Hippocampal “time cells” bridge the gap in memory for discontiguous events

By Christopher J. MacDonald, Kyle Q. Lepage, Uri T. Eden, Howard Eichenbaum. 2011

1,133 citations recorded by the source corpus.

Summary The hippocampus is critical to remembering the flow of events in distinct experiences and, in doing so, bridges temporal gaps between discontiguous events. Here we report a robust hippocampal representation of sequence memories, highlighted by “time cells” that encode successive moments during an empty temporal gap between the key events, while at the same times encoding location and ongoing behavior. Furthermore, just as most place cells “remap” when a salient spatial cue is altered, most time cells form qualitatively different representations (“re-time”) when the main temporal parameter is altered. Hippocampal neurons also differentially encode the key events and disambiguate different event sequences to compose unique, temporally organized representations of specific experiences. These findings suggest that hippocampal neural ensembles segment temporally organized memories much the same as they represent locations of important events in spatially defined environments.

Subfields: Cellular and Molecular Neuroscience, Cognitive Neuroscience, Neurology

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Citations in the corpus

Low-dimensional dynamics for working memory and time encoding (2020, neutral): “76 and 77) and in the striatum (78–80).”
Pattern separation, completion, and categorisation in the hippocampus and neocortex. (2016, background): “During learning of the synaptic weights in the network, adaptation might lead to each ‘time encoding’ population of neurons responding for only a limited period, helping to produce multiple sequentially activated populations of time encoding neurons (Macdonald et al., 2011; Rolls & Deco, 2010).”
Entorhinal–hippocampal neuronal circuits bridge temporally discontiguous events (2015, background): “In order to better understand how large neural ensembles of CA1 cells encode a distinct sequence of events, (MacDonald et al. 2011) trained rats on a sequence memory task that depends on the integrity of CA1 but not CA3 (Kesner et al. 2005).”
The neuroscience of learning: beyond the Hebbian synapse. (2013, background): “Dead reckoning, also known as path integration, plays a fundamental role in animal navigation (Cheung et al. 2008, Collett & Graham 2004, Gallistel 1990, Loomis et al. 1998, Wehner & Srinivasan 2003, Wittlinger et al. 2006).”
Cell type-specific genetic and optogenetic tools reveal novel hippocampal CA2 circuits (2013, neutral): “On the other hand, the direct ECIII input dedicated to CA1 has been implicated in temporal association memory 33 , and this input may also underlie encoding of the temporal order of events in an episode 50 .”
Hippocampal Reactivation of Random Trajectories Resembling Brownian Diffusion. (2019, background): “Moreover, sequential activation of place cells can signal the time elapsed during a task (MacDonald et al., 2011).”
Episodic-like memory trace in awake replay of hippocampal place cell activity sequences (2015, background): “…simultaneously represents a broad range of aspects of memory, including odors and their match/non-match status in a particular location, called the “place field”, as well as elapsed time (Otto and Eichenbaum, 1992; Sakurai, 1996; Wood et al., 1999; Pastalkova et al., 2008; MacDonald et al., 2011).”