title: Brain State Dependence of Hippocampal Subthreshold Activity in Awake Mice.
abstract: Monitoring the membrane potential of individual neurons has uncovered how single-cell properties contribute to network processing across different brain states in neocortex. In contrast, the subthreshold modulation of hippocampal neurons by brain state has not been systematically characterized. To address this, we combined whole-cell recordings from dentate granule cells and CA1 pyramidal neurons with multisite extracellular recordings and behavioral measurements in awake mice. We show that the average membrane potential, amplitude of subthreshold fluctuations, and distance to spike threshold are all modulated by brain state. Furthermore, even within individual states, rapid variations in arousal are reflected in membrane potential fluctuations. These factors produce depolarizing ramps in the membrane potential of hippocampal neurons that precede ripples and mirror transitions to a network regime conducive for ripple generation. These results suggest that there are coordinated shifts in the subthreshold dynamics of individual neurons that underlie the transitions between distinct modes of hippocampal processing.
authors.affiliation: Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, USA.
authors.forename: Brad K
authors.initials: BK
authors.lastname: Hulse
authors.affiliation: Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, USA.
authors.forename: Evgueniy V
authors.initials: EV
authors.lastname: Lubenov
authors.affiliation: Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, USA; Division of Engineering and Applied Science, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, USA; Computation and Neural Systems Program, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, USA. Electronic address: thanos@caltech.edu.
authors.forename: Athanassios G
authors.initials: AG
authors.lastname: Siapas
mesh_terms: D000818:Animals; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000502:physiology; D011680:Pupil / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*
keywords: arousal; brain state; hippocampus; large irregular activity; membrane potential; neuromodulation; ripples; sharp waves; small irregular activity; theta