title: Hippocampal-cortical interaction during periods of subcortical silence.
abstract: Hippocampal ripples, episodic high-frequency field-potential oscillations primarily occurring during sleep and calmness, have been described in mice, rats, rabbits, monkeys and humans, and so far they have been associated with retention of previously acquired awake experience. Although hippocampal ripples have been studied in detail using neurophysiological methods, the global effects of ripples on the entire brain remain elusive, primarily owing to a lack of methodologies permitting concurrent hippocampal recordings and whole-brain activity mapping. By combining electrophysiological recordings in hippocampus with ripple-triggered functional magnetic resonance imaging, here we show that most of the cerebral cortex is selectively activated during the ripples, whereas most diencephalic, midbrain and brainstem regions are strongly and consistently inhibited. Analysis of regional temporal response patterns indicates that thalamic activity suppression precedes the hippocampal population burst, which itself is temporally bounded by massive activations of association and primary cortical areas. These findings suggest that during off-line memory consolidation, synergistic thalamocortical activity may be orchestrating a privileged interaction state between hippocampus and cortex by silencing the output of subcortical centres involved in sensory processing or potentially mediating procedural learning. Such a mechanism would cause minimal interference, enabling consolidation of hippocampus-dependent memory.
authors.affiliation: Max Planck Institute for Biological Cybernetics, Spemannstraße 38, 72076 Tuebingen, Germany. Nikos.Logothetis@tuebingen.mpg.de
authors.forename: N K
authors.initials: NK
authors.lastname: Logothetis
authors.forename: O
authors.initials: O
authors.lastname: Eschenko
authors.forename: Y
authors.initials: Y
authors.lastname: Murayama
authors.forename: M
authors.initials: M
authors.lastname: Augath
authors.forename: T
authors.initials: T
authors.lastname: Steudel
authors.forename: H C
authors.initials: HC
authors.lastname: Evrard
authors.forename: M
authors.initials: M
authors.lastname: Besserve
authors.forename: A
authors.initials: A
authors.lastname: Oeltermann
mesh_terms: D000758:Anesthesia; D000818:Animals; D002540:Cerebral Cortex / Q000502:physiology*; D000882:Haplorhini / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008568:Memory / Q000502:physiology*; D008959:Models, Neurological; D009433:Neural Inhibition / Q000502:physiology*; D012146:Rest / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness