The Double-H Maze: A Robust Behavioral Test for Learning and Memory in Rodents

Summary

The goal of this protocol is to investigate spatial cognition in rodents. The double-H water maze is a novel test, which is particularly useful to elucidate the different components of learning, consolidation and memory, as well as the interplay of memory systems.

Abstract

Spatial cognition research in rodents typically employs the use of maze tasks, whose attributes vary from one maze to the next. These tasks vary by their behavioral flexibility and required memory duration, the number of goals and pathways, and also the overall task complexity. A confounding feature in many of these tasks is the lack of control over the strategy employed by the rodents to reach the goal, e.g., allocentric (declarative-like) or egocentric (procedural) based strategies. The double-H maze is a novel water-escape memory task that addresses this issue, by allowing the experimenter to direct the type of strategy learned during the training period. The double-H maze is a transparent device, which consists of a central alleyway with three arms protruding on both sides, along with an escape platform submerged at the extremity of one of these arms.

Rats can be trained using an allocentric strategy by alternating the start position in the maze in an unpredictable manner (see protocol 1; §4.7), thus requiring them to learn the location of the platform based on the available allothetic cues. Alternatively, an egocentric learning strategy (protocol 2; §4.8) can be employed by releasing the rats from the same position during each trial, until they learn the procedural pattern required to reach the goal. This task has been proven to allow for the formation of stable memory traces.

Memory can be probed following the training period in a misleading probe trial, in which the starting position for the rats alternates. Following an egocentric learning paradigm, rats typically resort to an allocentric-based strategy, but only when their initial view on the extra-maze cues differs markedly from their original position. This task is ideally suited to explore the effects of drugs/perturbations on allocentric/egocentric memory performance, as well as the interactions between these two memory systems.

Introduction

In animals, learning is principally mediated by the hippocampal- and striatal-based memory systems^1,2, which play central roles regarding place- and procedural-memory, respectively. The relationship between these two systems is complex, and they are known to interact with each other in cooperative or competitive manners^1,3. In addition, studies have shown that the influence of either of these memory systems on animal behavior can increase following the absence or damage of the other system^4-7. Both of these systems are connected to the prefrontal cortex via the thalamus.

Numerous neurological disorders and n....

Protocol

1. General Considerations

This protocol is approved by the Animal Care and Use Committee of University Hospital Freiburg (same for Strasbourg). Visual acuity is necessary for performance in tests of spatial learning. Rodents with impaired visual systems are thus not suitable. Also, lighting must be sufficient in order for the rats to see the different cues located on the surrounding walls. It is useful to utilize basic-shaped (square, circle, triangle) but well-contrasted cues (e.g., black-painted cues on a white-painted background). Likewise, severe motoric deficits are exclusion criteria because swimming is required for this test and drowni....

Results

Egocentric Learning Strategy

A study was carried out to determine whether the chosen memory strategy in rats changes based on alterations of their perspective of external environmental cues, following an egocentric-learning paradigm²⁵. Rats were trained over 4 days (4 trials/day) to reach a goal arm located at NE, and were subsequently tested on the fifth day using a misleading probe trial, in which the start arm was either moved 60 cm to the left (i.e., NE start for animals r.......

Discussion

Comments on Study Design and Analysis

Since its conception, the double-H maze has been utilized in a number of behavioral experiments in rats, which collectively were designed to study egocentric and/or allocentric responses in rats under normal^24,25 and altered^26-29 brain states. The latter studies include striatal deep-brain stimulation (DBS)²⁶, animal models of neurological disorders^27,28, as well as bilateral deactivations of various cortico-hippoca.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Rats or Mice	Charles River
Towels for drying	University Hospital		1 / animal
Water			~200 L / day
Skim milk powder	Grocery store		250 g / 200 L water
Garden Hose	Hardware store
Drying rack for towels	Hardware store
Kinect camera	Kinect
PC computer	any
[header]
Double H Maze, (plexiglass) (Custom-Built)
External lateral walls, 1600 × 350 × 6 mm			2
Internal lateral walls, 706 × 350 × 6 mm			8
Central corridor panels, 500 × 350 × 6 mm			4
Arm extremities, 188 × 350 × 6 mm			6
Guillotine doors, 187 × 350 × 6 mm			3
Extremity covers, 200 × 250 mm			6
Crossbars, 200 × 40 mm			6
[header]
Double-H Maze Platform (to be ballasted) (Custom-Built)
Metal platform, 100 mm diameter × 150 mm			2
Platform cover, 100 mm diameter × 6 mm			2