Inter and intratrial variation in cat locomotor behavior.

Four cats were trained to locomote on a treadmill at a variety of speeds. The cats were then filmed at weekly intervals for three weeks; additionally, one of the cats was filmed 35 days prior to the first weekly filming. The films were used to characterize the variation exhibited by the cats in total cycle and swing/stance durations, and in footfall patterns both across the weekly trials and within them, and across speeds. The intertrial comparison indicated the existence of a "training effect" (i.e., a consistent change in gait subsequent to continued training) for only one cat; the cat showed notable reductions in cycle duration at all speeds over time. The intertrial comparison also indicated that a limb (especially a forelimb) could exhibit slightly different (but internally consistent) footfall patterns during different trials. Furthermore, the variation in one forelimb's pattern was usually associated with corresponding, but reciprocal, variation in the other forelimb's pattern. The analysis comparing variation in cycle duration across speeds indicated generally more variability at slow speeds relative to fast speeds. However, maximum or near maximum variability in cycle duration as well as in footfall pattern often occurred at an intermediate speed near the walk-trot transition. The data also demonstrated that both swing and stance durations could be modified at all speeds, although individual cats may consistently modify one more than the other. Additionally, swing duration appeared to be the primary variable during galloping. These results are discussed in terms of their implications for comparative studies of cat locomotor behavior subsequent to surgically induced lesions, and in terms of achieving a better understanding of cat locomotion and its neural control.