title: Diversity of sharp-wave-ripple LFP signatures reveals differentiated brain-wide dynamical events.
abstract: Sharp-wave-ripple (SPW-R) complexes are believed to mediate memory reactivation, transfer, and consolidation. However, their underlying neuronal dynamics at multiple scales remains poorly understood. Using concurrent hippocampal local field potential (LFP) recordings and functional MRI (fMRI), we study local changes in neuronal activity during SPW-R episodes and their brain-wide correlates. Analysis of the temporal alignment between SPW and ripple components reveals well-differentiated SPW-R subtypes in the CA1 LFP. SPW-R-triggered fMRI maps show that ripples aligned to the positive peak of their SPWs have enhanced neocortical metabolic up-regulation. In contrast, ripples occurring at the trough of their SPWs relate to weaker neocortical up-regulation and absent subcortical down-regulation, indicating differentiated involvement of neuromodulatory pathways in the ripple phenomenon mediated by long-range interactions. To our knowledge, this study provides the first evidence for the existence of SPW-R subtypes with differentiated CA1 activity and metabolic correlates in related brain areas, possibly serving different memory functions.
authors.affiliation: Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany; Graduate School of Neural and Behavioral Sciences, International Max Planck Research School, Eberhard-Karls University of Tübingen, 72074 Tübingen, Germany;
authors.forename: Juan F
authors.initials: JF
authors.lastname: Ramirez-Villegas
authors.affiliation: Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany; Centre for Imaging Sciences, Biomedical Imaging Institute, The University of Manchester, Manchester M13 9PT, United Kingdom; michel.besserve@tuebingen.mpg.de nikos.logothetis@tuebingen.mpg.de.
authors.forename: Nikos K
authors.initials: NK
authors.lastname: Logothetis
authors.affiliation: Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany; Department of Empirical Inference, Max Planck Institute for Intelligent Systems, 72076 Tübingen, Germany michel.besserve@tuebingen.mpg.de nikos.logothetis@tuebingen.mpg.de.
authors.forename: Michel
authors.initials: M
authors.lastname: Besserve
mesh_terms: D000818:Animals; D058256:Brain Waves / Q000502:physiology*; D056547:CA1 Region, Hippocampal / Q000000981:diagnostic imaging / Q000502:physiology; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D008568:Memory / Q000502:physiology*; D019579:Neocortex / Q000000981:diagnostic imaging / Q000502:physiology; D011859:Radiography
keywords: fMRI; hippocampus; in vivo electrophysiology; local field potential; memory