A Behavioral Task Modeling 'Everyday Memory' in an Event Arena to Foster Allocentric Representations for Rodents

Summary

The goal of this optimized 'everyday memory' protocol in an event arena was to employ a stable home-base that encourages the use of allocentric spatial representations. This animal model provides an effective test-bed for future research into the formation and retention of event memories using behavioral and physiological techniques.

Abstract

The event arena provides an optimal platform to investigate learning and memory. The appetitive everyday memory task described in this paper provides a robust protocol for the investigation of episodic and spatial memory in rodents, which specifically fosters allocentric memory representation. Rats are trained to find and dig for food during the encoding phase and, after a time delay, rats are given a choice to find the reward food pellet in the correct location. There are two key elements that promote the use of an allocentric strategy in this protocol: 1) rats start from different start locations within and between sessions, 2) a stable home-base is deployed where rats have to carry their food to eat. By means of these modifications, we effectively encourage the rodents to use allocentric spatial representations to perform the task. In addition, the task provides a good paradigm for within-subject experimental design and allows experimenters to manipulate different conditions to reduce variability. Used in conjunction with behavioral and physiological techniques, the resulting rodent model provides an effective test-bed for future research into memory formation and retention.

Introduction

To investigate the neurobiology of learning and memory, invasive techniques are required, which are not generally feasible in humans. Thus, for over a century, behavioural protocols have been designed for laboratory animals to model various forms of human memory. The design and choice of both task and apparatus are central to the success of effective models of human memory. Numerous paradigms have been developed with diverse complexity, ranging from simple classical and instrumental conditioning protocols^1,2,3 to mazes such as the T-maze⁴, radial arm m....

Protocol

The methods described in this paper have been approved by the University of Edinburgh Ethical Review Committee; they are compliant with the UK Animals (Scientific Procedures) Act 1986 and the European Communities Council Directive of 24 November 1986 (86/609/EEC) legislation governing the maintenance of laboratory animals and their use in scientific experiments.

NOTE: The experimental subject of the protocol outlined below is Lister-hooded rats, but it can be adapted for other rodent strains.

1. Animal handling, housing, and food control

1. Allow 1 week for Lister-hooded male rats to set....

Results

This stable home-base protocol has been used to successfully train rats to learn this everyday memory task using allocentric representations. There are two important elements in this protocol. First, animals start from different black boxes (e.g., East, South, and West) within and between sessions (Figure 7A). There are two encoding trials and one recall choice trial per session (or probe trial instead of the choice trial in some cases), all starting from an alternate startbox. This encourag.......

Discussion

Humans automatically encode single events in everyday life. We readily recall some events and forget others. The episodic-like everyday memory protocol described above provides a robust method for researchers wishing to investigate this type of memory (episodic memory) in rodents. Because the task involves the daily act of finding and retrieving food pellets from a defined location, the natural instinct of rodents to forage for food is exploited. The task rests on the reasonable assumption that the act of finding and dig.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Camera	CCTVFirst	N/A
Event Arena	University of Edinburgh (designed and built in house)	University of Edinburgh (designed and built in house)	Event arena for everyday memory task
Lister-hooded rats	Charles River UK	603
Multitimer Labview	University of Edinburgh (designed and built in house)	University of Edinburgh (designed and built in house)
Pneumatics, frames, screws of event arena	RS Components Ltd.	University of Edinburgh (P. Spooner)	Tools for building event arena
Sandwells	Adam Plastics (http://www.adamplastics.co.uk)	University of Edinburgh (P. Spooner)	Sandwells for arena
Startboxes	Adam Plastics (http://www.adamplastics.co.uk)	University of Edinburgh (P. Spooner)
Video recording	Windows 10 computers with OBS software, Blackmagic Decklink Mini Recorder cards	N/A