Kinematic analysis of limb position during quadrupedal locomotion in rats

A test of locomotor behavior using the coordinates of ipsilateral limb positions of rats walking on a moving treadmill is described, Specific points on the forelimb and hindlimb were digitized from video records for 20-sec continuous sequences of locomotion, and step periods and step distances were calculated, The extent to which a given limb position would predict its own position-or the position of another limb-at different points in time was mathematically determined by autocorrelation and cross-correlation, respectively, Autocorrelation of position data was performed using a three-step window and the standard formula for correlating phasic data, A novel method of data preparation, which included normalization of the step data to eliminate variability introduced by differences in step period length, was used prior to cross-correlations of forelimb to hindlimb positions, Rats walking at 0.10, 0.15, and 0.25 m/sec had high limb autocorrelations, comparable forelimb/hindlimb phase relationships, and consistently high average cross-correlation coefficients, This analysis has resulted in the quantification of rat locomotor behavior in terms of the degree of limb movement rhythmicity and the strength of the forelimb/hindlimb coordination, and has provided baseline data for comparisons with spinal cord-injured rats that have retained or recovered alternating hindpaw movements.