Documentation

Introduction

The Juvenile Barnes Maze is a modified version of the Barnes Maze (Barnes, 1979) to assess spatial learning and memory in juvenile rodents. The rodents develop their spatial learning and memory after three weeks of the postnatal period that depicts that both juvenile and adult rodents have different spatial learning capacities (McHail, Valibeigi, & Dumas, 2018; (Valibeigi, McHail, Kimball, & Dumas, 2018). Due to the smaller size of the juvenile rodents, it is difficult to assess their spatial memory in the Adult Barnes Maze. 

The Juvenile Barnes Maze is a smaller version of the Barnes Maze that is specifically designed for the assessment of spatial learning and memory in juvenile rodents. Compared to the alternate Morris Maze test, the Juvenile Barnes Maze does not impose water and temperature stress on the subjects (Albani et al., 2014). The maze consists of a white circular platform with eight equidistant holes around the boundary. The subject locates the hidden end box situated beneath the end holes by utilizing the distal visual cues. The subject utilizes aversive behavior towards brightly lit light to find the location of the dark end box (McHail, Valibeigi, & Dumas, 2018; Valibeigi, McHail, Kimball, & Dumas, 2018). The juveniles Barnes maze can effectively assess hippocampal development and maturation in juvenile rodents. It can also be used for the assessment of memory impairment with aging. 

Other variants of the Barnes Maze used to study spatial learning and memory in rodents include the Randomized Barnes,  the Radial Arm Barnes Maze, the Delayed Matching to Place Barnes Maze, and the Labyrinth Barnes Maze.

Equipment and Apparatus

The Juvenile Barnes Maze is composed of a circular platform (1.2 m in diameter) with eight equidistant end holes (10 cm in diameter) around the boundary. The end holes are 5 cm away from the edge of the platform.  The platform is elevated 0.75 meters above the ground with the help of a PVC stand. The maze is also provided with rectangular escapes boxes, each measuring 9.19 inches in length and 3 inches width. A rotating PVC bar is placed below the circular platform to change the location of the end box as required. Foam cushions are provided to allow cushioned falls; they are placed around the maze’s circumference in the ground. The maze is also provided with four curtains with different geometric shapes:  horizontal rectangle (163 in length x 25 cm in width), triangle (55 cm base, 64 cm in height), circles (25 cm in diameter), vertical rectangle (25 in length x 147 width cm), stripes (8 cm in width x 163 cm in length). These shapes provide visual cues for the subject.

Task Performance

Clean the maze before each trial. Setup the maze by placing the visual cues (four curtains) around the maze in four directions. Keep them unaltered throughout the experiment. Rotate the maze between training blocks by keeping the escape location relative to the direction of the visual cues. Apply background white noise to mask the auditory cues. 

Habituation and Pretraining 

Conduct pretraining of the subjects for three days. On day 1, place the home cage of the subject in the testing room for 15 minutes before exposing the subject to the maze. After habituation, pre-train the subjects in dim light. Setup the maze by placing the cushion foams in the ground around the circumference of the maze. Place dime-sized droplets of liquid formula equally over the face of the circular platform with the help of an injection. Carry the subject from its home cage and place it in the center of the circular platform. Allow the subject to explore the maze for 15 minutes. In the case of fall, place the subject back to the center of the platform and allow it to explore. 

On days 2 and 3, pre-train the subjects in bright light.  First, habituate the subject by placing the home cage of the subject in the testing room for 15 minutes. Now set up the apparatus by allocating each end hole an alphabet from A to H in a clockwise fashion. Allocate one end hole with an escape box and attach it to the rotating arm beneath the hole. Divide the maze into four quadrants and assign four starting positions. Randomly select a start location and place the subject in the starting location in such a way that it faces the center of the maze, and its paws align with the left and the right end hole. Release the subject, hide behind the curtains, and observe the subject’s movement on the screen.  Allow the subject to search for the escape hole for 60 seconds. If the subjects couldn’t find the escape hole within 60 seconds, then guide the subject by moving its paws towards the escape hole. Conduct training in blocks where each block consists of four trails. Keep an inter-block interval of 15 minutes. Conduct 5 bright light training blocks on day 2 and 5 blocks on day 3.

After 5 training blocks on both day 2 and 3, conduct an immediate probe to test the subject’s ability to recall the escape hole location. Remove the escape box and place the subject in a start position that comes in front of the end hole previously used as an escape hole. Allow 60 seconds to locate the escape hole. 

Conduct a 6th block (a refresher block with four trails)  similar to the 5 bright light training blocks after immediate probe on day 3 only to keep the subjects motivated for the task. 

The Long term spatial memory task 

After 24 hours of final bright light training trial, conduct the long term spatial memory task. Remove the escape box and place the subject in a start position that comes in front of the end hole previously used as an escape hole. Allow 60 seconds for the subject to locate the escape hole. 

Data Analysis

• Escape latency 
• Path length 
• Average movement speed 
• Maximum movement speed 
• Dwell time 
• Distance from the end box each second
• Error nose pokes before reaching goal hole
• Nose pokes after reaching the first goal hole

Literature Review

Spatial Navigation in Juvenile Barnes Maze

McHail, Valibeigi, & Dumas, (2018) investigated spatial navigation in juvenile rats. Both male (n=27) and female (n=24) Long Evan rats were utilized and grouped into the younger and the older group. The Juvenile Barnes Maze was used for behavioral task performance. The subjects were habituated in the test rooms and were trained to find the escape hole for three days under dim and bright light, respectively. After training, a long term spatial memory task was performed on the fourth day. The results of the dim light training showed that younger subjects were hesitant towards a novel environment compared to the older subjects (P <0.05). The Number of pauses, duration of pauses, and the mean movement speed did not vary between the younger and the older groups in dim light training. After day 2 of the bright light training, both younger and older subjects learned to locate the escape hole (p<0.001); however, the older subjects outperformed the young subjects. There was a significant difference in escape latency and path length, while no difference was observed for moment speed. After the first day, the results of the immediate probe test revealed that neither of the groups showed a preference to escape hole. The results of the first day of bright light training revealed that older subjects were able to find the goal while younger subjects were not able to do so. The results of the second day of bright light training showed that both age groups learned to escape with a developmental improvement in performance level. Both the younger and the older group spatially navigate towards the escape hole. However, the older group outperform the younger group. The results of the long spatial memory task showed recall accuracy of the goal location in the older group compared to the younger group. The study concluded that there is a difference in spatial navigation and learning capacity between young and old rodents. 

Strengths and Limitations

Strengths

The Juvenile Barnes Maze is smaller than the Barnes Maze. Therefore, it allows to test spatial navigation in young rodents. Task performance is easy and requires less time. The maze does not allow water and temperature stress on the juvenile rats, unlike the Morris Maze. The presence of cushion foams allows cushioned fall that prevents injury of the subjects during task performance. The provision of large visual cues provides better visualization for juvenile subjects. The maze is efficient in measuring in-vivo electrophysiological recordings. 

Limitations 

Repeated and improper handling of subjects may alter observations. The presence of surrounding visual, olfactory, and auditory cues may alter task performance. Factors such as the subject’s size, age, and species may alter observations. 

Summary

• The Juvenile Barnes Maze is a modified version of the Barnes maze to assess spatial learning in juvenile rodents. 
• It consists of an elevated circular platform with eight equidistant holes around the circumference. 
• The maze is also provided with curtains with enlarged geometric shapes that serve as visual cues for the subjects. 
• The subject shows aversive behavior towards bright light and searches for the escape box using visual cues. 
• The Juvenile Barnes Maze requires imposes limited stress and requires a minimum amount of time for task performance. 
• The Juvenile Barnes Maze can be used to assess hippocampal maturation and memory impairments with aging in rodents.  

References

Albani, S. H., McHail, D. G, and Dumas, T. C. (2014). Developmental studies of the
hippocampus and hippocampal-dependent behaviors: insights from interdisciplinary studies and tips for new investigators. Neurosci Biobehav Rev 43: 183-190.

Barnes, C. A. (1979). Memory deficits associated with senescence: a neurophysiological and
behavioral study in the rat. J Comp Physiol Psychol 93(1): 74-104.

McHail, D. G., Valibeigi, N., & Dumas, T. C. (2018). A Barnes maze for juvenile rats delineates the emergence of spatial navigation ability. Learning & memory (Cold Spring Harbor, N.Y.), 25(3), 138–146. https://doi.org/10.1101/lm.046300.117

Valibeigi, N., McHail, D. G., Kimball, C. L., & Dumas, T. C. (2018). A Modified Barnes Maze for Juvenile Rats. Bio-protocol, 8(22), e3084. https://doi.org/10.21769/BioProtoc.3084