scholarly journals Mapping sequence structure in the human lateral entorhinal cortex

eLife ◽  
2019 ◽  
Vol 8 ◽  
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.

scholarly journals Structuring Time in Human Lateral Entorhinal Cortex

2018 ◽  
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.

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

2017 ◽  
Vol 38 (4) ◽  
pp. 2242-2259 ◽  
Author(s):  
Benjamin R. Geib ◽  
Matthew L. Stanley ◽  
Nancy A. Dennis ◽  
Marty G. Woldorff ◽  
Roberto Cabeza
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Whole Brain ◽  
Integrative Processing

scholarly journals Electrophysiological signatures of memory reactivation in humans

2020 ◽  
Vol 375 (1799) ◽  
pp. 20190293 ◽  
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’.

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

NeuroImage ◽  
2002 ◽  
Vol 15 (3) ◽  
pp. 501-508 ◽  
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

The meaning of “time” in episodic memory and mental time travel

2007 ◽  
Vol 30 (3) ◽  
pp. 323-323 ◽  
Author(s):  
William J. Friedman
Keyword(s):  
Episodic Memory ◽  
Time Travel ◽  
Mental Time Travel ◽  
Temporal Memory ◽  
The Past ◽  
The Future ◽  
Anticipation Time

AbstractThe role of time in episodic memory and mental time travel is considered in light of findings on humans' temporal memory and anticipation. Time is not integral or uniform in memory for the past or anticipation of the future. The commonalities of episodic memory and anticipation require further study.

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

2017 ◽  
Vol 28 (6) ◽  
pp. 599-615 ◽  
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.

scholarly journals The precision of retrieving temporal information : behavioral and electrophysiological studies

2020 ◽  
Author(s):  
◽  
John E. Scofield
Keyword(s):  
Episodic Memory ◽  
Temporal Precision ◽  
Event Sequences ◽  
Fine Grained ◽  
Electrophysiological Studies ◽  
Memory Time ◽  
Trial Basis ◽  
Temporal Judgments ◽  
Frequency Power

The knowledge of when an event took place provides benefits to episodic memory, such as distinguishing among multiple traces and learning event sequences. As a tool for understanding memory, time is appealing given its ever-changing quality, and the ease with which it is targeted at retrieval. Whereas studies of episodic retrieval typically employ categorical measures of retrieval, characterizing a continuous feature such as time warrants measures sensitive to the precision of retrieved information. Through four experiments, we adapted a paradigm for assessing the fine-grained precision of retrieval to understand the nature of judging the time at which a memory was encoded. Subjects studied a series of pictures and were subsequently tested on when they previously studied items. Temporal judgments were less accurate with passing time, with negligible guessing. Neurally, ERP amplitudes in left parietal electrodes tracked the precision of temporal judgments, with higher ERP amplitudes associated with better precision. Additionally, frequency power in both the alpha and theta bands were associated with temporal precision. Finally, while testing spatial retrieval, a correspondence emerged between spatial and temporal precision on a trial to trial basis, but a dissociation was found in which the recency effects found in temporal judgments was not present in spatial judgments. Together, these findings elucidate the role of time and space in episodic memory retrieval.

scholarly journals Time, Memory, and the Legacy of Howard Eichenbaum

2018 ◽  
Author(s):  
Charan Ranganath
Keyword(s):  
Episodic Memory ◽  
Temporal Structure ◽  
Neural Representation ◽  
The Past ◽  
To Come ◽  
New Research ◽  
Situational Information ◽  
New Framework ◽  
Representation Of Time

Over the past 15 years, there has been an explosion of new research on the role of the hippocampus in representation of information about time in memory. Much of this work was inspired by the ideas and research of Howard Eichenbaum, who made major contributions to our understanding of the neurobiology of episodic memory and the neural representation of time. In this paper, I will review evidence regarding the role of time in understanding hippocampal function. This review will cover a broad range of evidence from studies of humans and nonhuman animals with a narrative arc that follows Howard’s major discoveries. These studies demonstrate that the hippocampus encodes information in relation to an episodic context, and that time, as well as space, serves to define these contexts. Moreover, the research has shown that the hippocampus can encode temporal, spatial, and situational information in parallel. Building on this work, I present a new framework for understanding temporal structure in human episodic memory. I conclude by outlining current controversies and new questions that must be addressed by the field in the years to come.

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