Gamma Oscillations in Rat Hippocampal Subregions Dentate Gyrus, CA3, CA1, and Subiculum Underlie Associative Memory Encoding

• Type of Material: Article
• Authors: John B. Trimper, Emory University; Claire R. Galloway, Emory University; Andrew C. Jones, Emory University; Kaavya Mandi, Emory University; Joseph Manns, Emory University
• Language: English
• Date: 2017-11-28
• Publisher: Elsevier (Cell Press): OAJ
• Publication Version: Final Published Version
• Copyright Statement: © 2017 The Author(s)
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.celrep.2017.10.123
• Title of Journal or Parent Work: Cell Reports
• ISSN: 2211-1247
• Volume: 21
• Issue: 9
• Start Page: 2419
• End Page: 2432
• Grant/Funding Information: This work was supported in part by NIH F31 grant MH102956 to J.B.T.
• Keywords: Electrophysiology; Object; Memory; Hippocampus; Synchrony
• Research Categories: Psychology, Behavioral; Biology, Neuroscience

Abstract

Neuronal oscillations in the rat hippocampus relate to both memory and locomotion, raising the question of how these cognitive and behavioral correlates interact to determine the oscillatory network state of this region. Here, rats freely locomoted while performing an object-location task designed to test hippocampus-dependent spatial associative memory. Rhythmic activity in theta, beta, slow gamma, and fast gamma frequency ranges were observed in both action potentials and local field potentials (LFPs) across four main hippocampal subregions. Several patterns of LFP oscillations corresponded to overt behavior (e.g., increased dentate gyrus-CA3 beta coherence during stationary moments and CA1-subiculum theta coherence during locomotion). In comparison, slow gamma (~40 Hz) oscillations throughout the hippocampus related most specifically to object-location associative memory encoding rather than overt behavior. The results help to untangle how hippocampal oscillations relate to both memory and motion, and single out slow gamma oscillations as a distinguishing correlate of spatial associative memory.