Time cells in the hippocampus: a new dimension for mapping memories

Eichenbaum, Howard

doi:10.1038/nrn3827

Cited by 645 publications

(643 citation statements)

References 102 publications

(140 reference statements)

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“…The vivid recall that participants engaged in during the current study might be considered to have favored the kind of first-person perspective remembering associated with egocentric processing. Moreover, whereas the hippocampus may integrate elements of an episodic memory such as space and time (Burgess et al, 2002;Eichenbaum, 2014), AnG may integrate sensory elements of multimodal memories into a complete and vivid recollection. Examining the possible functional dissociation between these two regions is a critical next step for future research.…”

Section: Angular Gyrus and Episodic Memorymentioning

confidence: 99%

Multimodal Feature Integration in the Angular Gyrus during Episodic and Semantic Retrieval

et al. 2016

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Much evidence from distinct lines of investigation indicates the involvement of angular gyrus (AnG) in the retrieval of both episodic and semantic information, but the region's precise function and whether that function differs across episodic and semantic retrieval have yet to be determined. We used univariate and multivariate fMRI analysis methods to examine the role of AnG in multimodal feature integration during episodic and semantic retrieval. Human participants completed episodic and semantic memory tasks involving unimodal (auditory or visual) and multimodal (audio-visual) stimuli. Univariate analyses revealed the recruitment of functionally distinct AnG subregions during the retrieval of episodic and semantic information. Consistent with a role in multimodal feature integration during episodic retrieval, significantly greater AnG activity was observed during retrieval of integrated multimodal episodic memories compared with unimodal episodic memories. Multivariate classification analyses revealed that individual multimodal episodic memories could be differentiated in AnG, with classification accuracy tracking the vividness of participants' reported recollections, whereas distinct unimodal memories were represented in sensory association areas only. In contrast to episodic retrieval, AnG was engaged to a statistically equivalent degree during retrieval of unimodal and multimodal semantic memories, suggesting a distinct role for AnG during semantic retrieval. Modality-specific sensory association areas exhibited corresponding activity during both episodic and semantic retrieval, which mirrored the functional specialization of these regions during perception. The results offer new insights into the integrative processes subserved by AnG and its contribution to our subjective experience of remembering.

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Section: Angular Gyrus and Episodic Memorymentioning

confidence: 99%

Multimodal Feature Integration in the Angular Gyrus during Episodic and Semantic Retrieval

et al. 2016

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“…Direct evidence from single-neuron recordings in rats indicates that cells in the hippocampus fire in specific spatial locations (2)(3)(4)(5)(6) or at specific times during a temporal delay (7,8). Single-neuron and functional MRI (fMRI) studies in individuals navigating virtual environments have confirmed that cells coding for spatial location are also present in the human hippocampus (9)(10)(11).…”

mentioning

confidence: 99%

Human hippocampus represents space and time during retrieval of real-world memories

Nielson

Smith

Sreekumar

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

217

213

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Memory stretches over a lifetime. In controlled laboratory settings, the hippocampus and other medial temporal lobe brain structures have been shown to represent space and time on the scale of meters and seconds. It remains unclear whether the hippocampus also represents space and time over the longer scales necessary for human episodic memory. We recorded neural activity while participants relived their own experiences, cued by photographs taken with a custom lifelogging device. We found that the left anterior hippocampus represents space and time for a month of remembered events occurring over distances of up to 30 km. Although previous studies have identified similar drifts in representational similarity across space or time over the relatively brief time scales (seconds to minutes) that characterize individual episodic memories, our results provide compelling evidence that a similar pattern of spatiotemporal organization also exists for organizing distinct memories that are distant in space and time. These results further support the emerging view that the anterior, as opposed to posterior, hippocampus integrates distinct experiences, thereby providing a scaffold for encoding and retrieval of autobiographical memories on the scale of our lives.hippocampus | representational similarity analysis | lifelogging | episodic memory T he hippocampus plays a critical role in remembering the events of our lives (1). Direct evidence from single-neuron recordings in rats indicates that cells in the hippocampus fire in specific spatial locations (2-6) or at specific times during a temporal delay (7,8). Single-neuron and functional MRI (fMRI) studies in individuals navigating virtual environments have confirmed that cells coding for spatial location are also present in the human hippocampus (9-11). Similarly, place-responsive cell activity recorded in the hippocampus of patients with epilepsy during navigation of a virtual town was shown to reinstate during episodic memory retrieval of the previous virtual navigation (12). Together, these studies provide evidence that the same neurons in the medial temporal lobe (MTL) that are active during an experience also help represent the memory for that experience. These results, however, are limited to simple events in laboratory settings that occur on the scale of minutes and meters, thereby leaving unanswered whether we harness similar mechanisms in more natural settings and over larger temporal and spatial scales.Recent studies have used more naturalistic designs with incidentally acquired memories recorded via lifelogging devices that automatically capture photographs from the participants' lives (13,14). The typical finding is increased hippocampal activation when participants view images from their cameras as opposed to images from other participants' cameras (15-17), and this activation decays over the course of months (14). Still, there is no evidence to date that the hippocampus or other MTL structures actually represent space or time of autobiographical experiences. We a...

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“…Converging evidence from human and animal studies point to entorhinal cortical (EC)-hippocampal (HPC) circuits as being critical for episodic memory, and in particular for temporal associative learning (Eichenbaum 2014, MacDonald 2014. In this regard, Pavlovian conditioning protocols (Maren 2001) have proven especially useful.…”

mentioning

confidence: 99%

“…These two protocols, along with additional control conditions (e.g., unpaired pseudo-random CS-US presentations), provide a powerful means to evaluate the contribution of different brain regions to temporal associative learning. For these reasons, in this review we focus discussion primarily on these behavioral paradigms, the functional dissections of the EC-HPC circuits and the physiological mechanisms that subserve temporal aspects of episodic memory, although there are reviews that discuss additional physiological mechanisms of temporal associative learning (Hasselmo and Stern 2006;Yoshida et al 2012;Eichenbaum 2014).…”

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confidence: 99%

Entorhinal–hippocampal neuronal circuits bridge temporally discontiguous events

2015

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The entorhinal cortex (EC) -hippocampal (HPC) network plays an essential role for episodic memory, which preserves spatial and temporal information about the occurrence of past events. Although there has been significant progress toward understanding the neural circuits underlying the spatial dimension of episodic memory, the relevant circuits subserving the temporal dimension are just beginning to be understood. In this review, we examine the evidence concerning the role of the EC in associating events separated by time-or temporal associative learning-with emphasis on the function of persistent activity in the medial entorhinal cortex layer III (MECIII) and their direct inputs into the CA1 region of HPC. We also discuss the unique role of Island cells in the medial entorhinal cortex layer II (MECII), which is a newly discovered direct feedforward inhibitory circuit to CA1. Finally, we relate the function of these entorhinal cortical circuits to recent findings concerning hippocampal time cells, which may collectively activate in sequence to bridge temporal gaps between discontiguous events in an episode.

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Time cells in the hippocampus: a new dimension for mapping memories

Cited by 645 publications

References 102 publications

Multimodal Feature Integration in the Angular Gyrus during Episodic and Semantic Retrieval

Multimodal Feature Integration in the Angular Gyrus during Episodic and Semantic Retrieval

Human hippocampus represents space and time during retrieval of real-world memories

Entorhinal–hippocampal neuronal circuits bridge temporally discontiguous events

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