Representational dynamics of memories for real-life events

Abstract

The continuous flow of experience that characterizes real-life events is not recorded as such in episodic memory. The unfolding of events is represented as a succession of moments of prior experience (referred to as "experience units") that are separated by temporal discontinuities, such that events are temporally compressed when remembered. To unravel the neural basis of this temporal structure of episodic memories, we recorded a series of real-life events using wearable camera technology and then used fMRI to investigate brain activity during the temporal unfolding of these events in memory. We found that, compared to the representation of static scenes in memory, dynamically unfolding memory representations were associated with greater activation of posterior brain regions that support episodic recollection (i.e., the precuneus, posterior cingulate cortex, retrosplenial cortex, and angular gyrus). Strikingly, by analyzing the autocorrelation of brain activity patterns at successive time points throughout the retrieval period, we found that these brain regions showed higher temporal dynamics when remembering the unfolding of events compared to static scenes. Furthermore, these effects were more pronounced when recalling events that included a higher density of experience units (i.e., actions compared to spatial displacements). These results reveal the key role of the posterior medial network in representing the dynamic unfolding of event segments that constitute episodic memories.

Mixed selectivity coding of content-temporal detail by dorsomedial posterior parietal neurons

“…We argued that the long TRW allows the dmPPC to accumulate the continuous information of multifaceted representations from unimodal or integration of cross-modal inputs (Gilissen & Arckens, 2021) to support processing stream of past experiences for episode. This aligns with the higher temporal dynamics in the precuneus when remembering the unfolding of events that included a high density of experience units (Jeunehomme et al, 2022). Notably, the primate dmPPC has dense connections to the hippocampal formations in the primate (Kravitz et al, 2011).…”