title: Intracellular Impedance Measurements Reveal Non-ohmic Properties of the Extracellular Medium around Neurons.
abstract: Determining the electrical properties of the extracellular space around neurons is important for understanding the genesis of extracellular potentials, as well as for localizing neuronal activity from extracellular recordings. However, the exact nature of these extracellular properties is still uncertain. Here, we introduce a method to measure the impedance of the tissue, one that preserves the intact cell-medium interface using whole-cell patch-clamp recordings in vivo and in vitro. We find that neural tissue has marked non-ohmic and frequency-filtering properties, which are not consistent with a resistive (ohmic) medium, as often assumed. The amplitude and phase profiles of the measured impedance are consistent with the contribution of ionic diffusion. We also show that the impact of such frequency-filtering properties is possibly important on the genesis of local field potentials, as well as on the cable properties of neurons. These results show non-ohmic properties of the extracellular medium around neurons, and suggest that source estimation methods, as well as the cable properties of neurons, which all assume ohmic extracellular medium, may need to be reevaluated.
authors.affiliation: Unité de Neurosciences, Information et Complexité, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Gomes
authors.affiliation: Unité de Neurosciences, Information et Complexité, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Bédard
authors.affiliation: Centre Interdisciplinaire de Recherche en Biologie, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Collège de France, Paris, France.
authors.forename: Silvana
authors.initials: S
authors.lastname: Valtcheva
authors.affiliation: Institut du Cerveau et de la Moelle Epinière, Centre National de la Recherche Scientifique UMR 7225, Institut National de la Santé et de la Recherche Médicale UMRS 975, Hôpital de la Salpétrière, Université Pierre et Marie Curie, Paris, France.
authors.forename: Matthew
authors.initials: M
authors.lastname: Nelson
authors.affiliation: Unité de Neurosciences, Information et Complexité, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
authors.forename: Vitalia
authors.initials: V
authors.lastname: Khokhlova
authors.affiliation: Institut du Cerveau et de la Moelle Epinière, Centre National de la Recherche Scientifique UMR 7225, Institut National de la Santé et de la Recherche Médicale UMRS 975, Hôpital de la Salpétrière, Université Pierre et Marie Curie, Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Pouget
authors.affiliation: Centre Interdisciplinaire de Recherche en Biologie, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Collège de France, Paris, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Venance
authors.affiliation: Unité de Neurosciences, Information et Complexité, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Bal
authors.affiliation: Unité de Neurosciences, Information et Complexité, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France. Electronic address: destexhe@unic.cnrs-gif.fr.
authors.forename: Alain
authors.initials: A
authors.lastname: Destexhe
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology; D017097:Electric Impedance; D005110:Extracellular Space / Q000378:metabolism*; D042541:Intracellular Space / Q000378:metabolism*; D051379:Mice; D008959:Models, Neurological; D009474:Neurons / Q000166:cytology*; D051381:Rats