title: Fast Gamma Rhythms in the Hippocampus Promote Encoding of Novel Object-Place Pairings.
abstract: Hippocampal gamma rhythms increase during mnemonic operations (Johnson and Redish, 2007; Montgomery and Buzsáki, 2007; Sederberg et al., 2007; Jutras et al., 2009; Trimper et al., 2014) and may affect memory encoding by coordinating activity of neurons that code related information (Jensen and Lisman, 2005). Here, a hippocampal-dependent, object-place association task (Clark et al., 2000; Broadbent et al., 2004; Eacott and Norman, 2004; Lee et al., 2005; Winters et al., 2008; Barker and Warburton, 2011) was used in rats to investigate how slow and fast gamma rhythms in the hippocampus relate to encoding of memories for novel object-place associations. In novel object tasks, the degree of hippocampal dependence has been reported to vary depending on the type of novelty (Eichenbaum et al., 2007; Winters et al., 2008). Therefore, gamma activity was examined during three novelty conditions: a novel object presented in a location where a familiar object had been (NO), a familiar object presented in a location where no object had been (NL), and a novel object presented in a location where no object had been (NO+NL). The strongest and most consistent effects were observed for fast gamma rhythms during the NO+NL condition. Fast gamma power, CA3-CA1 phase synchrony, and phase-locking of place cell spikes increased during exploration of novel, compared to familiar, object-place associations. Additionally, place cell spiking during exploration of novel object-place pairings was increased when fast gamma rhythms were present. These results suggest that fast gamma rhythms promote encoding of memories for novel object-place associations.
authors.affiliation: Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712-0805; Department of Neuroscience, University of Texas at Austin, Austin, Texas 78712-0805.
authors.forename: Chenguang
authors.identifier: 0000-0002-4782-8732
authors.initials: C
authors.lastname: Zheng
authors.affiliation: Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712-0805; Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712-0805.
authors.forename: Kevin Wood
authors.initials: KW
authors.lastname: Bieri
authors.affiliation: Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712-0805; Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712-0805.
authors.forename: Ernie
authors.initials: E
authors.lastname: Hwaun
authors.affiliation: Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712-0805; Department of Neuroscience, University of Texas at Austin, Austin, Texas 78712-0805; Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712-0805.
authors.forename: Laura Lee
authors.initials: LL
authors.lastname: Colgin
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology; D005106:Exploratory Behavior; D065818:Gamma Rhythm / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology; D008124:Locomotion / Q000502:physiology; D008297:Male; D009415:Nerve Net / Q000502:physiology; D000071037:Place Cells / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D021641:Recognition, Psychology / Q000502:physiology*; D013057:Spectrum Analysis
keywords: CA1; gamma oscillations; gamma rhythms; hippocampus; memory; place cells