A modified beam-walking apparatus for assessment of anxiety in a rodent model of blast traumatic brain injury

• Anxiety and motor function often suffers as a result of traumatic brain injury.
• Elevated plus maze and beam-walking tasks are used to test these traits in rodents.
• A novel task, the modified beam-walking apparatus, combines these tasks into one.
• Anxiety scores show agreement between this novel and standard tests post-injury.
• This novel task is capable of dissociating how injury affects motor versus anxiety.

The elevated plus maze (EPM) is used to assess anxiety in rodents. Beam-walking tasks are used to assess vestibulomotor function. Brain injury in rodents can disrupt performance on both of these tasks. Developing novel paradigms that integrate tasks like these can reduce the need for multiple tests when attempting to assess multiple behaviors in the same animal. Using adult male rats, we evaluated the use of a modified beam-walking (MBW) apparatus as a surrogate indicator for anxiety. We used a model of blast-induced traumatic brain injury (bTBI). A total of 39 rats were assessed before and at 3, 6, 24, 72, and 168 h either post- bTBI (n = 33) or no-injury (n = 6) using both EPM and MBW. A novel anxiety index was calculated that encompassed peeks and re-emergences on MBW. The proposed MBW anxiety index was compared with the standard anxiety index calculated from exploration into different sections of EPM. Post- bTBI, rats had an increased anxiety index when measured using EPM. Similarly, they peeked or fully emerged less out of the safe box on MBW. It was found that this novel MBW anxiety index captured similar aspects of behavior when compared to the standard anxiety index obtained from EPM. Further, these effects were dissociated from the effects of bTBI on motor function simultaneously measured on MBW. Over the course of 168 h post-bTBI, rats gradually recovered on both EPM and MBW. The MBW apparatus succeeded at capturing and dissociating two separate facets of rat behavior, motor function and anxiety, simultaneously.