# Short-term plasticity influences episodic memory recall: an interplay of synaptic traces in a spiking neural network model

## TL;DR

The study explores how short-term memory processes affect episodic memory recall using a spiking neural network model inspired by rat experiments.

## Contribution

A novel computational model using Bayesian–Hebbian plasticity to explain how synaptic dynamics influence episodic memory tasks.

## Key findings

- The model reproduces experimental results on odor-in-context tasks in rats.
- Higher recency of old-in-context items enhances episodic memory in the model.
- The model provides a framework for studying synaptic mechanisms in memory paradigms.

## Abstract

We investigated the interaction of episodic memory processes with the short-term dynamics of recency effects. This work takes inspiration from a seminal experimental work involving an odor-in-context association task conducted on rats. In the experimental task, rats were presented with odor pairs in two arenas serving as old or new contexts for specific odor items. Rats were rewarded for selecting the odor that was new to the current context. These new-in-context odor items were deliberately presented with higher recency relative to old-in-context items, so that episodic memory was put in conflict with a short-term recency effect. To study our hypothesis about the major role of synaptic interplay of plasticity phenomena on different time-scales in explaining rats’ performance in such episodic memory tasks, we built a computational spiking neural network model consisting of two reciprocally connected networks that stored contextual and odor information as stable distributed memory patterns. We simulated the experimental task resulting in a dynamic context-item coupling between the two networks by means of Bayesian–Hebbian plasticity with eligibility traces to account for reward-based learning. We first reproduced quantitatively and explained mechanistically the findings of the experimental study, and then to further differentiate the impact of short-term plasticity we simulated an alternative task with old-in-context items presented with higher recency, thus synergistically confounding episodic memory with effects of recency. Our model predicted that higher recency of old-in-context items enhances episodic memory by boosting the activations of old-in-context items. We argue that the model offers a computational framework for studying behavioral implications of the synaptic underpinning of different memory effects in experimental episodic memory paradigms.