Integrating time from experience in the lateral entorhinal cortex

Abstract

The encoding of time and its binding to events are crucial for episodic memory, but how these processes are carried out in hippocampal-entorhinal circuits is unclear. Here we show in freely foraging rats that temporal information is robustly encoded across time scales from seconds to hours within the overall population state of the lateral entorhinal cortex. Similarly pronounced encoding of time was not present in the medial entorhinal cortex or in hippocampal areas CA3-CA1. When animals' experiences were constrained by behavioural tasks to become similar across repeated trials, the encoding of temporal flow across trials was reduced, whereas the encoding of time relative to the start of trials was improved. The findings suggest that populations of lateral entorhinal cortex neurons represent time inherently through the encoding of experience. This representation of episodic time may be integrated with spatial inputs from the medial entorhinal cortex in the hippocampus, allowing the hippocampus to store a unified representation of what, where and when.

Transcending time in the brain: How event memories are constructed from experience

“…Intriguingly, recent fMRI work in humans suggests that while hippocampal processes contribute to subjective mnemonic representations of time, lateral entorhinal cortex activity reflects the objective amount of time that has elapsed between events (Bellmund, Deuker, & Doeller, ; also see Montchal et al, ). In a similar finding, evidence in rodents suggests that the lateral entorhinal cortex, in particular, is important for encoding temporal information across short and long timescales (seconds‐to‐hours; Tsao et al, ). In the coming years, we expect that these convergent findings will ignite great interest in the entorhinal cortex's role in processing and organizing temporal information in memory.…”

Thirst regulates motivated behavior through modulation of brainwide neural population dynamics

“…Specific optogenetic stimulation of thirst-sensing neurons in sated mice was sufficient to recover activity along this thirsty state mode in a rapid and reversible manner and to restore the sub-sequent sensory- and behavior-related activity throughout the brain. Brain regions that did not fully represent the maximal level of thirst representation upon optogenetic stimulation could additionally be recipients of contextual or memory information on water consumption, visceral signals that normally cause animals to terminate drinking upon satiation [such as those relayed by oxytocin receptor–expressing neurons in the parabrachial nucleus (42)], or other slowly changing variables such as the passage of time (43). …”

A neural microcircuit model for a scalable scale‐invariant representation of time

“…Mechanisms of decaying persistent firing have also been observed in other structures such as hippocampus (Knauer, Jochems, Valero‐Aracama, & Yoshida, ) and prefrontal cortex (Haj‐Dahmane & Andrade, ). In addition, there are in vivo recordings showing a spectrum of timescales across cortex (Bernacchia, Seo, Lee, & Wang, ; Meister & Buffalo, ; Murray et al, ; Tsao et al, ).…”