Knowledge Base

The Y-Maze Test

Introduction

The Y-Maze

The Y-maze is constructed with three arms of equal length that extend from a central platform at a 120° angle. In the basic version, the animal is free to explore the maze arms. In a modified version, it is possible to close off some arms either to keep the animal in a specific arm for a fixed time once it has entered that arm, or to limit exploration to some arms, not others.

The Y-maze is generally used to investigate alternation behavior, where animals are supposed to alternate choices of maze arms on successive opportunities. Irrespective of the precise function of alternation, the animal must remember which arm it had entered on a previous occasion to enable it to alternate its choice on a following trial. Therefore, the use of the Y-maze is based on the assumption that, following some pharmacological manipulation, it is primarily modified memory processes that are reflected in changed alternation rates.

Spontaneous Alternation

Definition

Spontaneous Alternation is a behavioral test for measuring the willingness of rodents to explore new environments. Rodents typically prefer to investigate a new arm of the maze rather than returning to one that was previously visited. Many parts of the brain, including the hippocampus, septum, basal forebrain, and prefrontal cortex, are involved in this task (Conrad et al. 1996).

Classical Procedure

The animal is released in the center of the maze, and allowed to freely explore the three arms (A, B, C). Over the course of multiple arm entries, the subject is expected to show a tendency to enter a less recently visited arm (A > B > C > A > ...). The observer records the number of arm entries and the number of visits to the three arms without a re-visit in between (for example, A > B > C, B > C > A, etc.) in order to calculate the percentage of alternation. An arm entry is scored when all four limbs are within the arm.

Calculation of Alternation Index

Given a zone sequence:

A > B > C > B > ...

An alternation is defined as multiple entries into the three different arms on overlapping triplet sets. In this example the first three visits are an alternation:

A > B > C > B > ...

The next overlapping triplet set, B > C > B, is not an alternation.

The Alternation index is given by the number of alternations divided by the maximum number of possible alternations, that is, the number of alternations that would be obtained if the animal visited the zones in the sequence: A > B > C > A > B > C ...

For a 3-arm maze, like the Y-maze, the maximum number of alternations is equal to total number of visits minus 2.

The Alternation index is expressed as a percentage:

Alternation Index = Number of alternations / (Total number of zone visits - 2)

Spontaneous Alternation in EthoVision XT

You can easily calculate the Alternation index using the outputs Alternations and Max Alternations in the Zone alternation dependent variable. For more information, see Zone Alternation in the EthoVision XT Help.

Delayed Alternation

Definition

The delayed alternation task allows assessing spatial working memory in a T- or Y-maze. The main difference with spontaneous alternation is that performance is evaluated between trials.

Classical Procedure

In the first trial of the test, the animal is placed at the end of the start arm and has to choose between the two other arms that are baited. Once the choice is made, the subject is removed and after a variable delay, is returned to the start arm. In this second trial, the one arm baited is now the opposite arm to which was chosen during the first trial. The animal has to make a different choice than its first one (correct choice) to get the reward.

Delayed Alternation in EthoVision XT

For all tests where maze arms can be considered as targets of a choice, and others non-targets (errors), you can use outputs Target First Visits and Total Errors in the Target visits and errors dependent variable. For more information, see Target Visits and Errors in the EthoVision XT Help.

References

• Conrad, C.D., Galea, L.A., Kuroda, Y., McEwen, B.S. (1996). Chronic stress impairs rat spatial memory on the Y maze, and this effect is blocked by tianeptine pretreatment. Behav Neurosci: 1321–1334.
• Conrad, C.D., Lupien, S.J., Thanasoulis, L.C., McEwen, B.S. (1997). The effects of type I and type II corticosteroid receptor agonists on exploratory behavior and spatial memory in the Y-maze. Brain Res., 76–83.
• Hughes, R.N. (2004). The value of spontaneous alternation behavior (SAB) as a test of retention in pharmacological investigations of memory. Neurosci. Biobehav. Rev., 497–505.
• Detrait, E., Brohez, C., Hanon, E., De Ryck, M. (2010). Automation of Continuous Spontaneous Alternation to Increase the Throughput for In Vivo Screening of Cognitive Enhancers. Optimization of the Ethovision System for the Y-maze Test in Mice. Proceedings of Measuring Behavior 2010 (Eindhoven, The Netherlands, August 24–27, 2010), 141–144.

For a complete list of publications, see the results of Google Scholar.

Source: EthoVision XT 18 - Application Manual, Noldus Information Technology