Hippocampus

  • Article
    | Open Access

    The authors examine how we differentiate highly similar places from each other. They provide evidence for complementary neural mechanisms in the human hippocampus and prefrontal cortex involved in processing interfering and common elements important to remembering places that we have visited.

    • Li Zheng
    • , Zhiyao Gao
    •  & Arne D. Ekstrom
  • Article
    | Open Access

    The authors show that adult hippocampal neurogenesis is altered in the dentate gyrus of obese mice with subsequent inhibition of long-term potentiation and impairment of pattern separation. Inhibition of orexin-A action at orexin-1 receptors rescued both impairments in obese mice.

    • Nicola Forte
    • , Serena Boccella
    •  & Luigia Cristino
  • Article
    | Open Access

    Bilaterally projecting CA3 inputs may be crucial for integrating the left and right CA1 during memory but this has not been directly examined. Here, the authors show that projections from bilateral CA3 play a key role in the cross-hemispheric coordination of CA1 spatial coding.

    • Hefei Guan
    • , Steven J. Middleton
    •  & Thomas J. McHugh
  • Article
    | Open Access

    Memories are assumed to undergo a time-dependent systems consolidation, during which hippocampal contributions to memory decrease while neocortical contributions increase. Here, the authors show that noradrenergic arousal after encoding may reverse this course of systems consolidation in humans

    • Valentina Krenz
    • , Tobias Sommer
    •  & Lars Schwabe
  • Article
    | Open Access

    Male and female mice need to generate spatial maps that integrate vomeronasal signals of territory owners in the hippocampus-dependent memory. The authors show that vomeronasal information influences learning-related activity in the hippocampus via the amygdaloid PMCo, lateral entorhinal cortex, and dorsal CA1.

    • María Villafranca-Faus
    • , Manuel Esteban Vila-Martín
    •  & Vicent Teruel-Martí
  • Article
    | Open Access

    When two memories are similar, their encoding and retrieval can be disrupted by each other. Here the authors show that memory interference is resolved through abrupt remapping of activity patterns in the human hippocampal CA3 and dentate gyrus.

    • Guo Wanjia
    • , Serra E. Favila
    •  & Brice A. Kuhl
  • Article
    | Open Access

    Previous work has shown that in rodents phase precession – the phase of action potentials relative to the theta oscillation – is associated with the representation of sequential locations. Here the authors demonstrate that phase precession also occurs in the human hippocampus using single neuron and LFP recordings.

    • Leila Reddy
    • , Matthew W. Self
    •  & Pieter R. Roelfsema
  • Article
    | Open Access

    Hippocampal place cells contribute to navigation and memory formation. Here, the authors use in vivo glutamate imaging to reveal patterns of excitatory input received by place cell dendrites and find more spatially tuned and functionally organized inputs arriving in the place field.

    • Michael D. Adoff
    • , Jason R. Climer
    •  & Daniel A. Dombeck
  • Article
    | Open Access

    Here the authors compare place cell sequence coding during correct and error trials in a spatial memory task. Sequences coded paths that were longer and more temporally compressed during correct trials and developed a bias to replay paths to a goal location during rest periods of correct but not error trials.

    • Chenguang Zheng
    • , Ernie Hwaun
    •  & Laura Lee Colgin
  • Article
    | Open Access

    To understand how spatial representations emerge and evolve across hippocampal subfields, we compared trial-to-trial dynamics of place cells in CA1 and CA3 in new environments and across days. CA1 place fields form early, shift backwards and partially remap across days whereas in CA3 they develop gradually and are more stable, suggesting distinct functional roles in representing space.

    • Can Dong
    • , Antoine D. Madar
    •  & Mark E. J. Sheffield
  • Article
    | Open Access

    New microgrid recordings on the human hippocampal surface reveal that oscillations travel in reversing directions. The route of travel at a given moment was related to behavior and topographic patterns of activity strength, suggesting directions may be biomarkers of hippocampal cognitive processes.

    • Jonathan K. Kleen
    • , Jason E. Chung
    •  & Edward F. Chang
  • Article
    | Open Access

    Higher-order sequence learning using a structured graph representation - clone-structured cognitive graphs (CSCG) – can explain how the hippocampus learns cognitive maps. CSCG provides novel explanations for transferable schemas and transitive inference in the hippocampus, and for how place cells, splitter cells, lap-cells and a variety of phenomena emerge from the same set of fundamental principles.

    • Dileep George
    • , Rajeev V. Rikhye
    •  & Miguel Lázaro-Gredilla
  • Article
    | Open Access

    Perineuronal nets may stabilize synaptic connections. Here, the authors show that removal of perineuronal nets disrupts both the temporal and spatial organization of grid cell firing.

    • Ane Charlotte Christensen
    • , Kristian Kinden Lensjø
    •  & Torkel Hafting
  • Article
    | Open Access

    LTP and LTD are involved in shaping hippocampal place field representations. Here, the authors show that de novo pathway-specific hippocampal LTD changes dynamics and stability of newly formed place fields, regulating acquisition and maintenance of novel spatial information in adult rats.

    • Donovan M. Ashby
    • , Stan B. Floresco
    •  & Yu Tian Wang
  • Article
    | Open Access

    Theta and gamma rhythms are essential to ensure timely communication between brain structures during locomotion. Here the authors investigate the association between cerebral blood flow and neural oscillations in freely behaving mice running a linear track.

    • Antoine Bergel
    • , Elodie Tiran
    •  & Ivan Cohen
  • Article
    | Open Access

    Acute administration of EPA impairs learning and memory and hippocampal LTP in mice that was mediated through enhancing GABAergic transmission via the 5-HT6R. DHA can prevent EPA-induced impairments at a ratio of EPA to DHA similar to that in marine fish oil via the 5-HT2CR.

    • Ji-Hong Liu
    • , Qian Wang
    •  & Tian-Ming Gao
  • Article
    | Open Access

    Decisions under uncertainty involve a balance between exploiting familiar valuable options and exploring unfamiliar ones. Here, the authors study hippocampal responses using fMRI during a reinforcement learning task, and show the differential involvement of the anterior-posterior regions in the explore-exploit aspects of the task.

    • Alexandre Y. Dombrovski
    • , Beatriz Luna
    •  & Michael N. Hallquist
  • Article
    | Open Access

    Inhibitory interneuron subtypes differentially control place cell representations in CA1. Here, the authors show that parvalbumin and somatostatin interneuron synapses onto CA1 pyramidal neurons exhibit distinct plasticity mechanisms and incorporating this insight into circuit-level modeling leads to stable place cell representations.

    • Matt Udakis
    • , Victor Pedrosa
    •  & Jack R. Mellor
  • Article
    | Open Access

    The vCA1-BA projection is enriched in shock responsive neurons, which are necessary for fear memory encoding and become correlated with a network of neurons during retrieval. Here the authors show that the magnitude of vCA1 correlated activity is proportional to memory strength and requires the shock response during encoding.

    • Jessica C. Jimenez
    • , Jack E. Berry
    •  & Rene Hen
  • Article
    | Open Access

    When our expectations are violated, it is adaptive to update our internal models to improve predictions in the future. Here, the authors show that during mnemonic violations, hippocampal networks are biased towards an encoding state and away from a retrieval state to potentially update these predictions.

    • Oded Bein
    • , Katherine Duncan
    •  & Lila Davachi
  • Article
    | Open Access

    Keinath et al. show that information about the recent past is represented in the hippocampus through changes in firing rates in the absence of task demands. This representation is eliminated when DG–CA3 circuitry is inhibited.

    • Alexandra T. Keinath
    • , Andrés Nieto-Posadas
    •  & Mark P. Brandon
  • Article
    | Open Access

    Thalamic head direction (HD) cells are necessary to establish spatial maps in the hippocampus. Here, the authors show that HD cells tuned to a particular direction are coupled to individual hippocampal ripple events during sleep, suggesting an influence of the replay of specific trajectories during sleep memory consolidation.

    • Guillaume Viejo
    •  & Adrien Peyrache
  • Article
    | Open Access

    We show that the human hippocampus exhibits two distinct theta oscillations during spatial navigation with the faster oscillation in posterior regions showing movement modulation. This result suggests a distinct feature of the human hippocampus compared to rodents, which generally show a single 8 Hz rhythm.

    • Abhinav Goyal
    • , Jonathan Miller
    •  & Joshua Jacobs
  • Article
    | Open Access

    Trajectory-coding neurons in the hippocampus convey important information for performing memory tasks. Here, Kinsky et al. track long-term neural activity in the hippocampus to find that trajectory-coding emerges rapidly and remains stable across long time-scales.

    • Nathaniel R. Kinsky
    • , William Mau
    •  & Michael E. Hasselmo
  • Article
    | Open Access

    The formation of functional synaptic clusters (FSCs) and their impact on somatic membrane potential (sVm) in vivo are poorly understood. Here, the authors develop a computational approach to show that FSCs have to form via local rather than global plasticity and be moderately large to impact sVm.

    • Balázs B. Ujfalussy
    •  & Judit K. Makara
  • Article
    | Open Access

    Ageing affects several brain areas causing a decrease in cognitive abilities and memory. We find that increasing the endogenous potential of the hippocampus to generate new neurons throughout life rejuvenates learning and memory, indicating that neural reserves can be exploited during ageing to compensate for age- or disease-related cognitive impairments.

    • Gabriel Berdugo-Vega
    • , Gonzalo Arias-Gil
    •  & Federico Calegari
  • Article
    | Open Access

    Spatial maps in the medial temporal lobe (MTL) have been proposed to map abstract conceptual knowledge. Rather than grounding abstract knowledge in a spatial map, the authors propose a general-purpose clustering algorithm that explains how both spatial (including place and grid cells) and higher-dimensional conceptual representations arise during learning.

    • Robert M. Mok
    •  & Bradley C. Love
  • Article
    | Open Access

    Slow gamma oscillations are associated with memory and have been reported to be disrupted in patients with Alzheimer’s disease. Here the authors show that optogenetic stimulation of medial septum parvalbumin neurons at 40 Hz rescues memory retrieval in the J20 mouse model of Alzheimer’s disease.

    • Guillaume Etter
    • , Suzanne van der Veldt
    •  & Sylvain Williams
  • Article
    | Open Access

    In rodents, cells in the medial entorhinal cortex and subiculum are known to encode the allocentric direction to nearby walls and boundaries. Here, using fMRI the authors show that this is also true in humans, with allocentric boundary direction being encoded in posterior entorhinal cortex and subiculum.

    • J. P. Shine
    • , J. P. Valdés-Herrera
    •  & T. Wolbers
  • Article
    | Open Access

    Impairments in memory flexibility are associated with neuropsychiatric disorders such as PTSD and autism. Here, the authors report that the transcriptional repressor Wilm's Tumor 1 regulates synaptic plasticity leading to weakening of memory strength and enabling memory flexibility.

    • Chiara Mariottini
    • , Leonardo Munari
    •  & Ravi Iyengar
  • Article
    | Open Access

    Memory is hypothesised to depend on different brain regions that interact in a network. Here, the authors use case studies of stroke patients with amnesia from the literature to identify brain regions that are part of this network.

    • Michael A. Ferguson
    • , Chun Lim
    •  & Michael D. Fox
  • Article
    | Open Access

    Episodic memory retrieval is hypothesized to rely on hippocampal reinstatement of item-context associations which drives reinstatement of item information in cortex. Here, the authors confirm this sequence of events, using iEEG recordings from the human hippocampus and lateral temporal cortex.

    • D. Pacheco Estefan
    • , M. Sánchez-Fibla
    •  & P. F. M. J. Verschure
  • Article
    | Open Access

    The molecular mechanisms underlying contextual fear memory consolidation by sparse dentate gyrus (DG) neuronal populations remain unclear. Here using unbiased RNA sequencing of DG engram neurons the authors identify persistent transcriptome modifications during memory consolidation, in which CREB-dependent transcription features prominently

    • Priyanka Rao-Ruiz
    • , Jonathan J. Couey
    •  & Steven A. Kushner
  • Article
    | Open Access

    The hippocampus is involved both in episodic memory recall and scene processing. Here, the authors show that hippocampal neurons first process scene cues before coordinating memory-guided pattern completion in adjacent entorhinal cortex.

    • Bernhard P. Staresina
    • , Thomas P. Reber
    •  & Florian Mormann
  • Article
    | Open Access

    Medial entorhinal cortex (MEC) is involved in memory processes that entail the replay of sequential firing of hippocampal place cells during rest periods and during behaviour. Here, the authors show that MEC lesioned animals show intact replay after an epoch of rats running on a linear track, while replay during the behavioral epoch is reduced.

    • Alireza Chenani
    • , Marta Sabariego
    •  & Christian Leibold
  • Article
    | Open Access

    Although the CA2 region of the hippocampus has been implicated in social memory, its precise role has been unclear. Here, the authors show that the dorsal subregion of CA2 is required for the encoding, consolidation and recall of social memory through a circuit linking it to ventral CA1.

    • Torcato Meira
    • , Felix Leroy
    •  & Steven A. Siegelbaum
  • Article
    | Open Access

    The hippocampus is known to 'replay' experiences and memories during rest periods, but it is unclear how particular memories are prioritized for replay. Here, the authors show that information that is remembered less well is replayed more often, suggesting that weaker memories are selected for replay.

    • Anna C. Schapiro
    • , Elizabeth A. McDevitt
    •  & Kenneth A. Norman
  • Article
    | Open Access

    Circadian rhythms are known to modulate memory, but it’s not known whether clock genes in the hippocampus are required for memory consolidation. Here, the authors show that epigenetic regulation of clock gene Period1 in the hippocampus regulates memory and contributes to age-related memory decline, independent of circadian rhythms.

    • Janine L. Kwapis
    • , Yasaman Alaghband
    •  & Marcelo A. Wood
  • Article
    | Open Access

    Single nuclei RNA-seq has been used to characterize transcriptional signature of environment-related activity in cells of the dentate gyrus. Here the authors use this approach to show that whether a neuron will be reactivated in response to re-exposure to a previous environment can be predicted by its transcriptional signature.

    • Baptiste N. Jaeger
    • , Sara B. Linker
    •  & Fred H. Gage
  • Article
    | Open Access

    Hippocampus is necessary for integrating the context with sensory cues to retrieve memory for unique episodes. Here, the authors show that inhibiting topographically organized projections from hippocampus to the anterior olfactory nucleus independently impairs spatial and temporal odour memory recall.

    • Afif J. Aqrabawi
    •  & Jun Chul Kim