title: Cortical representations are reinstated by the hippocampus during memory retrieval.
abstract: The hippocampus is assumed to retrieve memory by reinstating patterns of cortical activity that were observed during learning. To test this idea, we monitored the activity of individual cortical neurons while simultaneously inactivating the hippocampus. Neurons that were active during context fear conditioning were tagged with the long-lasting fluorescent protein H2B-GFP and the light-activated proton pump ArchT. These proteins allowed us to identify encoding neurons several days after learning and silence them with laser stimulation. When tagged CA1 cells were silenced, we found that memory retrieval was impaired and representations in the cortex (entorhinal, retrosplenial, perirhinal) and the amygdala could not be reactivated. Importantly, hippocampal inactivation did not alter the total amount of activity in most brain regions. Instead, it selectively prevented neurons that were active during learning from being reactivated during retrieval. These data provide functional evidence that the hippocampus reactivates specific memory representations during retrieval.
authors.affiliation: Department of Psychology, UC Davis, Davis, CA 95618, USA; Center for Neuroscience, UC Davis, Davis, CA 95618, USA.
authors.forename: Kazumasa Z
authors.initials: KZ
authors.lastname: Tanaka
authors.affiliation: Center for Neuroscience, UC Davis, Davis, CA 95618, USA.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Pevzner
authors.affiliation: Center for Neuroscience, UC Davis, Davis, CA 95618, USA.
authors.forename: Anahita B
authors.initials: AB
authors.lastname: Hamidi
authors.affiliation: Center for Neuroscience, UC Davis, Davis, CA 95618, USA.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakazawa
authors.affiliation: Center for Neuroscience, UC Davis, Davis, CA 95618, USA.
authors.forename: Jalina
authors.initials: J
authors.lastname: Graham
authors.affiliation: Department of Psychology, UC Davis, Davis, CA 95618, USA; Center for Neuroscience, UC Davis, Davis, CA 95618, USA. Electronic address: bjwiltgen@ucdavis.edu.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Wiltgen
mesh_terms: D000679:Amygdala / Q000378:metabolism; D000818:Animals; D003213:Conditioning, Psychological / Q000502:physiology; D005239:Fear / Q000502:physiology; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology; D007858:Learning / Q000502:physiology*; D008568:Memory / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000378:metabolism*