Time regained: how the human brain constructs memory for time

Abstract

Life’s episodes unfold against a context that changes with time. Recent neuroimaging studies have revealed significant findings about how specific areas of the human brain may support the representation of temporal information in memory. A consistent theme in these studies is that the hippocampus appears to play a central role in representing temporal context, as operationalized in neuroimaging studies of arbitrary lists of items, sequences of items, or meaningful, lifelike events. Additionally, activity in a posterior medial cortical network may reflect the representation of generalized temporal information for meaningful events. The hippocampus, posterior medial network, and other regions—particularly in prefrontal cortex—appear to play complementary roles in memory for temporal context.

Time, memory, and the legacy of Howard Eichenbaum

“…Finally, voxel patterns differentiated between repetitions of the same object indistinct, but overlapping sequences. These findings converge with the lesion and single‐unit recording data in rats to suggest that the hippocampus plays a critical role in encoding sequences of events (Cohn‐Sheehy & Ranganath, ; Ranganath & Hsieh, ).…”

“…For most adults, experiences do not occur in a passive vacuum—instead, incoming experiences are interpreted with respect to structured knowledge about general classes of events, termed “event schemas” (Hard, Tversky, & Lang, ). An event schema can serve as a scaffold to enable retrieval and reconstruction of past events, rapid encoding of new events, and predictions about future events (Cohn‐Sheehy & Ranganath, ). For example, after attending a baseball game, you can develop a schema that specifies roles (e.g., pitcher, batter, umpire, etc.)…”

“…Research in humans (Kahn, Andrews‐Hanna, Vincent, Snyder, & Buckner, ; Libby, Ekstrom, Ragland, & Ranganath, ; Maass, Berron, Libby, Ranganath, & Duzel, ) and nonhuman primates (Kaplan et al, ; Kondo, Saleem, & Price, ) suggests that the hippocampus closely interacts with a “posterior medial” (PM) network that includes the medial entorhinal cortex, parahippocampal, retrosplenial, and ventrolateral parietal cortex, as well as the precuneus and posterior cingulate (Ranganath & Ritchey, ; Ritchey, Libby, & Ranganath, ). Activity in the PM network is elicited in studies of meaningfully structured events (see Cohn‐Sheehy & Ranganath, , for review). For instance, the PM network appears to process information about narratives or movies across long timescales (Baldassano et al, ; Chen et al, , ; Milivojevic, Varadinov, Vicente Grabovetsky, Collin, & Doeller, ; Milivojevic, Vicente‐Grabovetsky, & Doeller, ), and sequences of PM network activity patterns that are observed during meaningful events are recapitulated when these events are recalled (Baldassano et al, ; Chen et al, , ).…”

“…Building on ideas developed in collaboration with Sam Gershman, Ken Norman, and Jeff Zacks, I have a speculative framework for how the PM network and hippocampus might interact to support memory for temporally evolving events (see also Cohn-Sheehy & Ranganath, 2017). As noted above, an adult human can draw upon a library of event schemas acquired and refined through years of experiences.…”

Hierarchical representation of multi-step tasks in multiple-demand and default mode networks

“…The ability to organize sequences of events within a given context has also been a key topic in the study of episodic memory (Ezzyat and Davachi 2011;Eichenbaum 2013;Hsieh et al 2014;Cohn-Sheehy and Ranganath 2017;Radvansky and Zacks 2017). Tulving's original definition emphasized the importance of temporal events: "Episodic memory receives and stores information about temporally dated episodes or events, and temporal-spatial relations among these events (Tulving, 1972, p.385)."…”