title: Hippocampal CA2 activity patterns change over time to a larger extent than between spatial contexts.
abstract: The hippocampal CA2 subregion has a different anatomical connectivity pattern within the entorhino-hippocampal circuit than either the CA1 or CA3 subregion. Yet major differences in the neuronal activity patterns of CA2 compared with the other CA subregions have not been reported. We show that standard spatial and temporal firing patterns of individual hippocampal principal neurons in behaving rats, such as place fields, theta modulation, and phase precession, are also present in CA2, but that the CA2 subregion differs substantially from the other CA subregions in its population coding. CA2 ensembles do not show a persistent code for space or for differences in context. Rather, CA2 activity patterns become progressively dissimilar over time periods of hours to days. The weak coding for a particular context is consistent with recent behavioral evidence that CA2 circuits preferentially support social, emotional, and temporal rather than spatial aspects of memory.
authors.affiliation: Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Mankin
authors.affiliation: Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Diehl
authors.affiliation: Canadian Centre for Behavioural Neuroscience, Department of Neuroscience, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada.
authors.forename: Fraser T
authors.initials: FT
authors.lastname: Sparks
authors.affiliation: Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; Kavli Institute for Brain and Mind, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Leutgeb
authors.affiliation: Neurobiology Section and Center for Neural Circuits and Behavior, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA. Electronic address: jleutgeb@ucsd.edu.
authors.forename: Jill K
authors.initials: JK
authors.lastname: Leutgeb
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D056547:CA1 Region, Hippocampal / Q000502:physiology; D056651:CA2 Region, Hippocampal / Q000502:physiology*; D056654:CA3 Region, Hippocampal / Q000502:physiology; D004644:Emotions; D018728:Entorhinal Cortex / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology; D009474:Neurons; D051381:Rats; D013826:Theta Rhythm / Q000502:physiology; D013997:Time Factors