Documentation

Introduction

The Narrow Elevated Path Maze is used to study spatial learning and memory in rodents. It is also referred to as a “Skeleton Maze” due to its narrow elevated pathways, which measure 1 inch in width. The pathways are wide enough to test individual large adult rats. However, smaller rats can even pass each other in the pathways for experiments that require multiple animals to be tested simultaneously. 

The Narrow Elevated Path Maze comprises multiple straight and standing units adjoined to one another. Therefore, the units can be placed in different combinations, allowing for multiple maze configurations. The units usually make T-type patterns when joined together; however, L-type patterns can also be formed. The maze has several decision points, allowing the subject’s choice behavior to be analyzed multiple times. During the task, the subject is required to explore the maze and reach the food box, which is fastened in a notch at one end of a maze unit, which prevents the animal from seeing the food above the surface of the paths. This prevents the subjects from utilizing the food reward as a visual cue and ensures that only spatial information is utilized for the task. 

The open structure of the maze allows the rodent’s behaviors to be readily observed during maze runs. Moreover, the maze is easier to clean than closed Alley mazes. The Narrow Elevated Path Maze is also easier to store and transport since the units can be stacked compactly. 

Apparatus and Equipment

The Narrow Elevated Path Maze comprises an assembly of 19 standing straight units adjoined to one another. A food box is located at one end of a maze unit, fastened in a notch, preventing it from being observable from the surface of the paths. Hurdle-like frames make a horizontal path measuring 1 inch in width and 36 inches in length. The horizontal strip is ¾ inches thick and is supported 30 inches above the floor by two upright units braced together. A 4 x 6-inch base block is present for each upright unit. Each end of the horizontal bar projects 3 inches beyond the support. The unit can be arranged in several different combinations. The standard combination employs 19 maze frames with 14 T-choice, 1 L-choice, 15 cul-de-sacs (18 inches in length), and a true path (32 feet in length). The open space between the adjoining parallel paths measures 18 inches. The runways between turns mostly measure 18 inches; however, some measure 3 feet, and two measure 4 ½ feet in length. 

Training Protocol

Remove the animal’s excrement from the maze whenever needed. Wash the maze or clean it with ethanol after every trial.

Habituation and Pre-training

Train the subjects on the maze for six consecutive days before testing. On the first three days, feed an entire litter of animals at one time on the maze by randomly placing the food on the runways. On the fourth, fifth, and sixth days place individual subjects on the maze and feed them according to the following plan:

• On the fourth day – place the food on the 1st, 5th, and 6th cul-de-sacs
• On the fifth day – place the food on the 2nd, 4th, and 7th cul-de-sacs
• On the sixth day – place the food on the 3rd and starting position cul-de-sacs

Pre-training allows the subjects to be familiarized with the maze-food situation without providing an opportunity to learn any maze pattern. This pattern of feeding allows each subject to explore and obtain food from all the runways at least once. 

Narrow Elevated Path Maze Task 

Place the food in a food box on one end of a maze unit. Place a subject at the starting point of the maze. Allow the subject to explore the maze and reach the food reward. Conduct five trials a day per subject until five consecutive errorless trials are completed. Record the number of errors the subject makes where an error is characterized as the subject making a complete entrance into a cul-de-sac while the subject runs in a forward direction. Do not count entrances into a blind alley while the subject retraces its path as an error.

Literature Review

Investigation of sex difference in maze learning in rats 

Corey (1930) investigated sex differences in maze learning in white rats using the Narrow Elevated Path Maze. Male and female albino Wistar rats were used in the study. Different levels of physical activity were given to the animals used. Some of the litter were kept in extremely small cages where their access to exercise was severely restricted, while others were made to run for one to three hours per day in a motorized drum.

The subjects were habituated to the maze six days before the experiment by feeding on the maze. Food was kept on different maze pathways each day so that the subjects were familiarized with all pathways. During experimentation, the subjects were tested five times on the maze a day until they completed five consecutive errorless trials. Maze learning was analyzed by recording the number of errors made by the subjects, the total amount of time spent on the maze, the amount of time spent running the maze referred to as “active time,” and the number of trials required until the subjects achieved the learning criterion. 

The results indicated that regardless of the learning criterion utilized, there were statistically significant variations between the average performances of the two sexes. It was observed that the females displayed more rapid learning than the males in all instances. Additionally, males showed greater variability in their scores than females with respect to time and active time. No significant difference was observed in variability for errors and trials. 

Data Analysis

The following parameters can be observed using the Narrow Elevated Path Maze:

• The number of errors made
• The total amount of time the subject spends on the maze
• The amount of “active time” on the maze characterized as the subject running the maze
• The number of trials required to reach the learning criterion

Strengths and Limitations

The Narrow Elevated Path Maze is used to study the maze-learning abilities of rodents. A major advantage of the maze is that the maze units can be placed in different combinations, allowing multiple maze configurations to be made. The units can also be placed separately or blocked off, creating an Elevated Plus Maze or an Elevated T-Maze. Alternate paths, gaps, shortcuts, and other obstructions can be easily introduced during trials to observe changes in rodents’ behavior. The maze has several decision points, allowing the subjects’ choice behavior to be analyzed multiple times.

The 1-inch pathways are wide enough to test large adult rats. However, even smaller pathways may be suitable for very small rats. Smaller rats may be tested simultaneously since the narrow pathways are wide enough for small rats to cross each other. The rodent’s behaviors can be readily observed due to the maze’s open structure. Although the maze structure is open and the pathways are narrow, falls from the maze are rare. The open structure makes it easier to clean the maze. Differences in maze learning ability between genders may be a limitation since evidence of superior maze learning performance on the Narrow Elevated Maze is recorded in female rats.

Summary

• The Narrow Elevated Path Maze is used to study spatial learning and memory in rodents.
• It comprises multiple straight-standing units adjoined to one another. Hurdle-like frames make a horizontal path measuring 1 inch in width and 36 inches in length. 
• The units can be placed in different combinations, allowing for multiple maze configurations. Moreover, alternate paths, gaps, shortcuts, and other obstructions can be easily introduced.
• A food box is located at one end of a maze unit, which is fastened in a notch, preventing it from being observable from the surface of the paths
• The 1-inch elevated pathways are wide enough to test individual large adult rats. However, smaller rats can even pass each other in the pathways for experiments that require multiple animals to be tested simultaneously. 
• The rodent’s behaviors can be readily observed due to the maze’s open structure. Moreover, the open structure makes it easier to clean the maze.

References

1. Miles, W. R. (1927). The Narrow-Path Elevated Maze for Studying Rats. Experimental Biology and Medicine, 24(5), 454–456. doi:10.3181/00379727-24-3414
2. Corey, S. M. (1930). Sex differences in maze learning by white rats. Journal of Comparative Psychology, 10(4), 333–338. doi:10.1037/h0071778