Documentation

Introduction

The Modified Beam Walking Apparatus is used to measure motor coordination and anxiety-related behaviors in rodents. It comprises a narrow elevated beam with a safe box located on a platform at one end of the beam. During the task, the subject must traverse the beam and enter the safe box within the required time limit. Slips and falls from the beam and the time taken to traverse are used to measure motor coordination. On the other hand, anxiety is assessed by examining peeking behaviors and full-body emergencies from the safe box. 

Anxiety behaviors in rodents are commonly assessed using the Elevated Plus Maze, while the Beam-Walking Test measures motor coordination. The Modified Beam Walking Apparatus combines both apparatuses and allows these behavioral traits to be measured together. The black-colored safe box in the Modified Beam Walking Apparatus mimics the safe enclosed spaces present in the Elevated Plus Maze. Similarly, the narrow beam of the Modified Beam Walking Apparatus mimics the Beam Walking Test. Although anxiety and motor coordination are measured on different aspects of the Modified Beam Walking Apparatus, the measurement of both traits can be performed within five minutes in the same testing session without removing the subject from the apparatus. 

Anxiety and motor dysfunctions are characteristics of neuropsychiatric disorders such as autism spectrum disorder (ASD) and depression, and traumatic brain injury (Eltokhi, Kurpiers, & Pitzer, 2021; Ahmed et al., 2017). Behavioral tests in rodent models of these diseases are used to provide more insight into them and to test the effects of parameters such as drugs on these disorders. However, using separate behavioral apparatuses to measure anxiety and motor coordination can be time-consuming and costly. The Modified Beam Walking Apparatus is, therefore, a valuable tool for studying neuropsychiatric disorders and traumatic brain injury by measuring multiple behavioral traits using one apparatus. 

Apparatus and Equipment

The Modified Beam Walking Apparatus consists of a narrow beam measuring 120 cm in length and 5 cm in diameter. The beam contains dashed markings spaced 10 cm apart. The beam is placed 50 cm off the floor using two pillars. At the end of one pillar, a platform is present that supports a black-colored safe box. The safe box has a circular opening of ∼15 cm in diameter for the subject to enter easily. The safe box mimics the Elevated Plus Maze enclosed arms. 

Training Protocol

The Modified Beam Walking Task is divided into two phases: the motor coordination phase and the anxiety assessment phase. The phases are conducted back to back within the same training or testing session. Clean the apparatus after every session. 

Phase 1: Modified Beam Walking Motor Coordination Training 

Place the subject on the end of the beam opposite the safe box. Allow the subject to begin walking on the beam. Start the time once the subject’s nose passes the first dashed mark on the beam. End the time once the subject’s nose passes the last 10 cm mark on the beam before entering the safe box. Once the subject reaches the safe box, allow it to remain there for 5 minutes. Conduct extra training sessions if the subject does not cross the beam in less than 5 seconds.

Phase 2: Modified Beam Waking Anxiety Assessment Task

The anxiety assessment task is conducted directly after the motor coordination task. The anxiety of the rodents is measured by observing peeking and full-body emergence behaviors. Analyze peeking behaviors by measuring the time the subject spent peeking out of the safe box from which the tip of its nose to the back of its whiskers are out of the safe box. Analyze full-body emergence by measuring the time the subject fully emerged out of the safe and on the beam, exposing the tip of its nose to the base of its tail. 

Conduct fifteen training sessions, each lasting for five minutes, three times a day, with an inter-trial interval of one hour between sessions. Conduct test sessions in the same manner as training sessions in which the performance of experimental versus control animals can be assessed on the tasks. 

Literature Review

Investigation of the Effect of Blast Traumatic Brain Injury on Rodent Anxiety 

Sweis et al. (2016) utilized the Modified Beam Walking Apparatus to assess anxiety in rodents with blast traumatic brain injury (bTBI). Thirty-five male Wistar rats were used in the study. The subjects were also tested on the Elevated Plus Maze to compare anxiety behaviors between the two apparatuses. Additionally, the Modified Beam Walking Apparatus also assessed motor coordination in rodents. Therefore, training sessions on the Modified Beam Walking Apparatus comprised motor coordination training immediately followed by anxiety assessment. During motor coordination training, the subjects were required to transverse the beam and reach the safe box on the other end of the beam within 5 seconds. The subjects were allowed to remain in the safe box for 5 minutes, after which peeking behaviors and full body emergencies out of the safe box and onto the beam were measured. During testing sessions, the subjects were divided into the bTBI-induced group and the non-injured yoked controls group. Testing sessions were conducted in the same manner as training. The rodents’ anxiety index on the Modified Beam Walking apparatus was compared with the anxiety index on the Elevated Plus Maze. Results indicated that the bTBI rats had an increased anxiety index in both apparatuses. Results of motor coordination assessment revealed no significant difference in motor coordination between the injured and control groups, which dissociated the effects of bTBI on motor function. 

Data Analysis

The following parameters can be assessed using the Modified Beam Walking Apparatus:

• Number of times the subject displayed peeking behaviors 
• Duration of peeking behaviors
• Number of brief, shallow peeking behaviors 
• Number of long stretched-out peeking behaviors 
• Number of times the subject exhibited full body emergence 
• Duration of full body emergencies
• Number of rapid, brief full body emergencies
• Number of long, slow exploratory walks onto the beam
• Number of times the subject exhibited freezing behaviors, head rearing, defecation, and stretched-out postures 
• Motor function errors displayed while crossing the beam, including slips and falls off the beam

Strengths and Limitations

The Modified Beam Walking Apparatus measures anxiety and motor coordination in rodents. Therefore, multiple behavioral apparatuses are not needed to measure these traits. Additionally, it can also be used in experiments that want to examine only one of the traits. It is a valuable tool in studying rodent models of diseases characterized by both anxiety and motor coordination. Each training and testing session is performed within five minutes; however, multiple training sessions may be needed for the subject to learn the task. Another limitation is that stress from handling may induce anxiety in the subjects and affect experimental results. Moreover, unintentional stimuli in the experimental room, such as loud noise, may affect anxiety-related behaviors. 

Summary

• The Modified Beam Walking Apparatus is used to measure motor coordination and anxiety-related behaviors in rodents. 
• It comprises a narrow elevated beam with a safe box located on a platform at one end of the beam. 
• The Modified Beam Walking Apparatus combines the Elevated Plus Maze and Beam Walking Test tasks into one apparatus. Its black-colored safe box mimics the safe enclosed spaces present in the Elevated Plus Maze, and its narrow beam mimics the Beam Walking Test. 
• Anxiety is measured by observing the rodent’s tendency to peek out of the safe box or leave it and re-traverse the beam. 
• Motor coordination is measured by observing the subject’s ability to traverse the beam without slipping or falling. 
• It is a valuable tool in rodent models of disease characterized by both anxiety and motor coordination, such as traumatic brain injury and neuropsychiatric disorders. 

References

1. Sweis, B. M., Bachour, S. P., Brekke, J. A., Gewirtz, J. C., Sadeghi-Bazargani, H., Hevesi, M., & Divani, A. A. (2016). A modified beam-walking apparatus for assessment of anxiety in a rodent model of blast traumatic brain injury. Behavioural brain research, 296, 149–156. https://doi.org/10.1016/j.bbr.2015.09.015
2. Eltokhi, A., Kurpiers, B., & Pitzer, C. (2021). Comprehensive characterization of motor and coordination functions in three adolescent wild-type mouse strains. Scientific reports, 11(1), 6497. https://doi.org/10.1038/s41598-021-85858-3
3. Ennaceur, A., Michalikova, S., van Rensburg, R., & Chazot, P. L. (2006). Models of anxiety: Responses of mice to novelty and open spaces in a 3D maze. Behavioural Brain Research, 174(1), 9–38.
4. Ahmed, S., Venigalla, H., Mekala, H. M., Dar, S., Hassan, M., & Ayub, S. (2017). Traumatic Brain Injury and Neuropsychiatric Complications. Indian journal of psychological medicine, 39(2), 114–121. https://doi.org/10.4103/0253-7176.203129