title: Excitation and inhibition compete to control spiking during hippocampal ripples: intracellular study in behaving mice.
abstract: High-frequency ripple oscillations, observed most prominently in the hippocampal CA1 pyramidal layer, are associated with memory consolidation. The cellular and network mechanisms underlying the generation of the rhythm and the recruitment of spikes from pyramidal neurons are still poorly understood. Using intracellular, sharp electrode recordings in freely moving, drug-free mice, we observed consistent large depolarizations in CA1 pyramidal cells during sharp wave ripples, which are associated with ripple frequency fluctuation of the membrane potential ("intracellular ripple"). Despite consistent depolarization, often exceeding pre-ripple spike threshold values, current pulse-induced spikes were strongly suppressed, indicating that spiking was under the control of concurrent shunting inhibition. Ripple events were followed by a prominent afterhyperpolarization and spike suppression. Action potentials during and outside ripples were orthodromic, arguing against ectopic spike generation, which has been postulated by computational models of ripple generation. These findings indicate that dendritic excitation of pyramidal neurons during ripples is countered by shunting of the membrane and postripple silence is mediated by hyperpolarizing inhibition.
authors.affiliation: NYU Neuroscience Institute, School of Medicine, and.
authors.forename: Daniel F
authors.identifier: http://orcid.org/0000-0003-2284-870X
authors.initials: DF
authors.lastname: English
authors.affiliation: NYU Neuroscience Institute, School of Medicine, and.
authors.forename: Adrien
authors.initials: A
authors.lastname: Peyrache
authors.affiliation: NYU Neuroscience Institute, School of Medicine, and.
authors.forename: Eran
authors.initials: E
authors.lastname: Stark
authors.affiliation: NYU Neuroscience Institute, School of Medicine, and.
authors.forename: Lisa
authors.initials: L
authors.lastname: Roux
authors.affiliation: NYU Neuroscience Institute, School of Medicine, and.
authors.forename: Daniela
authors.identifier: http://orcid.org/0000-0002-7518-0566
authors.initials: D
authors.lastname: Vallentin
authors.affiliation: NYU Neuroscience Institute, School of Medicine, and Center for Neural Science, New York University, New York, New York 10016.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Long
authors.affiliation: NYU Neuroscience Institute, School of Medicine, and Center for Neural Science, New York University, New York, New York 10016 gyorgy.buzsaki@nyumc.org.
authors.forename: György
authors.identifier: http://orcid.org/0000-0002-3100-4800
authors.initials: G
authors.lastname: Buzsáki
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D058256:Brain Waves / Q000502:physiology; D056547:CA1 Region, Hippocampal / Q000166:cytology* / Q000502:physiology; D008297:Male; D051379:Mice; D008991:Monitoring, Physiologic; D009433:Neural Inhibition / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology*
keywords: action potential threshold; hippocampus; inhibition; intracellular in vivo recording; oscillations; sharp wave ripples