Time (and space) in the hippocampus

Over the past 15 years, there has been an explosion of new research on the role of the hippocampus in the 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 article, 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.

Section: Conclusion and Questions For Future Researchmentioning

confidence: 96%

Section: Conclusion and Questions For Future Researchmentioning

confidence: 99%

Time, memory, and the legacy of Howard Eichenbaum

Ranganath

2018

“…Episodic memory has long been recognized to entail the storage, in a neural substrate, of a large collection of arbitrarily associated features or items (“what”) in a specific spatial (“where”) and temporal (“when”) context. Furthermore, it has been argued that these properties of episodic memory imply temporal organization of correspondent neural representations in the hippocampus (Eichenbaum, ; Eichenbaum, ). Remarkably, recent work has shown that time is a representational correlate in the hippocampus, in analogous fashion as space (Eichenbaum, ; Eichenbaum, ; MacDonald, Lepage, Eden, & Eichenbaum, ; Pastalkova, Itskov, Amarasingham, & Buzsaki, ).…”

Section: Three Brain States In the Hippocampusmentioning

confidence: 99%

“…To specify, episodic memory involves (a) single episodes encompassing longer periods of time (seconds to minutes and longer) (Ferbinteanu, Kennedy, & Shapiro, ; Shapiro, Kennedy, & Ferbinteanu, ; Smith & Mizumori, ), (b) knowledge of temporal relationships across episodes, and (c) retrieval of episodes long after initial storage. Although recent work has provided promising clues (Attardo, Fitzgerald, & Schnitzer, ; Cai et al, ; Driscoll, Pettit, Minderer, Chettih, & Harvey, ; Eichenbaum, ; Eichenbaum, ; Eichenbaum, ; Ezzyat & Davachi, ; Ferbinteanu & Shapiro, ; Frank, Stanley, & Brown, ; Hsieh, Gruber, Jenkins, & Ranganath, ; Karlsson & Frank, ; Kitamura et al, ; Ludvig, ; Mankin et al, ; Mankin et al, ; Manning, Polyn, Baltuch, Litt, & Kahana, ; Manns, Howard, & Eichenbaum, ; Murray et al, ; Ranganath & Hsieh, ; Rubin, Geva, Sheintuch, & Ziv, ; Runyan, Piasini, Panzeri, & Harvey, ; Suh, Rivest, Nakashiba, Tominaga, & Tonegawa, ; Ziv et al, ), the neural representation of events at longer timescales remains unclear. More knowledge and insight are needed.…”

Section: Three Brain States In the Hippocampusmentioning

confidence: 99%

Three brain states in the hippocampus and cortex

Kay

Frank

2019

Contemporary brain research seeks to understand how cognition is reducible to neural activity. Crucially, much of this effort is guided by a scientific paradigm that views neural activity as essentially driven by external stimuli. In contrast, recent perspectives argue that this paradigm is by itself inadequate, and that understanding patterns of activity intrinsic to the brain is needed to explain cognition. Yet despite this critique, the stimulus-driven paradigm still dominates - possibly because a convincing alternative has not been clear. Here we review a series of experimental findings in the hippocampus suggesting such an alternative. These findings indicate that hippocampal neural activity occurs in one of three brain states that have radically different anatomical, physiological, representational, and behavioral correlates, together implying different roles in cognition. This three-state framework also indicates that hippocampal neural representations follow a surprising pattern of organization at the timescale of ∼1 s or longer. Lastly, beyond the hippocampus, recent breakthroughs indicate three parallel states in cortex, suggesting shared principles and brain-wide organization of intrinsic neural activity. This article is protected by copyright. All rights reserved.

“…There is considerable evidence that the hippocampus supports complex forms of associative memory; the hippocampus shows increased activity during the formation and retrieval of associations (Eichenbaum, ; Suzuki, ; Fortin, Agster, & Eichenbaum, ; Davachi, Mitchell, & Wagner, ; Ranganath et al, ), and hippocampal lesions impair the ability to encode and retrieve associations (Kesner, Gilbert, & Barua, ; Fortin et al, ; Farovik, Dupont, & Eichenbaum, ). However, these results do not clarify the mechanisms by which the hippocampus supports these associations.…”

Section: The Hippocampus and Serial‐order Memorymentioning

confidence: 99%

Hippocampal contributions to serial‐order memory

Long

Kahana

2018

Our memories form a record not only of our experiences, but also of their temporal structure. Although memory for the temporal structure of experience likely relies on multiple neural systems, numerous studies have implicated the hippocampus in the encoding and retrieval of temporal information. This review evaluates the literature on hippocampal contributions to human serial-order memory from the perspective of three cognitive theories: associative chaining theory, positional-coding theory and retrieved-context theory. Evaluating neural findings through the lens of cognitive theories enables us to draw more incisive conclusions about the relations between brain and behavior.