Use of an Eight-arm Radial Water Maze to Assess Working and Reference Memory Following Neonatal Brain Injury

Summary

The eight-arm radial water maze is designed to evaluate reference and working memory performance simultaneously by requiring subjects to use extra-maze cues to locate escape platforms and remedies the limitations observed in land based radial arm maze designs.

Abstract

Working and reference memory are commonly assessed using the land based radial arm maze. However, this paradigm requires pretraining, food deprivation, and may introduce scent cue confounds. The eight-arm radial water maze is designed to evaluate reference and working memory performance simultaneously by requiring subjects to use extra-maze cues to locate escape platforms and remedies the limitations observed in land based radial arm maze designs. Specifically, subjects are required to avoid the arms previously used for escape during each testing day (working memory) as well as avoid the fixed arms, which never contain escape platforms (reference memory). Re-entries into arms that have already been used for escape during a testing session (and thus the escape platform has been removed) and re-entries into reference memory arms are indicative of working memory deficits. Alternatively, first entries into reference memory arms are indicative of reference memory deficits. We used this maze to compare performance of rats with neonatal brain injury and sham controls following induction of hypoxia-ischemia and show significant deficits in both working and reference memory after eleven days of testing. This protocol could be easily modified to examine many other models of learning impairment.

Introduction

Working memory (WM) corresponds to a critical cognitive domain required for the representation of objects or places during goal directed behavior¹. Alternatively, reference memory (RM) is required for temporally stable representations of those objects or places. Working and reference memory have long been assessed in rodents using land based radial arm maze paradigms^2,3. However, these tasks frequently require pretraining, as rats are not predisposed to spontaneous maze running. This can significantly increase the time needed to complete an experiment and can interfere with time sensitive longitudinal designs. Other limitations of the land based ....

Protocol

All procedures were approved by the Rhode Island College Institutional Animal Care and Use Committee and adhere to the National Institutes of Health Guide for the Care and Use of Laboratory Animals.

1. Maze Configuration

1. Place clear, static, salient extra-maze cues (painted shapes, furniture or other stationary room features) around the maze.
   Note: Any extra-maze cues must remain in the same location for the duration of the experiment.
2. Place the hub and arms of the.......

Discussion

The eight-arm radial water maze paradigm has been utilized successfully in our lab and by others to assess working and reference memory performance in rats with and without neonatal brain injury^5-7,18-20. In the current paradigm, removal of an escape platform after each trial increases working memory demand (subjects have fewer escape options) on subsequent trials. Therefore, on trial four, only one platform remains and working memory demand is at its highest, increasing the probability that an animal will re-.......

Materials

Name	Company	Catalog Number	Comments
Plastic Tub	Gototanks http://www.gototanks.com	ARM-19455	Size can vary depending on species tested or individual lab needs.
iPad or other digital tablet	Apple Inc.	N/A	http://www.apple.com
Notability or other note taking application	Gingerlabs	N/A	http://www.gingerlabs.com Digital pdf writer or notetaking program
Digital timer	Any	N/A
Deltaphase isothermal heating pad	Braintree Scientific	ASS7D	http://www.braintreesci.com/
Stainless steel maze	Fabricated in house	N/A