From hippocampus to whole-brain: The role of integrative processing in episodic memory retrieval

Benjamin R. Geib; Matthew L. Stanley; Nancy A. Dennis; Marty G. Woldorff; Roberto Cabeza

doi:10.1002/hbm.23518

Electrophysiological signatures of memory reactivation in humans

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2019.0293 ◽

2020 ◽

Vol 375 (1799) ◽

pp. 20190293 ◽

Cited By ~ 4

Author(s):

Thomas Schreiner ◽

Tobias Staudigl

Keyword(s):

Episodic Memory ◽

Neural Activity ◽

Crucial Role ◽

Memory Retrieval ◽

Functional Significance ◽

State Of The Art ◽

Memory Reactivation ◽

Open Questions ◽

Neural Processes

The reactivation of neural activity that was present during the encoding of an event is assumed to be essential for human episodic memory retrieval and the consolidation of memories during sleep. Pioneering animal work has already established a crucial role of memory reactivation to prepare and guide behaviour. Research in humans is now delineating the neural processes involved in memory reactivation during both wakefulness and sleep as well as their functional significance. Focusing on the electrophysiological signatures of memory reactivation in humans during both memory retrieval and sleep-related consolidation, this review provides an overview of the state of the art in the field. We outline recent advances, methodological developments and open questions and specifically highlight commonalities and differences in the neuronal signatures of memory reactivation during the states of wakefulness and sleep. This article is part of the Theo Murphy meeting issue ‘Memory reactivation: replaying events past, present and future’.

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The Role of the Basal Forebrain in Episodic Memory Retrieval: A Positron Emission Tomography Study

NeuroImage ◽

10.1006/nimg.2001.0995 ◽

2002 ◽

Vol 15 (3) ◽

pp. 501-508 ◽

Cited By ~ 37

Author(s):

Toshikatsu Fujii ◽

Jiro Okuda ◽

Takashi Tsukiura ◽

Hiroya Ohtake ◽

Rina Miura ◽

...

Keyword(s):

Positron Emission Tomography ◽

Episodic Memory ◽

Basal Forebrain ◽

Memory Retrieval ◽

Emission Tomography ◽

Positron Emission Tomography Study ◽

Positron Emission

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0111 Emotional Memory-Associated Voxel-Extent Reactivation During Episodic Memory Retrieval Varies as a Function of Post-Learning Sleep

SLEEP ◽

10.1093/sleep/zsaa056.109 ◽

2020 ◽

Vol 43 (Supplement_1) ◽

pp. A44-A44

Author(s):

R M Bottary ◽

S M Kark ◽

R T Daley ◽

J D Payne ◽

E A Kensinger

Keyword(s):

Episodic Memory ◽

Rem Sleep ◽

Memory Retrieval ◽

Memory Performance ◽

Emotional Memory ◽

Single Subject ◽

Whole Brain ◽

Functional Brain ◽

Line Drawings ◽

Sleep Amount

Abstract Introduction Slow wave sleep (SWS) and rapid eye-movement (REM) sleep enhance neutral and emotional memory consolidation, respectively. Emotional episodic memory retrieval is also enhanced when encoding-specific functional brain patterns are reactivated at retrieval, especially in ventral visual stream and frontal brain regions as well as amygdala. Here we investigate how sleep impacts the association between memory-dependent brain pattern reactivation and episodic memory retrieval. Methods Healthy adults (N = 22; 11F, 11M; age: 19–29 years) were scanned during an incidental encoding task and a surprise recognition memory task 24h later. Overnight sleep was monitored with polysomnography. During encoding, participants viewed line drawings of negative, neutral, and positive images, each followed by their full-colored photo. At recognition, participants distinguished new from encoded line drawings. Brain reactivation was measured at the single-subject level as the percentage of voxels activated at encoding that were also activated during successful recognition (reactivation%); this metric was calculated independently in whole-brain and 3 ROI-based maps (inferior temporal lobe (ITL), medial prefrontal cortex, and amygdala). Multiple linear regression was performed to predict memory performance from functional brain reactivation and sleep physiology. Results In whole-brain analyses, the association between negative memory performance and reactivation% decreased with greater REM sleep amount. This interaction approached significance for positive, but was not significant for neutral, memory performance. Additionally, the association between neutral, but not emotional, memory performance and reactivation% decreased with greater amounts of SWS sleep. In ROI-based analyses, positive, but not negative or neutral, memory performance was independently predicted by REM sleep amount and ITL reactivation%. No effects of SWS amount were observed in ROI-based analyses. Conclusion Greater amounts of sleep decreased the association between brain reactivation and memory performance. Sufficient sleep may change cortical representations of episodic memories, resulting in less reliance on encoding-related reactivation during memory retrieval. Support NSF Grant BCS 1539361

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On the ‘data stirring’ role of the dentate gyrus of the hippocampus

Reviews in the Neurosciences ◽

10.1515/revneuro-2016-0080 ◽

2017 ◽

Vol 28 (6) ◽

pp. 599-615 ◽

Cited By ~ 1

Author(s):

Charles R. Legéndy

Keyword(s):

Episodic Memory ◽

Dentate Gyrus ◽

Memory Retrieval ◽

Granule Cells ◽

Large Cell ◽

Memory Storage ◽

Cell Assembly ◽

Cell Assemblies ◽

The Creation

AbstractUnderstanding hippocampal (HC) function, as it is presently known, includes exploring the HC role in episodic memory storage. As pointed out by Teyler and DiScenna in the 1980s, the apparatus needed for recalling a stored episode, and awakening all its components in a coordinated manner, by necessity includes a triggering device able to reach each of the mental entities that must be awakened. In the context of neuronal networks, the triggering device in question takes the form of a large cell assembly, a separate one made for every new episode stored. The present paper deals with the creation and the properties of these cell assemblies (‘pointer groups’). To perform the function of episodic memory retrieval, each of these must possess the information capacity (entropy) enabling it to single out an episode and the network connections enabling it to reach all components of it; further, to deal with the unpredictability of the memory items it has to address, it must have its member neurons well distributed through the length of the network (the HC). The requirements imply that the creation of a pointer group must include a randomizing step analogous to ‘stirring’. It is argued that many of the known peculiarities of granule cells in the dentate gyrus arise as solutions to the practical problems presented by the creation of the pointer groups and the details of ‘stirring’, and so do a series of other features of the HC network, some of them only discovered in the last few years.

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Mapping sequence structure in the human lateral entorhinal cortex

eLife ◽

10.7554/elife.45333 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 12

Author(s):

Jacob LS Bellmund ◽

Lorena Deuker ◽

Christian F Doeller

Keyword(s):

Episodic Memory ◽

Entorhinal Cortex ◽

Memory Retrieval ◽

Temporal Structure ◽

Sequence Structure ◽

Temporal Memory ◽

Event Sequences ◽

Mapping Sequence ◽

Virtual City

Remembering event sequences is central to episodic memory and presumably supported by the hippocampal-entorhinal region. We previously demonstrated that the hippocampus maps spatial and temporal distances between events encountered along a route through a virtual city (Deuker et al., 2016), but the content of entorhinal mnemonic representations remains unclear. Here, we demonstrate that multi-voxel representations in the anterior-lateral entorhinal cortex (alEC) — the human homologue of the rodent lateral entorhinal cortex — specifically reflect the temporal event structure after learning. Holistic representations of the sequence structure related to memory recall and the timeline of events could be reconstructed from entorhinal multi-voxel patterns. Our findings demonstrate representations of temporal structure in the alEC; dovetailing with temporal information carried by population signals in the lateral entorhinal cortex of navigating rodents and alEC activations during temporal memory retrieval. Our results provide novel evidence for the role of the alEC in representing time for episodic memory.

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Structuring Time in Human Lateral Entorhinal Cortex

10.1101/458133 ◽

2018 ◽

Cited By ~ 1

Author(s):

Jacob L.S. Bellmund ◽

Lorena Deuker ◽

Christian F. Doeller

Keyword(s):

Episodic Memory ◽

Entorhinal Cortex ◽

Memory Retrieval ◽

Temporal Structure ◽

Event Structure ◽

Temporal Memory ◽

Event Sequences ◽

Entorhinal Region ◽

Virtual City

AbstractRemembering event sequences is central to episodic memory and thought to be supported by the hippocampal-entorhinal region. We previously demonstrated that the hippocampus maps spatial and temporal distances between events encountered along a fixed route through a virtual city (Deuker et al., 2016), but the content of entorhinal mnemonic representations remains unclear. Here, we demonstrate that, after learning, multi-voxel representations in the anterior-lateral entorhinal cortex (alEC) specifically reflect the temporal event structure. Holistic representations of the temporal structure related to memory recall and the temporal event structure could be reconstructed from entorhinal multi-voxel patterns. Our findings demonstrate representations of temporal structure in the alEC in line with temporal information carried by population signals in the lateral entorhinal cortex of navigating rodents and activations of its human homologue during temporal memory retrieval. Our results provide novel evidence for the role of the human alEC in representing time for episodic memory.

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