A Novel Multi-Dimensional Analysis of Rodent Gait Reveals the Compensation Strategies Used during Spontaneous Recovery from Spinal Cord and Traumatic Brain Injury.

As rodent locomotion becomes a more popular behavioral assay, proper rodent gait analysis becomes more and more important. Gait measures, such as stride length, cycle time, and duty factor, are not independent of one another, making statistical comparisons between groups a tricky endeavor. Instead of identifying the mathematical relationships between a group of locomotor measures, we simply tracked the steps of rodents in x,y,t space. By plotting with respect to the reference limb, we are able to quantify locomotor changes in space, time, and coordination simultaneously. With our technique, we show that the overall locomotion of 77 rats 1 week after a C4/5 right overhemisection injury was significantly different than pre-injury. This difference was maintained in untreated animals for the entire 7 weeks of the study, but how this difference arose changed. Initially, the right forelimb exhibited very abnormal stepping, but eventually reduced its difference from pre-injury levels. Conversely, the left forelimb was initially mildly different from pre-injury, but further deviated from normal stepping as the weeks went on. Our new gait analysis technique helps to show the trade-off between the restoration of function and the spontaneous development of compensatory techniques. When we applied this new analysis technique to 13 mice after a severe controlled cortical impact, we found that their locomotion was no different from 12 sham mice for the entire 4 weeks of the study. We believe that this gait analysis method succinctly addresses the confound of interdependency of gait measures and does so across multiple injury models.