110:Extracellular Space / Q000737:chemistry; D006801:Humans; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods* / Q000592:standards
chemical_list: D000838:Anions; D002412:Cations
keywords: current source density; electrodiffusion; extracellular potential; ion diffusion